Experimental silicification of extremophilic Archaea, Methanococcus jannaschii. Applications for the search of evidence of life in early Earth and extraterrestrial rocks.

Abstract : Early life forms on Earth included chemolithotrophic organisms and such organisms would probably have existed on Mars, if life was present on that planet. Since the earliest life forms known to date (> 3 Gyr) were preserved due to the precipitation of dissolved silica on cellular structures (silicification), we undertook an experiment to silicify a type of microorganism that could have existed in the environmental conditions of early Earth and early Mars, given the different environmental conditions. We chose the thermophilic species Methanococcus jannaschii (methanogenic Archaea) as a representative of an anaerobic, autotrophic, thermophilic microorganism. This is the first time that an Archaea has been used in a simulated fossilisation experiment and one of the very first fossilisations of an hyperthermophile microorganism. Given the tentative identifications of CH4 gas in the atmosphere of Mars, this experiment is of high relevance to analogue martian studies.