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.