Conceptual Model for the Removal of Cold-Trapped H2O Ice on the Mars Northern Seasonal Springtime Polar Cap

The transport of H2O ice along the retreating north polar seasonal CO2 ice cap has previously been modeled and observed. Spectral observations show that H2O ice forms on the interior of the seasonal cap, while thermal observations show these regions to be consistent with CO2 ice. Prior to the sublimation of the seasonal CO2, the observed H2O ice deposits are diminished-and because H2O ice sublimation rates are extremely slow while in direct thermal contact with CO2 ice, an alternate removal process must be operating. We propose a model where the process of removing these H2O deposits starts with insolation-induced basal sublimation of the underlying CO2 ice. This sublimed gas would "seep" upward and into the interface between the two ices, increasing pressure until the gas pressure fractures the cold-trapped H2O ice. Small fragments would be suspended while larger fragments would be pushed aside, exposing the underlying CO2 ice.