Paper No. 146-6
Presentation Time: 2:45 PM
CERES’ NEAR SURFACE PROPERTIES FROM LANDSLIDES
CHILTON, Heather1, SCHMIDT, Britney E.1, FERRIER, Ken L.2, DUARTE, Kayla1, HUGHSON, Kynan H.G.3, SCULLY, Jennifer E.C.4, SIZEMORE, Hanna G.5, NATHUES, A.6, PLATZ, Thomas7, RUSSELL, Christopher T.3, RAYMOND, Carol A.8 and WRAY, James J.9, (1)School of Earth & Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, (2)School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, (3)Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA, (4)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, (5)Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, (6)Max-Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (7)Max Planck Institute for Solar System Research, Göttingen, 37077, Germany, (8)NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, (9)School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340, htchilton@gatech.edu
Dwarf planet Ceres shows evidence of several geological processes that are consistent with subsurface ice. One of these processes is landsliding, which is revealed by observations of large (5 – 20 km long) landslides in imagery from the orbiting Dawn spacecraft. We build on our prior work on Cerean landslides, in which we classified flows by morphology into three types (T1, T2, and T3), to improve constraints on the properties and structure of the top few kilometers below the surface. We focus on a more restricted group of T1 and T2 features that conform to morphological descriptions: T1 landslides lie along steep slopes and have a thick, rounded, and steep toe, while T2 landslides are thin and cover shallow slopes. Aside from this subset of Cerean landslides, there are intermediate landslides and the T3 landslides, which have been more closely associated with ejecta.
We estimated effective coefficients of friction using the ratio of landslide drop height to runout length (H/L), using the landslides’ maximum heights and lengths as well as from their center of mass. Using both methods, Ceres’ landslides possess H/L ratios that imply lower friction coefficients than for typical rock or saturated clays, consistent with the idea that subsurface ice enhanced their mobility. Landslide scar volume-area relationships for T1 landslides are consistent with terrestrial bedrock landslides, while those for T2 landslides are consistent with shallower failures.
Adjusting water equivalent hydrogen estimations of near-surface ice by removing hydrogen taken up by clay-bearing surface materials still results in 10-15% and 25-30% ice in the upper meter of surface material at the equator and poles, respectively. Taken together, this is consistent with an ice-depleted layer of clays and other materials, containing only interstitial ice or ice lenses, which is thickest at low latitudes and thins towards the poles. Below this layer is a comparatively ice-rich layer, which is present at or near the surface above 70° latitude, where increased ice content and decreased temperature allow stronger, more pervasive cementation.
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