The organic signatures of life on Mars

The search for extraterrestrial life is one of the ultimate challenges for science. Mars was the only planet ever to be targeted for a life searching mission (NASA’s Viking) and still remains the main focus regarding the search of extraterrestrial life. This thesis aims to find out what are the best locations on Mars to search for biosignatures of life (amino acids) and contribute to the preparation of future space missions to the Red Planet. In this thesis, two Mars soil analogues were studied: Rio Tinto in Spain and the hypersaline lakes of the Yilgarn Craton in Western Australia. Investigation of their mineralogical, microbiological and biosignature content provided hints of what future life searching missions may find in similar environments on Mars. A third set of samples, comprised of mineral standards that are relevant in the martian surface, was also used to study the influence of mineralogy in the preservation of biosignatures under simulated Mars conditions. Overall, results show that both Mars soil analogues contained minerals that are commonly found on Mars, such as iron oxides, clays and evaporites. Generally, microbiology analyses show that life on Mars was/may be based on iron metabolism and/or halophilic. No obvious correlations were found between mineralogy, microbiology communities and biosignature content on both analogues. Detection of biosignatures was not straightforward even when life is known to be present in the sediments. Therefore, in situ detection of biosignatures on Mars may be a very difficult task and frequent sampling should be considered in future life searching missions. Results from Mars Chamber simulations suggest that locations containing sulfate minerals and smectite clays should be priority targets for the search of organic signature of martian life, due to their potential to preserve biosignatures and the fact that they usually indicate the presence of habitable environments.Open Acces