Geological Society of America

T144 The Big Picture from Small Bodies: Dwarf Planets, Asteroids, and Comets

Monday, 23 September 2019
1:30 PM - 5:30 PM
Room 232BC, North Building

FRACTURED LOBATE FLOWS: MORPHOLOGIC EVIDENCE OF ICE CONTENT IN OCCATOR CRATER, CERES

Paper number: T144-6
Program: Technical Sessions
Time: 2:40 PM – 2:55 PM

Authors

Debra Buczkowski Presenting Author
Johns Hopkins University Applied Physics Laboratory, Laurel, MD
Christopher T. Russell
University of California, Los Angeles, CA
Britney E. Schmidt
Georgia Institute of Technology, Atlanta, GA
Margaret Landis
University of Colorado, Boulder, Boulder, CO
Hanna Sizemore
Planetary Science Institute, Tucson, AZ
Jennifer Scully
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
Paul M. Schenk
Space Science Division, Moffett Field, CA
Thomas H. Prettyman
NASA, Greenbelt, MD
Julie Castillo
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
Carol A. Raymond
California Institute of Technology, Pasadena, CA

Abstract

Dawn’s second extended mission (XM2) utilized low elliptical orbits to gain a resolution of ~5 m/pixel over some regions of Ceres, including Occator crater. Multiple fractures and lobate flows are observed on the floor of Occator; hypotheses for the formation of the flows have ranged from impact melt to volcanism. We present geomorphic evidence from the highest resolution XM2 data that shows that the fracture and furrow morphology of the lobate flows are consistent with that of ice-rich flows on Earth, either as rock glaciers (interstitial ice) and/or debris-covered glaciers (ice-cored). This morphology does not prove or disprove the formation of these flows by either impact melt or cryovolcanism, but rather is indicative of their enrichment in ice.

The large, thick sheet of lobate material in the NE quadrant of the crater was visible even in HAMO data, but in XM2 it became evident there is a veneer of lobate material coating the majority of the terraces. Also visible in XM2 data are the multiple instances of lobate flows superposing each other with overlapping lobes, highly reminiscent of the morphology of terrestrial rock glaciers.

Extensive fracturing of the large NE lobate material was mappable in HAMO and LAMO, but new smaller-scale fractures and furrows became evident with the higher-resolution XM2 data. These fractures are consistent with those that occur in flowing ice-rich material on Earth. One example is a 16.4 km long lobate flow in north-central Occator, which appears to be flowing south from the crater rim. Longitundal fractures only observable in XM2 data are found in the center of flow while en echelon fractures are identified at the edges. The flow ends in a series of overlapping flow fronts marked by a steep terminal embankment and splaying fractures.

More examples of small-scale fractures are found in a 14.9 km lobate flow originating from crater terrace material, and flowing south around other terrace outcrops. En echelon fractures are found where the lobate material flows around outcrops of highstanding terrace material. Chevron fractures are identified in a region where ice-rich material perched on top of terrace material would be flowing downslope to join the main flow. The flow terminates on top of the first flow

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-335081

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