Paper No. 13
Presentation Time: 11:10 AM


LEWIS, Kevin, Department of Geosciences, Princeton, Princeton, NJ 08544, BRIDGES, Nathan T., Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, EDGETT, Kenneth S., Jet Propulsion Laboratory, California Institute of Technolgy, 4800 Oak Grove Drive, Pasadena, CA 91109, FISK, Martin.R., College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Administration Building, Corvallis, OR 97331, HALLET, Bernard, Quaternary Research Center, University of Washington, Box 351310, 365 Johnson Hall, Seattle, WA 98195, KOCUREK, Gary, Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C9000, Austin, TX 78712, NEWMAN, Claire E., Ashima Research, 600 S. Lake Avenue, Suite 104, Pasadena, CA 91106, RUBIN, David M., Coastal and Marine Geology, US Geol Survey, US Geological Survey Pacific Sciences Center, 400 Natural Bridges Drive, Santa Cruz, CA 95060, SLETTEN, Ronald S., Quaternary Research Center, Univ of Washington, 19 Johnson Hall, University of Washington Box 351360, Seattle, WA 98195 and MSL SCIENCE TEAM, The,

Since landing last year, the Curiosity rover has been exploring a number of geologic units exposed intermittently on the floor of Gale crater, Mars. Geomorphic surfaces encountered over the course of this traverse reflect aeolian deposition, transport, and erosion in the modern environment. Exposed plains show strong sorting of fine-grained sediment, while accumulation of sand-sized grains can be found in the lee of larger rocks and topographic obstacles. Curiosity performed its first surface sampling campaign at a locally prominent sand shadow known as Rocknest. While a sharp crest and other features of the Rocknest bedform suggest equilibrium with the modern environment, the population of larger millimeter-sized grains which make up its surface indicate the rarity of modification events. Though orbital data has shown active transport within a larger dune field to the south of the landing site [Silvestro et. al, 2013], relatively little evidence has been seen for surface changes along the Curiosity traverse, with the exception of materials disturbed by the rover.

Additional features indicative of recent geomorphic activity include a number of seemingly pristine cracks and voids between polygonally fractured bedrock blocks in the Yellowknife Bay region, where Curiosity conducted several drilling experiments. While the majority of these fractures are filled with loose sediment, open holes were observed in a variety of locations and orientations within the region. In addition, an accumulation of dark, apparently fresh soil was observed alongside at least one bedrock block. Though no single explanation explains their occurrence, possible explanations include geologically recent subsurface volatile exchange and accumulated motion due to thermally-induced contraction/expansion. Although Curiosity attempted to detect potential motion over the diurnal cycle, no changes were detected at these locations, to the resolution of the rover's Mastcam instrument. Ongoing modeling work has begun to constrain plausible formation processes. Ultimately, Curiosity has observed abundant evidence of geologically recent surface modification at the Gale crater landing site, while detecting only limited surface changes over the timescales of the mission to date.