Surface Roughness Evolution and Implications for the Age of the North Polar Residual Cap of Mars. Issue 12 (17th December 2020)

• Record Type: Journal Article
• Authors: Wilcoski, A. X.; Hayne, P. O.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-17
• Subjects: Ice -- North Polar Layered Deposits -- North Polar Residual Cap -- Mars; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006570
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: An understanding of the current state of the Martian North Polar Residual Cap (NPRC) is needed to understand the North Polar Layered Deposits (NPLD) as a whole and the recent climate history of Mars. We investigate the evolution of small‐scale (∼10s of m) surface topography on the NPRC using an insolation‐driven ice accumulation/ablation model. We apply a coupled thermal and atmospheric model that calculates ice fluxes at each point on a model surface, allowing the topography to evolve through time. Our thermal model is validated using NPRC surface temperature data gathered by the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter (MRO). Roughness developed on the model surface is comparable to that of the NPRC, as we demonstrate using two examples of NPRC surface texture observed using the High‐Resolution Imaging Science Experiment (HiRISE) onboard MRO. We find that insolation‐driven accumulation and/or ablation yields surface roughness with characteristic spatial wavelengths ∼10 − 50 m—comparable to those observed on the NPRC—over timescales of 1–10 ka. The dominant topographic wavelength of a model surface increases as the surface evolves, implying that the wavelengths of topographic features observed on the NPRC may be indicative of the surface ages of those regions. Plain Language Summary: At the north pole of Mars lies a large ice cap composed of vertically stacked layers of water ice. These layers of ice can tell us about the history of the Martian climate over the last several million years, similar to how ice cores from glaciers here on Earth can tell us about Earth's past climate. Here, we focus on the surface of the topmost layer of the Martian ice cap, and model how it interacts with the current Martian atmosphere to better understand how other layers may have formed in the past. We model the growth or loss of ice on the surface, and how this growth or loss depends on the amount of water vapor in the atmosphere. Our results show that the size of mounds and depressions on the ice cap surface suggest that it took 1–10 thousand years to form these roughness features. Our results also suggest that the formation of features on the surface may depend on when water vapor is present in the atmosphere over the course of a year (e.g., summer or winter). Key Points: Insolation‐driven sublimation can reproduce observed textures on Mars' north polar residual ice cap The observed residual cap roughness emerges in 1, 000–10, 000 years Both accumulation and ablation can increase ice surface roughness