Development and Evolution of Icy Layer Outcrops on Mars' North Polar Ice Cap: Observations of Vertical and Lateral Variability

Abstract

Mars' north polar ice cap features troughs that cut into the ice, exposing subsurface layers of different brightness and topographic expression. Specifically, these layers represent two different stratum types: lower albedo (higher dust content) marker beds, which protrude out of the wall topographically, and higher albedo (i.e., icier) interbeds, which are recessed compared to the marker beds. Here, we investigate the role of local-scale processes by performing a detailed geomorphic characterization of variability in these strata across two sites, using a novel approach to calculating true layer protrusion which utilizes data from high-resolution Digital Terrain Models. We measure protrusions of the order of meters but find lateral variations within a single trough exposure, suggesting a role for local-scale processes in the evolution of the layers. We find that the topographic relief of protruding marker beds decreases as a function of decreasing trough slope and brightness (a proxy for dust cover/content). We also observe the presence of an insulative allochthonous dust veneer present on discrete sections of the trough wall, which we suspect plays an important role in modulating ice loss from the trough walls. A companion paper (Bramson et al., 2025, https://doi.org/10.1029/2024JE008360) models the contribution of insolation-induced sublimation to present a new framework, and potential timescales for the development of the marker bed protrusion observed here.