Methanogenic Archaea in terrestrial permafrost as a model for probable microbial life on Mars

Current ESA mission Mars Express determined water on Mars, fundamental requirement for life, and presence of CH4 in the Martian atmosphere, which could be originated only from active volcanism or from biological sources. This finding implicates that microbial life could still exist on Mars. One possibility for survival of Martian primitive life might be subsurface lithoautotrophic ecosystems, which are also exist in permafrost regions on Earth.Within the scope of DFG Priority Program Mars and the Terrestrial Planets we study the resistance of methanogenic archaea from Siberian permafrost to different extreme life conditions of terrestrial or extraterrestrial permafrost: desiccation, temperature extremes, radiation, high salt concentration and simulated Mars conditions. The methanogenic archaea in pure cultures as well as in their natural environment of Siberian permafrost represent high survival potential under these extreme conditions. Significant CH4 formation appeared even by incubation with saturated salt solution (0.02 nmol CH4 h-1 g-1), radiation dose up to 5000 Jm-2 (0.8 nmol CH4 h 1 g 1), desiccation for more than 3 weeks (5.24 nmol CH4 h-1 ml-1) and extremely low temperatures of -80°C (5.57 nmol CH4 h-1 ml-1). The capability of these organisms to grow under lithoautotrophic anaerobic conditions, long-term survival under harsh natural environments of permafrost and high resistance to the different extreme conditions as well as to the simulated Martian environments make methanogens to the most suitable keystone organism for the investigation of possible Martian life.