**3. Special regions on Mars**

### **3.1. Introduction**

of living on Mars can actually survive in the Mars environment. The Mars surface presents a very inhospitable habitat for life because of the intense radiation, highly oxidizing conditions, concentrated evaporative salts, and extremely low water activity. Determining if microbes can survive those surface conditions, including tolerance to radiation (both ionizing and non-ionizing), desiccation, and oxidizing environments of microorganisms that utilize the carbon and energy resources available on Mars is vital. Some information is available on the survival of spore-forming microbes in a Mars-like environment, but much more information is needed regarding survival potential of different types of microorganisms.

Although Mars is considered to be at the outer edge of the habitable zone of our solar system, the idea that there could potentially be life on Mars, especially in the subsurface, is not unfathomable. Although it can be expected that different areas of Mars would have somewhat different environments dependent on location, overall the Martian environment is quite inhospitable to most life as we know it. Average temperatures on Mars can range from −10 to −76°C with an average surface temperature of −65°C although temperatures can fluctuate

Mars is considered to be quite dry, but recent information suggests otherwise. Studies of the Gale Crater by the rover Curiosity found hydration of soils to be as much as 2.25 wt%. This finding was consistent with findings by both Viking 1 and 2 and the Mars Odyssey [9]. What is unknown is if there is an underground source of water. Geophysical and geochemical features on Mars indicate that there may have been water on the surface at some time in the past but it is unknown to what extent surface water would have existed. Features include alluvial fans in craters, dendritic valley networks, and the presence of specific minerals thought to only form in the presence of water. One hypothesis is that hydrothermal environments associated with craters from impacts and volcanism could have easily provided a source of liquid water on Mars [10].

The Martian atmosphere is much different from that on Earth. Mars has primarily a CO<sup>2</sup>

(78.1%) while there is only 2.7% N<sup>2</sup>

The surface of Mars is subjected to both cosmic ionizing radiation and solar UV radiation. Ionizing radiation on Mars is believed to be 100X higher than on Earth, ranging from 100 to

 [7]. Studies by Mumma et al. [11] showed the presence of methane in extended plumes that appeared to be released from discrete regions on Mars. One of the principal plumes contained as much as 19,000 metric tons of methane, an amount comparable to that of a massive hydrocarbon seep in Santa Barbara, California. However, analyses by the Mars rover Curiosity found no detectable atmospheric methane. Although results are contradictory, it is possible that the location of the rover was too far from the methane seeps and prevented the

concentration on Earth is 20.9% whereas Mars' atmosphere contains only about 0.1%

content in Earth's atmosphere (0.04%). Earth's atmo-

in the Martian atmosphere.

This chapter will focus on the search for life on planetary bodies.

210 Into Space - A Journey of How Humans Adapt and Live in Microgravity

**2. The Martian environment**

from as high as 25°C to −123°C [6–8].

atmosphere (95.3%) compared to the CO<sup>2</sup>

detection of methane in the atmosphere.

sphere consists mainly of N2

The O2

O2

Mars Special Regions are regions where organisms are likely to survive. NASA Procedural Requirement (NPR) 8020.12D [18] defines these areas as regions that have a high potential for the existence of extant Martian life forms, have sufficient water activity (0.5–1.0 aw) and have sufficiently warm temperatures (−25° C lower limit) to permit replication of Earth organisms. Areas that have observed features that may be associated with the presence of water must also be classified as Special Regions. It is noted that these parameters may need to be changed as our understanding of Mars and life on Earth evolve and as our technological capabilities improve [19, 20].

### **3.2. Formulating special regions**

The COSPAR colloquium on special regions stated that "Preventing terrestrial biological contamination from becoming established and widespread on Mars is essential to our ability to protect high-priority science goals on Mars" [20]. The current standards are based solely on protecting science goals and not on protecting Mars in and of itself. The NRC study takes a precautionary principle approach by stating that there is insufficient data to determine which regions of Mars should be considered "special" and that all of Mars should be considered "special" until it can be proven otherwise [19, 20]. The COSPAR disagreed and concluded that there was sufficient data to arrive at a conclusion as to which areas of Mars would be defined as "Special Regions" [20].

described as reproducing and thriving at temperatures as low as −15°C. Many microorgan-

in either very acidic or very alkaline environments. Microbes can conserve energy by respiring some of the most extreme compounds, such as U, Mn, Se, As, S and Cl-based molecules. Life at either high or low atmospheric pressures has been described, as well as organisms that are highly resistant to radiation and oxidative conditions. Most of the organisms surviving in these types of environments have a symbiotic relationship with other organisms in the same community. For example, methane-oxidizing archaea (MOA) are known to live in symbiosis with sulfate-reducing bacteria (SRB) in deep hydrothermal vents on the ocean floor. MOAs

, and others thrive

−2 to

213

is then utilized by the SRBs to reduce SO4

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

http://dx.doi.org/10.5772/intechopen.75437

atmosphere. The methanogens that survived best



isms can grow in salt at concentrations exceeding 20% NaCl, or 2 M MgSO<sup>4</sup>

, and the H<sup>2</sup>

[22]. These types of relationships between organisms are far from uncommon.

Earth microorganisms have developed physiological and biochemical mechanisms to be able to survive in a variety of extreme niches. As previously stated, it would not be unreasonable to expect niches on Mars, although considered extreme, to support microbial life of some sort as well. The remainder of this chapter will discuss what is known about how microorganisms survive some of these extreme environmental conditions and how this information is relative to the potential for life on Mars. Although this portion of the chapter will focus on bacteria, it should always be kept in mind that many of the topics discussed apply to archaea and fungi as well.

Average temperatures on Mars can range from −10 to −76°C with an average surface temperature of −65°C although temperatures can fluctuate from as high as 25°C to as low as −123°C [6–8]. For an organism to be able to thrive on Mars it would need to be able to grow and reproduce in these frigid temperatures. An exception would be a subsurface environment that was

A number of psychrophilic (cold-loving) organisms have been isolated from many regions of the Arctic and Antarctic where there are polar ice sheets, glaciers and permafrost. Additionally, microorganisms are known to inhabit the ocean floor where temperatures are ≤4°C [23]. These organisms are comprised of representatives from the Eukarya (algae, fungi and yeast), Bacteria and Archaea. Morozova et al. [24] identified several methanogenic archaea that were able to survive not only low temperatures ranging from −75 to 20°C, but could also simultaneously

under these conditions were isolated from permafrost. Six isolates from permafrost and nine known species of *Carnobacterium* were found to grow not only at 23°C, but also at 0°C, under

a common mesophilic organism often found as a contaminant in bathtubs, was shown to be

[26]. Mykytczuk et al. [27] identified a *Planococcus* isolate that grows and divided at −15°C and

Despite these organisms being interesting in themselves, what is even more interesting is the ability of these organisms to make both physiological and biochemical modifications to

geothermally heated though no such areas have been discovered on Mars.

capable of growth at 0°C as well as at low pressure and CO<sup>2</sup>

and H<sup>2</sup>

break down methane to CO<sup>2</sup>

**4.2. Survival at low temperatures**

survive low humidity and a 95.3% CO<sup>2</sup>

is still metabolically active at −25°C.

low pressure and in a CO<sup>2</sup>

HS−

The COSPAR colloquium concluded with the enactment of the standards that are currently in NPR 8020.12D [18]. Two main standards, water activity and temperature, are the basis for determining which regions should be taken into consideration. One area in need of additional research is that of microbial growth and reproduction at low temperatures. It was noted that most of the work in this area has been performed on laboratory isolates and more environmental data is needed to begin to define the lower temperature for life. It was concluded that investigations were needed to determine if microbial reproduction at water activities of lower than 0.6 is possible, that more studies are needed using Mars simulated environments, and that knowledge of reproduction of communities rather than isolates is essential to improve our understanding of life. COSPAR also noted that a larger phylogenetically diverse array of organisms needs to be studied and diurnal, seasonal and long-term variations in the Martian surface need to be better understood [20].

The NASA Planetary Protection Office made some initial suggestions to try to define special regions. The parameters were set as: (1) the existence of liquid water in "pure" form or in strong brines up to 5.5 M CaCl<sup>2</sup> ; (2) regions of current or active volcanism or enhanced heat flow which is yet unknown; (3) permafrost through 100% water ice, including segregated ground ice, icerich frozen ground, polar caps and subsurface ice; (4) subpermafrost groundwater and (5) any gully system that may be indicative of recent water activity within the last <50,000 years. The Special Regions Science Analysis Group (SRSAG) determined that regions should be defined as non-special if the temperature remains below −20°C or the water activity remains below 0.5 for a period of 100 years after spacecraft arrival [21]. Ultimately, the SRSAG developed a map of regions that are considered "significant" and of interest for determining special region boundaries. Of note is that the current definition of special regions mostly takes into account the known and sets the water activity and temperature parameters slightly below what is currently known.

### **4. The relationship between life on Earth, and the potential for life on Mars**

#### **4.1. Life in extreme environments**

Despite our limited knowledge of microbes on Earth, everywhere we have looked for microbes and we have been able to find them. It appears that life inhabits all places on Earth including some of the most extreme environments imaginable. Microorganisms have been discovered surviving and reproducing in hot springs, at terrestrial depths exceeding 2 km, in the most arid of deserts, and in hydrothermal vents on the ocean floor. Microbial life has been found in extremely cold places such as in Antarctica and Greenland, and microorganisms have been described as reproducing and thriving at temperatures as low as −15°C. Many microorganisms can grow in salt at concentrations exceeding 20% NaCl, or 2 M MgSO<sup>4</sup> , and others thrive in either very acidic or very alkaline environments. Microbes can conserve energy by respiring some of the most extreme compounds, such as U, Mn, Se, As, S and Cl-based molecules. Life at either high or low atmospheric pressures has been described, as well as organisms that are highly resistant to radiation and oxidative conditions. Most of the organisms surviving in these types of environments have a symbiotic relationship with other organisms in the same community. For example, methane-oxidizing archaea (MOA) are known to live in symbiosis with sulfate-reducing bacteria (SRB) in deep hydrothermal vents on the ocean floor. MOAs break down methane to CO<sup>2</sup> and H<sup>2</sup> , and the H<sup>2</sup> is then utilized by the SRBs to reduce SO4 −2 to HS− [22]. These types of relationships between organisms are far from uncommon.

Earth microorganisms have developed physiological and biochemical mechanisms to be able to survive in a variety of extreme niches. As previously stated, it would not be unreasonable to expect niches on Mars, although considered extreme, to support microbial life of some sort as well. The remainder of this chapter will discuss what is known about how microorganisms survive some of these extreme environmental conditions and how this information is relative to the potential for life on Mars. Although this portion of the chapter will focus on bacteria, it should always be kept in mind that many of the topics discussed apply to archaea and fungi as well.

#### **4.2. Survival at low temperatures**

precautionary principle approach by stating that there is insufficient data to determine which regions of Mars should be considered "special" and that all of Mars should be considered "special" until it can be proven otherwise [19, 20]. The COSPAR disagreed and concluded that there was sufficient data to arrive at a conclusion as to which areas of Mars would be

The COSPAR colloquium concluded with the enactment of the standards that are currently in NPR 8020.12D [18]. Two main standards, water activity and temperature, are the basis for determining which regions should be taken into consideration. One area in need of additional research is that of microbial growth and reproduction at low temperatures. It was noted that most of the work in this area has been performed on laboratory isolates and more environmental data is needed to begin to define the lower temperature for life. It was concluded that investigations were needed to determine if microbial reproduction at water activities of lower than 0.6 is possible, that more studies are needed using Mars simulated environments, and that knowledge of reproduction of communities rather than isolates is essential to improve our understanding of life. COSPAR also noted that a larger phylogenetically diverse array of organisms needs to be studied and diurnal, seasonal and long-term variations in the Martian

The NASA Planetary Protection Office made some initial suggestions to try to define special regions. The parameters were set as: (1) the existence of liquid water in "pure" form or in strong

is yet unknown; (3) permafrost through 100% water ice, including segregated ground ice, icerich frozen ground, polar caps and subsurface ice; (4) subpermafrost groundwater and (5) any gully system that may be indicative of recent water activity within the last <50,000 years. The Special Regions Science Analysis Group (SRSAG) determined that regions should be defined as non-special if the temperature remains below −20°C or the water activity remains below 0.5 for a period of 100 years after spacecraft arrival [21]. Ultimately, the SRSAG developed a map of regions that are considered "significant" and of interest for determining special region boundaries. Of note is that the current definition of special regions mostly takes into account the known and sets the water activity and temperature parameters slightly below what is currently known.

**4. The relationship between life on Earth, and the potential for life** 

Despite our limited knowledge of microbes on Earth, everywhere we have looked for microbes and we have been able to find them. It appears that life inhabits all places on Earth including some of the most extreme environments imaginable. Microorganisms have been discovered surviving and reproducing in hot springs, at terrestrial depths exceeding 2 km, in the most arid of deserts, and in hydrothermal vents on the ocean floor. Microbial life has been found in extremely cold places such as in Antarctica and Greenland, and microorganisms have been

; (2) regions of current or active volcanism or enhanced heat flow which

defined as "Special Regions" [20].

212 Into Space - A Journey of How Humans Adapt and Live in Microgravity

surface need to be better understood [20].

brines up to 5.5 M CaCl<sup>2</sup>

**on Mars**

**4.1. Life in extreme environments**

Average temperatures on Mars can range from −10 to −76°C with an average surface temperature of −65°C although temperatures can fluctuate from as high as 25°C to as low as −123°C [6–8]. For an organism to be able to thrive on Mars it would need to be able to grow and reproduce in these frigid temperatures. An exception would be a subsurface environment that was geothermally heated though no such areas have been discovered on Mars.

A number of psychrophilic (cold-loving) organisms have been isolated from many regions of the Arctic and Antarctic where there are polar ice sheets, glaciers and permafrost. Additionally, microorganisms are known to inhabit the ocean floor where temperatures are ≤4°C [23]. These organisms are comprised of representatives from the Eukarya (algae, fungi and yeast), Bacteria and Archaea. Morozova et al. [24] identified several methanogenic archaea that were able to survive not only low temperatures ranging from −75 to 20°C, but could also simultaneously survive low humidity and a 95.3% CO<sup>2</sup> atmosphere. The methanogens that survived best under these conditions were isolated from permafrost. Six isolates from permafrost and nine known species of *Carnobacterium* were found to grow not only at 23°C, but also at 0°C, under low pressure and in a CO<sup>2</sup> -enriched anoxic atmosphere [25]. A strain of *Serratia liquefaciens*, a common mesophilic organism often found as a contaminant in bathtubs, was shown to be capable of growth at 0°C as well as at low pressure and CO<sup>2</sup> -enriched anoxic atmospheres [26]. Mykytczuk et al. [27] identified a *Planococcus* isolate that grows and divided at −15°C and is still metabolically active at −25°C.

Despite these organisms being interesting in themselves, what is even more interesting is the ability of these organisms to make both physiological and biochemical modifications to survive in such environments. *Psychrobacter arcticus* 273-4, a bacterium capable of growing at temperatures as low as −10°C, was found to downregulate genes related to energy metabolism and carbon incorporation, and upregulate genes required for maintenance of membranes, cell walls and nucleic acid motion. Furthermore, this organism turns on the expression of a cold-shock DEAD-box RNA helicase A, a protein that may be key for maintaining life in cold temperatures [28]. *Planococcus halocryophilus* Or1 grew at subzero temperatures by forming encrustations around the cell and increasing the ratio of saturated to branched fatty acids in the cytoplasmic membrane [27]. This is unique because often growth at lower temperatures results in a higher content of unsaturated, polyunsaturated and methyl-branched fatty acids to increase membrane fluidity at these temperatures. In many organisms, enzymes involved in transcription, translation, protein folding and stabilization of DNA and RNA show activity at very low temperatures and are adapted to life in cold environments. Antifreeze-like proteins have been seen in Antarctic lake microbes and trehalose and exopolysaccharides might also provide cryoprotection for psychrophiles [29]. Although scientists are far from having a full understanding at life in cold temperatures, studies like the ones above provide insights as to how these organisms adapt to their extreme environment. Additionally, the microbes are models to further our understanding of how organisms may survive on Mars, and can be useful as we continue the search for life on cold planets and moons.

the overall microbial community was unique because the bacteria and archaea identified were not related to organisms normally found in seawater, and the archaea branched deeply within

in Oklahoma. Though the microbes were not identified, it was found that 35% of the organisms

Science Laboratory (MSL) pre-launch showed that a large percentage of the organisms from the

Although scientists are still learning more about how life survives in these extreme, high salt environments, we do know that the cells must have special physiological and biochemical properties to survive such environments. The primary factors for surviving these conditions are the amount of energy generated during dissimilatory metabolism and the mode of osmotic adaption utilized [33]. A review of studies from 1999 concluded that aerobic respiration, denitrification, and both oxygenic and anoxygenic photosynthesis can occur under the highest salt concentrations but autotrophic oxidation of ammonia and nitrate, some forms of methanogenesis and sulfate reduction were never found at salt concentrations >100–200 gl−1 [33]. Processes identified as occurring, albeit poorly, at salt concentrations >200 gl−1 included fermentation, aerobic autotrophic oxidation of sulfur compounds, sulfate reduction by incom-

Oren hypothesized based on his findings that life at high salt concentrations is energetically expensive, and the upper salt concentration limit at which dissimilatory processes occur is determined partly by bioenergetics constraints. Given this the main factors that determine whether a certain type of organism can make a living at high salt concentrations are the amount of energy gained during its dissimilatory metabolism and the mode of osmotic adaptation used. Based on his review of halophiles, Oren stated that the energy cost associated with salt exclusion and pumping ions out was unfavorable and that the "salt-in" strategy was energetically favored. Given this the following types of metabolism are most likely to occur under high salt concentrations: (i) those that use light as the energy source, (ii) aerobic respiration, denitrification, and other highly exergonic dissimilatroy processes coupled with large production of ATP and (iii) types of metabolism performed by organisms that use the "salt-in" strategy even when the amount of ATP obtained in their dissimilatory processes is low [33]. Oren hypothesizes that the salt-in option would be energetically favorable to organisms, and it is clear that organisms have made adaptations to their molecules to thrive under high salt conditions and allow for the "salt-in" option. Studies by Tehei et al. [34] identified a malate dehydrogenase and tRNA molecules, from the archaeon *Haloarcula marismortui*, that are protected in the presence of high salt. The salt protected the tRNA molecules from thermal degradation while the malate dehydrogenase was protected from thermal denaturation. While studying the lipid composition of *Halobacillus halophilus*, Lopalco et al. [35] found that the organism increased the number of shorter chains and incorporated unsaturated chains in the lipid core structures.

. Studies by Crisler et al. [17] focused on the growth of microorganisms

[17]. Studies using isolates collected from the Mars

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

(Smith, unpublished).

http://dx.doi.org/10.5772/intechopen.75437

concentrations using microorganisms collected from the Great Salt Plains

, with lower concentra-

and at least 80%

215

the Euryarchaeota indicating they comprised a new order.

MSL were able to grow in media containing 1 M or 2 M MgSO4

plete oxidizers and some other forms of methanogenesis.

tions of NaCl and CaCl<sup>2</sup>

could grow in the presence of 10% MgSO<sup>4</sup>

under high MgSO4

It is estimated that the majority of salt on Mars would likely be MgSO4

from the bacterial collection could grow in medium containing 2 M MgSO4

#### **4.3. Tolerance to high salt**

Due to the high salt concentrations found in Martian soils in the form of NaCl, MgSO<sup>4</sup> , CaSO<sup>4</sup> , FeSO4 , MgCl and CaCl<sup>2</sup> , salt tolerance would be required for life to survive and grow on Mars [17]. Salts can be chaotropic as they influence water activity, affect cell turgor, and are major stressors of cellular systems [30]. It is estimated that 1/4th of the Earth's land is covered by salt and salt water makes up the majority of Earth's water. On Mars, it is estimated that sulfurous salts are more common than chlorinated salts by a ratio of 3:1. On Earth the most common type of salt is NaCl but many brines also contain MgCl<sup>2</sup> , MgSO4 and other salts [17, 30]. Studying hypersaline environments from Earth increases our understanding of how organisms can adapt to these extreme environments.

Many *Bacillus* sp. are salt-tolerant and thus of special interest with regard to growth under high salt conditions. Previous studies in our laboratory have shown that many different species of *Bacillus*, including *pumilus*, *licheniformis*, *horti*, *mannailyticus* and *cellulosilyticus*, as well as species belonging to other genera including *Paenibacillus*, *Amphibacillus* and *Alkalibacterium*, could grow under salt concentrations as high as 10% NaCl. Several of these organisms also showed growth in media containing 20% NaCl. These isolates were collected from the Alvord Basin in Oregon where the soils are known to have elevated salt concentrations [31]. The ability of *Bacillus* sp. to grow under these conditions is not uncommon and many organisms which have been identified as non-spore formers can also grow in high NaCl concentrations.

A diversity of prokaryotes was discovered residing in deep hypersaline anoxic basins in the Mediterranean Sea; basins that are nearly saturated with MgCl<sup>2</sup> (5 M). In addition to growing in extremely high concentrations of MgCl<sup>2</sup> , the microorganisms were involved in sulfate reduction and methanogenesis, and contributed to the cycling of carbon [32]. Furthermore, the overall microbial community was unique because the bacteria and archaea identified were not related to organisms normally found in seawater, and the archaea branched deeply within the Euryarchaeota indicating they comprised a new order.

survive in such environments. *Psychrobacter arcticus* 273-4, a bacterium capable of growing at temperatures as low as −10°C, was found to downregulate genes related to energy metabolism and carbon incorporation, and upregulate genes required for maintenance of membranes, cell walls and nucleic acid motion. Furthermore, this organism turns on the expression of a cold-shock DEAD-box RNA helicase A, a protein that may be key for maintaining life in cold temperatures [28]. *Planococcus halocryophilus* Or1 grew at subzero temperatures by forming encrustations around the cell and increasing the ratio of saturated to branched fatty acids in the cytoplasmic membrane [27]. This is unique because often growth at lower temperatures results in a higher content of unsaturated, polyunsaturated and methyl-branched fatty acids to increase membrane fluidity at these temperatures. In many organisms, enzymes involved in transcription, translation, protein folding and stabilization of DNA and RNA show activity at very low temperatures and are adapted to life in cold environments. Antifreeze-like proteins have been seen in Antarctic lake microbes and trehalose and exopolysaccharides might also provide cryoprotection for psychrophiles [29]. Although scientists are far from having a full understanding at life in cold temperatures, studies like the ones above provide insights as to how these organisms adapt to their extreme environment. Additionally, the microbes are models to further our understanding of how organisms may survive on Mars, and can be

useful as we continue the search for life on cold planets and moons.

common type of salt is NaCl but many brines also contain MgCl<sup>2</sup>

Mediterranean Sea; basins that are nearly saturated with MgCl<sup>2</sup>

ing in extremely high concentrations of MgCl<sup>2</sup>

organisms can adapt to these extreme environments.

214 Into Space - A Journey of How Humans Adapt and Live in Microgravity

Due to the high salt concentrations found in Martian soils in the form of NaCl, MgSO<sup>4</sup>

Mars [17]. Salts can be chaotropic as they influence water activity, affect cell turgor, and are major stressors of cellular systems [30]. It is estimated that 1/4th of the Earth's land is covered by salt and salt water makes up the majority of Earth's water. On Mars, it is estimated that sulfurous salts are more common than chlorinated salts by a ratio of 3:1. On Earth the most

[17, 30]. Studying hypersaline environments from Earth increases our understanding of how

Many *Bacillus* sp. are salt-tolerant and thus of special interest with regard to growth under high salt conditions. Previous studies in our laboratory have shown that many different species of *Bacillus*, including *pumilus*, *licheniformis*, *horti*, *mannailyticus* and *cellulosilyticus*, as well as species belonging to other genera including *Paenibacillus*, *Amphibacillus* and *Alkalibacterium*, could grow under salt concentrations as high as 10% NaCl. Several of these organisms also showed growth in media containing 20% NaCl. These isolates were collected from the Alvord Basin in Oregon where the soils are known to have elevated salt concentrations [31]. The ability of *Bacillus* sp. to grow under these conditions is not uncommon and many organisms which have been identified as non-spore formers can also grow in high NaCl concentrations. A diversity of prokaryotes was discovered residing in deep hypersaline anoxic basins in the

reduction and methanogenesis, and contributed to the cycling of carbon [32]. Furthermore,

, salt tolerance would be required for life to survive and grow on

, MgSO4

(5 M). In addition to grow-

, the microorganisms were involved in sulfate

, CaSO<sup>4</sup> ,

and other salts

**4.3. Tolerance to high salt**

, MgCl and CaCl<sup>2</sup>

FeSO4

It is estimated that the majority of salt on Mars would likely be MgSO4 , with lower concentrations of NaCl and CaCl<sup>2</sup> . Studies by Crisler et al. [17] focused on the growth of microorganisms under high MgSO4 concentrations using microorganisms collected from the Great Salt Plains in Oklahoma. Though the microbes were not identified, it was found that 35% of the organisms from the bacterial collection could grow in medium containing 2 M MgSO4 and at least 80% could grow in the presence of 10% MgSO<sup>4</sup> [17]. Studies using isolates collected from the Mars Science Laboratory (MSL) pre-launch showed that a large percentage of the organisms from the MSL were able to grow in media containing 1 M or 2 M MgSO4 (Smith, unpublished).

