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We present improved Mars Odyssey Neutron Spectrometer (MONS) maps ofnear-surface Water-Equivalent Hydrogen (WEH) on Mars that have intriguingimplications for the global distribution of "excess" ice, which occurs when themass fraction of water ice exceeds the threshold amount needed to saturate thepore volume in normal soils. We have refined the crossover technique of Feldmanet al. (2011) by using spatial deconvolution and Gaussian weighting to createthe first globally self-consistent map of WEH. At low latitudes, our new mapsindicate that WEH exceeds 15% in several near-equatorial regions, such asArabia Terra, which has important implications for the types of hydratedminerals present at low latitudes. At high latitudes, we demonstrate that thedisparate MONS and Phoenix Robotic Arm (RA) observations of near surface WEHcan be reconciled by a three-layer model incorporating dry soil over fullysaturated pore ice over pure excess ice: such a three-layer model can alsopotentially explain the strong anticorrelation of subsurface ice content andice table depth observed at high latitudes. At moderate latitudes, we show thatthe distribution of recently formed impact craters is also consistent with ourlatest MONS results, as both the shallowest ice-exposing crater and deepestnon-ice-exposing crater at each impact site are in good agreement with ourpredictions of near-surface WEH. Overall, we find that our new mapping isconsistent with the widespread presence at mid-to-high Martian latitudes ofrecently deposited shallow excess ice reservoirs that are not yet inequilibrium with the atmosphere.

Driven by Excess? Climatic Implications of New Global Mapping of Near-Surface Water-Equivalent Hydrogen on Mars