Alien Aeolian Bedforms: A Comparative Sedimentary Analysis of the Dingo Gap Bedform and Hidden Valley Ripple Traverses, Gale Crater, Mars

摘要

At the end of January 2014 (Sols 528-540), the Mars Science Laboratory rover Curiosity approached the valley opening known as Dingo Gap. Spanning this gap was an unusual bedform with a maximum height of 1.34 m and a maximum width of ~8 m. Curiosity encountered, imaged, and successfully traversed this atypical bedform. In August of 2014, Curiosity began to traverse a field of ripples in Hidden Valley, but was forced to abort the attempt due to high wheel slip. The Hidden Valley ripples are ~1/6 of the height of the Dingo Gap bedform, and yet posed a serious hazard to the rover. Here, we present a sedimentological analysis of the Dingo Gap bedform and the Hidden Valley ripples and discuss how their differences may have impacted rover traversability. The Dingo Gap and Hidden Valley bedforms are morphologically similar to many commonly observed bedforms on Mars that have few clear analogs on Earth, and Curiosity's encounters provide a framework for studying these bedforms in detail. Furthermore, the rover tracks across the bedforms have persisted for >5 Earth years, even through a global dust storm. The longevity of the tracks demonstrates that on multi-year timescales (a) sediment transport on some Martian bedforms is inactive or slow enough that areas disturbed by the rover are not resurfaced, and (b) the rate of dust deposition on the Martian surface, even after a global dust storm, is too low to create an optically thick layer.