Development and Evolution of Icy Layer Outcrops on Mars' North Polar Ice Cap: A Sublimation-Based Framework

Abstract

Troughs carved into Mars' polar ice cap expose layers of different brightness and topography. These layers can be divided into two strata types: darker, higher dust content marker beds and brighter, lower dust content interbeds. In a companion paper (Pascuzzo et al., 2025, https://doi.org/10.1029/2024JE008377), we measure the topographic protrusion of the marker beds and interbeds. Here, we investigate processes and factors that contribute to the evolution of these layers to gain insight into the sublimation rates and timescales for active trough wall retreat, specifically the development of observed layer topography. We perform thermal modeling and ice sublimation calculations to explain the topography and its lateral variations. We use our results to develop a novel sublimation-based framework for the development of marker bed protrusion. Our results suggest that marker beds can develop the observed meter-scale protrusions in thousands of years via cyclical bursts of differential sublimation modulated by lag production and removal. We find that marker bed topography can easily be formed within a single period of high insolation driven by Mars' axial precession. If the present-day topographic signatures of exposed trough strata are driven strictly by the differential sublimation and lag processes proposed here, our results suggest that ice retreat may have occurred ∼60–125 kya, with the topographic relief forming in 1–20 kyr. These results also lead us to suggest that thick insulative allochthonous dust veneers (such as that observed in Pascuzzo et al. (2025, https://doi.org/10.1029/2024JE008377)) may play an important role in forcing hiatuses in trough wall retreat during high insolation periods.