GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 246-5
Presentation Time: 9:05 AM


GOLOMBEK, Matthew1, WARNER, Nicholas H.2, GRANT, John A.3, HAUBER, Ernst4, ANSAN, Veronique5, WEITZ, Catherine M.6, WILLIAMS, Nathan R.7, CHARALAMBOUS, Constantinos8, WILSON, Sharon A.3, PARKER, Timothy9, DAUBAR, Ingrid1, MARTEAU, Eloise1, MUELLER, Nils4, PIQUEUX, Sylvain1, PIKE, W.T.8, DEMOTT, Alyssa10, KOPP, Megan A.10, LETHCOE-WILSON, Heather A.1, BERGER, Lauren11, HAUSMANN, Rachel1, BANKS, Maria E.12, BAKER, Mariah M.13 and GARVIN, James14, (1)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, (2)Department of Geological Sciences, SUNY Geneseo, 1 College Circle, Geneseo, NY 14454, (3)Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Independence Ave at 6th St. SW, Washington, DC 20560, (4)DLR Deutsches Zentrum für Luft- und Raumfahrt, Berlin, Germany, (5)Laboratoire de Planetologie et Geodynamique, University of Nantes, France, Nantes, 44322, France, (6)Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719, (7)Jet Propulsion Laboratory, California Institute of Technology, M/S 183-301, 4800 Oak Grove Dr., Pasadena, CA 91109, (8)Department of Electrical and Electronic Engineering, Imperial College, London, United Kingdom, (9)Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, (10)Geological Sciences, SUNY-Geneseo, 1 College Circle, Geneseo, NY 14454, (11)Department of Geology, Occidental College, 1600 Campus Rd, Los Angeles, CA 90041, (12)NASA Goddard Space Flight Center, Greenbelt, MD 20771, (13)Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, MD 21210, (14)NASA Goddard Spaceflight Center, Greenbelt, MD 20771

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft landed successfully on Mars in western Elysium Planitia at 4.502°N, 135.623°E at an elevation of -2613.43 m on Nov. 26, 2018. Color panoramas from the lander show it is located within a quasi-circular depression, interpreted to be a degraded ~20 m diameter impact crater, informally named Homestead hollow, with a smooth pebble rich surface adjacent to a slightly rockier and rougher terrain. Ten 1-10 m diameter impact craters can be seen within 20 m of the lander. Some of these craters have very little relief and are filled with fine grained material. Farther afield, bright circular patches suggest soil filled, degraded craters (hollows) are common. Rock abundance is very low in the hollow (1-2% for rocks >10 cm diameter) and ~2 times higher in the rockier terrain. Pulsed retrorockets removed surficial fine-grained dust to create a dark spot (40 m diameter) and scoured loose sand and granules up to 5 m from the lander. Three pits ~10 cm deep beneath the lander have steep slopes (greater than the angle of repose) whose walls are composed of small rocks and pebbles weakly cemented in a finer-grained matrix (duricrust). Smaller clods and pieces of this material are scattered within the pits and adjacent areas and appear to bury one of the footpads. These observations suggest a near surface stratigraphy of surficial dust over thin cohesionless sand, underlain by duricrust, with poorly sorted, cohesionless sand and rocks beneath. Orbital and lander radiometer measurements of thermal inertia are consistent with a surface dominated by fine sand size particles, which is consistent with the very low rock abundance. The surface appears modified by impact, eolian and mass wasting processes with craters in various stages of degradation and dusty eolian bedforms (suggesting relative inactivity). These observations are consistent with expectations made from remote sensing data prior to landing indicating a surface composed of >3 m thick impact-fragmented regolith overlying Hesperian basalt flows that would be similar to the Spirit landing site.