Martian volatiles determined using the Mars observer gamma ray spectrometer

The relative abundances of H2O and CO2 and their latitude, longitude, and depth profiles on Mars sensitively reflect, as well as help control, past and present Martian climate patterns. Seasonal variations of their distributions at high latitudes also reflect and help control global weather patterns and erosion through surface weathering. A combined analysis of gamma ray line and neutron flux maps constructed from data measured using the Mars Observer Gamma Ray Spectrometer (MOGRS) should allow a determination of seasonal changes in both the horizontal and vertical structure of CO2 ice that covers the north polar cap during winter and the south polar cap throughout the year and both the horizontal and vertical structure of residual H2O ice within the top meter of the surface that was predicted from Viking observations to exist primarily at high latitudes. Particularly important in this regard will be maps of thermal and epithermal neutron fluxes measured using the MOGRS anticoincidence shield, the intensity of the hydrogen, neutron capture gamma ray line at 2.223 MeV, the intensity of a capture gamma ray line as 1.725 MeV from iron, and the intensity of an inelastic scatter gamma ray line as 1.779 MeV from silicon.