Extremophile Metabolite Study to Detect Potential Biosignatures and Interpret Future Gas Chromatography-Mass spectrometry Ocean Worlds in situ analysis (e.g. Dragonfly mission with its DraMS instrument and EuropaLander with its EMILI instrument).

International audienceOne of the objectives of the various space exploration missions carrying GC-MS (Gas chromatography coupled to mass spectrometry) instruments is the search for traces of life, in particular through the detection of biomolecules or bioindicators. This is for example the case of missions to Mars such as Mars Science laboratory and the SAM instrument but also the future ExoMars mission with the MOMA instrument. Up to date, we are looking for primary metabolites (such as fatty acids, amino acids or nucleobases) (Engel et al., 2001; Martins et al., 2008). Other organic molecules (produced by organisms) should also be considered for future space explorations of extant or present trace of life. More than 3.5 billion years ago, Mars had a similar weather and surface (in terms of geochemical composition, geodynamics, or resources necessary to define a planetary habitability (e.g. water, energy sources, complex organic molecules)) (Sterns et al., 2022; Raulin-Cerceau et al., 2004). Thus, the primordial soup necessary for the origin and evolution of life might be the same as on the Early-Earth. Therefore, if life exists or have existed on Mars, the primary cells produced on Mars might be similar to those found on Earth, and their (primary and secondary) metabolites might be identic. Based on this hypothesis, we have searched for biosignatures and bioindicators in extremophile cultures found in environmental Mars analogues, which may resist to the different stress measured on Mars (namely irradiation, salt matrices, low temperatures, water shortage, etc...): Chroococcidiopsis cubana and Halobacterium salinarum (Caiola et al., 2007; Ruginescu et al., 2019). To compare with a previous study conducted on these extremophiles with the TMAH thermochemolysis protocol, we conducted a parallel study with the two other wet chemistry protocols ahead the GC-MS analysis onboard the SAM , and the MOMA instruments, namely DMF-DMA and MTBSTFA derivatizations (Freissinet et al., 2010; Brault, 2016). The current study might help to understand which organic molecules are detectable with our space protocols and to construct a decisional tree for future in situ Mars results’ interpretations as it was a success analyzing ancient life fossils in Atacama desert (Crits-Cristopher et al., 2013; Santiago et al., 2018)