Coarse Sediment Transport in the Modern Martian Environment

Abstract

The occurrence of regional and global dust storms, observations of migrating ripples and dunes, and the recognition of aeolian sandstone outcrops demonstrate that aeolian processes have been and continue to be a significant agent of surface modification on Mars. However, the mechanisms of aeolian transport within Mars' low atmospheric pressure surface environment are still not fully understood. This work presents a synthesis of change detection observations conducted with the Mars Science Laboratory Curiosity rover in Gale crater over three Martian years. Sediment mobility during this period was highly variable, consistent with previous orbiter-based observations showing strong seasonal variability, with strongest winds expected during southern summer. Wind activity inferred at each change detection site helps test the accuracy of atmospheric models, as well as constrain the intensity of current atmosphere-surface interactions and the physics of sand transport in the tenuous Martian atmosphere. Results indicate an apparent discrepancy between predicted wind speeds and the wind strengths required by classical incipient-motion models to explain observed sediment motion. Observed mobilization of perched and/or isolated very coarse sand grains and fine pebbles (i.e., grain sizes 1 mm ≤d≤3 mm) likely requires an alternate explanation, such as very strong but infrequent wind gusts, drag-induced rolling, or impact-driven creep caused by smaller saltating particles.