Although scientists are still learning more about how life survives in these extreme, high salt environments, we do know that the cells must have special physiological and biochemical properties to survive such environments. The primary factors for surviving these conditions are the amount of energy generated during dissimilatory metabolism and the mode of osmotic adaption utilized [33]. A review of studies from 1999 concluded that aerobic respiration, denitrification, and both oxygenic and anoxygenic photosynthesis can occur under the highest salt concentrations but autotrophic oxidation of ammonia and nitrate, some forms of methanogenesis and sulfate reduction were never found at salt concentrations >100–200 gl−1 [33]. Processes identified as occurring, albeit poorly, at salt concentrations >200 gl−1 included fermentation, aerobic autotrophic oxidation of sulfur compounds, sulfate reduction by incomplete oxidizers and some other forms of methanogenesis.

Oren hypothesized based on his findings that life at high salt concentrations is energetically expensive, and the upper salt concentration limit at which dissimilatory processes occur is determined partly by bioenergetics constraints. Given this the main factors that determine whether a certain type of organism can make a living at high salt concentrations are the amount of energy gained during its dissimilatory metabolism and the mode of osmotic adaptation used. Based on his review of halophiles, Oren stated that the energy cost associated with salt exclusion and pumping ions out was unfavorable and that the "salt-in" strategy was energetically favored. Given this the following types of metabolism are most likely to occur under high salt concentrations: (i) those that use light as the energy source, (ii) aerobic respiration, denitrification, and other highly exergonic dissimilatroy processes coupled with large production of ATP and (iii) types of metabolism performed by organisms that use the "salt-in" strategy even when the amount of ATP obtained in their dissimilatory processes is low [33]. Oren hypothesizes that the salt-in option would be energetically favorable to organisms, and it is clear that organisms have made adaptations to their molecules to thrive under high salt conditions and allow for the "salt-in" option. Studies by Tehei et al. [34] identified a malate dehydrogenase and tRNA molecules, from the archaeon *Haloarcula marismortui*, that are protected in the presence of high salt. The salt protected the tRNA molecules from thermal degradation while the malate dehydrogenase was protected from thermal denaturation. While studying the lipid composition of *Halobacillus halophilus*, Lopalco et al. [35] found that the organism increased the number of shorter chains and incorporated unsaturated chains in the lipid core structures. It was believed that these changes compensated for an increase in phospholipid packing and rigidity, and sulfoglycolipid polar heads. It is believed that these changes allowed for homeostasis of membrane fluidity and permeability under high salt stress conditions.

water on the surface at some time in the past. It is not unreasonable to think that the water would have seeped into the subsurface and may still be present to some degree. Additionally, hydrothermal environments on Mars associated with craters from impacts and volcanism could have easily provided a source of liquid water, and crater impacts generating water are a potential concern today [11]. It may be possible for an organism to remain dormant for an extended period of time, then flourish after a wind storm has transferred the organism to a

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217

Several studies have shown that desiccation resistance in microorganisms is far from rare, and not only includes spore-forming microorganisms such as *Bacillus*, but non-spore-forming organisms such as *Moraxella* and *Staphylococcus* as well [37, 38]. Overall, dehydration of cells leads to severe cell damage by causing structural changes to lipid membranes and proteins, cross linking and polymerization of DNA molecules, inhibiting or altering enzyme activity, changing membrane permeability, and altering or mutating genetic information. DNA in the cell is at most risk to the desiccating environment since loss of water can lead to partial DNA denaturation [39]. Spore-forming organisms such as species belonging to the genera *Bacillus* and *Clostridium* are more likely to resist desiccation as the spore coat provides protection against a desiccating environment. The water content of spores is reduced to 25–45% of the cell's wet weight causing proteins to become immobile and ceasing enzymatic activity altogether [39]. However, the overall resistance of the spore to the desiccating environment is mostly due to protection of the dehydrated core by the cortex and spore coat layers while the DNA is protected by small DNA binding-acid soluble which protect the DNA from chemical and enzymatic reactivity [39].

Many non-spore-forming organisms have been shown to be resistant to desiccation. Studies by La Duc et al. [40] identified several isolates of *Pseudoaltermonas*, *Psychrobacte*r and *Acinetobacter* that survived a 7-day incubation at a Rh of 18 ± 3%. Several *Moraxella* sp. have been shown to survive a 30°C incubation for 35 days under dry conditions [37]. *Staphylococcus aureus* can survive on dry plastic surfaces for more than 1097 days [38]. The methanogens, *Methanobacterium wolfeii*, *Methanosarcina barkeri* and *Methanobacterium formicicum* survived desiccation for 90–120 day incubation periods [41]. Studies on Amazonian oxbow lake sediments showed that desiccation for 1 year at 4°C not only increased the overall abundance of *Methanocellales*

Although it is clear that the spore coat protects spore-forming organisms from a desiccating environment, it is relatively unclear how non-spore-formers survive similar environments. Studies by de Goffau et al. [45] have shown that cells can maintain intracellular water activity above that in their environment as long as the microbes can generate more water metabolically than is lost to the environment. However, this would require that the organisms were metabolically active which would be questionable under most desiccating environments such as the case of *Staphylococcus aureus* residing on a dry surface where there would be little to no nutrients [38]. Studies by Chaibenjawong and Foster [38] showed that the mutants *clpX*, *sigB* and *yjbH* were required for desiccation resistance in *Staphylococcus auerus*. *ClpX* and *yjbH* are both important for protein turnover while *sigB* plays a role in overall stress resistance [38]. It is likely that there are several factors involved in the desiccation resistance of non-sporeforming organisms but more studies on these unique organisms will need to be performed

production after rewetting [42].

water source or water flows from a crater impact.

and *Methanosarcinaceae*, but also increased the rates of CH<sup>4</sup>

before we have a comprehensive understanding of these systems.

Although many more studies need to be conducted to have a full understanding of how organisms survive these high salt environments, these studies do show that life under these conditions is possible and even, in some cases, protective. Given this, it would not be unreasonable to think that such microorganisms would be able to thrive on Mars in the salty Martian soils. Oren includes organisms using light as the energy source, however this would be unlikely on Mars since organisms living on this planet would also have to survive other conditions on the surface such as desiccation, and high radiation (to be discussed later). It is more likely that organisms on Mars would utilize exergonic dissimilatory processes or utilize types of metabolism which allowed for the "salt-in" strategy [33].

#### **4.4. Tolerance to pH extremes**

The ability of organisms to withstand alkaline pH is a factor to consider when discussing life on Mars. Initially, it was thought that the Martian soil was likely to be acidic but results by the Phoenix Lander showed that the soils at that site were mildly basic with a pH of 7.7 ± 0.5 [16]. Although the pH at the Phoenix Lander study site was only slightly basic, it is possible that other soils on Mars are more basic.

Alkaliphiles are organisms which grow above neutral pH whereas extreme alkaliphiles generally grow in the pH range of 10.0–14.0. Studies on alkaliphilic organisms have mostly focused on *Bacillus* sp. with the most extensive studies having been performed on *B. halodurans* and *B. pseudofirmus* [36]. The biggest hurdle facing alkaliphilic organisms is the ability to maintain homeostasis and maintain chemiosmosis. Alkaliphiles use transporters to help catalyze proton transport and these transporters include proton-pumping respiration chains, protoncoupled ATPases, and secondary active transporters. Often the uptake of protons is unequal where 2H<sup>+</sup> are exchanged for one Na+ ion. Studies have shown that even in extreme alkiliphiles, the pH remains relatively neutral to slightly alkaline in the cytoplasm even though the surrounding medium might be extremely alkaline. There is still much to be learned but it is clear that organisms have easily adapted to alkaline environments thus it would not be difficult for organisms to grow in Martian soils.

### **4.5. Surviving desiccation**

Surviving desiccation is absolutely necessary if a microorganism is to survive on Mars as organisms must be able to survive the desiccating environment until they can come into contact with a water source suitable for growth. Only after finding suitable water activity, such as a polar ice cap or subsurface water sources, could the organisms then potentially become active.

As previously discussed, Mars is considered to be quite dry, and soils contain only 2.25 wt% water [9]. However, this analysis was performed on soils on the Mars surface so we do not know what the soil water content is at deeper depths. It is not known if there is a source of subsurface water, but geographical features of Mars indicate that there may have been water on the surface at some time in the past. It is not unreasonable to think that the water would have seeped into the subsurface and may still be present to some degree. Additionally, hydrothermal environments on Mars associated with craters from impacts and volcanism could have easily provided a source of liquid water, and crater impacts generating water are a potential concern today [11]. It may be possible for an organism to remain dormant for an extended period of time, then flourish after a wind storm has transferred the organism to a water source or water flows from a crater impact.

It was believed that these changes compensated for an increase in phospholipid packing and rigidity, and sulfoglycolipid polar heads. It is believed that these changes allowed for homeo-

Although many more studies need to be conducted to have a full understanding of how organisms survive these high salt environments, these studies do show that life under these conditions is possible and even, in some cases, protective. Given this, it would not be unreasonable to think that such microorganisms would be able to thrive on Mars in the salty Martian soils. Oren includes organisms using light as the energy source, however this would be unlikely on Mars since organisms living on this planet would also have to survive other conditions on the surface such as desiccation, and high radiation (to be discussed later). It is more likely that organisms on Mars would utilize exergonic dissimilatory processes or utilize types of

The ability of organisms to withstand alkaline pH is a factor to consider when discussing life on Mars. Initially, it was thought that the Martian soil was likely to be acidic but results by the Phoenix Lander showed that the soils at that site were mildly basic with a pH of 7.7 ± 0.5 [16]. Although the pH at the Phoenix Lander study site was only slightly basic, it is possible that

Alkaliphiles are organisms which grow above neutral pH whereas extreme alkaliphiles generally grow in the pH range of 10.0–14.0. Studies on alkaliphilic organisms have mostly focused on *Bacillus* sp. with the most extensive studies having been performed on *B. halodurans* and *B. pseudofirmus* [36]. The biggest hurdle facing alkaliphilic organisms is the ability to maintain homeostasis and maintain chemiosmosis. Alkaliphiles use transporters to help catalyze proton transport and these transporters include proton-pumping respiration chains, protoncoupled ATPases, and secondary active transporters. Often the uptake of protons is unequal

les, the pH remains relatively neutral to slightly alkaline in the cytoplasm even though the surrounding medium might be extremely alkaline. There is still much to be learned but it is clear that organisms have easily adapted to alkaline environments thus it would not be dif-

Surviving desiccation is absolutely necessary if a microorganism is to survive on Mars as organisms must be able to survive the desiccating environment until they can come into contact with a water source suitable for growth. Only after finding suitable water activity, such as a polar ice

As previously discussed, Mars is considered to be quite dry, and soils contain only 2.25 wt% water [9]. However, this analysis was performed on soils on the Mars surface so we do not know what the soil water content is at deeper depths. It is not known if there is a source of subsurface water, but geographical features of Mars indicate that there may have been

cap or subsurface water sources, could the organisms then potentially become active.

ion. Studies have shown that even in extreme alkiliphi-

stasis of membrane fluidity and permeability under high salt stress conditions.

metabolism which allowed for the "salt-in" strategy [33].

216 Into Space - A Journey of How Humans Adapt and Live in Microgravity

**4.4. Tolerance to pH extremes**

other soils on Mars are more basic.

are exchanged for one Na+

ficult for organisms to grow in Martian soils.

**4.5. Surviving desiccation**

where 2H<sup>+</sup>

Several studies have shown that desiccation resistance in microorganisms is far from rare, and not only includes spore-forming microorganisms such as *Bacillus*, but non-spore-forming organisms such as *Moraxella* and *Staphylococcus* as well [37, 38]. Overall, dehydration of cells leads to severe cell damage by causing structural changes to lipid membranes and proteins, cross linking and polymerization of DNA molecules, inhibiting or altering enzyme activity, changing membrane permeability, and altering or mutating genetic information. DNA in the cell is at most risk to the desiccating environment since loss of water can lead to partial DNA denaturation [39]. Spore-forming organisms such as species belonging to the genera *Bacillus* and *Clostridium* are more likely to resist desiccation as the spore coat provides protection against a desiccating environment. The water content of spores is reduced to 25–45% of the cell's wet weight causing proteins to become immobile and ceasing enzymatic activity altogether [39]. However, the overall resistance of the spore to the desiccating environment is mostly due to protection of the dehydrated core by the cortex and spore coat layers while the DNA is protected by small DNA binding-acid soluble which protect the DNA from chemical and enzymatic reactivity [39].

Many non-spore-forming organisms have been shown to be resistant to desiccation. Studies by La Duc et al. [40] identified several isolates of *Pseudoaltermonas*, *Psychrobacte*r and *Acinetobacter* that survived a 7-day incubation at a Rh of 18 ± 3%. Several *Moraxella* sp. have been shown to survive a 30°C incubation for 35 days under dry conditions [37]. *Staphylococcus aureus* can survive on dry plastic surfaces for more than 1097 days [38]. The methanogens, *Methanobacterium wolfeii*, *Methanosarcina barkeri* and *Methanobacterium formicicum* survived desiccation for 90–120 day incubation periods [41]. Studies on Amazonian oxbow lake sediments showed that desiccation for 1 year at 4°C not only increased the overall abundance of *Methanocellales* and *Methanosarcinaceae*, but also increased the rates of CH<sup>4</sup> production after rewetting [42].

Although it is clear that the spore coat protects spore-forming organisms from a desiccating environment, it is relatively unclear how non-spore-formers survive similar environments. Studies by de Goffau et al. [45] have shown that cells can maintain intracellular water activity above that in their environment as long as the microbes can generate more water metabolically than is lost to the environment. However, this would require that the organisms were metabolically active which would be questionable under most desiccating environments such as the case of *Staphylococcus aureus* residing on a dry surface where there would be little to no nutrients [38]. Studies by Chaibenjawong and Foster [38] showed that the mutants *clpX*, *sigB* and *yjbH* were required for desiccation resistance in *Staphylococcus auerus*. *ClpX* and *yjbH* are both important for protein turnover while *sigB* plays a role in overall stress resistance [38]. It is likely that there are several factors involved in the desiccation resistance of non-sporeforming organisms but more studies on these unique organisms will need to be performed before we have a comprehensive understanding of these systems.

#### **4.6. Exposure to an oxidative environment**

Data from the Viking missions showed that the surface of Mars was highly oxidized compared to its atmosphere [13]. Additional studies of Mars have shown that H<sup>2</sup> O2 abundance can range from 15 ± 10 ppb to 40 ppb [14]. The formation of peroxides can occur in the presence of hematite, trace amounts of water, and UV radiation, and radiolysis of ice or water can create even larger amounts of peroxide formation approaching 0.13% as seen on Europa [7, 15]. For an organism to survive on Mars it would need to have mechanisms to protect itself from this oxidizing environment.

other coat oxidoreductases, contributes to the increased resistance of SAFR-032 to H<sup>2</sup>

resistance of SAFR-032 to H<sup>2</sup>

tion from GCR is modulated by SCR [51].

**4.7. Exposure to radiation**

O2 .

over other *Bacillus pumilus* strains. This work has greatly improved our knowledge of the

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

http://dx.doi.org/10.5772/intechopen.75437

The ability of an organism to survive radiation is paramount if the organism is to survive near the surface of Mars and pose a planetary protection threat. The radiation exposure on Mars is much more intense than it is on Earth because Mars lacks a magnetic field to deflect incoming charged particles and the atmosphere is <1% that of Earth [51]. There are 2 major types of radiation to be concerned with on Mars. The first type of radiation, Galactic Cosmic Rays (GCR), originates outside of our solar system and is formed from events such as supernovas. The second type of radiation, Solar Cosmic Radiation (SCR), originates from the sun and consists of both a constant flow of radiation as well as brief bursts [39, 51]. In the past, the overall radiation level on Mars has been based solely on calculations and modeling. New studies using data collected from the MSL found that the radiation in flight to Mars is approximately two times higher than the radiation on the surface of Mars (0.21 mGy/day vs. 0.48 mGy/day). The lower radiation level on the Mars surface is due in part to some atmospheric shielding by the Martian atmosphere, which is not provided to the spacecraft en route, and because radia-

SCR can consist of both ionizing (e.g. gamma radiation) and non-ionizing radiation (e.g. UV radiation). This section will focus mostly on UV radiation since that has been the focus of the majority of previous studies. It is of note that ionizing radiation can be of more concern since it can penetrate through the Martian soils thus potentially making the first meter of soil inhabitable [51]. Solar UV radiation is divided into 3 spectral ranges; UV-A (315–400 nm), UV-B (280–315 nm) and UV-C (200–280 nm). UV-B and UV-C radiation are of the most concern since DNA has high absorption at those wavelengths and can be mutated leading to cellular inactivation [39]. Radiation of biological cells can cause breaks in molecular bonds including single and double strand breaks in DNA and photolysis of amino acids [52]. Calculations have suggested that DNA weighted irradiance on the Martian surface would be three orders of magnitude greater than that on Earth meaning that microbes would need to be resistant to

Most of the research on radiation resistance and/or survival of microorganisms have been performed on spore-forming organisms since they are of the most interest to planetary protection and tend to be hardy due to their protective spore coat. Studies by Wassman et al. [54] exposed *Bacillus subtilis* spores to low Earth orbit and simulated Martian conditions for 559 days aboard the ESA's EXPOSE-E facility. Although results showed that there was 100% survival of *Bacillus subtilis* MW01 spores to simulated Martian conditions (UV λ ≥ 200 nm), only a ≤ 8% of spores survived low Earth orbit conditions (UV λ ≥ 110 nm). Studies on *Bacillus pumilus* spores showed 10–40% viability on the EXPOSE facility versus a survival rate of 85–100% under dark simulated Martian atmospheric conditions. However, when the same studies were performed on the super tolerant *Bacillus pumilus* SAFR-032 strain, a 7 log reduction in viability was observed [55]. Overall SAFR-032 spores showing UVC resistance remain

much higher levels of UV radiation to sustain life on the surface of Mars [53].

O2

219

A number of microbes collected directly from spacecraft assembly facilities or pre-launch spacecraft are highly resistant to 5% H<sup>2</sup> O2 . An isolate of *Acinetobacter radioresistens*, collected from the Mars Odyssey spacecraft, showed only a 2 log reduction after exposure to 100 mM H<sup>2</sup> O2 . Even after exposure to 320 mM H<sup>2</sup> O2 there was still incomplete killing of all of the microbes [44]. Studies by Kempf et al. [43] have shown recurrent isolation of H<sup>2</sup> O2 -resistant *Bacillus pumilus* from the JPL spacecraft assembly facility. Both vegetative cells and spores of these isolates survived exposure to 5% H<sup>2</sup> O2 . Spores were less susceptible to killing showing only a 1–5 log reduction compared to vegetative cells which experienced a 5–8 log reduction. The examples just mentioned are far from a comprehensive list of organisms that have resistance to H<sup>2</sup> O2 , but they demonstrate that organisms are able to withstand these types of exposures.

There have been numerous attempts to try to understand how microorganisms protect themselves from H<sup>2</sup> O2 exposure. Most of these studies have been performed in *Bacillus* species although there is some knowledge overall about how bacteria cope with this stress. Three well studied mechanisms are the peroxide responsive regulators OxyR, PerR and OhrR that also act as transcription regulators. OxyR and PerR are mainly involved in the detection of H2 O2 whereas OhrR is involved in the sensing of organic peroxides and sodium hypochlorite. When exposed to peroxides, specific cysteine residues on OxyR and OhrR and histidine residues on PerR are oxidized by an Fe-catalyzed reaction. These transcriptional regulators are not only involved in H<sup>2</sup> O2 sensing, but also serve in the formation of biofilms, host immune response evasion, and antibiotic resistance [46].

Beyond general sensing of H<sup>2</sup> O2, genes involved in protein protection, such as groES, dnaK and clp tend to be upregulated thus also serving to protect the cell [47]. These proteins may be important for stabilizing the enzymes involved in the actual conversion of H<sup>2</sup> O2 to water and O2 , including catalases, peroxiredoxins, and peroxidases [48]. Studies in *Bacillus subtilus* have identified σB-dependent stress genes that are also involved in resistance to oxidative stress. Ultimately, the work performed by Reder et al. [49] identified 47 general stress response genes that were required for survival to superoxide, 6 genes required for protection from H<sup>2</sup> O2 stress and 9 genes that were required to protect against both.

Studies of the highly resistant strain, *Bacillus pumilus* SAFR-032, collected from JPL's spacecraft assembly facility, have identified many genes involved in H<sup>2</sup> O2 resistance overall [48]. Checinska et al. [50] looked further into the role of two manganese catalase proteins in the SAFR-032 spore coat, YjqC and BPUM\_1305, which had been previously identified by others. It was concluded that the synergistic activity of YjqC and BPUM\_1305, along with other coat oxidoreductases, contributes to the increased resistance of SAFR-032 to H<sup>2</sup> O2 over other *Bacillus pumilus* strains. This work has greatly improved our knowledge of the resistance of SAFR-032 to H<sup>2</sup> O2 .

#### **4.7. Exposure to radiation**

**4.6. Exposure to an oxidative environment**

218 Into Space - A Journey of How Humans Adapt and Live in Microgravity

oxidizing environment.

craft are highly resistant to 5% H<sup>2</sup>

after exposure to 320 mM H<sup>2</sup>

survived exposure to 5% H<sup>2</sup>

O2

selves from H<sup>2</sup>

not only involved in H<sup>2</sup>

Beyond general sensing of H<sup>2</sup>

H2 O2

O2

Data from the Viking missions showed that the surface of Mars was highly oxidized com-

range from 15 ± 10 ppb to 40 ppb [14]. The formation of peroxides can occur in the presence of hematite, trace amounts of water, and UV radiation, and radiolysis of ice or water can create even larger amounts of peroxide formation approaching 0.13% as seen on Europa [7, 15]. For an organism to survive on Mars it would need to have mechanisms to protect itself from this

A number of microbes collected directly from spacecraft assembly facilities or pre-launch space-

from the JPL spacecraft assembly facility. Both vegetative cells and spores of these isolates

reduction compared to vegetative cells which experienced a 5–8 log reduction. The examples

There have been numerous attempts to try to understand how microorganisms protect them-

although there is some knowledge overall about how bacteria cope with this stress. Three well studied mechanisms are the peroxide responsive regulators OxyR, PerR and OhrR that also act as transcription regulators. OxyR and PerR are mainly involved in the detection of

and clp tend to be upregulated thus also serving to protect the cell [47]. These proteins may be

, including catalases, peroxiredoxins, and peroxidases [48]. Studies in *Bacillus subtilus* have identified σB-dependent stress genes that are also involved in resistance to oxidative stress. Ultimately, the work performed by Reder et al. [49] identified 47 general stress response genes

Studies of the highly resistant strain, *Bacillus pumilus* SAFR-032, collected from JPL's space-

Checinska et al. [50] looked further into the role of two manganese catalase proteins in the SAFR-032 spore coat, YjqC and BPUM\_1305, which had been previously identified by others. It was concluded that the synergistic activity of YjqC and BPUM\_1305, along with

important for stabilizing the enzymes involved in the actual conversion of H<sup>2</sup>

that were required for survival to superoxide, 6 genes required for protection from H<sup>2</sup>

 whereas OhrR is involved in the sensing of organic peroxides and sodium hypochlorite. When exposed to peroxides, specific cysteine residues on OxyR and OhrR and histidine residues on PerR are oxidized by an Fe-catalyzed reaction. These transcriptional regulators are

exposure. Most of these studies have been performed in *Bacillus* species

sensing, but also serve in the formation of biofilms, host immune

O2, genes involved in protein protection, such as groES, dnaK

O2

just mentioned are far from a comprehensive list of organisms that have resistance to H<sup>2</sup>

they demonstrate that organisms are able to withstand these types of exposures.

Mars Odyssey spacecraft, showed only a 2 log reduction after exposure to 100 mM H<sup>2</sup>

O2

. An isolate of *Acinetobacter radioresistens*, collected from the

O2

there was still incomplete killing of all of the microbes [44].

. Spores were less susceptible to killing showing only a 1–5 log

abundance can

O2 . Even

> O2 , but


O2

to water and

O2 stress

resistance overall [48].

pared to its atmosphere [13]. Additional studies of Mars have shown that H<sup>2</sup>

O2

O2

O2

O2

and 9 genes that were required to protect against both.

craft assembly facility, have identified many genes involved in H<sup>2</sup>

response evasion, and antibiotic resistance [46].

Studies by Kempf et al. [43] have shown recurrent isolation of H<sup>2</sup>

The ability of an organism to survive radiation is paramount if the organism is to survive near the surface of Mars and pose a planetary protection threat. The radiation exposure on Mars is much more intense than it is on Earth because Mars lacks a magnetic field to deflect incoming charged particles and the atmosphere is <1% that of Earth [51]. There are 2 major types of radiation to be concerned with on Mars. The first type of radiation, Galactic Cosmic Rays (GCR), originates outside of our solar system and is formed from events such as supernovas. The second type of radiation, Solar Cosmic Radiation (SCR), originates from the sun and consists of both a constant flow of radiation as well as brief bursts [39, 51]. In the past, the overall radiation level on Mars has been based solely on calculations and modeling. New studies using data collected from the MSL found that the radiation in flight to Mars is approximately two times higher than the radiation on the surface of Mars (0.21 mGy/day vs. 0.48 mGy/day). The lower radiation level on the Mars surface is due in part to some atmospheric shielding by the Martian atmosphere, which is not provided to the spacecraft en route, and because radiation from GCR is modulated by SCR [51].

SCR can consist of both ionizing (e.g. gamma radiation) and non-ionizing radiation (e.g. UV radiation). This section will focus mostly on UV radiation since that has been the focus of the majority of previous studies. It is of note that ionizing radiation can be of more concern since it can penetrate through the Martian soils thus potentially making the first meter of soil inhabitable [51]. Solar UV radiation is divided into 3 spectral ranges; UV-A (315–400 nm), UV-B (280–315 nm) and UV-C (200–280 nm). UV-B and UV-C radiation are of the most concern since DNA has high absorption at those wavelengths and can be mutated leading to cellular inactivation [39]. Radiation of biological cells can cause breaks in molecular bonds including single and double strand breaks in DNA and photolysis of amino acids [52]. Calculations have suggested that DNA weighted irradiance on the Martian surface would be three orders of magnitude greater than that on Earth meaning that microbes would need to be resistant to much higher levels of UV radiation to sustain life on the surface of Mars [53].

