Volatile-driven Morphologies Relating to Zones of High Weh in Xanthe Terra

Introduction: The Mars Odyssey Neutron Spectrometer has detected concentrations of hydrogen within the upper few decimeters of the martian surface using counts of thermal, epithermal, and fast neutrons [1]. Hydrogen concentrations are interpreted in terms of mass fractions of H2O , which is most likely in the form of ice at the highest latitudes and subsurface deposits of chemically/physically bound H2O and/or OH in the low to middle latitudes. A map of WEH concentrations can be seen in Figure 1. Prominent low to mid-latitude regions having moderate hydrogen concentration include western Xanthe Terra (Fig. 2), northeast of Vallis Marineris and centered near Shalbatana Vallis, and eastern Hellas Planitia in the southern hemisphere. Both regions are densely cratered and contain extensive and widespread channel systems. Relatively small impact craters (100’s of meters in diameter) and channels (10’s of meters in relief) can provide important clues to the history of volatiles within the upper few meters of crustal materials. In addition, relatively thin mantles (a few meters), and/or stacks of these, that display evidence for ductile flow (such as lobate fronts) may also be used to investigate the concentration of volatiles in the upper few meters of crustal materials. Impact craters in the eastern Hellas region have been thoroughly surveyed for evidence of volatile related degradation [2]. Numerous morphologies indicative of the deposition and flow of volatile-rich sediments are present on the walls and floors of craters in