Currently, the surface of Mars is probably too cold, too dry, and too oxidizing for life, as we know it, to exist. But the subsurface is another matter. Life forms that might exist below the surface could not obtain their energy from photosynthesis, but rather they would have to utilize chemical energy. Methanogens are one type of microorganism that might be able to survive below the surface of Mars. A potential habitat for existence of methanogens on Mars might be a geothermal source of hydrogen, possibly due to volcanic or hydrothermal activity, or the reaction of basalt and anaerobic water, carbon dioxide, which is abundant in the martian atmosphere, and of course, subsurface liquid water. We report here that certain methanogens can grow on a Mars soil simulant when supplied with carbon dioxide, molecular hydrogen, and varying amounts of water.
Due to the hostile conditions at the surface, any life forms existing on Mars today would most likely inhabit a subsurface environment where conditions are potentially wetter and warmer, but organic compounds may be lacking and light energy for photosynthesis would be absent. Methanogens, members of the domain Archaea, are microorganisms from planet Earth that can grow under these relatively extreme conditions. We have demonstrated that certain methanogenic species can indeed grow on a Mars soil simulant, JSC Mars-l , with limited amounts of water, under conditions approaching a possible subsurface environment on Mars.
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