Biogenic Methane on Mars?
The presence of methane in the near-surface atmosphere of Mars is a scientifically established fact (Krasnopolsky 2006; Formisano et al. 2004), and Formisano et al. (2004) have stressed the direct correlation to locations with an enhanced presence of water/ice. The global production rate of methane...
| Main Authors: | , |
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| Format: | Conference Object |
| Language: | unknown |
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2007
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| Online Access: | https://epic.awi.de/id/eprint/18118/ https://hdl.handle.net/10013/epic.28651 |
| Summary: | The presence of methane in the near-surface atmosphere of Mars is a scientifically established fact (Krasnopolsky 2006; Formisano et al. 2004), and Formisano et al. (2004) have stressed the direct correlation to locations with an enhanced presence of water/ice. The global production rate of methane on Mars has been estimated to be of the order of about 3 x 105 kg methane per (terrestrial) year, or about 34 kg methane per hour. Liquid interfacial water in form of premelted ice and adsorbed water is unavoidable in case of the presence of water-ice and of atmospheric water vapor, also under martian conditions (Möhlmann, 2007). The resulting freezing point depression will cause interfacial water to remain liquid down to about 190 K. Thus, the observed direct correlation between the local or regional presence of atmospheric methane and of ice is understood as an indication for a direct coupling between methane and liquid interfacial water in the subsurface of Mars.As been shown by laboratory experiments, terrestrial methanogenic archaea isolated from Siberian permafrost soils are well able to survive martian thermophysical conditions at least over the experiment duration of three weeks (Morozova et al., 2007). These martian conditions were a diurnal temperature profile between 210 K and 280 K, a related diurnal profile of the atmospheric water content between saturation (aW = 1) and dry (aW < 0.03) conditions, all at a total pressure of 6 mbar CO2. Methanogenic archaea from terrestrial permafrost survived these conditions, while methanogens from non-permafrost environments did not show any activity after the simulation, which correspond with a drastically decrease in their cell numbers (< 5% in comparison to the amount of the beginning of the experiment; Fig. 1). Furthermore, the survival potential of methanogens from permafrost exposed to different environmental stress conditions such as low temperature (down to 78°C), high salinity (up to 6 M NaCl), starvation (up to 3 months), long-term freezing (up to two ... |
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