Occator Crater, Ceres, at 35 km Altitude: Nature and Origin(s) of Bright Carbonate Deposits and Lobate Floor Materials
Abstract
Dawn XM2 very-high-resolution imaging of the 92-km-diameter Occator crater reveals a wealth of detail on the terraces, central structures, bright carbonate deposits and floor deposits within. The lobate floor deposit is complex. Smoother plains on the crater floor are densely pitted and interrupted by conical to irregular-shaped knobs, massifs, scarps, and irregular rings of non-impact origin. Clusters of irregular pits occur in several locations and are clearly non-impact, suggesting collapse or volatile release. The knobs and massifs could be impact debris (forming kipuka surrounded by flows) or post-emplacement pingo-like formations on top the floor deposit. Some of the knobs are capped by a cliff-forming resistant layer. Curvilinear scarps, 100-200 m high and often capped by a similar resistant layer, are observed in the terraces of the southeastern floor, and face inward. These scarps and cliff-forming units suggest partial withdrawal of cryolava beneath a refrozen carapace toward crater center, perhaps linked to cryolava break-outs to the north. These features have some resemblance to impact melt deposits on the Moon, but the distinct characteristics (rilles, pit clusters, ring structures, and possibly pingos) are likely related to Ceres' volatile rich crustal composition and lower impact velocities. Impact models indicate melting of water ice, which will mix with unmelted silicates, salts and carbonates to form floor deposit of "impact mud" or slurry. The observed features may be the result of the physical solidification and geochemical differentiation of this material, including possible hydrolaccolithic uplifts and localized venting.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5040903S