Sublimation of the Martian CO2 Seasonal South Polar Cap

TL;DR

This study uses near-infrared observations to analyze the asymmetric sublimation of the Martian CO2 seasonal south polar cap, revealing a two-phase process with implications for Martian climate and atmospheric circulation.

Contribution

It provides the first unambiguous detection of surface CO2 and estimates sublimation asymmetry, introducing a two-step sublimation model based on Mars Express data.

Findings

Sublimation is nearly symmetric from Ls=180° to 220° with a slight cryptic advantage.

Post Ls=220°, anti-cryptic sublimation dominates, leading to 22% more mass sublimated.

Results suggest more snow precipitation in the anti-cryptic region.

Abstract

The polar condensation/sublimation of CO2, that involve about one fourth of the atmosphere mass, is the major Martian climatic cycle. Early observations in visible and thermal infrared have shown that the sublimation of the Seasonal South Polar Cap (SSPC) is not symmetric around the geographic South Pole. Here we use observations by OMEGA/Mars Express in the near-infrared to detect unambiguously the presence of CO2 at the surface, and to estimate albedo. Second, we estimate the sublimation of CO2 released in the atmosphere and show that there is a two-step process. From Ls=180{\deg} to 220{\deg}, the sublimation is nearly symmetric with a slight advantage for the cryptic region. After Ls=220{\deg} the anti-cryptic region sublimation is stronger. Those two phases are not balanced such that there is 22% +/- 9 more mass the anti-cryptic region, arguing for more snow precipitation. We compare those results with the MOLA height measurements. Finally we discuss implications for the Martian atmosphere about general circulation and gas tracers, e.g. Ar.