Biological potential of low-temperature aqueous environments on Mars

Abstract

We have explored chemical weathering of probable martian materials at low temperatures based on the increasing evidence for non-hydrothermal water at or near the martian surface. Chemical weathering of minerals at low temperatures (as low as 0 °C) in aqueous environments on Mars can provide geochemical energy to support construction of potential martian organisms. Here, we examine the geochemical energy available from the interaction of the martian surface or near-surface materials with low-temperature water. We calculate the Gibbs free energy for 13 different weathering reactions that are likely to be important on Mars. The aqueous weathering of 1 kg of an ultramafic rock such as the Chassigny meteorite under present martian conditions can support the construction of ~30 g of microbes. The aqueous weathering of 1 kg of a basaltic rock on Mars can support the construction of ~26 g of biomass under present martian conditions and ~32 grams for conditions probable in the past. This means that ~1.3×10¹⁹ g of potential biomass could have been supported from weathering a global layer of rock 1 m thick. Thus, low-temperature water–rock reactions on Mars can produce abundant geochemical energy for potential martian microbes.