Carbonaceous chondrites as analogs for the composition and alteration of Ceres |
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| Authors: | Harry Y McSween Jr Joshua P Emery Andrew S Rivkin Michael J Toplis Julie C Castillo‐Rogez Thomas H Prettyman M Cristina De Sanctis Carle M Pieters Carol A Raymond Christopher T Russell |
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| Institution: | 1. Department of Earth & Planetary Sciences and Planetary Science Institute, University of Tennessee, Knoxville, Tennessee, USA;2. Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA;3. Institut de Recherche en Astrophysique et Planetologie, University of Toulouse, Toulouse, France;4. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA;5. Planetary Science Institute, Tucson, Arizona, USA;6. Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Rome, Italy;7. Department of Geological Sciences, Brown University, Providence, Rhode Island, USA;8. Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California, USA |
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| Abstract: | The mineralogy and geochemistry of Ceres, as constrained by Dawn's instruments, are broadly consistent with a carbonaceous chondrite (CM/CI) bulk composition. Differences explainable by Ceres’s more advanced alteration include the formation of Mg‐rich serpentine and ammoniated clay; a greater proportion of carbonate and lesser organic matter; amounts of magnetite, sulfide, and carbon that could act as spectral darkening agents; and partial fractionation of water ice and silicates in the interior and regolith. Ceres is not spectrally unique, but is similar to a few other C‐class asteroids, which may also have suffered extensive alteration. All these bodies are among the largest carbonaceous chondrite asteroids, and they orbit in the same part of the Main Belt. Thus, the degree of alteration is apparently related to the size of the body. Although the ammonia now incorporated into clay likely condensed in the outer nebula, we cannot presently determine whether Ceres itself formed in the outer solar system and migrated inward or was assembled within the Main Belt, along with other carbonaceous chondrite bodies. |
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