Most of the research on radiation resistance and/or survival of microorganisms have been performed on spore-forming organisms since they are of the most interest to planetary protection and tend to be hardy due to their protective spore coat. Studies by Wassman et al. [54] exposed *Bacillus subtilis* spores to low Earth orbit and simulated Martian conditions for 559 days aboard the ESA's EXPOSE-E facility. Although results showed that there was 100% survival of *Bacillus subtilis* MW01 spores to simulated Martian conditions (UV λ ≥ 200 nm), only a ≤ 8% of spores survived low Earth orbit conditions (UV λ ≥ 110 nm). Studies on *Bacillus pumilus* spores showed 10–40% viability on the EXPOSE facility versus a survival rate of 85–100% under dark simulated Martian atmospheric conditions. However, when the same studies were performed on the super tolerant *Bacillus pumilus* SAFR-032 strain, a 7 log reduction in viability was observed [55]. Overall SAFR-032 spores showing UVC resistance remain viable even after exposures up to 2000 J/m<sup>2</sup> [56]. Comparative proteomic studies showed that superoxide dismutase was present in higher concentrations in the space exposed isolates and exhibited higher UV-C resistance than the ground control counterparts [55]. Tauscher et al. [57] studied the effects of *Bacillus subtilis* spores exposed to simulated Mars solar radiation for an equivalent of 42 min of Mars solar radiation. Radiation exposure reduced spore viability by 3 logs but measure of germination metabolism was only reduced by <1 log. They concluded that the spores can retain the ability to initiate germination-associated metabolic processes and produce viable signature molecules despite being rendered nonviable.

**4.8. Conservation of energy**

(2.7%) and O<sup>2</sup>

high amounts of salts including MgSO4

to produce methane [63]. H<sup>2</sup>

4H<sup>2</sup> + SO4

and FeSO4

as iron or sulfur [8]. An electron donor such as H<sup>2</sup>

during respiration, with utilization of CO or CO<sup>2</sup>

The electron donor H<sup>2</sup>

form of MgSO4

view of the reaction might look something like this:

2H<sup>2</sup> + CO<sup>2</sup> → CH<sup>4</sup> + O2 (methanogenic archaea)

2CH<sup>4</sup> + 2H<sup>2</sup> O → CH3 COOH + 4H<sup>2</sup> (methane − oxidizing archaea)

in the Martian soils [17, 67].

amounts of N2

Unlike Earth, the Martian environment provides very little nutrients to sustain life. Any microbes that may already be on Mars would have to make a living using the limited nutrients that

presence of methane in extended plumes that appeared to be released from discrete regions containing as much as 19,000 metric tons of methane. Additionally, previous studies have shown

on Mars are Fe and S and there is evidence that there are large concentrations of sulfur in the Martian regolith [65]. Perchlorate, a strong oxidizing agent, was shown by the Phoenix Lander to be present in Martian soils in concentrations of 2.1–2.6 mM [16]. All of these compounds are

The large methane plumes on Mars are of unknown origin. These plumes seasonally fluctuate but the amount of methane produced is on par with methane plumes on Earth that are known to be of biotic origin. Although the Mars rover Curiosity has found no detectable atmospheric methane, it is possible that the location of the rover prevented the detection of methane in the atmosphere since these methane plumes have been seen at polar regions rather than midlatitude regions. Methanogenesis has become a well-known method for microorganisms to conserve energy. Many archaea, such as *Methanosarcina*, can use various carbon compounds

atmosphere to generate energy via methane production [64]. Once this methane is available, it could be oxidized by methanotrophicarchaea in the presence of sulfate-reducing bacteria to complete a methane cycle which would support at least 3 types of organisms [65]. An over-

<sup>2</sup><sup>−</sup> + H<sup>+</sup> → HS− + 4H<sup>2</sup> O (sulfate − reducing bacteria)

and it has already been determined that there are large amounts of sulfate, especially in the

More likely energy sources fairly abundant in near surface soils on Mars are inorganics such

tion by organisms on Earth have been very well studied. These organisms play very important roles in the biogeochemical cycling of carbon, nitrogen, sulfur, and other metals [68]. Studies by Karr et al. [69] identified a group of sulfate-reducing bacteria residing in the permanently frozen freshwater lake, Lake Fryxell, in Antarctica. These organisms are able to utilize the reduction of sulfate to conserve energy under very cold conditions (4°C). There have

could easily be generated by photochemical dissociation of water [66]

could be used to reduce Fe(III) or sulfate

as a source of carbon. Sulfate and iron reduc-

and FeSO4

potential chemical energy sources that can be used by microorganisms to survive.

(0.1%) [7]. However, studies by Mumma et al. [11] have shown the

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

can readily be oxidized with the large amounts of CO<sup>2</sup>

atmosphere (95.3%) with low

http://dx.doi.org/10.5772/intechopen.75437

in the

221

[17]. Two of the most abundant compounds

are available. As previously discussed, Mars has a mostly CO<sup>2</sup>

It has been estimated that spores are 10–50 times more resistant than growing cells to UV radiation at 254 nm. This is due to a difference in the UV photochemistry of the DNA as well as error-free repair of any photoproducts formed by the UV light. Instead of forming thymine dimers as a photoproduct, spores tend to form thymine adducts instead; furthermore, small acid soluble proteins (SASPs) appear to suppress cyclobutane pyrimidine dimers [26]. Relative to gamma radiation, spores are significantly more resistant due to the decreased levels of water in the spore coat compared to vegetative cells which may reduce the amount of hydroxyl radicals formed overall [58]. SASPs do not appear to play a role in γ-radiation resistance [26].

Many non-spore-forming organisms have also been identified as being UV-resistant. Studies by Montero-Calasanz Mdel et al. [59] identified an isolate of *Geodermatophilus tzadiensis* that showed resistance to UV light at 254 nm. A highly radiation resistant isolate from the *Moraxella-Acinetobacter* group showed increased survival after a repeated exposure to UV light. Ultimately, this isolate was able to withstand a UV dose of 5940 J/m<sup>2</sup> with a 48% survival rate [60]. Antarctic Dry Valley bacteria closely related to *Brevundimonas*, *Rhodococcus*, and *Pseudomonas*, all showed resistance to γ-radiation. Surprisingly, these organisms, along with *Deinococcus radiodurans*, all showed increased resistance to γ-radiation when irradiated at −79°C [52].

Although the ability of non-spore-forming organisms to survive radiation appears to be poorly understood, there are some studies which have given clues to how these organisms survive. Keller et al. showed that the UV light resistance mechanism for survival was not associated with increased mutagenesis when the *Moraxella-Acinetobacter* isolate was repeatedly exposed to UV [60]. Studies on several strains of *Staphylococcus aureus* showed that UV-C resistance increased as the organisms entered into stationary growth phase, a characteristic that was attributed in part to the expression of σB during this phase [61]. Exposure of the lipids and proteins of *Acinetobacter* sp. PT511.2G and *Pseudomonas* sp. NT511.2B to ultraviolet radiation caused an increase of methyl groups that were associated with lipids, causing lipid oxidation, and alterations in lipid composition in addition to changes in propionylation, glycosylation, and/or phosphorylation of cell proteins [62]. The authors concluded that these changes may account for differences in UV sensitivity.

Ultimately, there are many microorganisms, both spore-forming and non-spore-forming, that are able to survive exposure to radiation and could potentially survive on Mars. For example, *Deinococcus radiodurans* would only be eradicated from the top several meters of Martian soil after a period of a few million years based on the radiation that currently reaches Mars. However, if the organism were to start growing again, then the clock would start over, and organisms could continue to stay dormant and survive up through today. This has implications for the potential for life to exist on Mars.

#### **4.8. Conservation of energy**

viable even after exposures up to 2000 J/m<sup>2</sup>

220 Into Space - A Journey of How Humans Adapt and Live in Microgravity

[56]. Comparative proteomic studies showed that

with a 48% survival rate [60]. Antarctic

superoxide dismutase was present in higher concentrations in the space exposed isolates and exhibited higher UV-C resistance than the ground control counterparts [55]. Tauscher et al. [57] studied the effects of *Bacillus subtilis* spores exposed to simulated Mars solar radiation for an equivalent of 42 min of Mars solar radiation. Radiation exposure reduced spore viability by 3 logs but measure of germination metabolism was only reduced by <1 log. They concluded that the spores can retain the ability to initiate germination-associated metabolic processes

It has been estimated that spores are 10–50 times more resistant than growing cells to UV radiation at 254 nm. This is due to a difference in the UV photochemistry of the DNA as well as error-free repair of any photoproducts formed by the UV light. Instead of forming thymine dimers as a photoproduct, spores tend to form thymine adducts instead; furthermore, small acid soluble proteins (SASPs) appear to suppress cyclobutane pyrimidine dimers [26]. Relative to gamma radiation, spores are significantly more resistant due to the decreased levels of water in the spore coat compared to vegetative cells which may reduce the amount of hydroxyl radicals formed overall [58]. SASPs do not appear to play a role in γ-radiation resistance [26].

Many non-spore-forming organisms have also been identified as being UV-resistant. Studies by Montero-Calasanz Mdel et al. [59] identified an isolate of *Geodermatophilus tzadiensis* that showed resistance to UV light at 254 nm. A highly radiation resistant isolate from the *Moraxella-Acinetobacter* group showed increased survival after a repeated exposure to UV light. Ultimately,

Dry Valley bacteria closely related to *Brevundimonas*, *Rhodococcus*, and *Pseudomonas*, all showed resistance to γ-radiation. Surprisingly, these organisms, along with *Deinococcus radiodurans*, all

Although the ability of non-spore-forming organisms to survive radiation appears to be poorly understood, there are some studies which have given clues to how these organisms survive. Keller et al. showed that the UV light resistance mechanism for survival was not associated with increased mutagenesis when the *Moraxella-Acinetobacter* isolate was repeatedly exposed to UV [60]. Studies on several strains of *Staphylococcus aureus* showed that UV-C resistance increased as the organisms entered into stationary growth phase, a characteristic that was attributed in part to the expression of σB during this phase [61]. Exposure of the lipids and proteins of *Acinetobacter* sp. PT511.2G and *Pseudomonas* sp. NT511.2B to ultraviolet radiation caused an increase of methyl groups that were associated with lipids, causing lipid oxidation, and alterations in lipid composition in addition to changes in propionylation, glycosylation, and/or phosphorylation of cell proteins [62]. The authors concluded that these

Ultimately, there are many microorganisms, both spore-forming and non-spore-forming, that are able to survive exposure to radiation and could potentially survive on Mars. For example, *Deinococcus radiodurans* would only be eradicated from the top several meters of Martian soil after a period of a few million years based on the radiation that currently reaches Mars. However, if the organism were to start growing again, then the clock would start over, and organisms could continue to stay dormant and survive up through today. This has implica-

and produce viable signature molecules despite being rendered nonviable.

this isolate was able to withstand a UV dose of 5940 J/m<sup>2</sup>

changes may account for differences in UV sensitivity.

tions for the potential for life to exist on Mars.

showed increased resistance to γ-radiation when irradiated at −79°C [52].

Unlike Earth, the Martian environment provides very little nutrients to sustain life. Any microbes that may already be on Mars would have to make a living using the limited nutrients that are available. As previously discussed, Mars has a mostly CO<sup>2</sup> atmosphere (95.3%) with low amounts of N2 (2.7%) and O<sup>2</sup> (0.1%) [7]. However, studies by Mumma et al. [11] have shown the presence of methane in extended plumes that appeared to be released from discrete regions containing as much as 19,000 metric tons of methane. Additionally, previous studies have shown high amounts of salts including MgSO4 and FeSO4 [17]. Two of the most abundant compounds on Mars are Fe and S and there is evidence that there are large concentrations of sulfur in the Martian regolith [65]. Perchlorate, a strong oxidizing agent, was shown by the Phoenix Lander to be present in Martian soils in concentrations of 2.1–2.6 mM [16]. All of these compounds are potential chemical energy sources that can be used by microorganisms to survive.

The large methane plumes on Mars are of unknown origin. These plumes seasonally fluctuate but the amount of methane produced is on par with methane plumes on Earth that are known to be of biotic origin. Although the Mars rover Curiosity has found no detectable atmospheric methane, it is possible that the location of the rover prevented the detection of methane in the atmosphere since these methane plumes have been seen at polar regions rather than midlatitude regions. Methanogenesis has become a well-known method for microorganisms to conserve energy. Many archaea, such as *Methanosarcina*, can use various carbon compounds to produce methane [63]. H<sup>2</sup> can readily be oxidized with the large amounts of CO<sup>2</sup> in the atmosphere to generate energy via methane production [64]. Once this methane is available, it could be oxidized by methanotrophicarchaea in the presence of sulfate-reducing bacteria to complete a methane cycle which would support at least 3 types of organisms [65]. An overview of the reaction might look something like this:

2H<sup>2</sup> + CO<sup>2</sup> → CH<sup>4</sup> + O2 (methanogenic archaea)

2CH<sup>4</sup> + 2H<sup>2</sup> O → CH3 COOH + 4H<sup>2</sup> (methane − oxidizing archaea)

 4H<sup>2</sup> + SO4 <sup>2</sup><sup>−</sup> + H<sup>+</sup> → HS− + 4H<sup>2</sup> O (sulfate − reducing bacteria)

The electron donor H<sup>2</sup> could easily be generated by photochemical dissociation of water [66] and it has already been determined that there are large amounts of sulfate, especially in the form of MgSO4 and FeSO4 in the Martian soils [17, 67].

More likely energy sources fairly abundant in near surface soils on Mars are inorganics such as iron or sulfur [8]. An electron donor such as H<sup>2</sup> could be used to reduce Fe(III) or sulfate during respiration, with utilization of CO or CO<sup>2</sup> as a source of carbon. Sulfate and iron reduction by organisms on Earth have been very well studied. These organisms play very important roles in the biogeochemical cycling of carbon, nitrogen, sulfur, and other metals [68]. Studies by Karr et al. [69] identified a group of sulfate-reducing bacteria residing in the permanently frozen freshwater lake, Lake Fryxell, in Antarctica. These organisms are able to utilize the reduction of sulfate to conserve energy under very cold conditions (4°C). There have also been studies showing that Fe respiration under alkaline conditions is possible. Studies by Williamson et al. [70] identified organisms that could easily reduce Fe(III) at pH 10. These studies show that it is possible for these reactions to occur under cold or alkaline conditions. Once Fe or S has been reduced it is available for oxidation by other organisms.

**Conflict of interest**

**Author details**

Stephanie A. Smith1

**References**

The authors do not have any conflict of interest to report.

\*, Andrzej Paszczynski2

\*Address all correspondence to: steph.smith@wsu.edu

1 Washington State University, Pullman, WA, USA

2 University of Idaho, Moscow, ID, USA

Mars. Science. 2000;**288**:2330-2335

Mars. Science. 2003;**302**:1931-1934

2004;**2**(9):1260-1263

3 Colby College, Waterville, ME, USA

and Susan E. Childers3

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

http://dx.doi.org/10.5772/intechopen.75437

223

[1] Malin MC, Edgett KS. Evidence for recent groundwater seepage and surface runoff on

[2] Malin MC, Edgett KS. Evidence for persistent flow and aqueous sedimentation on early

[3] McKay CP. What is life-and how do we search for it in other worlds? PLoS Biology.

[4] Roth L, Saur J, Retherford KD, Strobel DF, Feldman PD, McGrath MA, Nimmo F. Transient water vapor at Europa's south pole. Science. 2014;**343**(6167):171-174

[5] Rasmussen B, Blake TS, Fletcher IR, Kilburn MR. Evidence for microbial life in synsedimentary cavities from 2.75 Ga terrestrial environments. Geology. 2009;**37**:423-426

[6] Schofield JT, Barnes JR, Crisp D, Haberle RM, Larsen S, Magalhães JA, Murphy JR, Seiff A, Wilson G. The Mars pathfinder atmospheric structure investigation/meteorology

[7] Horneck G. The microbial case for Mars and its implication for human expedition to

[8] Crawford RL, Newcombe DA. The potential for extant life in the soils of Mars. In: Dion P, Nautiyal CS, editors. Microbiology of Extreme Soils, Soil Biology. Vol. 13. NY: Springer-

[9] Meslin PY, Gasnault O, Forni O, Schröder S, Cousin A, Berger G, Clegg SM, Lasue J, Maurice S, Sautter V, Le Mouélic S, Wiens RC, Fabre C, Goetz W, Bish D, Mangold N, Ehlmann B, Lanza N, Harri A-M, Anderson R, Rampe E, McConnochie TH, Pinet P, Blaney D, Léveillé R, Archer D, Barraclough B, Bender S, Blake D, Blank JG, Bridges N,

(ASI/MET) experiment. Science. 1997;**278**(5344):1752-1758

Mars. Acta Astronautica. 2008;**63**:1015-1024

Verlag; 2008. pp. 225-243

Perchlorate, detected in soils by the Phoenix Mars Lander, is one of the more interesting potential electron acceptors recently discovered on Mars [16, 71]. More than 50 microorganisms on Earth are known to respire perchlorate coupled to the oxidation of H<sup>2</sup> or small organic acids, a metabolism that has been intensely studied over the past decade [72, 73]. This group of organisms is quite diverse and many have been found in environments that might seem, on the surface, to be inhospitable such as paper mill waste. Studies by Ju et al. [74] showed bacteria in sludge that were capable of oxidizing both Fe° and S° while reducing perchlorate. The enrichment culture was also able to oxidize S2− and S2 O3 2− to support the reduction of perchlorate, and they also confirmed the disproportionation of S° to S2− and SO4 2−. Thus perchlorate reduction would tie in neatly to both the Fe and S cycles.

Although Mars seems inhospitable and lacks an abundant supply of nutrients, there are plenty of nutrients available to support anaerobic life on the red planet. The studies discussed above show that the organisms could work together to supply nutrients for one another within a complex ecosystem. Additionally, many of the organisms discussed above can survive in extreme environments on Earth while still making a living as evidenced by many of these processes still taking place at low temperatures or in alkaline environments.

### **5. Conclusions**

Despite all that we know, there is still much to be learned with regard to the absolute limits for life. In order to answer these questions, we must have a better understanding of life on Earth. With regard to the potential for indigenous populations on other planets and moons, research has shown repeatedly that life can exist in the harshest of environments. Although this was not covered in depth in this chapter, life has been found in some of the most dry or frigid environments on Earth such as the Atacama Desert or Antarctica. It is not unreasonable to believe that microorganisms, similar to those found on Earth, could be thriving on locations such as Mars or Europa, especially in the subsurface where radiation would be lower and there would be a better chance for the existence of liquid water. While searching for life on other planets and moons, we look for the signs of life that are already known such as the presence of carbon and water. It may be possible that if we find life in these distant places that we may discover new limits to life in extremis.

### **Acknowledgements**

This work was funded by NASA ROSES award #15-PPR15-0006 NASA EPSCoR award # NNX11AQ30A. We wish to thank members of the NASA and JPL Planetary Protection groups for the financial and collaborative support of our research work. The opinions expressed in this article are the authors' own and do not reflect the view of JPL or NASA.

### **Conflict of interest**

also been studies showing that Fe respiration under alkaline conditions is possible. Studies by Williamson et al. [70] identified organisms that could easily reduce Fe(III) at pH 10. These studies show that it is possible for these reactions to occur under cold or alkaline conditions.

Perchlorate, detected in soils by the Phoenix Mars Lander, is one of the more interesting potential electron acceptors recently discovered on Mars [16, 71]. More than 50 microorgan-

acids, a metabolism that has been intensely studied over the past decade [72, 73]. This group of organisms is quite diverse and many have been found in environments that might seem, on the surface, to be inhospitable such as paper mill waste. Studies by Ju et al. [74] showed bacteria in sludge that were capable of oxidizing both Fe° and S° while reducing perchlorate.

Although Mars seems inhospitable and lacks an abundant supply of nutrients, there are plenty of nutrients available to support anaerobic life on the red planet. The studies discussed above show that the organisms could work together to supply nutrients for one another within a complex ecosystem. Additionally, many of the organisms discussed above can survive in extreme environments on Earth while still making a living as evidenced by many of these

Despite all that we know, there is still much to be learned with regard to the absolute limits for life. In order to answer these questions, we must have a better understanding of life on Earth. With regard to the potential for indigenous populations on other planets and moons, research has shown repeatedly that life can exist in the harshest of environments. Although this was not covered in depth in this chapter, life has been found in some of the most dry or frigid environments on Earth such as the Atacama Desert or Antarctica. It is not unreasonable to believe that microorganisms, similar to those found on Earth, could be thriving on locations such as Mars or Europa, especially in the subsurface where radiation would be lower and there would be a better chance for the existence of liquid water. While searching for life on other planets and moons, we look for the signs of life that are already known such as the presence of carbon and water. It may be possible that if we find life in these distant places that

This work was funded by NASA ROSES award #15-PPR15-0006 NASA EPSCoR award # NNX11AQ30A. We wish to thank members of the NASA and JPL Planetary Protection groups for the financial and collaborative support of our research work. The opinions expressed in

this article are the authors' own and do not reflect the view of JPL or NASA.

O3

or small organic

2−. Thus per-

2− to support the reduction of

Once Fe or S has been reduced it is available for oxidation by other organisms.

isms on Earth are known to respire perchlorate coupled to the oxidation of H<sup>2</sup>

perchlorate, and they also confirmed the disproportionation of S° to S2− and SO4

processes still taking place at low temperatures or in alkaline environments.

The enrichment culture was also able to oxidize S2− and S2

222 Into Space - A Journey of How Humans Adapt and Live in Microgravity

we may discover new limits to life in extremis.

**Acknowledgements**

**5. Conclusions**

chlorate reduction would tie in neatly to both the Fe and S cycles.

The authors do not have any conflict of interest to report.

### **Author details**

Stephanie A. Smith1 \*, Andrzej Paszczynski2 and Susan E. Childers3

\*Address all correspondence to: steph.smith@wsu.edu

1 Washington State University, Pullman, WA, USA

2 University of Idaho, Moscow, ID, USA

3 Colby College, Waterville, ME, USA

### **References**


Clark BC, DeFlores L, Delapp D, Dromart G, Dyar MD, Fisk M, Gondet B, Grotzinger J, Herkenhoff K, Johnson J, Lacour J-L, Langevin Y, Leshin L, Lewin E, Madsen MB, Melikechi N, Mezzacappa A, Mischna MA, Moores JE, Newsom H, Ollila A, Perez R, Renno N, Sirven J-B, Tokar R, de la Torre M, d'Uston L, Vaniman D, Yingst A, Science Team MSL. Soil diversity and hydration as observed by ChemCam at Gale Crater, Mars. Science. 2013;**341**:12386701-123867010

[21] Rummel JD. Special regions in Mars exploration: Problems and potential. Acta

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

http://dx.doi.org/10.5772/intechopen.75437

225

[22] Valentine DL, Reeburgh WS. New perspectives on anaerobic methane oxidation. Enviro-

[23] Pikuta EV, Hoover RB. Microbial extremophiles at the limits of life. Critical Reviews in

[24] Morozova D, Möhlmann D, Wagner D. Survival of Methanogenic Archaea from Siberian permafrost under simulated Martian thermal conditions. Origins of Life and Evolution

[25] Nicholson WL, Krivushon K, Gilichinsky D, Schuerger AC. Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has

[26] Nicholson WL, Munakata N, Horneck G, Melosh HJ, Setlow P. Resistance of *Bacillus* endospores to extreme terrestrial and extraterrestrial environments. Microbiology and

[27] Mykytczuk NCS, Foote SJ, Omelon CR, Southam G, Greer CW, Whyte LG. Bacterial growth at −15° C; molecular insights from the permafrost bacterium *Planococcus haloc-*

[28] Kuhn E. Toward understanding life under subzero conditions: The significance of

[29] D'Amico S, Collins T, Marx J-C, Feller G, Gerday C. Psychrophilic microorganisms:

[30] Hallsworth JE, Yakimov MM, Golyshin PN, Gillion JLM, D'Auria G, deLimaAlves F, La Cono V, Genovese M, McKew BA, Hayes SL, Harris G, Giuliano L, Timmis KM,

[31] Smith SA, Benardini III JN, Strap JL , Crawford RL. (2009) Diversity of aerobic and facultative alkalitolerant and halotolerant endospore formers in soil from the Alvord Basin,

[32] Van der Wielen PWJJ, Bolhuis SB, Daffonchio D, Corselli C, Giuliano L, D'Auria G, de Lange GJ, Huebner A, Varnavas SP, Thomson J, Tamburini C, Marty D, McGenity TJ, Timmis KN, BioDeep Scientific Party. The enigma of prokaryotic life in deep hypersaline

[33] Oren A. Thermodynamics limits to microbial life at high salt concentrations. Environ-

[34] Tehei M, Franzetti B, Maurel M-C, Vergne J, Hountondji C, Zaccai G. The search for traces of life: The protective effect of salt on biological macromolecules. Extremophiles.


implications for Earth microbes on Mars. PNAS. 2013;**110**(2):666-671

exploring "cold-shock" proteins. Astrobiology. 2012;**12**(11):1078-1086

Astronautica. 2009;**64**:1293-1297

Microbiology. 2007;**33**:183-209

of the Biosphere. 2007;**37**:189-200

nmental Microbiology. 2000;**2**(5):477-484

Molecular Biology Reviews. 2000;**64**(3):548-572

*ryophilus* Or1. ISME Journal. 2013;**7**(6):1211-1126

Challenges for life. EMBO Reports. 2006;**7**(4):385-389

window. Environmental Microbiology. 2007;**9**(3):801-813

Oregon.Systematic and Applied Microbiology 32:233-244

McGenity TJ. Limits of life in MgCl<sup>2</sup>

anoxic basins. Science. 2005;**307**:121-123

mental Microbiology. 2011;**13**(8):1908-1923

2002;**6**:427-430


[21] Rummel JD. Special regions in Mars exploration: Problems and potential. Acta Astronautica. 2009;**64**:1293-1297

Clark BC, DeFlores L, Delapp D, Dromart G, Dyar MD, Fisk M, Gondet B, Grotzinger J, Herkenhoff K, Johnson J, Lacour J-L, Langevin Y, Leshin L, Lewin E, Madsen MB, Melikechi N, Mezzacappa A, Mischna MA, Moores JE, Newsom H, Ollila A, Perez R, Renno N, Sirven J-B, Tokar R, de la Torre M, d'Uston L, Vaniman D, Yingst A, Science Team MSL. Soil diversity and hydration as observed by ChemCam at Gale Crater, Mars.

