Dust aerosols above the south polar cap of Mars as seen by OMEGA

TL;DR

This study uses OMEGA/Mars Express observations to map and analyze the temporal and spatial variations of dust aerosols above the south polar cap of Mars during 2005, revealing dynamic dust activity and its possible interactions with water ice clouds.

Contribution

First detailed mapping of dust aerosol optical depth above Mars' south polar cap using near-infrared data from OMEGA, highlighting dust variability and seasonal patterns.

Findings

Dust aerosols significantly influence surface reflectance in the near-IR.

Dust optical depth varies on small spatial and temporal scales.

Late summer dust peaks propagate to the south pole, possibly linked to water ice clouds.

Abstract

The time evolution of atmospheric dust at high southern latitudes on Mars has been determined using observations of the south seasonal cap acquired in the near infrared (1-2.65 {\mu}m) by OMEGA/Mars Express in 2005. Observations at different solar zenith angles and one EPF sequence demonstrate that the reflectance in the 2.64 {\mu}m saturated absorption band of the surface CO2 ice is mainly due to the light scattered by aerosols above most places of the seasonal cap. We have mapped the total optical depth of dust aerosols in the near-IR above the south seasonal cap of Mars from mid-spring to early summer with a time resolution ranging from one day to one week and a spatial resolution of a few kilometers. The optical depth above the south perennial cap is determined on a longer time range covering southern spring and summer. A constant set of optical properties of dust aerosols is consistent with OMEGA observations during the analyzed period. Strong variations of the optical depth are observed over small horizontal and temporal scales, corresponding in part to moving dust clouds. The late summer peak in dust opacity observed by Opportunity in 2005 propagated to the south pole contrarily to that observed in mid spring. This may be linked to evidence for dust scavenging by water ice-rich clouds circulating at high southern latitudes at this season.