**1. Introduction: from Schiaparelli to Mariner 9**

Before the space age, the best Mars observations were performed during the so called oppositions [1]. The distance between the orbits of Earth and Mars varies considerably, largely due to the comparatively large eccentricity of Mars's orbit. Every 780 days on average the Earth overtakes Mars and when, as seen from the Earth, Mars and the Sun are aligned, Mars is said to be in opposition. The opposition distance of Mars from the Earth varies considerably, depending on where Mars and the Earth are in their orbits at opposition. If Mars is near its closest to the Sun (perihelion) the distance is comparatively small, and the opposition is called favourable. Unfavourable oppositions are with Mars near aphelion. The opposition distance varies from 55.7–101 million km, and the corresponding angular diameter of Mars varies from 25.1–13.8 arcsec. Favourable oppositions occur roughly every 15 years.

The first person to draw a map of Mars that displayed terrain features was the Dutch astronomer Christiaan Huygens (**Figure 1**).

On November 28, 1659 he made an illustration of Mars that showed the distinct dark region now known as Syrtis Major Planum, and possibly one of the polar ice caps.

The same year, he succeeded in measuring the rotation period of the planet, giving it as approximately 24 hours.

**Figure 1.** *Syrtis Major, sketched by Christiaan Huygens in 1659. North is at the top.*

In 1666, Cassini detected several distinct dark spots on Mars, and from observing these ascertained that the planet had a rotation on its axis in about 24 hours 40 minutes.

In the oppositions of 1777, 1779, 1781, and 1783, Sir William Herschel determined that the axis of Mars was inclined of about 25° to the plane of its orbit (so having seasons) and measured its polar and equatorial diameters. He showed also that the white spots which formed round the poles of the planet, increased with the approach of winter, and diminished with the approach of summer.

In the oppositions of 1830, 1832, and 1837, Beer and Mädler, observing with a telescope of 4 inches aperture, made a series of drawings from which they were able to construct a chart of the entire globe of Mars. The features which they then drew have been recognised at every succeeding opposition, and some of them can be identified in the rough sketches of Sir William Herschel, and even in those of the year 1666, made by Hooke and Cassini. The surface of Mars therefore possesses permanent features.

In the 1800s, observatories with larger and larger telescopes were built around the world.

A particularly favorable perihelic opposition occurred in 1877 (Mars approcing to within 56 million km on September 5, in Aquarius) [2].

On August 11, 1877 the American astronomer Asaph Hall discovered the two moons of Mars, Phobos and Deimos, using a 660 mm (26 in) telescope at the U.S. Naval Observatory.

In the fall of October 1877, Giovanni Virginio Schiaparelli (1835–1910), scrutinised Mars visually at the Brera Observatory in Milan, where he was director (**Figure 2**). He used a 8<sup>0</sup> (21.8 cm, f/14.5) aperture Mertz refractor (magnifying power of 322x), that was installed here in 1865. He named the Martian "seas" and "continents" (dark and light areas) with names from historic and mythological sources [3].

Starting from 1886, Brera was equipped by a larger new instrument, a 16<sup>0</sup> (48.7 cm, f/14.3) Mertz-Repsold refractor. Schiaparelli used it, during a couple of following Mars oppositions (1992–1994), to confirm not only the Martian canals but

*This drawing of the two hemispheres of Mars was made by the Italian astronomer G.V. Schiaparelli (1835– 1910) between the years 1877 and 1888. He named the 'seas' and 'continents' of Mars, and called the straight*

*Original drawings of Mars, made by G.V. Schiaparelli during the 1877 opposition.*

In 1894, Percival Lowel, a member of a rich family from Boston, decided to become a planetary astronomer after reading 'The Planet Mars' a famous book of *Camille Flammarion. He* made his first observations of Mars from a private observatory that he built in Flagstaff, Arizona (Lowell Observatory). He was convinced that the canals were real and ultimately mapped hundreds of them (**Figure 4**).

Lowell believed that the straight lines were artificial canals created by intelligent Martians and were built to carry water from the polar caps to the equatorial regions. In 1895, he published his first book on *Mars* with many illustrations and, over the

next two decades, published two more popular books advancing his ideas.

also some duplications of them!

*surface features channels (mistranslated as canals).*

*New Insights into the Search for Life on Mars DOI: http://dx.doi.org/10.5772/intechopen.97176*

**Figure 2.**

**Figure 3.**

**137**

But he is best remembered for about 40 fine lines that he drew crossing the bright red areas, *canali* as he called them. Canali means channels, but it was mistranslated into "canals" implying intelligent life on Mars (**Figure 3**).