[10] Westall F, Loizeau D, Foucher F, Bost N, Betrand M, Vago J, Kminek G. Habitability on

[11] Mumma MJ, Villanueva GL, Novak RE, Hewagama T, Bonev BP, DiSanti MA, Mandell AM, Smith MD. Strong release of methane on Mars in northern summer. Science.

[12] Cockell CS. The ultraviolet environment of Mars: Biological implications past, present

[13] Slesak I, Slesak H, Kruk J. Oxygen and hydrogen peroxide in the early evolution of life on earth: In silico comparative analysis of biochemical pathways. Astrobiology. 2012;

[14] Encrenaz T, Greathouse TK, Richter MJ, Bezard B, Fouchet T, Lefevre F, Montmessin F,

[15] Johnson RE, Quickenden TI, Cooper PD, McKinley AJ, Freeman CG. Europa the produc-

[16] Hecht MH, Kounaves SP, Quinn RC, West SJ, Young SMM, Ming DW, Catling DC, Clark BC, Boynton WV, Hoffman J, DeFlores LP, Gospodinova K, Kapit J, Smith PH. Detection of perchlorate and the soluble chemistry of Martian soil at the phoenix lander site.

[17] Crisler JD, Newville TM, Chen F, Clark BC, Schneegurt MA. Bacterial growth at the high concentrations of magnesium sulfate found in Martian soils. Astrobiology. 2012;

[18] NASA. Planetary Protection Provisions for Robotic Extraterrestrial Missions. NPR

[19] National Research Council. Preventing the Forward Contamination of Mars. National Research Council of the National Academies. Washington, D.C.: The National ACADEMIES

[20] Kminek G, Rummel JD, Cockell CS, Atlas R, Barlow N, Beaty D, Boynton W, Carr M, Clifford S, Conley CA, Davila AF, Debus A, Doran P, Hecht M, Heldmann J, Helbert J, Hipkin V, Horneck G, Kieft TL, Klingelhoefer A, Meyer M, Newsom H, Ori GG, Parnell J, Prieur D, Raulin F, Schulze-Makuch D, Spry JA, Stabekis PE, Stackebrandt E, Vago J, Viso M, Voytek M, Wells L, Westall F. Report of the COSPAR mars special regions col-

O and H<sup>2</sup>

O2

on Mars from

Forget F, Lebonnois S, Atreya SK. Simultaneous mapping of H<sup>2</sup>

infrared high-resolution imaging spectroscopy. Icarus. 2008;**195**:547-556

tion of oxidants in Europa's surface. Astrobiology. 2003;**3**(4):823-850

Mars from a microbial point of view. Astrobiology. 2013;**13**(9):887-897

Science. 2013;**341**:12386701-123867010

224 Into Space - A Journey of How Humans Adapt and Live in Microgravity

and future. Icarus. 2000;**146**:343-359

Science. 2009;**325**(5936):64-67

8020.12. Washington, D.C: NASA; 2011

loquium. Advances in Space Research. 2010;**46**:811-829

2009;**323**:1041-1045

**12**(8):775-784

**12**(2):98-106

PRESS; 2006


[35] Lopalco P, Angelini R, Lobasso S, Köcher S, Thompson M, Müller V, Corcelli A.Adjusting membrane lipids under salt stress: The case of the moderate halophilic organism *Halobacillus halophilus*. Environmental Microbiology. 2013;**15**(4):1078-1087

[49] Reder A, Höper D, Gerth U, Hecker M. Contributions of individual σB-dependent general stress genes to oxidative stress resistance of *Bacillus subtilis*. Journal of Bacteriology.

Are We Alone? The Search for Life on Mars and Other Planetary Bodies

http://dx.doi.org/10.5772/intechopen.75437

227

[50] Checinska A, Burbank M, Paszczynski AJ. Protection of *Bacillus pumilus* spores by cata-

[51] Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL, Brinza DE, Weigle G, Böttcher S, Böhm E, Burmeister S, Guo J, Köhler J, Martin C, Reitz G, Cucinotta FA, Kim M, Grinspoon D, Bullock MA, Posner A, Gómez-Elvira J, Vasavada A, Grotzinger JP, MSL Science Team. Mars' surface radiation environment measured with the Mars Science Laboratory's Curiosity Rover. Science. 2013;**343**(6169):1244797

[52] Dartnell LR, Hunter SJ, Lovell KV, Coates AJ, Ward JM. Low-temperature ionizing radiation resistance of Deinococcusradiodurans and Antarctic Dry Valley bacteria.

[53] Rontó G, Bérces A, Lammer H, Cockell CS, Molina-Cuberos GJ, Patel MR, Selsis F. Solar UV irradiation conditions on the surface of Mars. Photochemistry and Photobiology.

[54] Wassman M, Moeller R, Rabbow E, Panitz C, Horneck G, Reitz G, Douki T, Cadet J, Stan-Lotter H, Cockell CS, Rettberg P. Survival of spores of the UV resistant *Bacillus subtilus* strain MW01 after exposure to low-Earth orbit and simulated Martian conditions: Data from the space experiment ADAPT on EXPOSE-E. Astrobiology. 2012;**12**(5):498-507 [55] Vaishampayan PA, Rabbow E, Horneck G, Venkateswaran KJ. Survival of *Bacillus pumilus* spores for a prolonged period of time in real space conditions. Astrobiology.

[56] Link L, Sawyer J, Venkateswaran K, Nicholson W. Extreme spore UV resistance of *Bacillus pumilus* isolates obtained from an ultraclean spacecraft assembly facility. Micro-

[57] Tauscher C, Schuerger AC, Nicholson WL. Survival and germinability of *Bacillus subtilis* spores exposed to simulated Mars solar radiation: Implications for life detection and

[58] Moeller R, Raguse M, Reitz G, Okayasu R, Li Z, Klein S, Setlow P, Nicholson WL. Resistance of *Bacillus subtilis* spore DNA to lethal ionizing radiation damage relies primarily on spore core components and DNA repair, with minor effects of oxygen radical

[59] Montero-Calasanz Mdel C, Göker M, Broughton WJ, Cattaneo A, Favet J, Pötter G, Rohde M, Spröer C, Schumann P, Klenk H-P, Gorbushina AA. *Geodermatophilus tzadiensis* sp. nov., a UV radiation resistant bacterium isolated from sand of the Saharan desert.

[60] Keller LC, Thompson TL, Maxcy RB. UV light induced survival response in a highly radiation resistant isolate of the Moraxella-Acinetobacter group. Applied and Environmental

detoxification. Applied and Environmental Microbiology. 2014;**80**(1):104-109

lases. Applied and Environmental Microbiology. 2013;**78**(18):6413-6422

2012;**194**(14):3601-3610

Astrobiology. 2010;**10**(7):717-732

2003;**77**(1):34-40

2012;**12**(5):487-497

bial Ecology. 2004;**47**:159-163

Microbiology. 1982;**43**(2):424-429

planetary protection. Astrobiology. 2006;**6**(4):592-605

Systematic and Applied Microbiology. 2013;**36**:177-182


[49] Reder A, Höper D, Gerth U, Hecker M. Contributions of individual σB-dependent general stress genes to oxidative stress resistance of *Bacillus subtilis*. Journal of Bacteriology. 2012;**194**(14):3601-3610

[35] Lopalco P, Angelini R, Lobasso S, Köcher S, Thompson M, Müller V, Corcelli A.Adjusting membrane lipids under salt stress: The case of the moderate halophilic organism

[36] Krulwich TA, Sachs G, Padan E. Molecular aspects of bacterial pH sensing and homeo-

[37] Kubota H, Mitani A, Niwano Y, Takeuchi K, Tanaka A, Yamaguchi N, Kawamura Y, Hitomi J. *Moraxella* species are primarily responsible for generating malodor in laundry.

[38] Chaibenjawong P, Foster SJ. Desiccation tolerance in *Staphylococcus aureus*. Archives of

[39] Horneck G, Klaus DM, Mancinelli RL. Space microbiology. MMBR. 2010;**74**(1):121-156 [40] La Duc MT, Benardini JN, Kempf MJ, Newcombe DA, Lubarsky M, Venkateswaran K.Microbial diversity of Indian Ocean hydrothermal vent plumes: Microbes tolerant of dessication, peroxide exposure and ultraviolet and γ-irradiation. Astrobiology.

[41] Kral TA, Altheide ST. Methanogen survival following desiccation, low pressure and

[42] Conrad R, Ji Y, Noll M, Klose M, Claus P, Enrich-Prast A. Response of methanogenic microbial communities in Amazonian oxbow lake sediments to desiccation stress.

[43] Kempf MJ, Chen F, Kern R, Venkateswaran K. Recurrent isolation of hydrogen peroxide-resistant spores of *Bacillus pumilus* from a spacecraft assembly facility. Astrobiology.

[44] McCoy KB, Derecho I, Wong T, Tran HM, Huynh TD, La Duc MT, venkateswaran K, Mogul R. Insights into the extremotolerance of *Acinetobacter radioresistens* 50v1, a Gram-negative bacterium isolated from the Mars Odyssey spacecraft. Astrobiology.

[45] De Goffau MC, Maarten van Dijl J, Harmsen HJM. Microbial growth on the edge of des-

[46] Dubbs JM, Mongkolsuk S. Peroxide-sensing transcriptional regulators in bacteria.

[47] Mols M, Abee T. Primary and secondary oxidative stress in bacillus. Environmental

[48] Gioia J, Yerrapragada S, Qin X, Jiang H, Igboeli OC, Muzny D, Dugan-Rocha S, Ding Y, Hawes A, Liu W, Perez L, Kovar C, Dinh H, Lee S, Nazareth L, Blyth P, Holder M, Buhay C, Tirumalai MR, Liu Y, Dasgupta I, Bokhetache L, Fujita M, Karouia F, Moorthy PE, Siefert J, Uzman A, Buzumbo P, Verma A, Zwiya H, McWilliams BD, Olowu A, Clinkenbeard KD, Newcombe D, Golebiewski L, Petrosino JF, Nicholson WL, Fox GE, Venkateswaran K, Highlander SK, Weinstock GM. Paradoxical DNA repair and peroxide resistance gene conservation in Bacillus pumilus SAFR-032. PLoS ONE. 2007;**2**(9):e928

martian regolith analogs. Planetary and Space Science. 2013;**89**:167-171

*Halobacillus halophilus*. Environmental Microbiology. 2013;**15**(4):1078-1087

stasis. Nature Reviews Microbiology. 2011;**9**:330-343

226 Into Space - A Journey of How Humans Adapt and Live in Microgravity

Environmental Microbiology. 2013;**16**(6):1682-1694

iccation. Environmental Microbiology. 2011;**13**(8):2328-2335

Journal of Bacteriology. 2012;**194**(20):5495-5502

Microbiology. 2011;**13**(6):1387-1394

Microbiology. 2011;**193**:125-135

2007;**7**:416-431

2005;**5**:391-405

2012;**12**(9):1-9

Applied and Environmental Microbiology. 2012;**78**(9):3317-3324


[61] Gayán E, García-Gonzalo D, Álvarez I, Condón S. Resistance of *Staphylococcus aureus* to UV-C light and combined UV-heat treatments at mild temperatures. International Journal of Food Microbiology. 2013;**172**:30-39

**Chapter 13**

**Provisional chapter**

**Exploring the Stratosphere: What We Missed by**

**Exploring the Stratosphere: What We Missed by** 

DOI: 10.5772/intechopen.73602

Similar to outer space, the stratosphere experiences freezing temperatures, with atmospheric pressures and oxygen levels far below the level required for human survival. Exposure to this environment causes unique injuries to the human body that can be deadly if the correct management is not promptly initiated. The preceding decades are filled with stories of deadly failures from such exposures and marked achievement as we began to explore this section of our outer atmosphere. Through advances in technology, we have developed pressure suits and vehicles used for high altitude and outer space that provide protection and allow us to not only survive, but also explore these dangerous environments. The recent high altitude missions are examples of the remarkable capability of human innovation and ingenuity. These missions have fostered an explosion of interest and wonder, creating new demand for a commercial space industry that was virtually nonexistent in the previous century. Though recent tragedies have temporarily delayed the travel of eager citizens into space, the boom of the commercial space industry is pushing forward with new promises of space exploration available to the next

**Keywords:** high altitude, ebullism, stratosphere, StratEx, Stratos, pressure suit,

In 1969, when Aldrin and Armstrong first stepped onto the Moon's surface, the world was ablaze with excitement. This event generated a spark that had nearly vanished among those on earth watching the repetitive orbital missions. People organized "moonwalk" parties while children's imaginations across the world came alive with the thought of being able to float

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Shooting for the Moon**

**Shooting for the Moon**

http://dx.doi.org/10.5772/intechopen.73602

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

paying customer, anticipated in the next few years.

commercial space industry

**1. Introduction**

Laura Galdamez

**Abstract**

Laura Galdamez


#### **Exploring the Stratosphere: What We Missed by Shooting for the Moon Exploring the Stratosphere: What We Missed by Shooting for the Moon**

DOI: 10.5772/intechopen.73602

#### Laura Galdamez Laura Galdamez

[61] Gayán E, García-Gonzalo D, Álvarez I, Condón S. Resistance of *Staphylococcus aureus* to UV-C light and combined UV-heat treatments at mild temperatures. International

[62] Santos AL, Moreirinha C, Lopes D, Esteves AC, Henriques I, Almeida A, Domingues MRM, Delgadillo I, Correia A, Cunha A. Effects of UV radiation on the lipids and proteins of bacteria studies by mid-infrared spectroscopy. Environmental Science &

[63] Smith MR, Mah RA. Growth and methanogenesis by *Methanosarcina* strain 227 on acetate and methanol. Applied and Environmental Microbiology. 1978;**36**(6):870-879 [64] Kral TA, Bekkum CR, McKay CP. Growth of methanogens on a Mars soil simulant.

[65] Caldwell SL, Laidler JR, Brewer EA, Eberly JO, Sandborgh SC, Colwell FS. Anaerobic oxidation of methane: Mechanisms, bioenergetics, and the ecology of associated micro-

[66] Krasnopolsky VA, Feldman PD. Detection of molecular hydrogen in the atmosphere of

[67] Schulze-Makuch D, Fairen AG, Davila AF. The case for life on Mars. International

[68] Zhou J, He Q, Hemme CL, Mukhopadhyay A, Hillesland K, Zhou A, He Z, Van Nostrand JD, Hazen TC, Stahl DA, Wall JD, Arkin AP. How sulphate-reducing microorganisms cope with stress: Lessons from systems biology. Nature Reviews Microbiology.

[69] Karr EA, Sattley WM, Rice MR, Jung DO, Madigan MT, Achenbach LA. Diversity and distribution of sulfate-reducing bacteria in permanently frozen Lake Fryxell, McMurdo Dry Valleys, Antarctica. Applied and Environmental Microbiology. 2005;**71**(10):6353-6359

[70] Williamson AJ, Morris K, Shaw S, Byrne JM, Boothman C, Llyod JR. Microbial reduction of Fe(III) under alkaline conditions relevant to geological disposal. Applied and

[72] Coates JD, Michaelidou U, Bruce RA, O'Connor M, Crespi JN, Achenbach LA. Ubiquity and diversity of dissimilatory (per)chlorate-reducing bacteria. Applied and Environ-

[73] Coates JD, Achenbach LA. Microbial perchlorate reduction: Rocket-fueled metabolism.

[74] Ju X, Sierra-Alvarez R, Field JA, Byrnes DJ, Bentley H, Bentley R. Microbial perchlorate reduction with elemental sulfur and other inorganic electron donors. Chemosphere.

Origins of Life and Evolution of the Biosphere. 2004;**34**:615-626

organisms. Environmental Science & Technology. 2008;**42**(18):6791-6799

Journal of Food Microbiology. 2013;**172**:30-39

228 Into Space - A Journey of How Humans Adapt and Live in Microgravity

Technology. 2013;**47**(12):6306-6315

Mars. Science. 2001;**294**:1914-1917

2011;**9**:452-466

2008;**71**:114-122

Journal of Astrobiology. 2008;**7**(2):117-141

Environmental Microbiology. 2013;**79**(11):3320-3326

mental Microbiology. 1999;**65**:5234-5241

Nature Reviews Microbiology. 2004;**2**:569-580

[71] Hand T. Phoenix fades away (news). Nature. 2008;**456**(6):8-9

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73602

#### **Abstract**

Similar to outer space, the stratosphere experiences freezing temperatures, with atmospheric pressures and oxygen levels far below the level required for human survival. Exposure to this environment causes unique injuries to the human body that can be deadly if the correct management is not promptly initiated. The preceding decades are filled with stories of deadly failures from such exposures and marked achievement as we began to explore this section of our outer atmosphere. Through advances in technology, we have developed pressure suits and vehicles used for high altitude and outer space that provide protection and allow us to not only survive, but also explore these dangerous environments. The recent high altitude missions are examples of the remarkable capability of human innovation and ingenuity. These missions have fostered an explosion of interest and wonder, creating new demand for a commercial space industry that was virtually nonexistent in the previous century. Though recent tragedies have temporarily delayed the travel of eager citizens into space, the boom of the commercial space industry is pushing forward with new promises of space exploration available to the next paying customer, anticipated in the next few years.

**Keywords:** high altitude, ebullism, stratosphere, StratEx, Stratos, pressure suit, commercial space industry

#### **1. Introduction**

In 1969, when Aldrin and Armstrong first stepped onto the Moon's surface, the world was ablaze with excitement. This event generated a spark that had nearly vanished among those on earth watching the repetitive orbital missions. People organized "moonwalk" parties while children's imaginations across the world came alive with the thought of being able to float

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

and bounce above that gray, dusty surface they saw on the television [1]. Yet in our hurry to aim for the lunar surface, we flew right through an unexplored and unconquered area of our own planet: the higher atmosphere.

### **2. Stratosphere and human physiology**

#### **2.1. Stratosphere**

The stratosphere is the second lowest layer of Earth's atmosphere, stretching from 12 to 55 km above sea level (**Figure 1**) [2]. For comparison, the Everest summit sits at 8.85 km, and jumbo jets cruise at an average altitude of 12–16 km [3, 4]. To optimize fuel efficiency, the typical commercial airliner cruises at 9–12 km (just above the troposphere in the lower reaches of the stratosphere), where temperatures and air density are lowest [5]. Temperatures in the stratosphere are stratified and, somewhat non-intuitively, increase with higher altitude secondary to ability of the ozone layers to absorb ultraviolet light [5]. Due to increased energy absorption at higher altitudes, the top of the stratosphere remains near 0°C while the tropopause (which occurs between the troposphere and stratosphere) exhibits temperatures of −46 to −57°C [2, 4].

Humans on Earth live well below the altitudes that represent our species' physical limitations. Although only 15.6% of inhabited land occurs below 100 m, in 1994 approximately 33.5% of the world's population lived within these elevations [6]. While human beings can adapt to higher altitudes, the Everest "death zone" (mountain's altitude above 8000 m) earned its name for good reason. When people who are not acclimatized are exposed to equivalent levels of ambient hypoxia that exist at altitudes over 8500 m, they lose consciousness within 2–3 min [3]. Why does this occur and what changes in the environment lead to this? At sea level the average atmospheric pressure is 101.325 kPa, but at higher altitudes air pressure decreases. The mean atmospheric pressure on the summit of Everest is only 33.7 kPa, and atmospheric pressure at the top of the stratosphere is 1/1000 that of sea level [2, 7]. According to Dalton's law, the total pressure of a mixture of gases is made up of the sum of the partial pressures of each individual gas [8]. Given this, it is easier to understand how the partial pressure of oxygen is also much lower at these higher altitudes, which also results in lower partial pressures of oxygen in our blood at these altitudes. A study of the mean partial pressure of arterial oxygen (PaO2) in the blood gas of Everest climbers taken at 8400 m found their average PaO2 to be 24.6 mmHg, while normal is considered to be >80 mmHg [3]. But what happens when the human body is exposed to even higher altitudes than we are able to achieve via these hiking expeditions, such as the stratosphere or outer space?

#### **2.2. Physics and human physiology**

To understand this question, it is important to understand Boyle's law and the effect of pressure on liquids and gases as well. According to Boyle's law, pressure and volume have an inverse relationship; as the pressure on a given volume of gas decreases, the volume of the gas will increase [8]. This means that there will be fewer molecules of gas occupying any given space. For liquid to transform to vapor, consider vaporization or boiling, molecules on the liquid's surface must be able to leave, which means they either need sufficient energy (added via heat energy water boils), or the number of molecules above the liquid (i.e. vapor pressure) needs to be sufficiently low to allow the surface molecules to escape (achieved by lowering the pressure above the liquid) [8]. Using these two concepts we better understand what happens

**Figure 1.** Comparison of international standard atmosphere, temperature and pressure at various altitudes including

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231

A human's normal body temperature is 98.6°F or 37°C, well below the boiling point of water at our usual, livable altitudes. However, a man named of H.G. Armstrong defined the altitude at which the ambient pressure decreases to the point that spontaneous evolution of liquid water to

at higher altitudes, both to the gas filled compartments and the water in our bodies.

*2.2.1. Ebullism*

Armstrong limit and Mt. Everest death zone.

**Figure 1.** Comparison of international standard atmosphere, temperature and pressure at various altitudes including Armstrong limit and Mt. Everest death zone.

via heat energy water boils), or the number of molecules above the liquid (i.e. vapor pressure) needs to be sufficiently low to allow the surface molecules to escape (achieved by lowering the pressure above the liquid) [8]. Using these two concepts we better understand what happens at higher altitudes, both to the gas filled compartments and the water in our bodies.

#### *2.2.1. Ebullism*

and bounce above that gray, dusty surface they saw on the television [1]. Yet in our hurry to aim for the lunar surface, we flew right through an unexplored and unconquered area of our

The stratosphere is the second lowest layer of Earth's atmosphere, stretching from 12 to 55 km above sea level (**Figure 1**) [2]. For comparison, the Everest summit sits at 8.85 km, and jumbo jets cruise at an average altitude of 12–16 km [3, 4]. To optimize fuel efficiency, the typical commercial airliner cruises at 9–12 km (just above the troposphere in the lower reaches of the stratosphere), where temperatures and air density are lowest [5]. Temperatures in the stratosphere are stratified and, somewhat non-intuitively, increase with higher altitude secondary to ability of the ozone layers to absorb ultraviolet light [5]. Due to increased energy absorption at higher altitudes, the top of the stratosphere remains near 0°C while the tropopause (which occurs between the troposphere and stratosphere) exhibits temperatures of −46 to −57°C [2, 4]. Humans on Earth live well below the altitudes that represent our species' physical limitations. Although only 15.6% of inhabited land occurs below 100 m, in 1994 approximately 33.5% of the world's population lived within these elevations [6]. While human beings can adapt to higher altitudes, the Everest "death zone" (mountain's altitude above 8000 m) earned its name for good reason. When people who are not acclimatized are exposed to equivalent levels of ambient hypoxia that exist at altitudes over 8500 m, they lose consciousness within 2–3 min [3]. Why does this occur and what changes in the environment lead to this? At sea level the average atmospheric pressure is 101.325 kPa, but at higher altitudes air pressure decreases. The mean atmospheric pressure on the summit of Everest is only 33.7 kPa, and atmospheric pressure at the top of the stratosphere is 1/1000 that of sea level [2, 7]. According to Dalton's law, the total pressure of a mixture of gases is made up of the sum of the partial pressures of each individual gas [8]. Given this, it is easier to understand how the partial pressure of oxygen is also much lower at these higher altitudes, which also results in lower partial pressures of oxygen in our blood at these altitudes. A study of the mean partial pressure of arterial oxygen (PaO2) in the blood gas of Everest climbers taken at 8400 m found their average PaO2 to be 24.6 mmHg, while normal is considered to be >80 mmHg [3]. But what happens when the human body is exposed to even higher altitudes than we are able to achieve

via these hiking expeditions, such as the stratosphere or outer space?

To understand this question, it is important to understand Boyle's law and the effect of pressure on liquids and gases as well. According to Boyle's law, pressure and volume have an inverse relationship; as the pressure on a given volume of gas decreases, the volume of the gas will increase [8]. This means that there will be fewer molecules of gas occupying any given space. For liquid to transform to vapor, consider vaporization or boiling, molecules on the liquid's surface must be able to leave, which means they either need sufficient energy (added

**2.2. Physics and human physiology**

own planet: the higher atmosphere.

