Mars simulations relevant to planetary protection

We have recently investigated the native amino acid composition of two analogs of martian soil, JSC-1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low-latitudes on the martian surface. We have quantified the amino acid content of these two martian regolith simulants using high performance liquid chromatography (HPLC). In doing so we have obtained data that are useful for biological, chemical, and physical studies of analogs to martian surface materials. We have also investigated the influence of UV radiation, low temperatures and gaseous CO2 on the intrinsic amino acid composition of both martian soil analogs. Exposure to energetic ultraviolet light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which has been interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H2O are at work within the martian soil analogs. We also tested the radiation resistance of Natronorubrum sp. HG-1 (halophilic bacteria) in air and repeated those experiments in the Mars simulation chamber by mixing the halophilic microbe into martian regolith analogs. In this paper we discuss the relevance of Mars simulations for life detection and for planetary protection issues.