Topographic control of hydrogen deposits at low latitudes to midlatitudes of Mars

Correlations between the longitudinal wave number two distribution of water-equivalent hydrogen (WEH) at low latitudes to midlatitudes of Mars with variations in topography, surface albedo, thermal inertia, regional dust storms, and atmospheric water vapor are explored to provide guidance in determining the mechanisms that recharge or maintain these WEH reservoirs. The closest match is with low thermal inertia coupled with orographic control of the present-day atmospheric circulation dynamics. The engine for the simulated longitudinal two-wave pattern (maxima in Arabia and Tharsis) is relatively cold nighttime surface temperatures and large-amplitude temperature inversions that concentrate water ice over these regions. Geologically recent precipitated water ice, by itself, is insufficient to account for the observed distribution of WEH. Retention of precipitate by hydratable minerals is necessary. While current research cannot presently identify the hydration mechanism for the WEH distribution (whether it be from a past obliquity, present climate conditions, or some convolution of both), this research suggests that current climatic conditions can sustain, if not emplace, the observed longitudinally constrained distribution of equatorial WEH.