**3. Start of the surface missions: Viking program**

As the United States started showing a position of dominance in the space race, the urge for committing to launches at every opportunity relaxed (also due to a reduced economic impulse). This way, the 1973 launch window was not used, and the first Viking launch occurred during the summer of 1975. This program was born with three objectives: acquire high-resolution images from the Martian surfaces; continue with the surface and atmosphere chemical analysis; and to look for evidences of life on the Martian surface. Viking was also conceived as a twin mission (similar to Mapc 2 and 3), each of them with an orbiter plus a lander.

### **3.1 The Viking orbiters**

The main objective of the Viking orbiters was to help on the selection of the landing sites for the landers, as well as serve as communication relays. This was central to the mission, considering the lessons learned from the Soviet Mapc 2 and 3 failures, which could not select the landing site, and needed direct contact with Earth for operation. During more than 1 month, the information gathered by the landers was used to localize and certify the best possible locations to perform the soft landing.

However, the orbiters were also equipped with their own payload, which was reduced compared to their Mariner predecessors, as the lander was onboard. This payload included the IR Mars atmospheric water detector (MAWD), to study the presence of atmospheric water vapor and its latitude and seasonal potential variations [9, 10]. The infrared thermal mapper (IRTM) instrument measured the surface temperature, confirming the night/day cycle temperature variations, as well as characterizing its variability associated with latitude, seasons and atmosphere [11]. Finally, the visual imaging subsystem (VIS) included two high-resolution

**93**

even a wind gust [16].

*Evolution of the Scientific Instrumentation for* In Situ *Mars Exploration*

television cameras with a 17 m/pixel resolution. The geologic analysis of these samples supported the theory that vast ancient liquid water surfaces were present on the surface of Mars. Not only hydro fluvial systems but also geological features compatible with lakes or other water reservoirs were related to weathering process

The landers started their mission the moment they were released from the orbiters. During their descent, information regarding the composition, structure, and temperature of the planet ionosphere was obtained. Furthermore, the UAMS mass spectrometer analyzed the higher layers of the atmosphere, while the lander monitored the atmosphere pressure and temperature along the descent. But of course, the leap forward by the Viking landers was the success of sending the first-ever images of the Martian surface after a soft landing, setting a new milestone in the technological development for planetary exploration. This way, on July 20, 1976, Viking 1 landed on the western area of Chryse Planitia (22.27 deg N latitude and 312.05 deg E longitude); and her twin landed on September 3, 1975, 200 km west from the Mie

crater in Utopia Planitia (47.6673 deg N latitude, 134.2809 deg E longitude).

The 600 kg Viking landers were equipped with a very complete suite of experiments to try to reach the ambitious objectives planned for the mission: the analysis of the surface and ambient properties derived from the erosion and eolian sedimentations; morphology, organic, and inorganic chemical composition and magnetic properties, based on the mineralogical analysis of the landing site; seismology; meteorology; and to look for potential Martian organisms with a biological experiment attached to a gas chromatographer/mass spectrometer (GC/MS) instrument. The panoramic cameras on the landers covered a region of 360° of the Martian horizon, but also allowed photographing the lander and its sample-extraction arm, as well as the sun or the Martian moons, Phobos and Deimos. These cameras were the first to be operated, starting to transmit the first data to ground only after 25 s. The 3000 images of Viking 1 plus the 6500 of Viking 2 showed a desertic, powdery, and inhospitable landscape. Also, the images greatly helped in the interpretation of

The temperature and magnetism of the rock samples in the reach of the landers were analyzed by sensors placed in the arm tip, showing a great abundance of magnetic minerals in the Martian surface [13]. The X-ray fluorescence spectroscopy (XRFS) were used to obtain the chemical nature of the surface regolith, showing a great abundance of Si and Fe, with significative concentrations of Mg, Al, S, Ca, and Ti. When compared with the abundances of these elements on Earth, it was observed that the presence of S was up to two orders of magnitude higher in Mars, while K abundance was 5 times lower than the average found in the Earth crust [14]. The Viking meteorological station was deployed in a mast after landing and included temperature and wind sensors. It also included a pressure sensor under the belly of the lander. All these instruments gathered data as configured from ground, varying the data logging along the mission as required. The results showed and allowed the characterization of the day/night cycles, as well as throughout the

One of the Martian unknowns was related to the seismic activity of the red planet. The Viking landers seismometers were included for this reason. Even the Viking 2 instrument failed (probably due to the landing impact); the seismometer on Viking 1 worked for 2000 h without registering any important events, with the exception of one, which could have been caused by a micro-meteorite impact or

*DOI: http://dx.doi.org/10.5772/intechopen.93377*

throughout the planet [12].

**3.2 The Viking landers**

the instrumental data.

seasons during the years the missions lasted [15].

television cameras with a 17 m/pixel resolution. The geologic analysis of these samples supported the theory that vast ancient liquid water surfaces were present on the surface of Mars. Not only hydro fluvial systems but also geological features compatible with lakes or other water reservoirs were related to weathering process throughout the planet [12].
