Estimation of H2O content (in wt%) stored in hydrated silicates at Mars

In the past decades, numerous hydrated silicates have been detected at the surface of Mars from orbital and in situ characterization. The study of their distribution and their quantification can enable to trace the history of water at the surface of the red planet. By quantifying the content of each minerals at the hydrated sites, we can have an estimation of the water content stored at the surface within these minerals. Our study is based on the modal compositional maps of 11 hydrated silicates that were detected with the OMEGA/MEx instrument (Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité). The maps were computed using a radiative transfer model applied to the hyperspectral images of OMEGA, where hydrated minerals features were previously detected. They results in global maps of modal composition at a resolution sub-kilometric of: Fe,Mg,Al-phyllosilicates, Al-smectite, AlSiOH, Opal, Mg-carbonates, Chlorite, Fe/Mg-Micas, Serpentine and Fe-hydroxide and were recently published in Riu et al., 2022. By estimating the water content of each individual end-members we were able to convert the 11 mineralogical maps into one final map of H₂O content (in wt%). The average content of water, based on the content stored in hydrated silicates, is estimated to be slightly above 5 wt%, with some rare occurrences > 20 wt%. The ongoing studies now aim at a detailed analysis of the water distribution in order to look for new regions with high past aquability (stable liquid water) potential and/or exobiological potential, if such locations exist. The map will be studied locally in combination with high resolution images in order to correlate the high-water content with their context and highlight new regions of interest. A detailed analysis of the ExoMars22 Rosalind Franklin Rover is also foreseen in order to help the future in situ analysis of the ExoMars mission and contribute to ISRU (in situ ressource utilization).