14:00 〜 14:15
[MIS19-02] エネルギー代謝論から推定する火星の湖水ー地下水混合域におけるハビタビリティ
キーワード：ハビタビリティ、火星、水－岩石反応
Geochemical and mineralogical analyses of sedimentary deposits in Gale crater, Mars, as well as experiments and simulations based on these data, revealed that liquid water that existed on early Mars was suitable for microbial life [1]. However, the possible energetic habitability of Mars has not been quantitatively constrained.
In this study, we conducted water-rock reaction modeling and Gibbs free energy calculations to constrain (i) the water chemistry of ancinet lake water and groundwater that may exist in Gale crater and (ii) the potential energetic availability for metabolic reactions in the lake-water-groundwater mixing zone. Water-rock reaction modeling considered both reducing (H2 0.1 bar + CO2 0.9 bar) and oxidizing (O2 2 mbar + CO2 0.998 bar) Martian atmospheres. In the case of oxidizing atmosphere, sulfide oxidation provides the most catabolic energy. Under reducing atmospheric conditions, hydrogenotrophic methanogenesis and hydrogenotrophic sulfate reduction can be exergonic. The predicted free energy density (kJ/ kg groundwater) in reducing and oxidizing Martian atmospheres is comparable to that of the Earth’s seawater-hydrothermal mixing zone, where active microbial activity exists. Thus, the modeling results suggest that the ancient Gale crater lake may have been an energetically suitable environment for microorganisms if life had evolved on Mars.
Reference
[1]Grotzinger et al. (2014) Science, 242, 1242777.
In this study, we conducted water-rock reaction modeling and Gibbs free energy calculations to constrain (i) the water chemistry of ancinet lake water and groundwater that may exist in Gale crater and (ii) the potential energetic availability for metabolic reactions in the lake-water-groundwater mixing zone. Water-rock reaction modeling considered both reducing (H2 0.1 bar + CO2 0.9 bar) and oxidizing (O2 2 mbar + CO2 0.998 bar) Martian atmospheres. In the case of oxidizing atmosphere, sulfide oxidation provides the most catabolic energy. Under reducing atmospheric conditions, hydrogenotrophic methanogenesis and hydrogenotrophic sulfate reduction can be exergonic. The predicted free energy density (kJ/ kg groundwater) in reducing and oxidizing Martian atmospheres is comparable to that of the Earth’s seawater-hydrothermal mixing zone, where active microbial activity exists. Thus, the modeling results suggest that the ancient Gale crater lake may have been an energetically suitable environment for microorganisms if life had evolved on Mars.
Reference
[1]Grotzinger et al. (2014) Science, 242, 1242777.