The Physical Properties and Geochemistry of Grains on Aeolian Bedforms at Gale Crater, Mars

This study reports on the physical properties and geochemistry of aeolian bedform grains along the Curiosity rover traverse in Gale crater from Vera Rubin Ridge to the Sands of Forvie (Sols 1902-2995), and includes comparisons to results made earlier in the mission. Volumetrically, <150 mu m grains dominate active aeolian bedforms in the study area, similar to previous findings elsewhere at Gale crater and at other locations on Mars. Coarser grains, up to 2.9 mm long, are present on larger active bedforms. The larger 1-3 mm active grains commonly are reddish or whitish in color and irregular in shape, suggesting erosion of local bedrock as sources. One inactive megaripple had a surface of dust-covered 2-15 mm grains, with smaller <150 mu m grains between and within the bedform interior. Geochemical measurements show element concentrations vary according to position on the bedform, sand activity, and grain contributions from local bedrock. A strong positive correlation between Mg and Ni is identified on active bedform surfaces, with the highest Ni always corresponding to ripple crests where the coarsest gray and clear grains were commonly found. There is also a correlation between Ti and Cr for the majority of active sands, with the finer active sands in ripple troughs and sand patches having the greatest number of red grains and highest Cr concentrations. These results show the smaller scale physical properties and geochemistry of several types of aeolian bedforms on Mars formed under current and ancient environments.