**2.1. Stratosphere**

**2. Stratosphere and human physiology**

230 Into Space - A Journey of How Humans Adapt and Live in Microgravity

A human's normal body temperature is 98.6°F or 37°C, well below the boiling point of water at our usual, livable altitudes. However, a man named of H.G. Armstrong defined the altitude at which the ambient pressure decreases to the point that spontaneous evolution of liquid water to vapor gas can occur at our body's temperature, a process called ebullism [9]. He coined this altitude "Armstrong's band", which occurs at approximately 18–19 km above sea level [9]. While survival at these altitudes without protection of a pressurized compartment is possible for several minutes, it can quickly lead to dangerous consequences [9]. The human body consists of >50% water, which exists ubiquitously throughout our bodies. During exposure to such low pressures, any water on our skin will vaporize, and resulting pressure in the extremity muscle compartments from the expanding gas can increase to the point that effective blood circulation may cease [10]. Water vapor forms in the thoracic cavity causing vapothorax, increasing intrathoracic pressure, impeding blood flow and inducing vagal stimulation which can lead to bradycardia and decreased blood pressures [9]. Investigations following human exposure have demonstrated intra-alveolar edema, hemorrhagic atelectasis, regional atelectasis, and simple or tension pneumothoraces [9]. A similar process occurs in the abdominal cavity and vapoperitoneum can lead to increased pressure on all the involved organs. In animal models, greater than 2 min of exposure to these simulated pressures led to vascular congestion and hemorrhage in the liver, spleen, kidneys and GI tract, as well as the brain. These findings were more pronounced if the exposure to these pressures was sudden and the decompression was explosive [9].

bubbles can also have a significant effect on the heart. Irritation of the myocardium caused by these bubbles has been demonstrated in animal models to lead to various life threatening cardiac dysrhythmias such as ventricular fibrillation and heart block [9]. It was once believed that placing the exposed person on their left side with their lower body elevated above the heart was the optimal position, and would help prevent any arterial and venous gas emboli from entering cerebral circulation. Animal studies have demonstrated little utility to this approach. The key to treating neurologic DCI Is to provide 100% supplemental oxygen and

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233

Decompression injury is most concerning for astronauts during their extra-vehicular activities, but fortunately is rare in space travel. There are only three astronaut deaths reportedly due to decompression from space exposure. On June 30, 1971, *Soyuz 11* was re-entering the atmosphere when the ship depressurized, leading to the death of the three crew members [13]. Two others experienced decompression during training missions in a chamber but for

Barotrauma occurs as decreased ambient pressures lead to increased volumes of gas within our gas-filled cavities, including the sinuses, ears and thoracic cavity. Usually, barotrauma to the sinuses and ears is less likely when the Eustachian tube and sinus passageways are functional; they act as connections between these cavities and the outside environment and normally allow any expanded volume of gas to exit before causing significant damage [9]. Typically, our airway acts in a similar fashion, but if a person were to hold their breath at the time of exposure, the closed glottis would not allow air to escape from the lungs, and air in the tiny alveoli of lung tissue would expand until their thin walls broke. The direct injection of a large volume of bubbles into the vasculature can result from the rupture of these alveoli, which directly exposes the nearby blood vessels [9]. This massive bubble load can proceed in a retrograde fashion to the right side of the heart and slow blood transport in the major veins, leading to congestion in the capillaries and subsequent tissue damage [9, 11]. As the bubbles prevent forward flow of blood, venous pressure increases and eventually equals that of arterial pressure, at which point cardiac output decreases and there is no effective circulation [11]. This can occur within 1 min of exposure and is a catastrophic condition known as 'vapor lock' [9, 11].

The goal of the first high altitude explorers quickly became focused on finding a way to survive brief periods in this extreme environment. As stated earlier, a protective barrier is needed to survive the life-threatening pressures and temperatures, and so imaginations became focused on how to solve these challenges. Engineers designed pressurized suits which could prevent injuries such as ebullism; but the first suits were heavy, restricted movement and caused high thermal load [9]. Full pressure suits were such units, designed to be pressurized externally and then hold pressure

repressurization via a hyperbaric chamber as soon as possible [9].

less than 5 min and survived without neurologic sequelae [14].

*2.2.4. Barotrauma*

**3. High altitude exploration**

**3.1. Pressure suits**

#### *2.2.2. Anoxia and hypothermia*

Tissue damage following exposure to the low environmental pressure above Armstrong's band, or the near vacuum of space, is secondary to more than simply ebullism. The combination of anoxia, gas bubble formation, gas expansion and rapid fluid loss underlie the array of injuries seen after these incidents. The extremely low partial pressure of oxygen at these altitudes can quickly lead to anoxic anoxia, which is most prominently demonstrated by cerebral hypoxia [9, 11]. The time of useful consciousness following exposure to this low pressure is approximately 9–11 s, at which time they lose voluntary control of their muscles, vomit, lose bowel and bladder control and collapse [9, 11]. Within 30 s severe neurologic manifestations ensue including tonicclonic seizures which progress to spastic rigidity and eventually total flaccid paralysis [9, 11]. Hypothermia is also likely, and ensuing tissue damage depends on the length of exposure as well as the temperature [10]. Although actual tissue freezing is not commonly seen, the increased evaporative cooling on mucosal surfaces has been found to lead to ice formation in those areas [10].

#### *2.2.3. Decompression illness*

Gas bubbles form in three different ways: vaporization of water within tissues (previously discussed), evolution of dissolved gas in the vasculature (decompression illness), and direct injection of gas via ruptured alveoli, resulting in venous and arterial embolism [10]. Decompression illness (DCI) is related to diving, however a similar process can occurs any time the body experiences significantly decreased ambient pressures. In a manner similar to ebullism, pressure decreases to the point that dissolved gases in the blood spontaneously evolve out and form small bubbles that can become trapped within the smaller capillaries of the skin and organs including kidneys, brain and lungs [9]. Skin findings are more prominent in DCI with divers, but neurologic findings are more common in high altitude exposure [12]. DCI should be suspected in anyone with such exposure who displays altered mental status or abnormal neurologic findings that persist despite initial supportive treatment [9]. These bubbles can also have a significant effect on the heart. Irritation of the myocardium caused by these bubbles has been demonstrated in animal models to lead to various life threatening cardiac dysrhythmias such as ventricular fibrillation and heart block [9]. It was once believed that placing the exposed person on their left side with their lower body elevated above the heart was the optimal position, and would help prevent any arterial and venous gas emboli from entering cerebral circulation. Animal studies have demonstrated little utility to this approach. The key to treating neurologic DCI Is to provide 100% supplemental oxygen and repressurization via a hyperbaric chamber as soon as possible [9].

Decompression injury is most concerning for astronauts during their extra-vehicular activities, but fortunately is rare in space travel. There are only three astronaut deaths reportedly due to decompression from space exposure. On June 30, 1971, *Soyuz 11* was re-entering the atmosphere when the ship depressurized, leading to the death of the three crew members [13]. Two others experienced decompression during training missions in a chamber but for less than 5 min and survived without neurologic sequelae [14].

#### *2.2.4. Barotrauma*

vapor gas can occur at our body's temperature, a process called ebullism [9]. He coined this altitude "Armstrong's band", which occurs at approximately 18–19 km above sea level [9]. While survival at these altitudes without protection of a pressurized compartment is possible for several minutes, it can quickly lead to dangerous consequences [9]. The human body consists of >50% water, which exists ubiquitously throughout our bodies. During exposure to such low pressures, any water on our skin will vaporize, and resulting pressure in the extremity muscle compartments from the expanding gas can increase to the point that effective blood circulation may cease [10]. Water vapor forms in the thoracic cavity causing vapothorax, increasing intrathoracic pressure, impeding blood flow and inducing vagal stimulation which can lead to bradycardia and decreased blood pressures [9]. Investigations following human exposure have demonstrated intra-alveolar edema, hemorrhagic atelectasis, regional atelectasis, and simple or tension pneumothoraces [9]. A similar process occurs in the abdominal cavity and vapoperitoneum can lead to increased pressure on all the involved organs. In animal models, greater than 2 min of exposure to these simulated pressures led to vascular congestion and hemorrhage in the liver, spleen, kidneys and GI tract, as well as the brain. These findings were more pronounced if

the exposure to these pressures was sudden and the decompression was explosive [9].

Tissue damage following exposure to the low environmental pressure above Armstrong's band, or the near vacuum of space, is secondary to more than simply ebullism. The combination of anoxia, gas bubble formation, gas expansion and rapid fluid loss underlie the array of injuries seen after these incidents. The extremely low partial pressure of oxygen at these altitudes can quickly lead to anoxic anoxia, which is most prominently demonstrated by cerebral hypoxia [9, 11]. The time of useful consciousness following exposure to this low pressure is approximately 9–11 s, at which time they lose voluntary control of their muscles, vomit, lose bowel and bladder control and collapse [9, 11]. Within 30 s severe neurologic manifestations ensue including tonicclonic seizures which progress to spastic rigidity and eventually total flaccid paralysis [9, 11]. Hypothermia is also likely, and ensuing tissue damage depends on the length of exposure as well as the temperature [10]. Although actual tissue freezing is not commonly seen, the increased evaporative cooling on mucosal surfaces has been found to lead to ice formation in those areas [10].

Gas bubbles form in three different ways: vaporization of water within tissues (previously discussed), evolution of dissolved gas in the vasculature (decompression illness), and direct injection of gas via ruptured alveoli, resulting in venous and arterial embolism [10]. Decompression illness (DCI) is related to diving, however a similar process can occurs any time the body experiences significantly decreased ambient pressures. In a manner similar to ebullism, pressure decreases to the point that dissolved gases in the blood spontaneously evolve out and form small bubbles that can become trapped within the smaller capillaries of the skin and organs including kidneys, brain and lungs [9]. Skin findings are more prominent in DCI with divers, but neurologic findings are more common in high altitude exposure [12]. DCI should be suspected in anyone with such exposure who displays altered mental status or abnormal neurologic findings that persist despite initial supportive treatment [9]. These

*2.2.2. Anoxia and hypothermia*

232 Into Space - A Journey of How Humans Adapt and Live in Microgravity

*2.2.3. Decompression illness*

Barotrauma occurs as decreased ambient pressures lead to increased volumes of gas within our gas-filled cavities, including the sinuses, ears and thoracic cavity. Usually, barotrauma to the sinuses and ears is less likely when the Eustachian tube and sinus passageways are functional; they act as connections between these cavities and the outside environment and normally allow any expanded volume of gas to exit before causing significant damage [9]. Typically, our airway acts in a similar fashion, but if a person were to hold their breath at the time of exposure, the closed glottis would not allow air to escape from the lungs, and air in the tiny alveoli of lung tissue would expand until their thin walls broke. The direct injection of a large volume of bubbles into the vasculature can result from the rupture of these alveoli, which directly exposes the nearby blood vessels [9]. This massive bubble load can proceed in a retrograde fashion to the right side of the heart and slow blood transport in the major veins, leading to congestion in the capillaries and subsequent tissue damage [9, 11]. As the bubbles prevent forward flow of blood, venous pressure increases and eventually equals that of arterial pressure, at which point cardiac output decreases and there is no effective circulation [11]. This can occur within 1 min of exposure and is a catastrophic condition known as 'vapor lock' [9, 11].

### **3. High altitude exploration**

#### **3.1. Pressure suits**

The goal of the first high altitude explorers quickly became focused on finding a way to survive brief periods in this extreme environment. As stated earlier, a protective barrier is needed to survive the life-threatening pressures and temperatures, and so imaginations became focused on how to solve these challenges. Engineers designed pressurized suits which could prevent injuries such as ebullism; but the first suits were heavy, restricted movement and caused high thermal load [9]. Full pressure suits were such units, designed to be pressurized externally and then hold pressure for prolonged periods of time. They are typically are used for routine operations in hazardous environments [9]. In contrast, partial pressure suits have a low baseline profile and are worn overtop elastic undergarments which provide passive mechanical counter pressure. They are pneumatic and inflate when activated to provide near-instant pressurized conditions. They are less cumbersome than full pressure suits, but are not ideal for prolonged, routine activity, and are better used as a redundant protective measure in the event of a vehicle hull breach [9].

barely connected. If it had detached, the suit would have depressurized [16]. It was then that he realized that this suit had protected him from the life-threatening low pressures and

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However, as with most great feats, examples of exemplary achievement are likewise met with examples of great tragedy and failure. Pyotr Dolgov, a Soviet Air Force colonel, was part of a unit designing a pressure suit to allow for safe high altitude pilot bail-outs. In 1962, during field testing of this suit at an altitude just over 28.5 km, he attempted to exit the gondola when he accidently hit his helmet on part of the structure, cracking the visor which caused immediate suit depressurization. This led to catastrophic ebullism and hypoxia resulting in death [4, 12]. Another instance (1966), a Houston technician in a low-pressure chamber was testing a space suit when the suit suddenly lost pressurization. The technician was immediately exposed to atmospheric pressures equivalent to an altitude of 120,000 ft, and quickly lost consciousness. The chamber was repressurized and he awoke as the monitor read 14,000 ft. He reported recalling the feeling of saliva boiling off his tongue just before he passed out [17]. Amazingly, the technician had a quick recovery and did not require any hospitalization nor had any neurologic sequelae from the exposure. A similar incident occurred in 1982 when a technician was inside of a decompression chamber that unexpectedly began dropping pressure [17]. The technician experienced pressures correlating with altitudes greater than 74,000 ft for over 3 min, and was held at the maximum altitude for over 60 s. The chamber manager was forced to kick in the glass ionization gauge to repressurize the chamber by letting air in [17]. By the time the technician arrived at the hospital he was noted to be cyanotic, frothing at the mouth, bleeding from the lungs and had severe barotrauma in both ear drums. However, as serious as his presentation appeared, within 24 h he was awake and alert, and by day five he had been extubated. He, too, suffered no long term neurologic sequelae [17].

Nick Piantanida, a truck driver from New Jersey with virtually no experience or training, became obsessed with the idea of high altitude jumps and breaking the world free fall record [12, 19]. He rallied a large amount of sponsor money and a group of volunteers to help him achieve this goal. However, his first attempt in 1965 with balloon ascent failed when wind shear tore off the balloon's top at 23,000 ft, forcing him to parachute into a nearby city dump [19]. During his second attempt, he successfully climbed to 123,500 ft but could not disconnect his oxygen hose from the gondola's oxygen supply in order to connect to a portable tank, and therefore he could not exit the capsule. Piantanida was then instructed by his ground crew to reattach his seat belt and re-secure the belt across the capsule door, but his bulky gloves made this an impossible task [19]. He was forced to wedge himself inside as the gondola tipped forward at a 45° angle during its 15 s free-fall at 600 miles per hour, then brace inside the open gondola to avoid falling out when the cargo chute opened [20]. He reportedly said afterward: "If only I had a damned \$1.25 wrench, gravity would have done the rest" [19]. His third and final attempt took place on May 1, 1966. Piantanida ascended uneventfully in a styrofoam-insulated gondola (**Figure 2**) when a loud 'whoosh' of rushing air was heard over the communications link by his ground crew, followed by the cut-off call of Nick's voice saying "Emerg-!" [19, 20]. The balloon was cut away and the mission immediately aborted. The gondola, with the pilot still inside, fell

extreme cold. He referred to the suit later as his 'own escape capsule' [15].

**3.3. Nick Piantanida and Strato Jump I-III**

Pressure suit design is a very specialized field and the David Clark Company Incorporated (DCCI) has pioneered the field starting in the 1940s by developing partial pressure suits both for NASA as well as full pressure suits for the D558-2 and North American X-15 research aircraft [15]. DCCI created some of the first pressure suits used in high altitude missions, which then became the basis of the suits used by NASA for the space shuttle missions [15, 16]. The pressure suit designed for NASA, termed the Launch Entry Suit (LES), was modeled after the high-altitude protective outfit due to its combination of comfort and protection that could be provided in a short time. The LES was a counter-pressure garment with two separate bladders: one for acceleration, one for altitude protection [16]. The first worn by astronauts is made of athletic underwear, over which the counter-pressure garment fits. A nylon restraint layer is worn overtop which allows the counter-pressure garment to push inwards when inflated. The outer, waterproof, nomex cover is worn over this and is bright orange to assist in search and rescue operations [16]. The astronauts have a parachute harness, flotation devices and other supplies on the outside of their suit. The helmet is connected via a bearing assembly and gloves also strap on separately. The LES was used on 42 Space Shuttle missions from 1988 to 2001, at which time the new, full-pressure Advanced Crew Escape Suit was designed. It was lighter, less bulky, cooler and more comfortable with better physiologic protection and mobility [16]. This model was used through the discontinuation of the Shuttle program in 2011. It was developed in parallel with the S1034 PPA which became the standard pressure suit used by the United States Air Force and Department of Defense [15]. The S1034 and S1035 were the basis for the specialized suits developed for the latest high altitude missions, StratEx and Stratos [15].

#### **3.2. Early near misses and failures**

The modern quest to explore high altitudes began with Paul Bert in 1878, who developed the first altitude chamber complete with supplemental oxygen [17]. He was followed by Wiley Post, who in 1934 developed and demonstrated the effectiveness of the first pressure suit for high altitude flight [17]. New pressure suits that were thinner and more comfortable continued to feature improvements, and they became regular equipment for all high altitude pilots. In 1966, during a failed flight test of the Blackbird aircraft, one of these new pressure suits led to the safe landing and survival of its pilot, Bill Weaver. Weaver was piloting the Blackbird at Mach 3 and 75,000 ft when a structural failure caused the cockpit to detach from the fuselage [16, 18]. He was wearing the new S901 pressure suit, and after being violently ripped away from the disintegrating aircraft and ejection seat, he lost consciousness in free fall. His small drogue chute opened automatically, followed by his main chute at a lower altitude. He regained consciousness during the main parachute deployment, but his visor had completely frosted over and he could not see anything around him [15, 18]. After landing he noted that one of the two oxygen lines supplying his pressure suit had detached, and the second was barely connected. If it had detached, the suit would have depressurized [16]. It was then that he realized that this suit had protected him from the life-threatening low pressures and extreme cold. He referred to the suit later as his 'own escape capsule' [15].

However, as with most great feats, examples of exemplary achievement are likewise met with examples of great tragedy and failure. Pyotr Dolgov, a Soviet Air Force colonel, was part of a unit designing a pressure suit to allow for safe high altitude pilot bail-outs. In 1962, during field testing of this suit at an altitude just over 28.5 km, he attempted to exit the gondola when he accidently hit his helmet on part of the structure, cracking the visor which caused immediate suit depressurization. This led to catastrophic ebullism and hypoxia resulting in death [4, 12]. Another instance (1966), a Houston technician in a low-pressure chamber was testing a space suit when the suit suddenly lost pressurization. The technician was immediately exposed to atmospheric pressures equivalent to an altitude of 120,000 ft, and quickly lost consciousness. The chamber was repressurized and he awoke as the monitor read 14,000 ft. He reported recalling the feeling of saliva boiling off his tongue just before he passed out [17]. Amazingly, the technician had a quick recovery and did not require any hospitalization nor had any neurologic sequelae from the exposure. A similar incident occurred in 1982 when a technician was inside of a decompression chamber that unexpectedly began dropping pressure [17]. The technician experienced pressures correlating with altitudes greater than 74,000 ft for over 3 min, and was held at the maximum altitude for over 60 s. The chamber manager was forced to kick in the glass ionization gauge to repressurize the chamber by letting air in [17]. By the time the technician arrived at the hospital he was noted to be cyanotic, frothing at the mouth, bleeding from the lungs and had severe barotrauma in both ear drums. However, as serious as his presentation appeared, within 24 h he was awake and alert, and by day five he had been extubated. He, too, suffered no long term neurologic sequelae [17].

#### **3.3. Nick Piantanida and Strato Jump I-III**

for prolonged periods of time. They are typically are used for routine operations in hazardous environments [9]. In contrast, partial pressure suits have a low baseline profile and are worn overtop elastic undergarments which provide passive mechanical counter pressure. They are pneumatic and inflate when activated to provide near-instant pressurized conditions. They are less cumbersome than full pressure suits, but are not ideal for prolonged, routine activity, and are better used as a redundant protective measure in the event of a vehicle hull breach [9].

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Pressure suit design is a very specialized field and the David Clark Company Incorporated (DCCI) has pioneered the field starting in the 1940s by developing partial pressure suits both for NASA as well as full pressure suits for the D558-2 and North American X-15 research aircraft [15]. DCCI created some of the first pressure suits used in high altitude missions, which then became the basis of the suits used by NASA for the space shuttle missions [15, 16]. The pressure suit designed for NASA, termed the Launch Entry Suit (LES), was modeled after the high-altitude protective outfit due to its combination of comfort and protection that could be provided in a short time. The LES was a counter-pressure garment with two separate bladders: one for acceleration, one for altitude protection [16]. The first worn by astronauts is made of athletic underwear, over which the counter-pressure garment fits. A nylon restraint layer is worn overtop which allows the counter-pressure garment to push inwards when inflated. The outer, waterproof, nomex cover is worn over this and is bright orange to assist in search and rescue operations [16]. The astronauts have a parachute harness, flotation devices and other supplies on the outside of their suit. The helmet is connected via a bearing assembly and gloves also strap on separately. The LES was used on 42 Space Shuttle missions from 1988 to 2001, at which time the new, full-pressure Advanced Crew Escape Suit was designed. It was lighter, less bulky, cooler and more comfortable with better physiologic protection and mobility [16]. This model was used through the discontinuation of the Shuttle program in 2011. It was developed in parallel with the S1034 PPA which became the standard pressure suit used by the United States Air Force and Department of Defense [15]. The S1034 and S1035 were the basis for the specialized suits developed for the latest high altitude missions, StratEx and Stratos [15].

The modern quest to explore high altitudes began with Paul Bert in 1878, who developed the first altitude chamber complete with supplemental oxygen [17]. He was followed by Wiley Post, who in 1934 developed and demonstrated the effectiveness of the first pressure suit for high altitude flight [17]. New pressure suits that were thinner and more comfortable continued to feature improvements, and they became regular equipment for all high altitude pilots. In 1966, during a failed flight test of the Blackbird aircraft, one of these new pressure suits led to the safe landing and survival of its pilot, Bill Weaver. Weaver was piloting the Blackbird at Mach 3 and 75,000 ft when a structural failure caused the cockpit to detach from the fuselage [16, 18]. He was wearing the new S901 pressure suit, and after being violently ripped away from the disintegrating aircraft and ejection seat, he lost consciousness in free fall. His small drogue chute opened automatically, followed by his main chute at a lower altitude. He regained consciousness during the main parachute deployment, but his visor had completely frosted over and he could not see anything around him [15, 18]. After landing he noted that one of the two oxygen lines supplying his pressure suit had detached, and the second was

**3.2. Early near misses and failures**

Nick Piantanida, a truck driver from New Jersey with virtually no experience or training, became obsessed with the idea of high altitude jumps and breaking the world free fall record [12, 19]. He rallied a large amount of sponsor money and a group of volunteers to help him achieve this goal. However, his first attempt in 1965 with balloon ascent failed when wind shear tore off the balloon's top at 23,000 ft, forcing him to parachute into a nearby city dump [19]. During his second attempt, he successfully climbed to 123,500 ft but could not disconnect his oxygen hose from the gondola's oxygen supply in order to connect to a portable tank, and therefore he could not exit the capsule. Piantanida was then instructed by his ground crew to reattach his seat belt and re-secure the belt across the capsule door, but his bulky gloves made this an impossible task [19]. He was forced to wedge himself inside as the gondola tipped forward at a 45° angle during its 15 s free-fall at 600 miles per hour, then brace inside the open gondola to avoid falling out when the cargo chute opened [20]. He reportedly said afterward: "If only I had a damned \$1.25 wrench, gravity would have done the rest" [19]. His third and final attempt took place on May 1, 1966. Piantanida ascended uneventfully in a styrofoam-insulated gondola (**Figure 2**) when a loud 'whoosh' of rushing air was heard over the communications link by his ground crew, followed by the cut-off call of Nick's voice saying "Emerg-!" [19, 20]. The balloon was cut away and the mission immediately aborted. The gondola, with the pilot still inside, fell

**Figure 2.** Styrofoam-insulated gondola used by Nick Piantanida during the Strato Jump III mission. Now on exhibit at Smithsonian Institution's National Air and Space Museum.

for an agonizing 26 min descent from a height of 56,000 ft using the gondola's own emergency parachute. By the time the crew made it to the downed gondola Nick was outside the capsule, barely alive and conscious [19, 20]. Piantanida lapsed into a coma before arrival to the nearest hospital, and the doctors, with very little knowledge or training on high altitude pathology and management, did their best to help him [19, 20]. He had experienced massive tissue damage and brain injury secondary to emboli. He died 4 months later, never having come out of his coma [19]. While the exact circumstance that led to the incident may never be known, it is believed that Piantanida, who frequently reported discomfort from his pressure suit and had been known to quickly open and shut the faceplate to quickly depressurize the suit, had in fact opened his faceplate at that high altitude and experienced explosive decompression illness [19].

#### **3.4. Joseph Kittinger and Project Excelsior**

*"There is a hostile sky above me. Man will never conquer space. He may live in it, but he will never conquer it. The sky above is void and very black and very hostile."*

*—Joseph Kittinger (12)*

the previous records for high altitude free fall [4]. During his first high altitude jump in late 1959 at just over 23 km, his drogue chute malfunctioned and deployed early causing him to go into a flat spin [12, 21]. A flat spin occurs in free fall when your body is horizontal and essentially spins in a cartwheel motion. A jumper can spin at a rate of up to 180–250 rotations per minute; the centrifugal force from a rapid spin creates negative G's that draw the blood to stagnate in the feet and head [4]. This can lead to headache, shortness of breath, vision failure, altered mentation, and loss of consciousness [4]. This is exactly what happened as Kittinger lost consciousness shortly into his flat spin, but was rescued by the automatic opening of his emergency parachute at 10,000 ft [12, 21]. Following this incident, Kittinger decided to have his small drogue chute open automatically after he jumped from the capsule, which helps to stabilize him in free fall and prevent flat spins. This slows freefall somewhat, but provides an extra layer of safety during that dangerous period [4]. His second jump proceeded unevent-

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His third attempt on August 16, 1960, would be his final, and although this jump at 102,800 ft (**Figure 3**) was ultimately a success, it was not without problems [22]. During the ascent at approximately 43,000 ft, Kittinger noticed that his right hand began to feel strange. On inspection, he noticed the glove's airbladder was not inflated and realized that the pressurizing mechanism in his glove had malfunctioned. He decided not to notify ground control, knowing that he could still operate all of the necessary components of the gondola with minimal hand function since most of the controls were operated by a flick of a switch or nudge of the hand [21]. As he ascended higher his hand became increasingly swollen causing him extreme

**Figure 3.** Joseph Kittinger just after jumping from his capsule during the record-breaking skydive mission, Excelsior III.

fully, however he did not achieve his desired altitude [22].

