Geological study of the hydrated formations on the plateaus around Valles Marineris, Mars: Implications for the evolution of geochemical conditions through time

We realized a geological study of the hydrated formations located on the plateaus around Valles Marineris based on the analysis of HiRISE and CRISM data. We showed that the upper part of the Noachian basement locally displays an Alphyllosilicate-rich formation, which is topographically and stratigraphically above a Fe/Mgphyllosilicate-rich formation. This mineralogical stratigraphy is consistent with the aqueous alteration of the Noachian plateaus by pedogenesis under alkaline to neutral conditions. These formations are overlain by the sulfate/opaline silica-rich formation, which was formed under acidic conditions at the Hesperian time or later.