Because of the then recent completion of the Suez Canal in 1869 (the engineering wonder of the era), the misinterpretation was taken to mean that large-scale artificial structures had been discovered on Mars. The importance of canals for worldwide commerce at that time without a doubt influenced the popular interest in "canals" on Mars.

**Figure 2.** *Original drawings of Mars, made by G.V. Schiaparelli during the 1877 opposition.*

#### **Figure 3.**

In 1666, Cassini detected several distinct dark spots on Mars, and from observing these ascertained that the planet had a rotation on its axis in about 24 hours

In the oppositions of 1777, 1779, 1781, and 1783, Sir William Herschel determined that the axis of Mars was inclined of about 25° to the plane of its orbit (so having seasons) and measured its polar and equatorial diameters. He showed also that the white spots which formed round the poles of the planet, increased with the

In the oppositions of 1830, 1832, and 1837, Beer and Mädler, observing with a telescope of 4 inches aperture, made a series of drawings from which they were able to construct a chart of the entire globe of Mars. The features which they then drew have been recognised at every succeeding opposition, and some of them can be identified in the rough sketches of Sir William Herschel, and even in those of the year 1666, made by Hooke and Cassini. The surface of Mars therefore possesses

In the 1800s, observatories with larger and larger telescopes were built around

A particularly favorable perihelic opposition occurred in 1877 (Mars approcing

On August 11, 1877 the American astronomer Asaph Hall discovered the two moons of Mars, Phobos and Deimos, using a 660 mm (26 in) telescope at the U.S.

In the fall of October 1877, Giovanni Virginio Schiaparelli (1835–1910), scrutinised Mars visually at the Brera Observatory in Milan, where he was director (**Figure 2**). He used a 8<sup>0</sup> (21.8 cm, f/14.5) aperture Mertz refractor (magnifying power of 322x), that was installed here in 1865. He named the Martian "seas" and "continents" (dark and light areas) with names from historic and mythological

But he is best remembered for about 40 fine lines that he drew crossing the bright red areas, *canali* as he called them. Canali means channels, but it was mistranslated into "canals" implying intelligent life on Mars (**Figure 3**).

Because of the then recent completion of the Suez Canal in 1869 (the engineering wonder of the era), the misinterpretation was taken to mean that large-scale artificial structures had been discovered on Mars. The importance of canals for worldwide commerce at that time without a doubt influenced the popular interest

approach of winter, and diminished with the approach of summer.

*Syrtis Major, sketched by Christiaan Huygens in 1659. North is at the top.*

to within 56 million km on September 5, in Aquarius) [2].

40 minutes.

**Figure 1.**

*Solar System Planets and Exoplanets*

permanent features.

Naval Observatory.

in "canals" on Mars.

**136**

the world.

sources [3].

*This drawing of the two hemispheres of Mars was made by the Italian astronomer G.V. Schiaparelli (1835– 1910) between the years 1877 and 1888. He named the 'seas' and 'continents' of Mars, and called the straight surface features channels (mistranslated as canals).*

Starting from 1886, Brera was equipped by a larger new instrument, a 16<sup>0</sup> (48.7 cm, f/14.3) Mertz-Repsold refractor. Schiaparelli used it, during a couple of following Mars oppositions (1992–1994), to confirm not only the Martian canals but also some duplications of them!

In 1894, Percival Lowel, a member of a rich family from Boston, decided to become a planetary astronomer after reading 'The Planet Mars' a famous book of *Camille Flammarion. He* made his first observations of Mars from a private observatory that he built in Flagstaff, Arizona (Lowell Observatory). He was convinced that the canals were real and ultimately mapped hundreds of them (**Figure 4**).

Lowell believed that the straight lines were artificial canals created by intelligent Martians and were built to carry water from the polar caps to the equatorial regions. In 1895, he published his first book on *Mars* with many illustrations and, over the next two decades, published two more popular books advancing his ideas.

**Figure 4.** *Mars in 1905, drawn by Percival Lowell. Note the canals. Note also the south polar hood of cloud (at the top).*

Lowell's theories influenced the young English writer H.G. Wells, who in 1898 published *The War of the Worlds*. In this novel, Wells created an invasion of Earth by deadly aliens from Mars and launched a whole new genre of alien science fiction.

On Halloween in 1938, Orson Welles and The Mercury Theater on the Air broadcast a radio version of The War of the Worlds. The story, presented as a series of "live" news bulletins, panicked thousands of listeners who believed that America was being attacked by hostile Martians.

