Potential Persistence of Ground Ice at Gale Crater, Mars Constrained Using Curiosity Rover REMS Data

Abstract:

Shallow ground ice in the equatorial region on Mars would be quickly lost to sublimation under current Martian climate conditions; however, it may persist at depth since its suggested formation during the most recent high obliquity of 32º approximately 500 ka ago when ice is believed to have been stable here. Ground‑based measurements by Curiosity Rover’s Environmental Monitoring Station (REMS) enable a detailed study of the processes that determine the rate of sublimation and the subsurface transport of heat and water vapor at Gale Crater. This study is prompted by an analogous investigation in the Dry Valleys of Antarctica where ground ice is currently unstable but has persisted ~0.5 m below the surface for over 1 Ma. A heat and vapor diffusion model is developed to understand the ground thermal regime and the persistence of potential ground ice in the equatorial region of Mars using the first year of data collected by Curiosity. Based on the derived thermal properties of dry regolith, including thermal inertia values ranging from 300 to 450 J m^–2 K^–1 s^–1/2, diurnal and annual temperature variations propagate to depths of 0.05 m and 1.3 m, respectively. The modeled rate of water‑vapor escape from the ground ice to the atmosphere corresponds to a sublimation rate of ~350 m Ma⁻¹ for ice at the ground surface; however, the sublimation rates increasingly deceases with depth as overlying dry regolith thickens. We explore whether interstitial ground ice that formed at Gale Crater ~500 ka ago during the last high obliquity period could currently exist at shallow depths. While this study does not account for the effects of replenishing processes, adsorption, diffusion-advection, and climate change influenced by obliquity, it highlights the potential persistence of ground ice and implications for future missions on Mars.