P070-01
New evidence for climate and erosion history in Gale crater, Mars, from Curiosity’s ascent onto the Greenheugh pediment

Tuesday, 15 December 2020: 05:30
Virtual
Alexander B Bryk1, William E Dietrich1, Michael P. Lamb2, John P Grotzinger3, Ashwin R Vasavada4, Kathryn Stack5, Ray E Arvidson6, Christopher Fedo7, Valerie K Fox8, Kristen A Bennett9, Sanjeev Gupta10, Roger C Wiens11, Rebecca M. E. Williams12, Rachel Kronyak13, Kevin W Lewis14, David M Rubin15, William Rapin16, Laetitia Le Deit17, Stephane Le Mouelic18, Kenneth S Edgett19, Abigail Fraeman2, Steven Banham20, Candice Bedford21, Madison N Hughes22, Linda C Kah23, Jennifer L Eigenbrode24 and Gwénaël Caravaca25, (1)University of California Berkeley, Earth and Planetary Science, Berkeley, CA, United States, (2)California Institute of Technology, Pasadena, CA, United States, (3)Caltech, Pasadena, CA, United States, (4)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (5)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (6)Washington University in St Louis, Department of Earth and Planetary Sciences, St. Louis, MO, United States, (7)University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN, United States, (8)University of Minnesota, Earth and Environmental Sciences, Minneapolis, MN, United States, (9)Arizona State University, Tempe, AZ, United States, (10)Imperial College London, Earth Science and Engineering, London, United Kingdom, (11)Space Science and Applications, Los Alamos, NM, United States, (12)Planetary Science Institute Tucson, Tucson, AZ, United States, (13)Jet Propulsion Laboratory California Institute of Technology, Pasadena, California, United States, (14)Johns Hopkins University, Morton K. Blaustein Department of Earth & Planetary Sciences, Baltimore, MD, United States, (15)University of California-Santa Cruz, Santa Cruz, CA, United States, (16)Universite de Toulouse, Toulouse Cedex 4, France, (17)University of Nantes, Nantes, France, (18)CNRS, Paris Cedex 16, France, (19)Malin Space Science Systems, San Diego, CA, United States, (20)Imperial College London, London, SW7, United Kingdom, (21)Lunar and Planetary Institute, Houston, United States, (22)Washington University, Earth & Planetary Sciences, Saint Louis, MO, United States, (23)University of Tennesse, Earth and Planetary Sciences, Knoxville, TN, United States, (24)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (25)University of Nantes, Laboratory of Planetology and Geodynamics, Nantes, France
Recorded Presentation
Abstract:
Curiosity’s southward traverse up the lower north slope of Mt. Sharp (in Gale crater, Mars) and across Glen Torridon has brought it in contact with the organics-bearing sediments of the Knockfarril Hill member, the light-toned, nodule-rich strata found at Western, Central, and Tower buttes, and to the abrupt truncation of these altered Murray sediments at the Greenheugh pediment. Curiosity ascended the steep northern edge of the Greenheugh pediment near Tower butte, thus accessing strata identified ~20 years ago as recording a major environmental transition in the history of Gale. The basal truncation surface of the pediment is the Siccar Point group (SPg) basal unconformity, which extends past Vera Rubin ridge (VRR) to the north. Above the unconformity lies a <~5m thick cross-bedded sandstone capping unit interpreted to be an outcrop of the aeolian Stimson formation. Locally, these rocks exhibit extensive nodule formation. The pediment capping unit is lithified and is itself erosionally truncated, exposing a washboard pattern of low amplitude (~1m) ridges with ~6-12m wavelength. Eventual pediment scarp retreat may have been episodic as evidenced by sloping mantles of regolith flanking parts of the pediment escarpment. These new rover observations suggest that the Gediz Vallis (GV) ridge likely overlies the Stimson sandstone, and consists of layered boulder-bearing sediments, likely of fluvial and/or debris flow origin, interstratified with finer-grained sediments. The bedding within the GV ridge dips much less than the planation surface, supporting an interpretation that the sediments may have entered a succession of lakes. At the most distal end of the Gediz Vallis ridge, boulder deposits may be traceable across Glen Torridon and onto VRR suggesting the GV ridge sediments post-date the Stimson, as well as at least the initial development of the Glen Torridon trough. One possible sequence of climate-driven events that could explain these observations is: termination of Murray lake deposition; erosional planation; sand erg formation; sand lithification and nodule formation; a second erosional truncation event above the Stimson, pediment scarp retreat forming the initial Glen Torridon trough; successive sedimentation events from Gediz Vallis, desiccation and erosion to form the modern landscape.
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