In the 1953, the story of The War of the Worlds of H. G. Wells was adapted in a famous American science fiction film from Paramount Pictures, produced by George Pal and directed by Byron Haskin. Earth was suddenly and unexpectedly invaded by Martians. Many of the major world capitals were destroyed by the Martians, being Martians impervious to all humanity's weapons (enclosed an atomic bomb!) . But, after all that men could do had failed, the Martians were destroyed by terrestrial bacteria to which only mankind have long since become immune.

The real origin of the Mars canals was revealed by another Italian astronomer, Vincenzo Cerulli (1859–1927), founder in 1890 of the Astronomical Observatory in Teramo (in the Abruzzo region), equipped by a Cook Refractor of 40 cm. Starting from 1897, he gave a convincing explanation, still generally accepted. He suggested that the lines were a sort of optical illusion, created by the human brain that "needs" to interpret even vague and indistinct images with familiar shapes. Therefore, poor quality images, such as those that low quality telescopes would provide, would be interpreted as structured shapes, for example connecting individual roughly aligned "dots" into straight lines. This has been demonstrated by many laboratory and field experiments.

During the great opposition of 1909, on the night of September 2020, thanks to exceptional seeing conditions, Eugène M. Antoniadi (1870–1944), one of the most skilled observer of his time, using the new big 83 cm reflector of Meudon observatory, gives some exquisite drawings of Mars, in which all "canals" having some feedback in the past vanished (**Figure 5**).

geological activity and lack of extensive weathering by water, which would have erased these craters in a fraction of the age of Mars. Moreover, when Mariner 4 passed beyond Mars as viewed from the Earth, the changes induced by the atmosphere enabled the surface pressure of the atmosphere to be determined: the value was a mere 6 millibars, ten time less than previously believed. A pressure of 6 millibars is close to the triple pressure of water, below which water cannot exist in a

*Images sent to Earth by Mariner 4 and Marine 6 during their flyby of Mars in July1965 and July 1969.*

*In 1909, E.M. Antoniadi got the chance to use the great 33″ refracting telescope at Meudon, on the outskirts of Paris, and on the first night, Sep. 20, he saw Mars so clearly that he could not believe his eyes. It was covered*

*with detail, but not a bit of it was geometric–there was not a canal in sight.*

*New Insights into the Search for Life on Mars DOI: http://dx.doi.org/10.5772/intechopen.97176*

**Figure 5.**

**Figure 6.**

**139**

On 15 July 1965 the NASA spacecraft Mariner 4 flew past Mars, at a minimum distance of only 9800 km. This first Mars flyby gave a major negative surprise: all 22 of the images sent to Earth showed a cratered landscape more akin to the Moon (**Figure 6**). The heavily cratered (and hence ancient) surfaces indicate lack of

#### **Figure 5.**

Lowell's theories influenced the young English writer H.G. Wells, who in 1898 published *The War of the Worlds*. In this novel, Wells created an invasion of Earth by deadly aliens from Mars and launched a whole new genre of alien science fiction. On Halloween in 1938, Orson Welles and The Mercury Theater on the Air broadcast a radio version of The War of the Worlds. The story, presented as a series of "live" news bulletins, panicked thousands of listeners who believed that America

*Mars in 1905, drawn by Percival Lowell. Note the canals. Note also the south polar hood of cloud (at the top).*

In the 1953, the story of The War of the Worlds of H. G. Wells was adapted in a

The real origin of the Mars canals was revealed by another Italian astronomer, Vincenzo Cerulli (1859–1927), founder in 1890 of the Astronomical Observatory in Teramo (in the Abruzzo region), equipped by a Cook Refractor of 40 cm. Starting from 1897, he gave a convincing explanation, still generally accepted. He suggested that the lines were a sort of optical illusion, created by the human brain that "needs" to interpret even vague and indistinct images with familiar shapes. Therefore, poor quality images, such as those that low quality telescopes would provide, would be interpreted as structured shapes, for example connecting individual roughly aligned "dots" into straight lines. This has been demonstrated by many laboratory and field

During the great opposition of 1909, on the night of September 2020, thanks to exceptional seeing conditions, Eugène M. Antoniadi (1870–1944), one of the most skilled observer of his time, using the new big 83 cm reflector of Meudon observatory, gives some exquisite drawings of Mars, in which all "canals" having some

On 15 July 1965 the NASA spacecraft Mariner 4 flew past Mars, at a minimum distance of only 9800 km. This first Mars flyby gave a major negative surprise: all 22 of the images sent to Earth showed a cratered landscape more akin to the Moon (**Figure 6**). The heavily cratered (and hence ancient) surfaces indicate lack of

famous American science fiction film from Paramount Pictures, produced by George Pal and directed by Byron Haskin. Earth was suddenly and unexpectedly invaded by Martians. Many of the major world capitals were destroyed by the Martians, being Martians impervious to all humanity's weapons (enclosed an atomic bomb!) . But, after all that men could do had failed, the Martians were destroyed by terrestrial bacteria to which only mankind have long since become immune.

was being attacked by hostile Martians.

