New Publication - Thermodynamic Constraints on H2 Production and Habitability From Mg-Rich Serpentinites as Mars Analogs

Mg-rich serpentinite and magnesite minerals on Mars may have supported microbial life during their formation, much like active serpentinization zones on Earth support microbes today. These serpentine-bearing terrains are significant because serpentinization generates hydrogen and methane gas through water-rock interactions, providing chemical energy for subsurface microbial communities. However, previous studies of terrestrial serpentines as Mars habitability analogs have focused primarily on Fe-rich systems, which produce more biologically useful H2 and secondary gases than their Mg-rich counterparts. This created uncertainty about whether Mars's abundant Mg-rich serpentines could support life. In this study, we used fluid and rock chemical equilibrium models to understand past conditions responsible for the formation of five Mg-rich serpentinite zones across Sri Lanka. Our models successfully reproduced both serpentinite and magnesite minerals (co-occurring as observed on Mars), showing that these minerals form naturally under specific temperature and water-rock conditions. Despite being Mg-rich, these systems contain sufficient iron to produce H2 yields comparable to Mars-relevant estimates. Across the region, serpentine formation conditions were predicted to support high biomass microbial populations using H2, and secondarily, CH4. This study shows that Mg-enriched serpentine zones should not be dismissed as potential habitats, since the key factor has sufficient ferrous iron and appropriate water-rock ratios.