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T. B. McCord (U. of Hawaii HIGP/SOEST and the Planet. Sci. Inst.), C. Sotin (University of Nantes)
Ceres orbits the sun and is large enough (~1000 km diameter) to have experienced many of the processes normally associated with planetary evolution. Ceres’ planet-like nature and survival from the earliest stages of solar system formation make it an extremely important object for understanding this early period as well as basic planetary processes. Thus, DAWN, a new mission to orbit Ceres (and Vesta) was selected. We modeled the plausible thermal evolution scenarios for Ceres and developed predictions of its current state and what DAWN might find. We started with the most likely basic physical properties derived from existing measurements and assumed primitive chondrite-like materials and current available information on the conditions during the early formation of Ceres. Ceres' current low density (~2) suggests at least 20 % ice content, consistent with reports of OH escaping from the north pole region and models indicating that water can exist near the surface over geologic time. Our models indicate that, even with only long-lived radionuclide heating, Ceres' interior was likely at least warm enough to melt ice and differentiate into rock and ice layers and in the process circulate warm water. More energetic models seem likely. This would have resulted in active chemistry and mineralization and dimensional changes, with further energy and compositional implications. The surface layer probably did not melt and the liquid layer probably has frozen out by now, but the surface and interior expressions of this earlier, perhaps violent, activity, including mineral deposits on the surface and topographic features, might exist today for discovery by DAWN. For example, the relatively high albedo might be due to salts. Organic material evolution is another important possibility. Such discoveries would help greatly to constrain the evolution models for Ceres, other solar system objects and the early solar system.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.