*Solar System Planets and Exoplanets*

feedback in the past vanished (**Figure 5**).

experiments.

**138**

**Figure 4.**

*In 1909, E.M. Antoniadi got the chance to use the great 33″ refracting telescope at Meudon, on the outskirts of Paris, and on the first night, Sep. 20, he saw Mars so clearly that he could not believe his eyes. It was covered with detail, but not a bit of it was geometric–there was not a canal in sight.*

*Images sent to Earth by Mariner 4 and Marine 6 during their flyby of Mars in July1965 and July 1969.*

geological activity and lack of extensive weathering by water, which would have erased these craters in a fraction of the age of Mars. Moreover, when Mariner 4 passed beyond Mars as viewed from the Earth, the changes induced by the atmosphere enabled the surface pressure of the atmosphere to be determined: the value was a mere 6 millibars, ten time less than previously believed. A pressure of 6 millibars is close to the triple pressure of water, below which water cannot exist in a stable liquid phase at any temperature. Because all life on Earth requires liquid water, the prospect of finding life on Mars faded a lot.

The next two successful missions to Mars, were the flyby (at a distance of about 3400 km) of Mariner 6 on July 31, 1969 and the flyby of Mariner 7 a few days later on August 5, 1969, flying by over the equator and south polar regions and analyzing the Martian atmosphere and surface with remote sensors, as well as recording and relaying hundreds of pictures. The two spacecraft returned a combined total of 143 approach pictures of the planet and 55 close-up pictures (**Figure 7**).

Again the small amount of martian surface investigated was found covered by impact craters. More, the temperature of the south polar cap was measured and found to correspond to the solid–gas phase boundary of CO2 at a pressure of a few millibars. This provided strong evidence that a polar cap of CO2 was roughly in equilibrium with the CO2 atmosphere.

Subsequent studies have confirmed that the seasonal cap at both poles is indeed predominantly CO2 snow and frost, but that this overlies a permanent cap mainly composed of dusty water ice at the North Pole, and dusty CO2 ice at the colder South Pole, perhaps underlain by dusty water ice.

The results of Mariner 4,6,7 were very disappointing. But it was soon realized that some fast flybys over no more than 20% of the martian surface, could not give a satisfactory knowledge of a complex planet as Mars. It would have been necessary to map the *whole* planet and make continous obsevations for a long period of time, objectives that only an orbital mission could carry out. The Mariner 9 mission was born.

On November 14, 1971 the spacecraft Mariner 9 was placed, for the first time in the history, in orbit around Mars. But, unbelievably, Mariner 9 arrived when Mars was obscured by the largest dust storm ever observed. The surface was totally obscured for a couple of months and the imaging program did not get underway until mid-January 1972. The spacecraft was turned off on October 27, 1972, after 349 days in orbit, and 7,329 images transmitted, covering 85% of Mars'surface. With two astonishing discoveries (**Figure 8**).

The first main discovery was the existence of several huge 'young'shield volca-

The two Viking Landers in the '70 years made the first direct search of traces of

The results were so contentious that, after more than 45 years, no unambiguous

The GCMS instruments (Gas Chromatograph-Mass Spectrometer) on board both Viking Landers [6, 7] were tasked with detecting organic compounds. GC–MS heated many samples of martian soil up to 500°C, but did not detect any trace of complex organic molecules, even if detected an amount of 0,1–1% of H2O and 50–500 ppm CO2 respectively (**Figure 11**) and the enigmatic release of about 15 ppb of CH3Cl (chloro-methane) and up to 20–30 ppb of CH2Cl2 (methylene chloride) (**Figure 12**). At that time, the two light chloro-derivatives, being released together with some trace of a solvent of sure terrestrial origin such as Freon-E, were considered as a terrestrial contamination, ruling out the occurrence of any form of martian life [8]. In the meantime the H2O and CO2 release upon heating were explained as thermal

noes, so high that their peaks emerged also from the dust storm. Most of these volcanoes were located in the Tharsis Regio, a vast plateau 4.000 m high, centered near the Martian equator, that formed about 2 billion years ago, giving rise to an enormous canyon system, named Mariner Valley, after Mariner 9 in honor of its achievements. The second main discovery was that of hundreds of extinct riverbeds, that seem to have been carved by the flow of liquid water early in Martian history: an indication that Mars was much warmer and wetter in the past. Certainly most exciting discoveries as far as life on Mars is concerned, that convinced NASA to plan a mission to directly search for life on Mars. The Viking program was born.

