Wet inside and out? Constraints on water in the Martian mantle and on outgassed water, based on melt inclusions in SNC meteorites

Constraints on the volatile inventory and outgassing history of Mars are critical to understanding the origin of ancient valley systems and paleoclimates. Planetary accretion models for Mars allow either a volatile-rich or volatile-poor mantle, depending on whether the accreted materials were fully oxidized or whether accretion was homogeneous so that water was lost through reaction with metallic iron. The amount of water that has been outgassed from the interior is likewise a contentious subject, and estimates of globally distributed water based on various geochemical and geological measurements vary from a few meters to more than a thousand meters. New data on SNC meteorites, which are thought to be Martian igneous rocks, provide constraints on both mantle and outgassed water.