Colonel Joseph Kittinger is a pilot who personally understands the dangers of high altitude flight. He is a retired United States Airforce Colonel and, like Piantanida, desired to break the previous records for high altitude free fall [4]. During his first high altitude jump in late 1959 at just over 23 km, his drogue chute malfunctioned and deployed early causing him to go into a flat spin [12, 21]. A flat spin occurs in free fall when your body is horizontal and essentially spins in a cartwheel motion. A jumper can spin at a rate of up to 180–250 rotations per minute; the centrifugal force from a rapid spin creates negative G's that draw the blood to stagnate in the feet and head [4]. This can lead to headache, shortness of breath, vision failure, altered mentation, and loss of consciousness [4]. This is exactly what happened as Kittinger lost consciousness shortly into his flat spin, but was rescued by the automatic opening of his emergency parachute at 10,000 ft [12, 21]. Following this incident, Kittinger decided to have his small drogue chute open automatically after he jumped from the capsule, which helps to stabilize him in free fall and prevent flat spins. This slows freefall somewhat, but provides an extra layer of safety during that dangerous period [4]. His second jump proceeded uneventfully, however he did not achieve his desired altitude [22].

His third attempt on August 16, 1960, would be his final, and although this jump at 102,800 ft (**Figure 3**) was ultimately a success, it was not without problems [22]. During the ascent at approximately 43,000 ft, Kittinger noticed that his right hand began to feel strange. On inspection, he noticed the glove's airbladder was not inflated and realized that the pressurizing mechanism in his glove had malfunctioned. He decided not to notify ground control, knowing that he could still operate all of the necessary components of the gondola with minimal hand function since most of the controls were operated by a flick of a switch or nudge of the hand [21]. As he ascended higher his hand became increasingly swollen causing him extreme

for an agonizing 26 min descent from a height of 56,000 ft using the gondola's own emergency parachute. By the time the crew made it to the downed gondola Nick was outside the capsule, barely alive and conscious [19, 20]. Piantanida lapsed into a coma before arrival to the nearest hospital, and the doctors, with very little knowledge or training on high altitude pathology and management, did their best to help him [19, 20]. He had experienced massive tissue damage and brain injury secondary to emboli. He died 4 months later, never having come out of his coma [19]. While the exact circumstance that led to the incident may never be known, it is believed that Piantanida, who frequently reported discomfort from his pressure suit and had been known to quickly open and shut the faceplate to quickly depressurize the suit, had in fact opened his faceplate at that high altitude and experienced explosive decompression illness [19].

**Figure 2.** Styrofoam-insulated gondola used by Nick Piantanida during the Strato Jump III mission. Now on exhibit at

*"There is a hostile sky above me. Man will never conquer space. He may live in it, but he will never* 

Colonel Joseph Kittinger is a pilot who personally understands the dangers of high altitude flight. He is a retired United States Airforce Colonel and, like Piantanida, desired to break

*—Joseph Kittinger (12)*

**3.4. Joseph Kittinger and Project Excelsior**

Smithsonian Institution's National Air and Space Museum.

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*conquer it. The sky above is void and very black and very hostile."*

**Figure 3.** Joseph Kittinger just after jumping from his capsule during the record-breaking skydive mission, Excelsior III.

pain and losing most of its circulation. By the time Kittinger made it to the ground, his right hand was nearly twice the size of his left due to swelling. However, 3 h after landing his hand had returned to normal size with no residual pain or deficits [21]. He would hold this record for many decades, until 2012 when another adventurous explorer would come along.

recorded inside the capsule was 13°F (−10.5°C), while the lowest recorded outside the capsule was −95.62°F (−70.9°C). The capsule consisted of fiberglass composite housing, with a hingeless acrylic door designed to pressurize at launch [22]. The capsule housing material selection was very important, as it would need to accommodate significant expansion and contraction expected with extreme variations of temperature. The hingeless door allowed for maximum range of movement within and outside the capsule, and was designed to maximize efficiency and ease of opening [22]. The capsule contained redundant life support systems including 10 h of breathable oxygen, glove and foot heaters, carbon dioxide and water scrubbers, among other systems. It would descend using a 100 foot diameter parachute; the typical landing

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Baumgartner's pressure suit (**Figure 4**) was specifically designed to facilitate the capsule egress and exit. The major challenges of suit design were to provide adequate protection and life support during freefall yet allow the transition from sitting to standing, provide thermal protection, mitigate visor fogging, and create a system to sense and prevent the potential violent flat spin that trapped Kittinger. Baumgartner wore a baseline suit with standard undergarments which provided necessary thermal protection [15]. His chest pack contained three GPS units, an accelerometer, a mach speed indicator, a camera, a battery to heat the face plate and a power supply [22]. He also had an emergency cutaway knife in case the reserve chute opened at to high altitude, which would cause a slow descent and probably oxygen shortage. The helmet acted as an airtight gas container, impermeable to nitrogen and oxygen, yet breathable to allow water vapor to pass out and prevent fogging. The exterior of the suite included a fireproof cover [22]. Underneath he wore a fully integrated medical diagnostic tracking unit (Hidalgo Equivital) which provided continuous information on heart rate, respiratory rate and acceleration [22]. Taking another lesson from Kittinger's jumps, Baumgartner decided not to have a drogue chute deploy at the beginning of the jump, as this add unacceptable drag and he would not achieve his desired speed nor hope to achieve a new speed record [4]. Instead he wore a safety device on his right wrist which measured the amount of G-force throughout the entire mission. If he were to fall into a flat spin similar to Kittinger, and the device measured 3.5 G or higher for six continuous seconds, his drogue chute would automatically deploy, which would act to stabilize and

The balloons used for these high altitude missions are also specially designed (**Figure 5**). They are made of thin plastic film, no more than 0.0009 inches (0.02 mm) thick [4]. As Piananida learned on his first failed ascent, the material needs to be thin and light enough to optimize the weight to lift ratio, but also needs to have a high drag limit (the point at which upward velocity creates drag strong enough to threaten damaging the balloon) to withstand the high winds of the upper altitudes [4, 21]. A lower drag limit could be mitigated by slowing the ascent, but only to the extent that the life support systems could allow. The Stratos balloon was made of 40 acres of polyethylene, at launch was twice as tall as a Saturn 5 rocket, and used 180,000 cubic feet of helium to launch [22]. Restraining fabric was placed around it for the initial ascent, holding the circumference to just under 17 ft. The balloon was released at

20,000 ft (6000 m) to allow its full expansion to 100 ft (30 m) diameter [22].

shocks ranged from 4.5 to 8.0 G [22].

pull him out of the spin [22].

#### **3.5. Felix Baumgartner and the Red Bull Stratos mission**

On October 14, 2012, history was made as the Red Bull Stratos Capsule Jump set a precedent for high altitude exploration. The mission was no small feat; the goal was to safely ascend beyond Kittinger's previous altitude in a capsule and then free fall in a specially designed pressure suit, eventually using a parachute to descend the remaining elevation [22]. It was a huge success. The ascent was uneventful and the exit altitude for the pilot, Felix Baumgartner, was 127,852 ft (38.97 m). His maximum vertical speed was 843 miles per hour, at Mach 1.25 (377 m/s), making Baumgartner the first person to break the speed of sound in a freefall [22]. He was supersonic for 30 s of his 4 min 23 s freefall, during which he fell 119,431 ft (36,402 m). Other records broken during this jump include the largest balloon flown with a human aboard and the highest manned balloon ascent without a vehicle [22].

Unlike Joseph Kittinger's jump, the capsule (**Figure 4**) was pressurized, which allowed for continuous pre-breathing of oxygen throughout the entire ascent. Pre-breathing oxygen helps to decrease the risk of decompression illness. Increasing the amount of time the pilot can prebreathe oxygen closer to the actual jump time increases the safety profile of the jump [22]. Using a pressurized capsule also prevents the discomfort and exertion of having to pressurize the suit prior to egress. The capsule provided thermoprotection; the lowest temperature

**Figure 4.** Gondola and pressure suit used by Felix Baumgartner during the Red Bull Stratos Mission. Now on exhibit in the National Air and Space Museum.

recorded inside the capsule was 13°F (−10.5°C), while the lowest recorded outside the capsule was −95.62°F (−70.9°C). The capsule consisted of fiberglass composite housing, with a hingeless acrylic door designed to pressurize at launch [22]. The capsule housing material selection was very important, as it would need to accommodate significant expansion and contraction expected with extreme variations of temperature. The hingeless door allowed for maximum range of movement within and outside the capsule, and was designed to maximize efficiency and ease of opening [22]. The capsule contained redundant life support systems including 10 h of breathable oxygen, glove and foot heaters, carbon dioxide and water scrubbers, among other systems. It would descend using a 100 foot diameter parachute; the typical landing shocks ranged from 4.5 to 8.0 G [22].

pain and losing most of its circulation. By the time Kittinger made it to the ground, his right hand was nearly twice the size of his left due to swelling. However, 3 h after landing his hand had returned to normal size with no residual pain or deficits [21]. He would hold this record

On October 14, 2012, history was made as the Red Bull Stratos Capsule Jump set a precedent for high altitude exploration. The mission was no small feat; the goal was to safely ascend beyond Kittinger's previous altitude in a capsule and then free fall in a specially designed pressure suit, eventually using a parachute to descend the remaining elevation [22]. It was a huge success. The ascent was uneventful and the exit altitude for the pilot, Felix Baumgartner, was 127,852 ft (38.97 m). His maximum vertical speed was 843 miles per hour, at Mach 1.25 (377 m/s), making Baumgartner the first person to break the speed of sound in a freefall [22]. He was supersonic for 30 s of his 4 min 23 s freefall, during which he fell 119,431 ft (36,402 m). Other records broken during this jump include the largest balloon flown with a human

Unlike Joseph Kittinger's jump, the capsule (**Figure 4**) was pressurized, which allowed for continuous pre-breathing of oxygen throughout the entire ascent. Pre-breathing oxygen helps to decrease the risk of decompression illness. Increasing the amount of time the pilot can prebreathe oxygen closer to the actual jump time increases the safety profile of the jump [22]. Using a pressurized capsule also prevents the discomfort and exertion of having to pressurize the suit prior to egress. The capsule provided thermoprotection; the lowest temperature

**Figure 4.** Gondola and pressure suit used by Felix Baumgartner during the Red Bull Stratos Mission. Now on exhibit in

the National Air and Space Museum.

for many decades, until 2012 when another adventurous explorer would come along.

**3.5. Felix Baumgartner and the Red Bull Stratos mission**

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aboard and the highest manned balloon ascent without a vehicle [22].

Baumgartner's pressure suit (**Figure 4**) was specifically designed to facilitate the capsule egress and exit. The major challenges of suit design were to provide adequate protection and life support during freefall yet allow the transition from sitting to standing, provide thermal protection, mitigate visor fogging, and create a system to sense and prevent the potential violent flat spin that trapped Kittinger. Baumgartner wore a baseline suit with standard undergarments which provided necessary thermal protection [15]. His chest pack contained three GPS units, an accelerometer, a mach speed indicator, a camera, a battery to heat the face plate and a power supply [22]. He also had an emergency cutaway knife in case the reserve chute opened at to high altitude, which would cause a slow descent and probably oxygen shortage. The helmet acted as an airtight gas container, impermeable to nitrogen and oxygen, yet breathable to allow water vapor to pass out and prevent fogging. The exterior of the suite included a fireproof cover [22]. Underneath he wore a fully integrated medical diagnostic tracking unit (Hidalgo Equivital) which provided continuous information on heart rate, respiratory rate and acceleration [22]. Taking another lesson from Kittinger's jumps, Baumgartner decided not to have a drogue chute deploy at the beginning of the jump, as this add unacceptable drag and he would not achieve his desired speed nor hope to achieve a new speed record [4]. Instead he wore a safety device on his right wrist which measured the amount of G-force throughout the entire mission. If he were to fall into a flat spin similar to Kittinger, and the device measured 3.5 G or higher for six continuous seconds, his drogue chute would automatically deploy, which would act to stabilize and pull him out of the spin [22].

The balloons used for these high altitude missions are also specially designed (**Figure 5**). They are made of thin plastic film, no more than 0.0009 inches (0.02 mm) thick [4]. As Piananida learned on his first failed ascent, the material needs to be thin and light enough to optimize the weight to lift ratio, but also needs to have a high drag limit (the point at which upward velocity creates drag strong enough to threaten damaging the balloon) to withstand the high winds of the upper altitudes [4, 21]. A lower drag limit could be mitigated by slowing the ascent, but only to the extent that the life support systems could allow. The Stratos balloon was made of 40 acres of polyethylene, at launch was twice as tall as a Saturn 5 rocket, and used 180,000 cubic feet of helium to launch [22]. Restraining fabric was placed around it for the initial ascent, holding the circumference to just under 17 ft. The balloon was released at 20,000 ft (6000 m) to allow its full expansion to 100 ft (30 m) diameter [22].

**Figure 5.** The balloon used for the StratEx mission being filled just as dawn breaks. The restraining fabric can be seen tied near the bottom, restricting the fill of the lower part of the balloon.

> would allow for air passage into the helmet from the suit in an event of depressurization [25]. The equipment module included the life support and electronic support machinery which was primarily located in a large chest plate. The oxygen supply used a demand regulated system similar to SCUBA systems, where gas is supplied only when the pilot takes a breath and is not free flowing. Oxygen use was calculated beforehand based on suit pressure, suit temperature and pilot metabolic rate (breathing rate) during the various stages of the flight process. The oxygen cylinders used were modified standard aerospace composite cylinders [25]. The thermoregulatory system used a cartridge heater to heat a water-based fluid which was then pumped through a liquid thermal garment in order warm the pilot at high altitudes and cool the pilot while on the ground. This liquid cooling system was also used to help regulate the temperature of the electronic systems housed in the equipment module. This module also housed a power supply along with the voice and data communications hardware. The main parachute design was based on the Sigma tandem system, the most widely used tandem parachute [25]. These parachutes are normally built to support an instructor/student pair weighing up to 500 lbs, and fulfilled the needs of the StratEx system which weighed approximately 430 lbs (including the pilot). The parachute pack also acted as a suspension point during ascent, which provided the ideal 45° angle. The ascent balloon was similar to

> **Figure 6.** Gary Eustace begins his ascent for the StratEx mission. He is barely visible in his special pressure suit secured

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to the bottom of the large balloon.

#### **3.6. Gary Eustace and the StratEx mission**

The StratEx (Stratospheric Explorer) mission (**Figure 6**) would take placed just over 2 years following Stratos, and though one goal was to break Baumgartner's record, a new dream was about to unfold. Unlike Stratos, a highly publicized project, StratEx was a privately financed scientific endeavor with focus on creating new technology to allow a less expensive, reusable way to explore the stratosphere without need for a constrictive and cumbersome capsule. Alan Eustace, the son of an aerospace engineer, worked as Google's senior vice president at the time of StratEx's development [23]. His vision was to use a balloon ascent system to transport a pilot, independent of a capsule, in a self-sustained pressure suit complete with all necessary life support systems for both ascent and descent [24].

The pressure suit designed for this mission required three distinct components: the actual pressure suit itself, an equipment module, and the parachute pack. The pressure suit was sandwiched between the equipment module in front, and the parachute pack in back. The pressure controller was housed inside the pressure suit, and the helmet was specially designed to force exhaled air down a valve and away from the facemask. The suit and helmet were essentially separate pressurized chambers, but the helmet had a suffocation valve that

**Figure 6.** Gary Eustace begins his ascent for the StratEx mission. He is barely visible in his special pressure suit secured to the bottom of the large balloon.

**3.6. Gary Eustace and the StratEx mission**

near the bottom, restricting the fill of the lower part of the balloon.

240 Into Space - A Journey of How Humans Adapt and Live in Microgravity

necessary life support systems for both ascent and descent [24].

The StratEx (Stratospheric Explorer) mission (**Figure 6**) would take placed just over 2 years following Stratos, and though one goal was to break Baumgartner's record, a new dream was about to unfold. Unlike Stratos, a highly publicized project, StratEx was a privately financed scientific endeavor with focus on creating new technology to allow a less expensive, reusable way to explore the stratosphere without need for a constrictive and cumbersome capsule. Alan Eustace, the son of an aerospace engineer, worked as Google's senior vice president at the time of StratEx's development [23]. His vision was to use a balloon ascent system to transport a pilot, independent of a capsule, in a self-sustained pressure suit complete with all

**Figure 5.** The balloon used for the StratEx mission being filled just as dawn breaks. The restraining fabric can be seen tied

The pressure suit designed for this mission required three distinct components: the actual pressure suit itself, an equipment module, and the parachute pack. The pressure suit was sandwiched between the equipment module in front, and the parachute pack in back. The pressure controller was housed inside the pressure suit, and the helmet was specially designed to force exhaled air down a valve and away from the facemask. The suit and helmet were essentially separate pressurized chambers, but the helmet had a suffocation valve that would allow for air passage into the helmet from the suit in an event of depressurization [25]. The equipment module included the life support and electronic support machinery which was primarily located in a large chest plate. The oxygen supply used a demand regulated system similar to SCUBA systems, where gas is supplied only when the pilot takes a breath and is not free flowing. Oxygen use was calculated beforehand based on suit pressure, suit temperature and pilot metabolic rate (breathing rate) during the various stages of the flight process. The oxygen cylinders used were modified standard aerospace composite cylinders [25]. The thermoregulatory system used a cartridge heater to heat a water-based fluid which was then pumped through a liquid thermal garment in order warm the pilot at high altitudes and cool the pilot while on the ground. This liquid cooling system was also used to help regulate the temperature of the electronic systems housed in the equipment module. This module also housed a power supply along with the voice and data communications hardware. The main parachute design was based on the Sigma tandem system, the most widely used tandem parachute [25]. These parachutes are normally built to support an instructor/student pair weighing up to 500 lbs, and fulfilled the needs of the StratEx system which weighed approximately 430 lbs (including the pilot). The parachute pack also acted as a suspension point during ascent, which provided the ideal 45° angle. The ascent balloon was similar to those used previously, however was much larger than Stratos, reaching 400 ft high at launch and spanned 275 ft in diameter at the maximum altitude [25].

providing wealthy ticketed passengers a few days of space training camp to then board a private spacecraft and float weightless for several minutes before returning to earth [27, 28]. In 2011, NASA began to lose much of United States government funding and was forced to shut down many programs and projects [29]. The new budget set forth by President Obama cut out the Constellation program, canceling the creation of the Orion spacecraft and Ares rockets. These crafts were supposed to replace NASA's three space shuttles which were set to retire that year. This effectively ended the shuttle missions, and NASA became more dependent on Russian colleagues for transport to the ISS, where they continued to perform many active research projects [30]. During this time the government has attempted to facilitate formation of the commercial space industry by providing only loose regulations, allowing an extended 'learning period' in order to support growth and practice of the

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The first commercial aerospace vehicle, known as SpaceShip One, reached space in 2004. Developed by a Paul Allen (cofounder of Microsoft), in partnership with Burt Rutan, the project won the Ansari X contest which came with a 10 million dollar prize [27]. Their company, Vulcan Aerospace, has since begun building Stratolaunch, set to be the world's largest airplane with a wingspan wider than a football field, including the end zones. It is designed to carry a rocket tethered to its belly to an altitude of 35,000 ft, which then drops away and fires

Space X, another growing commercial space company, was founded by Elon Musk, who made his first fortune on Zip2 and Paypal. However, Musk's dream extends beyond many other companies, with his main focus on eventual transport to Mars [27]. His goal is to build a 'Union Pacific' to Mars which would open entrepreneurial opportunities to anyone willing to make the journey. The initial plan of the company was to have its first unmanned flight to Mars by 2019, which would make Space X the first commercial space flight company to dare such a feat [27]. He also stated his next goal would be to execute a manned landing on Mars within the following 20 years [31]. Up to this point only 18 of the 43 robotic missions to Mars

Some of the newly developed technology from Space X includes the Dragon Spacecraft (**Figure 7**), selected as one of five competitors for NASA's commercial orbital transportation service to take astronauts to the International Space Station (ISS). With the NASA contract, Space X is granted the ability to use Kennedy Space Center's Launch Complex 39A, the same complex that launched Neil Armstrong and Buzz Aldrin to the moon in 1969 [27]. Following the discontinuation of NASA's shuttle program, US astronauts have become increasingly reliant on Russian flights for this transport service. The Dragon Spacecraft is approximately 9.5 ft in height, 11.8 ft in diameter, and weighs 9260 pounds. It contains a solar array, giving the

companies [27].

*4.1.2. Space X*

*4.1.1. Vulcan Aerospace*

**4.1. Commercial space companies**

its engines to perform an 'air-launch' into orbit [27].

have been successful, including flybys [27].

A total of five test runs were performed, the second of which had to be aborted due to rising suit pressures caused by freezing with in the pressure control device [25]. The mission successfully concluded on October 24, 2014, when Eustace ascended to an altitude of 136,410 ft (41.5 km), and was released at 135,897 ft (41.4 km) to take the 9 min and 52 s ride back to earth. His free fall lasted 4 min and 27 s and spanned over 123,435 ft (37.6 m) [24].

### **3.7. Emergency medical planning for high altitude missions**

The principles of medical coverage for this type of mission revolve around planning for the conventional expected injuries of a traumatic accident and well as those injuries specific to high altitude exposure. Medical conditions like those listed above are not routinely covered in medical training, so having a team of professionals familiar with the management of those specific injuries is paramount. Given the potential variability in landing location based on ascent time, wind speed and direction, as well as responding to emergency bail outs, having multiple recovery crews in a variety of vehicles is ideal. For instance, the StratEx mission utilized four vehicle chase teams, including two ground teams driving Suburbans, a helicopter and a fixed wing aircraft, which would deploy an additional parachutist to assist the StratEx pilot to identify a landing zone (limited sight due to the helmet design made clear ground views challenging) [24]. A central Mission Control coordinated these field teams, monitored all communications and worked to anticipate and mitigate any failures throughout the mission [26]. All chase teams included a combination of suit technicians, who specialized in rapid removal of the pressure suit, and volunteer medical personnel (mainly physicians and EMS) who were prepared with large selections of equipment to rapidly stabilize a downed pilot [24]. Each chase team had redundant means of communication including cell phones, laptops and tablets, in case of poor cellular signal [26]. Due to the well-supported utility of ultrasound in remote environments, two machines were carried along with the chase teams in order to perform a rapid, pre-specified, diagnostic and therapeutic assessment in the worst case scenario of an unstable, unconscious pilot [12]. One of the greatest challenges of these high altitude flights is the austere location of the launches in relation to medical facilities. The StratEx flight launched at a remote location in New Mexico, 500 miles from the closest hyperbaric chamber and 175 miles from the nearest level 1 trauma center [24]. Air transport was available in case of severe injury, but actual transport time was still daunting [26].

### **4. Commercial space industry**

With the broadening scope of these high altitude missions, a new kind of space race has taken the Earth by storm, full of wealthy entrepreneurs who are now leading the commercial space industry [27]. In the 1980s two companies, Society Expeditions and Space Travel, proposed to NASA to begin offering passenger tickets aboard the space shuttle, but both were rejected. Through time, the once imagined concept of 'orbital space tourism' slowly shifted to 'suborbital space tourism', and the idea of experiencing longer time in lower earth orbit became a more feasible business strategy [28]. From that dream, companies emerged with the goal of providing wealthy ticketed passengers a few days of space training camp to then board a private spacecraft and float weightless for several minutes before returning to earth [27, 28].

In 2011, NASA began to lose much of United States government funding and was forced to shut down many programs and projects [29]. The new budget set forth by President Obama cut out the Constellation program, canceling the creation of the Orion spacecraft and Ares rockets. These crafts were supposed to replace NASA's three space shuttles which were set to retire that year. This effectively ended the shuttle missions, and NASA became more dependent on Russian colleagues for transport to the ISS, where they continued to perform many active research projects [30]. During this time the government has attempted to facilitate formation of the commercial space industry by providing only loose regulations, allowing an extended 'learning period' in order to support growth and practice of the companies [27].

#### **4.1. Commercial space companies**

#### *4.1.1. Vulcan Aerospace*

those used previously, however was much larger than Stratos, reaching 400 ft high at launch

A total of five test runs were performed, the second of which had to be aborted due to rising suit pressures caused by freezing with in the pressure control device [25]. The mission successfully concluded on October 24, 2014, when Eustace ascended to an altitude of 136,410 ft (41.5 km), and was released at 135,897 ft (41.4 km) to take the 9 min and 52 s ride back to earth.

