SUBLIMATION OF POLAR ICES UNDERLYING DUNE SANDS ON MARS

Water once played a crucial role in shaping the Martian landscape; however, at present, aeolian processes are the dominant force. In the polar regions, a combination of cryogenic and aeolian processes creates unique features, such as dunes superimposed on polar ice. A study looking over the North Polar dune fields, specifically Chasma Boreale and near Olympia Cavi, identified shallow pits (~100s of meters in length and width) within and around these dune fields. These pits are resolvable in images from the High-Resolution Imaging Science Experiment (HiRISE) camera. Some of them contain lineations that resemble barchan dune cross-stratification, which leads to the question of whether the pits form in association with the migrating dunes.

Our study investigates whether the presence of the dunes is causing the formation of these shallow pits in the ice. Specifically, we hypothesize that if the dune sands, warmed by the Sun, generate enough basal heat, they could sublimate the underlying ice, leading to the formation of these pits.

Using KRC, a numerical thermal modeling program that uses thermal inertia values alongside other material properties, we model surface and subsurface temperature profiles starting with a 1D profile of sand atop ice. Profile combinations include basalt sand and gypsum sand over H₂O ice and CO₂ ice. We stacked the 1D models to create a 2D model of a dune in cross-section. We observed that under current Martian climate conditions, sublimation is possible beneath thinner sand portions of the dunes with either basalt or gypsum sand atop CO₂ ice. However, temperatures do not get warm enough to sublimate H₂O ice with either basalt or gypsum sand. We speculate that the pits may result from a possible mixture of both H₂O and CO₂ ice, as Mars’ North Polar region is primarily composed of H₂O ice with a seasonal CO₂ ice cap.

Understanding the formation and evolution of these pits can provide insight into the climate history and current environmental conditions of Mars, which is essential for future exploration and the search for life on Mars.