Future missions

The Viking experiments indicate that life is not widely distributed across the martian surface. However, there are localized areas that might be more conducive to life forms. In addition, past conditions may have been more hospitable and traces of extinct life might be retained in certain areas of the planet. Thus the question of martian life (extinct or extant) still remains to be answered unconditionally. Future missions are being planned which will help address these issues.

The first post-Viking mission specifically designed to look for evidence of martian life was the Beagle 2 lander (Figure 8.5), which separated from the Mars Express orbiter in December 2003. Beagle 2 carried instruments designed to identify water in the soil, rocks, and atmosphere and traces of life through direct measurement of carbon compounds (Chicarro, 2002). It landed in the Isidis Basin but no signal was returned from the spacecraft after landing.

Figure 8.5 Artist's concept of the Beagle 2 lander after deployment at its Isidis Planitia landing site. Unfortunately no signal was ever received from Beagle 2. (Image ESA20MGBCLC, ESA/Denman Productions.)

Figure 8.6 Phoenix is scheduled to land on Mars in 2008 and will investigate the martian soil and its ability to contain biologic material. This artist's concept shows Phoenix after landing in the northern plains. (NASA/JPL.)

The next mission that will include instruments to look for evidence of life is NASA's Phoenix mission (Figure 8.6), which was launched on 4 August 2007. The objectives of the Phoenix mission are (1) study the history of water in all of its phases, and (2) search for evidence of habitable zones and assess the biological potential of the ice-soil boundary (Smith and the Phoenix Science Team, 2004). To achieve its objectives, Phoenix will land in May 2008 within the 65° to 70 °N latitude zone, which has been characterized as a region of high near-surface ice content by GRS. Its instruments will investigate subsurface H2O and its interaction with the atmosphere as well as characterize the composition of the martian regolith

Figure 8.6 Phoenix is scheduled to land on Mars in 2008 and will investigate the martian soil and its ability to contain biologic material. This artist's concept shows Phoenix after landing in the northern plains. (NASA/JPL.)

Figure 8.7 The Mars Science Laboratory is expected to arrive on Mars in 2010 and will contain instruments designed to look for evidence of current or past martian life. (Image PIA04892, NASA/JPL.)

down to 0.5 meter depth. The Thermal and Evolved Gas Analyzer (TEGA) instrument will determine the isotopic ratios of hydrogen, oxygen, carbon, and nitrogen within the soil and provide constraints on the role of biological processes in forming these isotopes.

NASA plans to launch the Mars Science Laboratory (MSL) (Figure 8.7)in the fall of 2009 with arrival in October 2010. MSL is a larger, more robust version of the Mars Exploration Rovers currently operating on the planet. MSL will characterize the biology, geology, geochemistry, and radiation environment of its landing location (Vasavada and the MSL Science Team, 2006). Its specific objectives relative to biology include determining the nature and inventory of organic carbon compounds, making an inventory of the chemical building blocks of life, and identifying features which may be representative of biological processes. To achieve these objectives, it will collect rock and soil samples for distribution among on-board test chambers. These experiments will determine the elemental composition of the samples, including organic compounds such as proteins and amino acids which could be produced by life.

ESA has recently selected the ExoMars mission as its first flagship mission in the Aurora program of Moon and Mars exploration (Figure 8.8). ExoMars will launch in 2013 with arrival at Mars in 2015. It will contain a rover and a small fixed surface station (Vago et al., 2006). The rover will carry the Pasteur science package designed to investigate the geology and exobiological properties of the planet. Proposed instruments include cameras, spectrometers (IR, Mossbauer, and Raman), aground-penetrating radar, X-ray diffractometer, Mars Organics and Oxidants Detector, GCMS, radiation detector, and a meteorological package. An important part of the rover is the incorporation of a drill which will be able to access the subsurface to a depth of 2 m to explore the possibility of subsurface biologic oases. The surface

Figure 8.8 ESA's ExoMars mission will consist of a rover and a fixed surface station. The rover, shown in this artist's conception, will be able to drill to depths of 2 m to determine if life might exist underground. (ESA/AOES Medialab.)

station will contain the Geophysics/Environment Package (GEP), although the specific instruments have not been selected.

Other missions focused on searching for evidence of martian biology are being discussed. These include additional landers and sample return missions. In addition, many studies are being conducted in remote regions of Earth to characterize the extreme conditions under which terrestrial lifeforms survive and reproduce. These include dry, cold environments such as the Dry Valleys region of Antarctica (Doran et al., 1998; Wentworth et al., 2005; Abyzov et al., 2006), volcanic regions where thermophilic organisms might prosper (Farmer, 1998; Bishop et al., 2004), sulfur-rich volcanic environments (Fernández-Remolar et al., 2005; Knoll et al., 2005), and salt-rich environments (Mancinelli et al., 2004; Reid et al., 2006). These studies help us to better understand the environments under which terrestrial organisms have flourished and provide us with insights into possible astrobiological niches on Mars.

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