The principles of medical coverage for this type of mission revolve around planning for the conventional expected injuries of a traumatic accident and well as those injuries specific to high altitude exposure. Medical conditions like those listed above are not routinely covered in medical training, so having a team of professionals familiar with the management of those specific injuries is paramount. Given the potential variability in landing location based on ascent time, wind speed and direction, as well as responding to emergency bail outs, having multiple recovery crews in a variety of vehicles is ideal. For instance, the StratEx mission utilized four vehicle chase teams, including two ground teams driving Suburbans, a helicopter and a fixed wing aircraft, which would deploy an additional parachutist to assist the StratEx pilot to identify a landing zone (limited sight due to the helmet design made clear ground views challenging) [24]. A central Mission Control coordinated these field teams, monitored all communications and worked to anticipate and mitigate any failures throughout the mission [26]. All chase teams included a combination of suit technicians, who specialized in rapid removal of the pressure suit, and volunteer medical personnel (mainly physicians and EMS) who were prepared with large selections of equipment to rapidly stabilize a downed pilot [24]. Each chase team had redundant means of communication including cell phones, laptops and tablets, in case of poor cellular signal [26]. Due to the well-supported utility of ultrasound in remote environments, two machines were carried along with the chase teams in order to perform a rapid, pre-specified, diagnostic and therapeutic assessment in the worst case scenario of an unstable, unconscious pilot [12]. One of the greatest challenges of these high altitude flights is the austere location of the launches in relation to medical facilities. The StratEx flight launched at a remote location in New Mexico, 500 miles from the closest hyperbaric chamber and 175 miles from the nearest level 1 trauma center [24]. Air transport was available in case of severe injury, but actual transport time was still daunting [26].

With the broadening scope of these high altitude missions, a new kind of space race has taken the Earth by storm, full of wealthy entrepreneurs who are now leading the commercial space industry [27]. In the 1980s two companies, Society Expeditions and Space Travel, proposed to NASA to begin offering passenger tickets aboard the space shuttle, but both were rejected. Through time, the once imagined concept of 'orbital space tourism' slowly shifted to 'suborbital space tourism', and the idea of experiencing longer time in lower earth orbit became a more feasible business strategy [28]. From that dream, companies emerged with the goal of

and spanned 275 ft in diameter at the maximum altitude [25].

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**3.7. Emergency medical planning for high altitude missions**

**4. Commercial space industry**

His free fall lasted 4 min and 27 s and spanned over 123,435 ft (37.6 m) [24].

The first commercial aerospace vehicle, known as SpaceShip One, reached space in 2004. Developed by a Paul Allen (cofounder of Microsoft), in partnership with Burt Rutan, the project won the Ansari X contest which came with a 10 million dollar prize [27]. Their company, Vulcan Aerospace, has since begun building Stratolaunch, set to be the world's largest airplane with a wingspan wider than a football field, including the end zones. It is designed to carry a rocket tethered to its belly to an altitude of 35,000 ft, which then drops away and fires its engines to perform an 'air-launch' into orbit [27].

### *4.1.2. Space X*

Space X, another growing commercial space company, was founded by Elon Musk, who made his first fortune on Zip2 and Paypal. However, Musk's dream extends beyond many other companies, with his main focus on eventual transport to Mars [27]. His goal is to build a 'Union Pacific' to Mars which would open entrepreneurial opportunities to anyone willing to make the journey. The initial plan of the company was to have its first unmanned flight to Mars by 2019, which would make Space X the first commercial space flight company to dare such a feat [27]. He also stated his next goal would be to execute a manned landing on Mars within the following 20 years [31]. Up to this point only 18 of the 43 robotic missions to Mars have been successful, including flybys [27].

Some of the newly developed technology from Space X includes the Dragon Spacecraft (**Figure 7**), selected as one of five competitors for NASA's commercial orbital transportation service to take astronauts to the International Space Station (ISS). With the NASA contract, Space X is granted the ability to use Kennedy Space Center's Launch Complex 39A, the same complex that launched Neil Armstrong and Buzz Aldrin to the moon in 1969 [27]. Following the discontinuation of NASA's shuttle program, US astronauts have become increasingly reliant on Russian flights for this transport service. The Dragon Spacecraft is approximately 9.5 ft in height, 11.8 ft in diameter, and weighs 9260 pounds. It contains a solar array, giving the

*4.1.3. Blue Origin*

*4.1.4. Virgin Galactic*

Another giant of the commercial space industry is Blue Origin, founded by Jeff Bezos who made his fortune as founder, chairman and chief executive officer of Amazon.com and in 2013 purchased Washington Post. There appears to be some tension between Blue Origin and Space X, and Bezos and Musk have been known to make harsh comments about each other's accomplishments. The focus of Bezos' company is more to reduce the cost and increase the reliability of the commercial spacecraft, intended to open the opportunity for a suborbital experience to a greater consumer market [27]. His goal is to 'build a highway to lower orbit' so that contemporary infrastructure can be used by the next generation's entrepreneurs to further develop new technology and expand the space market. Blue Origin's rockets are designed to be fully reusable and can achieve a maximum altitude of 62.4 miles [27]. Their first unmanned test flight took place in April 2015, achieving an altitude of 93 km (57.8 miles) and speed of Mach 3. Since then, the same booster has been reflown four times during subsequent test flights from their secured launch space in Cape Canaveral [28]. However, Blue Origin has yet to send a rocket into space, and does not currently possess a rocket that is qualified to carry people [27].

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Virgin Galactic, a competitive entity in the commercial space industry, was developed by Richard Branson. Their spaceport is located in New Mexico, and Branson's stated goal is to be the first large volume commercial space line [27]. The company's main spacecraft is the SS2/ WK2, a combination spacecraft and mothership design. The SS2 is an air-launched glider with capacity to carry six passengers and two pilots, and contains a rocket motor and extra systems for spaceflight [28]. Some 700 people jumped on the company's pre-sale tickets, some paying as much as \$250,000. However, a tragic accident in 2014 involving one of their aircraft led to many delays in the planned flights [27, 28]. The incident occurred in California's Mojave Desert, involving a test pilot who was operating one of Virgin Galactic's newest spacecraft, SpaceShip Two [28]. According to the official report released by the National Transportation Safety Board, the pilot was believed to have unlocked the spaceship's 'feather system' prematurely, causing the vehicle to break apart in-flight, killing both the pilot and co-pilot [28, 33]. Three years from that tragic day, Virgin Galactic has yet to test any further powered spacecraft flights. Its newest vehicle, Spaceship Unity, has performed only a small number of glide flights. The company anticipates returning to unmanned, powered flights in late 2017 or early 2018. During the downtime, Virgin Galactic created a spin-off company called Virgin Orbit, which develops airlaunched platforms for small satellites, with plans to begin launching 300 kg missions to Earth's lower orbit by 2018 [33]. The ultimate goal of Virgin Orbit is to distribute satellites around the solar system, starting with the low-Earth orbit constellation [33, 34]. This constellation will be part of the larger SpaceBelt satellite system, and will serve as a space-based data storage network. The company plans the first rocket test in 2018, using the Boeing 747-400 as part of its two-stage LauncherOne system, providing both an expendable and reusable air-launched platform [34].

*4.1.5. Sierra Nevada Corporation, XCOR and other commercial space startups*

There are a number of other smaller commercial space flight companies vying for position in this competitive market. Newer engineering including electronics miniaturization, advanced

**Figure 7.** SpaceX's Dragon spacecraft pictured in Orbit.

aircraft a longer in-orbit duration which allows it to remain on the ISS for 1 week with astronauts aboard, or 1 year with only cargo aboard [31].

Space X has also developed a new rocket system. Their Falcon Heavy rockets (**Figure 8**) are designed to be twice as powerful as others currently in use, and can reach a maximum altitude of 75.8 miles. The goal for these rockets is to achieve high altitude and then arc parallel to the Earth's surface at 5 miles per second in order to stay aloft, which would allow them to circle the Earth in less time than it takes to watch a Star Wars movie [27]. However, their story has been laced with challenges. In 2016 one of the Falcon 9 rockets intended to transport cargo to the ISS incurred a malfunction which caused it to explode on the launchpad. That incident led the company to delay all further launches for 6 months, and created a backlog of over 70 missions, costing the company more than 10 billion dollars in revenue [27]. According to Musk, the company hopes to send two civilians around the moon in late 2018. Musk reportedly said this was "an important milestone as we work towards our ultimate goal of transporting humans to Mars" [32].

**Figure 8.** SpaceX's Falcon 9 v1.1 rocket being wheeled to the Cape Canaveral Space Launch Complex in preparation for the April 27, 2015 launch.

#### *4.1.3. Blue Origin*

Another giant of the commercial space industry is Blue Origin, founded by Jeff Bezos who made his fortune as founder, chairman and chief executive officer of Amazon.com and in 2013 purchased Washington Post. There appears to be some tension between Blue Origin and Space X, and Bezos and Musk have been known to make harsh comments about each other's accomplishments. The focus of Bezos' company is more to reduce the cost and increase the reliability of the commercial spacecraft, intended to open the opportunity for a suborbital experience to a greater consumer market [27]. His goal is to 'build a highway to lower orbit' so that contemporary infrastructure can be used by the next generation's entrepreneurs to further develop new technology and expand the space market. Blue Origin's rockets are designed to be fully reusable and can achieve a maximum altitude of 62.4 miles [27]. Their first unmanned test flight took place in April 2015, achieving an altitude of 93 km (57.8 miles) and speed of Mach 3. Since then, the same booster has been reflown four times during subsequent test flights from their secured launch space in Cape Canaveral [28]. However, Blue Origin has yet to send a rocket into space, and does not currently possess a rocket that is qualified to carry people [27].

#### *4.1.4. Virgin Galactic*

**Figure 8.** SpaceX's Falcon 9 v1.1 rocket being wheeled to the Cape Canaveral Space Launch Complex in preparation for

aircraft a longer in-orbit duration which allows it to remain on the ISS for 1 week with astro-

Space X has also developed a new rocket system. Their Falcon Heavy rockets (**Figure 8**) are designed to be twice as powerful as others currently in use, and can reach a maximum altitude of 75.8 miles. The goal for these rockets is to achieve high altitude and then arc parallel to the Earth's surface at 5 miles per second in order to stay aloft, which would allow them to circle the Earth in less time than it takes to watch a Star Wars movie [27]. However, their story has been laced with challenges. In 2016 one of the Falcon 9 rockets intended to transport cargo to the ISS incurred a malfunction which caused it to explode on the launchpad. That incident led the company to delay all further launches for 6 months, and created a backlog of over 70 missions, costing the company more than 10 billion dollars in revenue [27]. According to Musk, the company hopes to send two civilians around the moon in late 2018. Musk reportedly said this was "an important milestone as we work towards our ultimate goal of transporting humans

nauts aboard, or 1 year with only cargo aboard [31].

244 Into Space - A Journey of How Humans Adapt and Live in Microgravity

**Figure 7.** SpaceX's Dragon spacecraft pictured in Orbit.

the April 27, 2015 launch.

to Mars" [32].

Virgin Galactic, a competitive entity in the commercial space industry, was developed by Richard Branson. Their spaceport is located in New Mexico, and Branson's stated goal is to be the first large volume commercial space line [27]. The company's main spacecraft is the SS2/ WK2, a combination spacecraft and mothership design. The SS2 is an air-launched glider with capacity to carry six passengers and two pilots, and contains a rocket motor and extra systems for spaceflight [28]. Some 700 people jumped on the company's pre-sale tickets, some paying as much as \$250,000. However, a tragic accident in 2014 involving one of their aircraft led to many delays in the planned flights [27, 28]. The incident occurred in California's Mojave Desert, involving a test pilot who was operating one of Virgin Galactic's newest spacecraft, SpaceShip Two [28]. According to the official report released by the National Transportation Safety Board, the pilot was believed to have unlocked the spaceship's 'feather system' prematurely, causing the vehicle to break apart in-flight, killing both the pilot and co-pilot [28, 33].

Three years from that tragic day, Virgin Galactic has yet to test any further powered spacecraft flights. Its newest vehicle, Spaceship Unity, has performed only a small number of glide flights. The company anticipates returning to unmanned, powered flights in late 2017 or early 2018. During the downtime, Virgin Galactic created a spin-off company called Virgin Orbit, which develops airlaunched platforms for small satellites, with plans to begin launching 300 kg missions to Earth's lower orbit by 2018 [33]. The ultimate goal of Virgin Orbit is to distribute satellites around the solar system, starting with the low-Earth orbit constellation [33, 34]. This constellation will be part of the larger SpaceBelt satellite system, and will serve as a space-based data storage network. The company plans the first rocket test in 2018, using the Boeing 747-400 as part of its two-stage LauncherOne system, providing both an expendable and reusable air-launched platform [34].

#### *4.1.5. Sierra Nevada Corporation, XCOR and other commercial space startups*

There are a number of other smaller commercial space flight companies vying for position in this competitive market. Newer engineering including electronics miniaturization, advanced design of stronger and lighter materials, and new standards make it feasible for many of these developing companies to enter a market previously available only to those with the billionaires' backing. From 2007 to 2017, roughly 115 space-related companies were founded, with nearly 84 focusing on satellite technology [35]. The development of newer "microsatellites", weighing as little as 22–220 pounds, and "nanosatellites" which weigh less than 22 pounds, are sold by many of these companies. Roughly 2400 are projected to be launched within the next 6 years. The Cubesat is one satellite example, which weighs two pounds, is the size of a baseball and costs less than \$100,000 to build [35].

ing process for these aircraft. However, the actual two-seated rocket that XCOR plans to use

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Naveen Jain, another visionary, plans to launch the Moon Express in late 2017 in an attempt to win Google's Lunar Xprize, a \$20 million award for the first company to successfully land a robotic spacecraft on the moon and accomplish a variety of technical challenges. After landing, the Moon Express will need to extract iron ore, water, minerals and precious metals from the lunar soil, as well as capture nitrogen and hydrogen. Jain's vision is that the moon will one day become a fuel

Robert Bigelow, owner of Bigelow Aerospace which produces inflatable space habitats, has a similar vision. He even asked for government assistance to develop a 'lunar depot' that orbits the moon to allow for easier access to the lunar surface [39]. His company is currently testing a prototype, Bigelow Expandable Activity Module on the ISS, and has demonstrated free-flying prototypes in orbit. This could potentially give Bigelow a huge future advantage in the area

Interorbital Systems, a small 12-person operation, is also based in the Mojave desert. Cofounders Roderick and Rnada Milliron started the company with the personal goal to eventually live on the moon. They also plan to compete for the Lunar XPrize. Currently, Interorbital Systems primarily sells satellites, with plans to launch more than 100 in the next year to provide revenue for equipment needed to achieve their moon landing goal [35].

Considering these commercial space industry startups, where will the next decades take us? Axiom Space, a Houston-based company, has partnered with Made In Space, a California company that specializes in 3D printing products. This partnership is intended to help facilitate Axiom's goal to develop a commercial version of the ISS, proposed as an outpost for private individuals and companies to conduct research and space exploration [40]. Its ultimate purpose is to help grow the space-tourism business. Made In Space's involvement is to expedite the logistics of creating an actual in-space factory that can produce equipment without the burden of transport from Earth's surface to the station [40]. Axiom has NASA backing; the current ISS has available funding currently to carry only through 2024. The full ISS expense cannot be overlooked; each day an astronaut is housed on the ISS costs roughly \$7.5 million. The hope is that this deadline will be extended by at least 4 years, however there is a looming possibility that this extraordinary \$100 billion structure will be brought down from orbit just over 25 years following its initial launch [35]. Axiom's current plan is to attach its first commercial module directly to the ISS in 2020. Upon ISS decommissioning, the module would

Beyond a commercial ISS, plans to place orbital hotels have been the dream of many countries for some time. Consider the Space Hotel Berlin and Space Hotel Europe, which share a similar circular design with individual pods on the perimeter; each would provide accommodation for about 50 tourists [41]. A group from MIT won a NASA sponsored competition in early 2017 by designing a luxury space hotel purposed to help offset the cost of NASA research

detach and begin formation of the Axiom commercial space station [35].

depot for spacecraft to dock and resupply before heading out on longer journey's [35].

remains under development in their Mojave, CA warehouse [38].

of space tourism hotels.

**4.2. Future of commercial space industry**

Sierra Nevada Corporation (SNC) Space exploration a model company, with its Dream Chaser spacecraft (**Figure 9**) [28]. This winged spacecraft will reportedly allow for flexible, trustworthy, and affordable transport. This craft won NASA's Commercial Crew Integrated Capability award in 2012 as a potential spacecraft to provide transport of crews to the ISS, however SNC did not win NASA's commercial crew contract in 2014. The craft experienced some issues during a 2013 test flight in which the landing gear failed to deploy and sent the craft skidding off the runway after landing. Despite this setback, the company continued development of the a Dream Chaser cargo version and secured a Commercial Resupply Services-2 contract with NASA as one of three companies (including SpaceX's Dragon) to deliver cargo to and from the ISS from 2019 to 2024 [36]. SNC partnered with the United Launch Alliance, announcing in 2017 that they would employ the use of the Atlas 5 rocket, which includes 5 strap-on boosters and a twin engine upper stage, to send the first two Dream Chaser cargo aircraft to the ISS in 2020 and 2021. Utilizing these powerful rockets, the aircraft will be able to deliver nearly 12,000 pounds (5500 kg) of equipment and supplies on each non-piloted mission [37].

XCOR is a smaller commercial spaceflight company whose primary focus is a higher tempo flight operation. Their spacecraft, the Lynx Suborbital Vehicle, is a two seated, piloted transport with room for one pilot and one passenger or a specified payload [38]. XCOR plans to have a fast flight turnaround time and will prioritize low cost operations with minimal maintenance necessary for the fully reusable rockets between flights. This would potentially allow their goal of offering up to four flights per day. They are the first, and at the present time, the only, company to have successfully passed the Federal Aviation Administration's licens-

**Figure 9.** Dream Chaser spacecraft being lifted by an Erickson Air-Crane helicopter during a captive-carry flight test.

ing process for these aircraft. However, the actual two-seated rocket that XCOR plans to use remains under development in their Mojave, CA warehouse [38].

Naveen Jain, another visionary, plans to launch the Moon Express in late 2017 in an attempt to win Google's Lunar Xprize, a \$20 million award for the first company to successfully land a robotic spacecraft on the moon and accomplish a variety of technical challenges. After landing, the Moon Express will need to extract iron ore, water, minerals and precious metals from the lunar soil, as well as capture nitrogen and hydrogen. Jain's vision is that the moon will one day become a fuel depot for spacecraft to dock and resupply before heading out on longer journey's [35].

Robert Bigelow, owner of Bigelow Aerospace which produces inflatable space habitats, has a similar vision. He even asked for government assistance to develop a 'lunar depot' that orbits the moon to allow for easier access to the lunar surface [39]. His company is currently testing a prototype, Bigelow Expandable Activity Module on the ISS, and has demonstrated free-flying prototypes in orbit. This could potentially give Bigelow a huge future advantage in the area of space tourism hotels.

Interorbital Systems, a small 12-person operation, is also based in the Mojave desert. Cofounders Roderick and Rnada Milliron started the company with the personal goal to eventually live on the moon. They also plan to compete for the Lunar XPrize. Currently, Interorbital Systems primarily sells satellites, with plans to launch more than 100 in the next year to provide revenue for equipment needed to achieve their moon landing goal [35].

#### **4.2. Future of commercial space industry**

**Figure 9.** Dream Chaser spacecraft being lifted by an Erickson Air-Crane helicopter during a captive-carry flight test.

design of stronger and lighter materials, and new standards make it feasible for many of these developing companies to enter a market previously available only to those with the billionaires' backing. From 2007 to 2017, roughly 115 space-related companies were founded, with nearly 84 focusing on satellite technology [35]. The development of newer "microsatellites", weighing as little as 22–220 pounds, and "nanosatellites" which weigh less than 22 pounds, are sold by many of these companies. Roughly 2400 are projected to be launched within the next 6 years. The Cubesat is one satellite example, which weighs two pounds, is the size of a

Sierra Nevada Corporation (SNC) Space exploration a model company, with its Dream Chaser spacecraft (**Figure 9**) [28]. This winged spacecraft will reportedly allow for flexible, trustworthy, and affordable transport. This craft won NASA's Commercial Crew Integrated Capability award in 2012 as a potential spacecraft to provide transport of crews to the ISS, however SNC did not win NASA's commercial crew contract in 2014. The craft experienced some issues during a 2013 test flight in which the landing gear failed to deploy and sent the craft skidding off the runway after landing. Despite this setback, the company continued development of the a Dream Chaser cargo version and secured a Commercial Resupply Services-2 contract with NASA as one of three companies (including SpaceX's Dragon) to deliver cargo to and from the ISS from 2019 to 2024 [36]. SNC partnered with the United Launch Alliance, announcing in 2017 that they would employ the use of the Atlas 5 rocket, which includes 5 strap-on boosters and a twin engine upper stage, to send the first two Dream Chaser cargo aircraft to the ISS in 2020 and 2021. Utilizing these powerful rockets, the aircraft will be able to deliver nearly

12,000 pounds (5500 kg) of equipment and supplies on each non-piloted mission [37].

XCOR is a smaller commercial spaceflight company whose primary focus is a higher tempo flight operation. Their spacecraft, the Lynx Suborbital Vehicle, is a two seated, piloted transport with room for one pilot and one passenger or a specified payload [38]. XCOR plans to have a fast flight turnaround time and will prioritize low cost operations with minimal maintenance necessary for the fully reusable rockets between flights. This would potentially allow their goal of offering up to four flights per day. They are the first, and at the present time, the only, company to have successfully passed the Federal Aviation Administration's licens-

baseball and costs less than \$100,000 to build [35].

246 Into Space - A Journey of How Humans Adapt and Live in Microgravity

Considering these commercial space industry startups, where will the next decades take us? Axiom Space, a Houston-based company, has partnered with Made In Space, a California company that specializes in 3D printing products. This partnership is intended to help facilitate Axiom's goal to develop a commercial version of the ISS, proposed as an outpost for private individuals and companies to conduct research and space exploration [40]. Its ultimate purpose is to help grow the space-tourism business. Made In Space's involvement is to expedite the logistics of creating an actual in-space factory that can produce equipment without the burden of transport from Earth's surface to the station [40]. Axiom has NASA backing; the current ISS has available funding currently to carry only through 2024. The full ISS expense cannot be overlooked; each day an astronaut is housed on the ISS costs roughly \$7.5 million. The hope is that this deadline will be extended by at least 4 years, however there is a looming possibility that this extraordinary \$100 billion structure will be brought down from orbit just over 25 years following its initial launch [35]. Axiom's current plan is to attach its first commercial module directly to the ISS in 2020. Upon ISS decommissioning, the module would detach and begin formation of the Axiom commercial space station [35].

Beyond a commercial ISS, plans to place orbital hotels have been the dream of many countries for some time. Consider the Space Hotel Berlin and Space Hotel Europe, which share a similar circular design with individual pods on the perimeter; each would provide accommodation for about 50 tourists [41]. A group from MIT won a NASA sponsored competition in early 2017 by designing a luxury space hotel purposed to help offset the cost of NASA research through commercial rental income [42]. The project, known as the Managed, Reconfigurable, In-space Nodal Assembly (MARINA), would be commercially owned and include a luxury hotel to serve as the primary anchor and a separate hub to serve as a temporarily co-anchor for NASA. The innovative aspect of MARINA is the external International Docking Adapter ports which allow modular service pods to connect to various points and, if standardized among space vehicles, would allow companies of all sizes to provide and request products and services from other companies in space [42].

[3] Grocott MPW, Martin DS, Levett DZH, McMorrow R, Windsor J, Montgomery HE Arterial blood gases and oxygen content in climbers on Mount Everest. The New England Journal of Medicine [Internet]. 2009 Jan 8;**360**(2):140-149. Available from: http://

Exploring the Stratosphere: What We Missed by Shooting for the Moon

http://dx.doi.org/10.5772/intechopen.73602

249

[4] Mott N. Supersonic skydive's 5 biggest risks: Boiling blood, deadly spins and worse. National Geographic [Internet]. 2010 Oct. Available from: https://news.nationalgeographic.com/news/2012/10/121005-felix-baumgartner-skydive-science-sound-barrier-

[5] The Great Leap Forward. Wired [Internet]. 2001 Aug. Available from: https://www.wired.

[6] Cohen JE, Small C. Hypsographic demography: The distribution of human population by altitude. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 1998;**95**(24):14009-14014. Available from: http://www.pnas.org/con-

[7] West JB. Barometric pressures on Mt. Everest: New data and physiological significance.

[9] Murray DH, Pilmanis AA, Blue RS, Pattarini JM, Law J, Bayne CG, et al. Pathophysiology, prevention, and treatment of ebullism. Aviation, Space, and Environmental Medicine.

[10] Stegmann B. Considerations for the Survival of Ebullism [Internet]. Fairborn, OH: Wright State University; 1989. Available from: http://www.geoffreylandis.com/ebullism.

[11] Parker JF, West VR. Bioastronautics Data Book. 2nd ed. Arlington, VA: National

[12] Galdamez LA, Clark JB, Antonsen EL. Point-of-care ultrasound utility and potential for high altitude crew recovery missions. Aerosp Med Hum Perform. 2017 Feb;**88**(2):128-136

[13] Stewart LH, Trunkey D, Rebagliati GS. Emergency medicine in space. The Journal of Emergency Medicine [Internet]. 2007 Jan 1 [cited 2017 Dec 6];**32**(1):45-54. Available from:

[14] Pilmanis AA, Sears WJ. Physiological hazards of flight at high altitude. Lancet (London, England) [Internet]. 2003 Dec 1 [cited 2017 Dec 10];**362**(Suppl):s16-s17. Available from:

[15] Jacobs SE. Pressure suit design for commercial spaceflight: Lessons learned from Red Bull Stratos. In: 43rd International Conference on Environmental Systems [Internet]. Reston, Virginia: American Institute of Aeronautics and Astronautics; 2013 [cited 2017

Oct 23]. Available from: http://arc.aiaa.org/doi/10.2514/6.2013-3398

[8] Myers RL. The Basics of Physics. Westport, CT: Greenwood Press; 2006. pp. 113-120

Journal of Applied Physiology. 1999 Mar;**86**(3):1062-1066

Aeronautics and Space Administration; 1973

http://www.ncbi.nlm.nih.gov/pubmed/17239732

http://www.ncbi.nlm.nih.gov/pubmed/14698113

dx.doi.org/10.1056/NEJMoa0801581

joseph-kittinger/

com/2001/08/scale/

tent/95/24/14009.full.pdf

2013;**84**(2):89-96

html

### **5. Conclusion**

Twenty-first century space exploration has transformed and taken on new meaning. What was once thought to be travel only to the moon or nearby planets now includes stratospheric exploration and commercial high atmosphere flights. Experiences available to only a select group of people with years of advanced training, are now close to being offered to a much wider group of eager customers.

