Survival of non-psychrophilic methanogens exposed to martian diurnal and 48-h temperature cycles

Abstract

Polygonal ground and other geomorphological features reminiscent of recent freeze/thaw cycling are evident on Mars, despite the widespread belief that the planet is currently inhospitably cold and dry. On Earth, permafrost microbial communities are subjected to wide ranges in temperature and are often active at subfreezing temperatures. The existence of active microbial communities within permafrost on Earth suggests that permafrost on Mars may constitute a habitable environment.Terrestrial microbial permafrost communities typically contain methane-producing Archaea, which is cause for concern as global temperatures rise, resulting in permafrost thaw and the release of the potent greenhouse gas. Similarly, on Mars, the overlap between patterned ground and detections of localized methane plumes suggest that the compound may have been released from thawing permafrost.Analyses of permafrost ice cores and soil samples on Earth note that (1) archaeal communities often contain both mesophiles and psychrophiles at different depths and (2) active methane is being produced at subfreezing temperatures over geological timescales. Thus, the purpose of the experiments described here was to determine the effect of extreme temperature changes (reminiscent of the martian diurnal temperature cycle) on the growth and survival of four non-psychrophilic methanogens previously used as models for potential life on Mars. The results indicate that non-psychrophilic methanogens are capable of survival during extreme diurnal and 48-h temperature changes, similar to those on Mars.