Search for past life on Mars:: Physical and chemical characterization of minerals of biotic and abiotic origin

One of the major objectives of the future Martian surface probes will be to reveal a past or present biological activity. We propose that biominerals could have recorded such an activity at Mars, and thus could be interesting targets for these missions. Therefore, we try to find a method capable to discriminate biominerals from their geochemical counterparts. With this aim, various terrestrial aragonites of biotic and abiotic origins were studied as reference minerals, because they could have also been produced at Mars. Their thermal properties were studied with differential thermal analysis, and then compared. The results show that biotic aragonites thermally decompose at temperatures at least 20 degrees C lower than the temperatures of decomposition of abiotic aragonites. Therefore, the temperatures of thermal degradation of such biominerals could be a relevant parameter to find a past biological activity at Mars, and differential thermal analysis could be useful for situ astrobiological exploration of Mars.