MINERAL RECORDS OF HABITABILITY: LESSONS LEARNED FROM CONTINENTAL SERPENTINITES

Recent work has shown that serpentinization, the aqueous alteration of ultramafic rocks to serpentine-dominated assemblages, generates ample chemical energy to support microbial life in the deep subsurface. Primary problems with serpentinite-hosted life involve the profound dearth of carbon and the stresses of extremely high pH on rock-hosted organisms. The thermodynamic cases for a suite of feasible metabolisms driven by free energy can be ground-truthed only by evidence of microbiological activity in real rocks. Here I (a) report results of geochemical modeling of metabolisms driven by redox disequilibria related to the reducing chemistry of serpentinizing formation fluids in continental sites and (b) relate them to known microbiological groups. This strategy of inferring habitability from mineralogy remains pertinent to assessments of deep life on Earth and also to discourse on the origin of life on Earth and astrobiology.