Recherche d'indices de vie sur Mars :
détermination de signatures spécifiques de biominéraux et étude expérimentale de l'évolution de molécules organiques dans des conditions environnementales martiennes

摘要

The essential conditions of a terrestrial life emergence have been present at the beginning of Mars' story. Therefore, Martian life forms could have appeared and their clues could have perpetuated. In the purpose of searching for those clues, our work took into consideration two targets of exobiological interest: the carbonated biominerals and the organic matter. In the first part, we have suggested the possibility that the thermal resistance temperatures of biotic and abiotic carbonates differ due to their intrinsic characteristics. We have compared them with DTA-TG thermal analysis and we have observed a difference of 15°C between the biological and abiotic domains. Hence, we have access to a non-equivocal biological signature. In the second part, we have tested the photostability and the evolution of carboxylic acids and a bacterial biomarker, exposed to the solar simulated UV radiations on Mars surface. To do so, we have developed a laboratory simulation experiment: M.O.M.I.E (Martian Organic Molecules Irradiation and Evolution). We have observed that the majority of the organic molecules have been destroyed. Only the mellitic acid produces one or further resistant organics. We have thus access to the organic matter rates, potentially present on the Mars surface/subsurface. Those two followed research orientations are therefore of great exobiological interest because they enable us to define the future experimental strategies in order to detect in situ a possible Martian biological activity.