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B. M. Jakosky, E. S. Varnes, T. M. McCollom (LASP, Univ. of Colorado)
We have developed numerical geochemical models of martian hydrothermal systems to address the question of whether they are capable of supporting life. Models simulate the geochemical consequences of mixing hydrothermal fluids, formed from the interaction of water with rock in the vicinity of a heat source, with fresh groundwater. Host rock compositions are based upon the compositions of the martian meteorites, and are reacted at high temperature with one of three different waters to form the vent fluid. The resulting vent fluids are reacted with increments of fresh groundwater, simulating the mixing that occurs in hydrothermal systems. Water compositions are pure water either in equilibrium with the martian atmosphere or with Pathfinder-composition soils and the atmosphere. During mixing, oxidation and reduction reactions are kinetically inhibited; organisms may exploit this inhibition to derive metabolic energy. For each model run, the free energy is calculated for methanogenesis and for sulfate reduction; these reactions are important for terrestrial chemosynthetic organisms and are taken as representative for putative martian organisms. Results indicate that substantial amounts of energy may be derived from these reactions, depending most sensitively upon the aqueous hydrogen content of the hydrothermal fluid, type of host rock, and to a lesser extent upon whether saturated species precipitate to equilibrium. Energy yields are largest when the host rock is ultramafic. Given the lack of knowledge about martian crustal composition, groundwater abundance, and the abundance and history of hydrothermal systems, it is uncertain whether sufficient energy is available to support martian life, although it is likely that suitable environments exist.
(This research supported through the NASA Astrobiology Institute.)
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.