*The largest dust storm ever observed obscured all the surface of Mars in November 1971, when Mariner 9 entered orbit for the first time. When the storm subsides, Mariner 9 made two main discoveries: big volcanoes*

**2. The intringuing results of the Vikings program**

interpretation was found.

**141**

**Figure 8.**

*and hundreds of extinct riverbeds.*

*New Insights into the Search for Life on Mars DOI: http://dx.doi.org/10.5772/intechopen.97176*

present or past biological life on Mars [5] (**Figures 9** and **10**).

decomposition of hydrous silicates and carbonates respectively.

#### **Figure 7.**

*South polar cap of Mars as seen by Mariner 7 in August 1969. The IRS spectrometer on board of Mariner 7 demonstrated the presence of CO2 ice and, possibly, also trace of NH3 and CH4 [4].*

*New Insights into the Search for Life on Mars DOI: http://dx.doi.org/10.5772/intechopen.97176*

#### **Figure 8.**

stable liquid phase at any temperature. Because all life on Earth requires liquid

approach pictures of the planet and 55 close-up pictures (**Figure 7**).

The next two successful missions to Mars, were the flyby (at a distance of about 3400 km) of Mariner 6 on July 31, 1969 and the flyby of Mariner 7 a few days later on August 5, 1969, flying by over the equator and south polar regions and analyzing the Martian atmosphere and surface with remote sensors, as well as recording and relaying hundreds of pictures. The two spacecraft returned a combined total of 143

Again the small amount of martian surface investigated was found covered by impact craters. More, the temperature of the south polar cap was measured and found to correspond to the solid–gas phase boundary of CO2 at a pressure of a few millibars. This provided strong evidence that a polar cap of CO2 was roughly in

Subsequent studies have confirmed that the seasonal cap at both poles is indeed predominantly CO2 snow and frost, but that this overlies a permanent cap mainly composed of dusty water ice at the North Pole, and dusty CO2 ice at the colder

The results of Mariner 4,6,7 were very disappointing. But it was soon realized that some fast flybys over no more than 20% of the martian surface, could not give a satisfactory knowledge of a complex planet as Mars. It would have been necessary to map the *whole* planet and make continous obsevations for a long period of time, objectives that only an orbital mission could carry out. The Mariner 9 mission was

On November 14, 1971 the spacecraft Mariner 9 was placed, for the first time in the history, in orbit around Mars. But, unbelievably, Mariner 9 arrived when Mars was obscured by the largest dust storm ever observed. The surface was totally obscured for a couple of months and the imaging program did not get underway until mid-January 1972. The spacecraft was turned off on October 27, 1972, after 349 days in orbit, and 7,329 images transmitted, covering 85% of Mars'surface.

*South polar cap of Mars as seen by Mariner 7 in August 1969. The IRS spectrometer on board of Mariner 7*

*demonstrated the presence of CO2 ice and, possibly, also trace of NH3 and CH4 [4].*

water, the prospect of finding life on Mars faded a lot.

equilibrium with the CO2 atmosphere.

*Solar System Planets and Exoplanets*

born.

**Figure 7.**

**140**

South Pole, perhaps underlain by dusty water ice.

With two astonishing discoveries (**Figure 8**).

*The largest dust storm ever observed obscured all the surface of Mars in November 1971, when Mariner 9 entered orbit for the first time. When the storm subsides, Mariner 9 made two main discoveries: big volcanoes and hundreds of extinct riverbeds.*

The first main discovery was the existence of several huge 'young'shield volcanoes, so high that their peaks emerged also from the dust storm. Most of these volcanoes were located in the Tharsis Regio, a vast plateau 4.000 m high, centered near the Martian equator, that formed about 2 billion years ago, giving rise to an enormous canyon system, named Mariner Valley, after Mariner 9 in honor of its achievements. The second main discovery was that of hundreds of extinct riverbeds, that seem to have been carved by the flow of liquid water early in Martian history: an indication that Mars was much warmer and wetter in the past. Certainly most exciting discoveries as far as life on Mars is concerned, that convinced NASA to plan a mission to directly search for life on Mars. The Viking program was born.
