Evidence for Seismogenic Hydrogen Gas, a Potential Microbial Energy Source on Earth and Mars

摘要

The oxidation of molecular hydrogen (H-2) is thought to be a major source of metabolic energy for life in the deep subsurface on Earth, and it could likewise support any extant biosphere on Mars, where stable habitable environments are probably limited to the subsurface. Faulting and fracturing may stimulate the supply of H-2 from several sources. We report the H-2 content of fluids present in terrestrial rocks formed by brittle fracturing on fault planes (pseudotachylites and cataclasites), along with protolith control samples. The fluids are dominated by water and include H-2 at abundances sufficient to support hydrogenotrophicmicroorganisms, with strong H-2 enrichments in the pseudotachylites compared to the controls. Weaker and less consistent H-2 enrichments are observed in the cataclasites, which represent less intense seismic friction than the pseudotachylites. The enrichments agree quantitatively with previous experimental measurements of frictionally driven H-2 formation during rock fracturing. We find that conservative estimates of current martian global seismicity predict episodic H-2 generation by Marsquakes in quantities useful to hydrogenotrophs over a range of scales and recurrence times. On both Earth andMars, secondary release of H-2 may also accompany the breakdown of ancient fault rocks, which are particularly abundant in the pervasively fractured martian crust. This study strengthens the case for the astrobiological investigation of ancient martian fracture systems.