Surface Dust Coverages on Rock Targets in Gale Crater: Influence of Elevation, Proximity to Aeolian Sand Fields and Seasonality

Martian dust is mobilized throughout the year by local, regional, and global dust storms, influencing atmospheric opacity and inhibiting observations of the surface. Using Mars Hand Lens Imager (MAHLI) images and methods of Schmidt et al. (2018), https://doi.org/10.1029/2018je005553, areal dust coverages on 368 near-horizontal, undisturbed rock surfaces were estimated along six Mars Years of the Mars Science Laboratory (MSL) Curiosity rover's geologic traverse from mission sols 46–3,409, corresponding to Mars Year 31 (MY#; Clancy et al., 2000, https://doi.org/10.1029/1999JE001089), areocentric solar longitude (Ls) 175.9° through MY36, Ls 177.6°. Targets were evaluated for potential geospatial and seasonal (Ls) correlations. Dust coverages increased at each spring equinox (Ls = 0°) with the highest coverage (76.6%) recorded at the top of Vera Rubin Ridge (VRR) prior to the Mars Year 34 (MY34) global dust storm. Dust coverages annually decreased as prevailing wind strengths in the Gale crater increased during southern summer. Following the ascent of VRR, New Year maximums have decreased by approximately 15% annually (MY35 60.7%, and MY36 52.8%), suggesting that dust is less abundant at higher elevations on Mount Sharp, and/or that dust suspension or removal is enhanced at higher elevations by stronger winds at higher elevations. Two regions with relatively low dust coverages (<20%) were found in proximity to active aeolian sand dunes and are interpreted to result from saltating sand particles striking and lofting dust particles. This research represents the single longest recording of surface dust deposits to date for landed missions.