MORPHOLOGICAL DIVERSITY OF MARTIAN EOLIAN BEDFORMS AS REVEALED BY THE CURIOSITY ROVER AT GALE CRATER, MARS

During its ascent from Aeolis Palus to Aeolis Mons, the Curiosity rover has made observations of a variety of eolian bedforms, revealing a diverse suite of eolian processes that shape the Martian landscape. In particular, between December 2015 and May 2017, Curiosity traversed the Bagnold Dune Field, the first dune field investigated in situ on another planet. The first half of the investigation along the dune field’s northern trailing margin investigated southwestward migrating barchan dunes at the base of Aeolis Mons. The second half focused on a set of linear dunes further to the south, which are interpreted to be longitudinal or oblique to the average wind direction, based on their morphometrics, their migration across sediment-limited bedrock surfaces, and the measured bimodal wind distribution. Meter-scale ripples that cover the dunes are of particular interest because they are rare on Earth and only form in coarse sediment where they occur. On Mars, the gross morphology of these bedforms is readily observable from orbital imagery, but as seen from the ground, they display a variety of detailed morphologies, finer-scale structures such as wind impact ripples, and grain-size distributions that cannot be resolved from orbit. The large ripples form in a wide variety of well and poorly sorted grain sizes, form transverse and longitudinal to the average wind direction, and exhibit varying degrees of modern activity. Given the range over which these large ripples form and their morphologic similarity to both current and coarse-grained ripples on Earth, rover observations suggest there may exist a continuum of bedform morphologies that can be related by low-intensity sediment-transport processes, enabled on Mars by the thinner atmosphere and resulting dominant bedload flux. This hypothesis is consistent with recent modeling and laboratory work that predicts sand transport at wind speeds well below the theoretical fluid threshold.