Metabolic energy-based invasibility of methanotrophic life on Mars

English Abstract:

Potential evidence of the existence of methane in the Martian atmosphere on the order of parts per billion by volume (ppbv) has been reported over the past decade. Here, we demonstrate the possibility that methanotrophic microorganisms can be provided sufficient metabolic energy from methane oxidation, even at the extremely low mixing ratio of methane in the Martian atmosphere. Based on thermodynamic and kinetic calculations, the minimum methane mixing ratio requirements of various methanotrophic strains on the Martian surface or subsurface at low temperature and pressure extremes (180-270 K and 6-10 hPa) were estimated by balancing the cell-specific potential energy gain from methane oxidation and the minimum metabolic energy requirement. Our estimation suggested that methanotrophic bacteria can possibly maintain even at methane mixing ratios on the order of ppbv in the Martian atmosphere, but unlikely to proliferate in the absence of constant release of methane.