RE-EVALUATING HYPOTHESES OF SINUOUS RIDGE FORMATON IN SOUTHEASTERN ARGYRE PLANITIA, MARS

High-resolution datasets from recent Mars missions provide unprecedented views of the Red Planet's surface. In turn, these datasets allow for critical re-testing of hypotheses regarding Martain surface processes and landform development, which may ultimately provide insight into Mars' geologic and climatic history. In light of this potential insight, a series of landforms that warrant further examination are sinuous ridges in southeastern Argyre Planitia in Mars' southern hemisphere. Ridges in this region have an overall northeast trend (although local northwest trends occur), are approximately 100s of kilometers long, up to 2 kilometers wide, 10s of meters tall, and include braided and discontinuous traces. Despite over two decades of work, the formation mechanism of these ridges remains unconstrained; previous workers propose ridge formation through tectonic, fluvial, glacial, or lacustrine processes. Here, I use THermal EMission Imaging System (THEMIS) daytime infrared, Mars Orbital Camera (MOC), and Mars Orbiter Laser Altimeter (MOLA) datasets to re-evaluate hypotheses of sinuous ridge formation in southeastern Argyre Planitia; each process proposed to form the ridges makes distinct predictions testable using THEMIS, MOC, and MOLA datasets. Specifically, MOC imagery reveals that the ridges consist of horizontal to sub-horizontal meter-scale bedding that contains boulder-sized material. MOC imagery also reveals the presence of numerous pits approximately 10 m in diameter that are randomly distributed across the region; the pits lack a raised rim and obvious ejecta blankets and are located on top of and along side the ridges. In addition, MOLA profiles taken perpendicular to the ridge crests indicate that the ridges do not follow a topographic gradient, but instead appear to have formed independently of local topography. When taken together, these observations are consistent with these ridges originating as sub-glacial channels (eskers), an interpretation that is consistent with a growing body of evidence that Mars was, at least once, a glacially active planet. Finally, THEMIS daytime infrared imagery reveals a paucity of impact craters in this region, suggesting that glacial processes here operated in the recent Martian past.