An Astrobiology Strategy for the Exploration of Mars (2007) / Chapter Skim
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1 Introduction
1 Introduction
Pages 11-18
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From page 11... ...
that evidence for past life could be found in the martian meteorite ALH 84001.2 Although that hypothesis has now been widely criticized, the ensuing discussion brought out the scientific value of incorporating astrobiology science goals into a broad exploration strategy for Mars. In the late 1990s, the NASA Mars Exploration Program plan emphasized the study of Mars as an integrated system.
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From page 12... ...
The combination of high-resolution imaging; multispectral mapping in the visible, near-infrared, and thermal infrared; compositional mapping using gamma-ray and neutron techniques; and radar mapping of the subsurface has provided detailed information on the geological history of Mars and on processes that pertain to the potential for liquid water and for life. In situ analysis by the Mars Exploration Rovers Spirit and Opportunity investigated two sites for which there was evidence for significant water-related activity and confirmed that liquid water played an important role at both.
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From page 13... ...
Rather, such a finding would be just as important scientifically as a finding of life, in terms of constraining our views on the origin, evolution, and distribution of living organisms in the universe. Lessons Learned from Past Searches for Life The committee assumes, based on experience garnered from previous searches for martian life associated with the Viking mission in the 1970s and analysis of the martian meteorite ALH 84001 in the 1990s and 2000s, that a single mission will not necessarily be able to determine if martian life is or ever was present and to characterize the boundary conditions of martian habitability.
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From page 14... ...
The generic characteristics of life as we know it -- terran life, in the terminology of the Limits report -- can be summarized as the following: • Uses water as a solvent; • Is built from cells, and exploits a metabolism that focuses on the C=O carbonyl group; • Is a thermodynamically dissipative structure exploiting chemical energy gradients; and • Exploits a two-biopolymer architecture that uses nucleic acids to perform most genetic functions, and proteins to perform most catalytic functions. What complicates the discussion is the fact that martian life might be terran or nonterran.
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From page 15... ...
The simplifying assumption that martian life is terran was excluded because the committee was specifically asked to address a search for life that might be non-Earth-like in its characteristics. But scientists and science-fiction writers have been highly inventive in their speculations about the possibilities of "life as we don't know it."15 A systematic discussion of all of the hypothetical nonterran life
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From page 16... ...
7. National Research Council, An Assessment of Balance in NASA's Science Programs, The National Academies Press, Washington, D.C., 2006, pp.
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From page 17... ...
" pp. 59-63 and 64-67 in National Research Council, Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques, The National Academies Press, Washington, D.C., 2002.
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