Distribution and state of H2O in the high-latitude shallow subsurface of Mars

The state and distribution of H2O molecules at high latitudes are evaluated numerically with emphasis on the effects of seasonal temperatures on the kinetics of H2O transport. The investigation is carried out with a thermal model for the regolith regions from the surface through the ice interface and an atmospheric model for the H2O vapor density at the surface as a function of latitude. Few differences are found in the state and distribution of H2O whether the regolith is composed of Montmorillonite or basalt. During an obliquity cycle, the average exchanged H2O mass is determined to be in the range 1-20 gr/sq cm over the planetary surface, with a total maximum exchanged volume of 1500 cu km of H2O. The exchanged mass would arise mainly from ground ice in the case of a basalt regolith and from adsorbed H2O with Montmorillonite. Finally, seasonal ice stabilization is expected to occur at latitudes above 40 deg when obliquities exceed 25 deg.