Implications for volcanogenic volatile release on the weathering of Mars

Volcanism on Mars has been widespread in both space and time. Notwithstanding important specific differences between the mantles of Earth and Mars, the similarities are such that the suite of gases emitted from martian volcanic activity surely includes gases such as H2O, CO2, S-containing gases (H2S, SO3, or SO2), and Cl-containing gases (e.g. Cl or HCl). Both H2O and CO2 are present in the atmosphere of Mars; both are also present as surface condensates. Spectroscopic observations of the martian atmosphere clearly show that the S- and Cl-containing gases are severely depleted. Likewise, there is no evidence of surface condensates of compounds of these elements. Within the soil, there is direct evidence of incorporation of H2O and some compounds of sulfur and chlorine. None of the resultant weathering products have been directly identified, but both clays and salts have been indirectly implicated. Other aspects of the implications for volcanogenic volatile release on the weathering of Mars are discussed.