NASA Astrobiology Institute (NAI)

We are exploring the geochemical environment of the martian surface and near-surface regions, in order to understand constraints on habitability by microorganisms. In particular, we are examining the chemical reactions that take (or took) place in the geological environment, and calculating the amounts of energy that are released that could by used by microbes to support metabolism. As chemical energy is the likely source of energy to support martian organisms, its tabulation provides a strong constraint on the amount of life that could have or can be supported there. We can compare the results to similar calculations in terrestrial environments, in order to compare martian and terrestrial habitability.

We completed our analysis of the Meridiani site where the Opportunity rover explored. We utilized likely mineralogical starting points and used observations of the current state, and determined the energy released during the history of the surface materials. This provides a specific estimate of the habitability of this location and the locations occupied by the surface materials in the past. As this is a low-temperature aqueous environment, it constrains habitability of similar locations on Mars.
We began comparable analysis of the Spirit site. This site shows evidence for alteration at raised temperatures, and would provide complementary information related to sites of possible hydrothermal alteration.
In both cases, we are determining the ability of these sites to have sustained life in the past, and the viability of these sites as locations from which samples of the martian surface could be returned to Earth for more-detailed study.