Human ingenuity prevails yet again; we have developed technology to keep us safe in one of the most hostile environments of our home planet. As we continue to explore, we must never lose the sense of awe and respect for those visionary pilots and adventurers that helped us better understand and appreciate this aspect of our Earth. As Col. Joseph Kittinger said upon landing from his final mission: "Now that I am safely down, I realize once again how dependent upon the protection of the Almighty are all seekers of the unknown" [21].

### **Conflict of interest**

There are no conflicts of interest to declare.

### **Author details**

Laura Galdamez

Address all correspondence to: laura@outdoorem.com

Department of Emergency Medicine, Baylor College of Medicine, Houston, TX, United States of America

### **References**


[3] Grocott MPW, Martin DS, Levett DZH, McMorrow R, Windsor J, Montgomery HE Arterial blood gases and oxygen content in climbers on Mount Everest. The New England Journal of Medicine [Internet]. 2009 Jan 8;**360**(2):140-149. Available from: http:// dx.doi.org/10.1056/NEJMoa0801581

through commercial rental income [42]. The project, known as the Managed, Reconfigurable, In-space Nodal Assembly (MARINA), would be commercially owned and include a luxury hotel to serve as the primary anchor and a separate hub to serve as a temporarily co-anchor for NASA. The innovative aspect of MARINA is the external International Docking Adapter ports which allow modular service pods to connect to various points and, if standardized among space vehicles, would allow companies of all sizes to provide and request products

Twenty-first century space exploration has transformed and taken on new meaning. What was once thought to be travel only to the moon or nearby planets now includes stratospheric exploration and commercial high atmosphere flights. Experiences available to only a select group of people with years of advanced training, are now close to being offered to a much wider group of eager customers. Human ingenuity prevails yet again; we have developed technology to keep us safe in one of the most hostile environments of our home planet. As we continue to explore, we must never lose the sense of awe and respect for those visionary pilots and adventurers that helped us better understand and appreciate this aspect of our Earth. As Col. Joseph Kittinger said upon landing from his final mission: "Now that I am safely down, I realize once again how depen-

dent upon the protection of the Almighty are all seekers of the unknown" [21].

Department of Emergency Medicine, Baylor College of Medicine, Houston, TX,

[1] Kirkpatrick R. 1969: The Year Everything Changed. New York: Skyhorse Publishing;

[2] Zhu X. Radiative damping revisited: Parameterization of damping rate in the middle atmosphere. Journal of the Atmospheric Sciences [Internet]. 1993 Sep 1;**50**(17):3008-3021. Available from: https://doi.org/10.1175/1520-0469(1993)050%3C3008:RDRPOD%3E2.0.CO

and services from other companies in space [42].

248 Into Space - A Journey of How Humans Adapt and Live in Microgravity

**5. Conclusion**

**Conflict of interest**

**Author details**

Laura Galdamez

**References**

2011

United States of America

There are no conflicts of interest to declare.

Address all correspondence to: laura@outdoorem.com


[16] Jenkins DR. Dressing for Altitude. Washington, DC: National Aeronautics and Space Administration; 2012. pp. 408-410

[30] Malik T. NASA grieves over canceled program [Internet]. NBC News. 2010. Available from: http://www.nbcnews.com/id/35209628/ns/technology\_and\_science-space/t/nasa-

Exploring the Stratosphere: What We Missed by Shooting for the Moon

http://dx.doi.org/10.5772/intechopen.73602

251

[32] Mosher D. Elon Musk: SpaceX is going to launch 2 space tourists "beyond the moon" [Internet]. Business Insider. 2017. Available from: http://www.businessinsider.com/

[33] Sheetz M. Virgin Galactic is returning to powered flights, CEO says, in a crucial next step for the spaceship company [Internet]. CNBC. 2017. Available from: https://www. cnbc.com/2017/09/07/virgin-galactic-ceo-company-is-returning-to-powered-flights.html

[34] Sheetz M. Virgin Orbit announces contract to launch a dozen Cloud Constellation satellites. CNBC [Internet]. 2017. Available from: https://www.cnbc.com/2017/09/14/virgin-

[35] Alsever J. Space startups are booming in the Mojave Desert. Fortune [Internet]. 2017. Available from: http://fortune.com/2017/02/20/space-startups-travel-satellites/

[36] Forest J. Sierra Nevada Corp. prepares for next round of Dream Chaser tests. Space News [Internet]. 2016 Jul. Available from: http://spacenews.com/sierra-nevada-

[37] Clark S. Sierra Nevada confirms ULA will launch first two Dream Chaser cargo missions. Spaceflight Now [Internet]. 2017 Jul. Available from: https://spaceflightnow. com/2017/07/22/sierra-nevada-awaiting-direction-from-nasa-confirms-ula-will-launch-

[38] Chang Y-W. The first decade of commercial space tourism. Acta Astronautica [Internet]. 2015 Mar 1 [cited 2017 Oct 23];**108**:79-91. Available from: http://www.sciencedirect.com/

[39] King L. The commercial space industry wants updated regulations, more aid. USA Today [Internet]. 2017 Apr 27. Available from: https://www.usatoday.com/story/news/ politics/2017/04/27/commecial-space-industry-wants-updated-regulations-more-aid/

[40] David L. Private space station coming soon? Company aiming for 2020 launch [Internet]. Space.com. 2017. Available from: https://www.space.com/35488-private-space-station-

[41] Reichert M. The future of space tourism. In: 50th International Astronautical Congress.

[42] Malone D. This space hotel design from MIT won NASA's graduate design competition. Building Design and Construction [Internet]. 2017. Available from: https://www.bdcnet-

work.com/space-hotel-design-mit-won-nasa's-graduate-design-competition

Amsterdam: American Institute of Aeronautics and Astronautics; 1999

orbit-announces-contract-to-launch-a-dozen-cloud-constellation-satellites.html

[31] Szondy D. SpaceX Dragon's ultimate mission is Mars colonization. New Atlas. 2012

grieves-over-canceled-program/#.Wi1iCEqnHD4

corp-prepares-for-next-round-of-dream-chaser-tests/

first-two-dream-chaser-cargo-missions/

science/article/pii/S0094576514005013

100948378/

2020-axiom-space.html

spacex-moon-mission-elon-musk-2017-2


[16] Jenkins DR. Dressing for Altitude. Washington, DC: National Aeronautics and Space

[17] Czarnik TR. Ebullism at 1 Million Feet: Surviving Rapid/Explosive Decompression.

[18] Graham RH. Technical features of the SR-71. In: SR-71 Revealed: The Inside Story.

[19] Sherman T. A deadly fall: 46 years ago, a Jersey daredevil died while trying to set record. The Star Ledger [Internet]. 2012 Oct 12. Available from: http://www.nj.com/news/index.

[20] McKay B, McKay K. Skydiving from space part II: Nick Piantanida's "magnificent failure" [Internet]. The Art of Manliness. 2010. Available from: http://www.artofmanliness. com/2010/10/07/skydiving-from-space-part-ii-nick-piantanidas-magnificent-failure/

[23] Shetty S. How working at Google led this man to jump from the stratrosphere. CNBC [Internet]. 2016. Available from: https://www.cnbc.com/2016/11/18/how-working-at-

[24] Menon AS, Jourdan D, Nusbaum DM, Garbino A, Buckland DM, Norton S, et al. Crew recovery and contingency planning for a manned stratospheric balloon flight – The StratEx program. Prehospital and Disaster Medicine [Internet]. 2016 Oct 30 [cited 2017 Oct 23];**31**(5):524-531. Available from: http://www.journals.cambridge.org/

[25] Leidich J, Maccagnano Z, McFatter D, Lee GR, Hahn N. StratEx pressure suit assembly design and performance. In: 45th International Conference on Environmental Systems [Internet]; 2015. Available from: https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/64411/

[26] Law J, Clark JB, Blue RS. Medical mission control planning and operations for a manned stratospheric flight test program. Space Operations Communicator. 2013;**10**(3):1-7 [27] Davenport C. The inside story of how billionaires are racing to take you to outer space.

[28] Chang Y, Chern J. Ups and downs of space tourism development in 60 years from moon register to spaceshiptwo CRASH. Acta Astronautica [Internet]. 2016 Oct 1 [cited 2017 Oct 23];**127**:533-541. Available from: http://www.sciencedirect.com/science/article/pii/

[29] Sykes MV. The Obama legacy in planetary exploration (Op-Ed) [Internet]. Space.com. 2014. Available from: https://www.space.com/24157-obama-legacy-in-planetary-explo-

Administration; 2012. pp. 408-410

250 Into Space - A Journey of How Humans Adapt and Live in Microgravity

abstract\_S1049023X16000601

The Washington Post. 2016 Aug 19

S0094576516300066

ration.html

Fairborn, OH: Wright State University; 1999

ssf/2012/10/a\_deadly\_fall\_46\_years\_ago\_a\_j.html

Minneapolis, MN: MBI Publishing Company; 1996. pp. 87-90

[21] Luce HR, editor. Fantastic catch in the sky. Life. 1960;**49**(9):20-24

google-led-this-man-to-jump-from-the-stratosphere.html

ICES\_2015\_submission\_138.pdf?sequence=1&isAllowed=y

[22] Walshe A, et. al. Red Bull Stratos Summit Report Final. Los Angeles; 2013


**Chapter 14**

**Provisional chapter**

**The Mortality of Space Explorers**

**The Mortality of Space Explorers**

DOI: 10.5772/intechopen.73603

Outer space exploration poses unique risks to human survival. Here, we review the cur‑ rent literature on United States astronauts and Soviet and Russian cosmonauts and pro‑ vide updated and original research findings. As in previous research, both astronauts and cosmonauts are shown to have reduced risk of death by natural causes, particularly from chronic diseases such as cardiovascular disease and cancer, compared with appro‑ priately matched general populations. Simultaneously, space explorers are at increased risk of death by external forces, particularly accidents such as plane crashes and space‑ craft accidents. In total, both astronauts and cosmonauts are at reduced risk of all-cause mortality in comparison to the general populations of the United States and Russia. However, in comparison to astronauts, cosmonauts have been at equal risk of accidental death, but increased risk of death by chronic disease. We conjecture that the lack of risk from chronic disease may be due to the excellent health and medical monitoring of space explorers coupled with the deliberate attempts to limit their radiation exposure levels below those that would be detrimental. The differences in the astronaut and cosmonaut mortality experiences are likely due to lifestyle factors and the background rates of mor‑

**Keywords:** astronauts, cosmonauts, mortality, cancer, cardiovascular

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

and reproduction in any medium, provided the original work is properly cited.

For nearly 60 years, space exploration has captured our imagination and advanced human knowledge. Yet, in many ways, our understanding of space exploration is in its infancy. This is particularly true regarding possible long-term health consequences of living and working in space. For example, it is unknown whether humans will be able to safely explore deep space, colonize other planets, or live indefinitely on space stations even within Earth's orbit.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Robert J. Reynolds and Steven M. Day

Robert J. Reynolds and Steven M. Day

http://dx.doi.org/10.5772/intechopen.73603

tality in the two nations.

**1. Introduction**

**Abstract**

#### **The Mortality of Space Explorers The Mortality of Space Explorers**

Robert J. Reynolds and Steven M. Day Robert J. Reynolds and Steven M. Day

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73603

#### **Abstract**

Outer space exploration poses unique risks to human survival. Here, we review the cur‑ rent literature on United States astronauts and Soviet and Russian cosmonauts and pro‑ vide updated and original research findings. As in previous research, both astronauts and cosmonauts are shown to have reduced risk of death by natural causes, particularly from chronic diseases such as cardiovascular disease and cancer, compared with appro‑ priately matched general populations. Simultaneously, space explorers are at increased risk of death by external forces, particularly accidents such as plane crashes and space‑ craft accidents. In total, both astronauts and cosmonauts are at reduced risk of all-cause mortality in comparison to the general populations of the United States and Russia. However, in comparison to astronauts, cosmonauts have been at equal risk of accidental death, but increased risk of death by chronic disease. We conjecture that the lack of risk from chronic disease may be due to the excellent health and medical monitoring of space explorers coupled with the deliberate attempts to limit their radiation exposure levels below those that would be detrimental. The differences in the astronaut and cosmonaut mortality experiences are likely due to lifestyle factors and the background rates of mor‑ tality in the two nations.

DOI: 10.5772/intechopen.73603

**Keywords:** astronauts, cosmonauts, mortality, cancer, cardiovascular

### **1. Introduction**

For nearly 60 years, space exploration has captured our imagination and advanced human knowledge. Yet, in many ways, our understanding of space exploration is in its infancy. This is particularly true regarding possible long-term health consequences of living and working in space. For example, it is unknown whether humans will be able to safely explore deep space, colonize other planets, or live indefinitely on space stations even within Earth's orbit.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Data that will shed light on such questions have been, and continue to be, collected, and ongoing epidemiological analyses of those data will be required to determine the long-term hazards of space travel and to test whether countermeasures designed to mitigate those hazards are effective [1].

Measures of injury and morbidity, including incidence rates of acute physiological side effects or injuries related to space travel, and incidence rates or prevalence of chronic dis‑ ease are important indicators of the relative safety of space exploration. Measures of mortal‑ ity provide one kind of summary measure of such injury and morbidity outcomes that can potentially answer a fundamental question: is space exploration altering the lifespan of those who participate in it?

Exposures accrued during space exploration may elevate the risk of some causes of death, including those related to equipment failures or other accidents and cancers that may be related to exposure to radiation in space. Such elevated risks may be counterbalanced by the rigorous physical fitness and other health requirements of programs that have traditionally provided humans the opportunity for space travel, which may protect against some causes of death. In this chapter, we carefully examine the current evidence on mortality rates of space explorers, including cause-specific rates, and how they compare to those of age-, calendar year-, geogra‑ phy- and sex-matched general populations. We discuss the implications of this evidence and consider future steps in ongoing surveillance of the mortality and longevity of space explorers. Because space exploration to date has been largely confined to government-sponsored corps of astronauts from the United States and cosmonauts from Russia (via the former Soviet Union and current Russian Federation), our review will focus on these cohorts. As we shall see, evi‑ dence compiled and analyzed to date, as well as updated data and current analyses reported here for the first time, demonstrate that mortality rates for astronauts and cosmonauts differ in important ways from those of the general population and from each other.

### **2. Astronaut and cosmonaut cohorts**

#### **2.1. Demographic characteristics**

The United States and Soviet manned space programs started at roughly the same time, with the selection of the first National Aeronautics and Space Administration (NASA) astronaut class in April 1959, the first group of United States Air Force (USAF) astronauts in June 1959, and the first Soviet cosmonauts in March 1960. The USAF eventually relinquished all astro‑ naut training and manned space activities to NASA in 1969. The Soviet Space Agency is con‑ sidered to have operated from 1957 to its official dissolution in 1991, after which its successor Roscosmos has continued space exploration for Russia. For purposes of analysis, we consider the "Soviet era" to be from the selection of the first Soviet cosmonaut class (March 15, 1960) until approximately the time of the fall of the Berlin Wall, which marked the beginning of the dissolution of the Soviet Union (December 31, 1989). The demographics of astronauts and cosmonauts are displayed in **Table 1**.

In spite of the Soviets sending the first female to space in 1963, the U.S. Astronaut Corps has selected a larger percentage of females (14% vs. 7%) over the entirety of the follow-up period. The NASA group is also more ethnically diverse, with about 10% of the astronauts selected

**Table 2** shows the average ages for the cohorts, including age at selection, average age at death for those who died, and average age of survivors as of 31 October 2017. Cosmonauts were slightly younger at the time of selection, on average, at 31.3 years versus 34.4 years for astronauts. There were no significant differences in the age at death or the mean age at the end

**Table 3** lists selected actuarial characteristics of the astronaut and cosmonaut cohorts as of 31 October 2017, including counts of astronauts and cosmonauts, total amount of follow-up time

of the study; thus, the cosmonauts were followed for 2.6 years longer, on average.

**Table 1.** Demographic characteristics of astronauts and cosmonauts, 1959–2017.

**Characteristic Astronauts, n (%) Cosmonauts, n (%) ALL NASA USAF USSR Russia** *Total cohort size* 338 (100) 22 (100) 194 (100) 68 (100) 622 (100)

Female 50 (14.8) 0 (0) 14 (7.2) 4 (5.9) 68 (10.9) Male 288 (85.2) 22 (100) 180 (92.8) 64 (94.1) 554 (89.1)

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255

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Asian/E. Indian 4 (1.2) 0 (0) 0 (0) 4 (5.9) 8 (1.3) Black 17 (5) 2 (9.1) 0 (0) 0 (0) 19 (3.1) Hispanic 12 (3.6) 0 (0) 0 (0) 0 (0) 12 (1.9) White 304 (90.0) 20 (90.9) 194 (100) 64 (94.1) 581 (93.4) Other 1 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 1 (0.0)

Yes 237 (70.1) 22 (100) 127 (65.5) 36 (52.9) 422 (67.8) No 101 (29.9) 0 (0) 67 (34.5) 32 (47.1) 200 (32.2)

High School 0 (0) 2 (9.1) 0 (0) 0 (0) 2 (0.3) Bachelor 55 (16.3) 10 (45.5) 130 (67) 51 (75) 246 (39.5) Master 173 (51.2) 9 (40.9) 6 (3.1) 6 (8.8) 194 (31.2) Doctoral 110 (32.5) 1 (4.5) 58 (29.9) 11 (16.2) 180 (28.9)

having non-White race/ethnicity.

*Sex*

*Race/ethnicity*

*Military*

*Education*

**2.2. Actuarial characteristics**


**Table 1.** Demographic characteristics of astronauts and cosmonauts, 1959–2017.

In spite of the Soviets sending the first female to space in 1963, the U.S. Astronaut Corps has selected a larger percentage of females (14% vs. 7%) over the entirety of the follow-up period. The NASA group is also more ethnically diverse, with about 10% of the astronauts selected having non-White race/ethnicity.

**Table 2** shows the average ages for the cohorts, including age at selection, average age at death for those who died, and average age of survivors as of 31 October 2017. Cosmonauts were slightly younger at the time of selection, on average, at 31.3 years versus 34.4 years for astronauts. There were no significant differences in the age at death or the mean age at the end of the study; thus, the cosmonauts were followed for 2.6 years longer, on average.

#### **2.2. Actuarial characteristics**

Data that will shed light on such questions have been, and continue to be, collected, and ongoing epidemiological analyses of those data will be required to determine the long-term hazards of space travel and to test whether countermeasures designed to mitigate those

Measures of injury and morbidity, including incidence rates of acute physiological side effects or injuries related to space travel, and incidence rates or prevalence of chronic dis‑ ease are important indicators of the relative safety of space exploration. Measures of mortal‑ ity provide one kind of summary measure of such injury and morbidity outcomes that can potentially answer a fundamental question: is space exploration altering the lifespan of those

Exposures accrued during space exploration may elevate the risk of some causes of death, including those related to equipment failures or other accidents and cancers that may be related to exposure to radiation in space. Such elevated risks may be counterbalanced by the rigorous physical fitness and other health requirements of programs that have traditionally provided humans the opportunity for space travel, which may protect against some causes of death. In this chapter, we carefully examine the current evidence on mortality rates of space explorers, including cause-specific rates, and how they compare to those of age-, calendar year-, geogra‑ phy- and sex-matched general populations. We discuss the implications of this evidence and consider future steps in ongoing surveillance of the mortality and longevity of space explorers. Because space exploration to date has been largely confined to government-sponsored corps of astronauts from the United States and cosmonauts from Russia (via the former Soviet Union and current Russian Federation), our review will focus on these cohorts. As we shall see, evi‑ dence compiled and analyzed to date, as well as updated data and current analyses reported here for the first time, demonstrate that mortality rates for astronauts and cosmonauts differ in

The United States and Soviet manned space programs started at roughly the same time, with the selection of the first National Aeronautics and Space Administration (NASA) astronaut class in April 1959, the first group of United States Air Force (USAF) astronauts in June 1959, and the first Soviet cosmonauts in March 1960. The USAF eventually relinquished all astro‑ naut training and manned space activities to NASA in 1969. The Soviet Space Agency is con‑ sidered to have operated from 1957 to its official dissolution in 1991, after which its successor Roscosmos has continued space exploration for Russia. For purposes of analysis, we consider the "Soviet era" to be from the selection of the first Soviet cosmonaut class (March 15, 1960) until approximately the time of the fall of the Berlin Wall, which marked the beginning of the dissolution of the Soviet Union (December 31, 1989). The demographics of astronauts and

important ways from those of the general population and from each other.

**2. Astronaut and cosmonaut cohorts**

**2.1. Demographic characteristics**

cosmonauts are displayed in **Table 1**.

hazards are effective [1].

254 Into Space - A Journey of How Humans Adapt and Live in Microgravity

who participate in it?

**Table 3** lists selected actuarial characteristics of the astronaut and cosmonaut cohorts as of 31 October 2017, including counts of astronauts and cosmonauts, total amount of follow-up time


person-years. The vast majority of astronauts have been selected by NASA: 338 versus just 22 from the USAF. The last of the USAF astronauts were selected in 1967, while NASA astronauts have been periodically selected across the follow-up period. This makes the USAF astronauts some of the oldest in the overall cohort; this is reflected in their large crude mortality rate in

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Data on cosmonauts are shown stratified by era of selection: the era of the Soviet Space Program (1960–1989) and the post-Soviet era of the Russian Space Program under the Russian Space Agency, Roscosmos. The 262 Soviet and Russian cosmonauts have accrued 8171.1 per‑ son-years of follow-up and 96 deaths, yielding a crude mortality rate of 11.75 deaths per 1000

We focus here and throughout this chapter on underlying cause of death as reported in official NASA astronaut biographies and in the news media. In this way, astronaut and cosmonaut

Though there are many ways to quantify the mortality experience of groups such as astro‑ nauts and cosmonauts, here, we will focus on the Standardized Mortality Ratio (SMR). SMR is a risk ratio; it is computed by dividing the observed number of deaths in a group by the number of deaths that would be counterfactually "expected" were the group subject to a set of death rates from a reference population. (By convention, the resulting ratio is multiplied by 100.) Thus, SMRs of 100 represent equal risk between the group under study and the reference population, SMRs above 100 represent increased risk for the group under study, and SMRs

**Figure 1** shows the distribution by cause of the 80 astronaut deaths recorded through 31 October 2017. More than half of all deaths (46/80) were due to natural causes. Among natu‑ ral causes, most deaths have been due to cancer (41.3%), followed by cardiovascular disease

The 34 deaths from external (i.e., not natural) causes are dominated by 33 accidental deaths. Plane crashes and space craft accidents account for 29 of these deaths, with vehicular acci‑ dents accounting for the other 4. The only nonaccidental externally caused death was attrib‑

For comparisons, all-cause United States general population mortality rates were taken from the Human Mortality Database for years 1960 through 2015 [2] and cause-specific rates from the CDC WONDER database for 1970 to 2015 [3–5]. The 2015 rates were used as the compari‑

**3. Causes of death and comparative mortality for United States** 

deaths are categorized according to a single underlying cause of death.

below 100 represent decreased risk for the same.

son rates for astronaut data from 2016 and 2017.

**3.1. Numbers and causes of death**

(CVD) (23.9%).

uted to suicide (**Figure 1**).

comparison to that of NASA astronauts.

person-years (**Table 3**).

**astronauts**

**Table 2.** Average ages and follow-up time for astronauts and cosmonauts, 1959–2017.

(in person-years), and counts of deaths. Crude death rates, being in each case the ratio of total deaths to total person-years lived by a respective group, are also reported. Crude rates are highly dependent on the age structure of each cohort, and differences in crude rates may be due to differences in one or more cause-specific rates, or due to age differences in the cohorts, or both. To better understand whether and to what extent the rates in the various cohorts may differ, a more careful examination of these issues is required.

There have been 622 individuals selected and trained as astronauts or cosmonauts between April 1959 and October 2017. These men and women have contributed a total of 18462.8 per‑ son-years of observation time and 176 deaths, for an overall crude mortality rate of 9.53 deaths per 1000 person-years of observation.

The United States space programs account for 360 astronauts, contributing 10,291.8 personyears of follow-up and 80 deaths, yielding a crude mortality rate of 7.77 deaths per 1000


\*Pooled observation time since selection, expressed as person-years.

† Crude death rate, expressed as deaths per 1000 person-years.

**Table 3.** Actuarial characteristics of astronauts and cosmonauts, 1959–2017.

person-years. The vast majority of astronauts have been selected by NASA: 338 versus just 22 from the USAF. The last of the USAF astronauts were selected in 1967, while NASA astronauts have been periodically selected across the follow-up period. This makes the USAF astronauts some of the oldest in the overall cohort; this is reflected in their large crude mortality rate in comparison to that of NASA astronauts.

Data on cosmonauts are shown stratified by era of selection: the era of the Soviet Space Program (1960–1989) and the post-Soviet era of the Russian Space Program under the Russian Space Agency, Roscosmos. The 262 Soviet and Russian cosmonauts have accrued 8171.1 per‑ son-years of follow-up and 96 deaths, yielding a crude mortality rate of 11.75 deaths per 1000 person-years (**Table 3**).
