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Prettyman TH, Yamashita N, Toplis MJ, McSween HY, Schörghofer N, Marchi S, Feldman WC, Castillo-Rogez J, Forni O, Lawrence DJ, Ammannito E, Ehlmann BL, Sizemore HG, Joy SP, Polanskey CA, Rayman MD, Raymond CA, Russell CT. Extensive water ice within Ceres' aqueously altered regolith: Evidence from nuclear spectroscopy. Science 2016; 355:55-59. [PMID: 27980087 DOI: 10.1126/science.aah6765] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 11/23/2016] [Indexed: 11/03/2022]
Abstract
The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA's Dawn mission, we determined the concentrations of elemental hydrogen, iron, and potassium on Ceres. The data show that surface materials were processed by the action of water within the interior. The non-icy portion of Ceres' carbon-bearing regolith contains similar amounts of hydrogen to those present in aqueously altered carbonaceous chondrites; however, the concentration of iron on Ceres is lower than in the aforementioned chondrites. This allows for the possibility that Ceres experienced modest ice-rock fractionation, resulting in differences between surface and bulk composition. At mid-to-high latitudes, the regolith contains high concentrations of hydrogen, consistent with broad expanses of water ice, confirming theoretical predictions that ice can survive for billions of years just beneath the surface.
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Affiliation(s)
- T H Prettyman
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA.
| | - N Yamashita
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - M J Toplis
- Institut de Recherche d'Astrophysique et Planétologie, CNRS, Université Paul Sabatier, Toulouse 31400, France
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - N Schörghofer
- University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - W C Feldman
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - J Castillo-Rogez
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - O Forni
- Institut de Recherche d'Astrophysique et Planétologie, CNRS, Université Paul Sabatier, Toulouse 31400, France
| | - D J Lawrence
- Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA
| | - E Ammannito
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
| | - B L Ehlmann
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA.,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - H G Sizemore
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - S P Joy
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
| | - C A Polanskey
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - M D Rayman
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C A Raymond
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C T Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
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2
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Ammannito E, DeSanctis MC, Ciarniello M, Frigeri A, Carrozzo FG, Combe JP, Ehlmann BL, Marchi S, McSween HY, Raponi A, Toplis MJ, Tosi F, Castillo-Rogez JC, Capaccioni F, Capria MT, Fonte S, Giardino M, Jaumann R, Longobardo A, Joy SP, Magni G, McCord TB, McFadden LA, Palomba E, Pieters CM, Polanskey CA, Rayman MD, Raymond CA, Schenk PM, Zambon F, Russell CT. Distribution of phyllosilicates on the surface of Ceres. Science 2016; 353:353/6303/aaf4279. [PMID: 27701086 DOI: 10.1126/science.aaf4279] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 07/29/2016] [Indexed: 11/02/2022]
Abstract
The dwarf planet Ceres is known to host phyllosilicate minerals at its surface, but their distribution and origin have not previously been determined. We used the spectrometer onboard the Dawn spacecraft to map their spatial distribution on the basis of diagnostic absorption features in the visible and near-infrared spectral range (0.25 to 5.0 micrometers). We found that magnesium- and ammonium-bearing minerals are ubiquitous across the surface. Variations in the strength of the absorption features are spatially correlated and indicate considerable variability in the relative abundance of the phyllosilicates, although their composition is fairly uniform. These data, along with the distinctive spectral properties of Ceres relative to other asteroids and carbonaceous meteorites, indicate that the phyllosilicates were formed endogenously by a globally widespread and extensive alteration process.
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Affiliation(s)
- E Ammannito
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA.
| | - M C DeSanctis
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M Ciarniello
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - A Frigeri
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - F G Carrozzo
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - J-Ph Combe
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - B L Ehlmann
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - A Raponi
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M J Toplis
- Institut de Recherche en Astrophysique et Planétologie (UMR 5277), Université de Toulouse, F-31400 Toulouse, France
| | - F Tosi
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - F Capaccioni
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M T Capria
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - S Fonte
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M Giardino
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - R Jaumann
- Institute of Planetary Research, Deutsches Zentrum für Luft- und Raumfahrt, 12489 Berlin, Germany
| | - A Longobardo
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - S P Joy
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - G Magni
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - T B McCord
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - L A McFadden
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - E Palomba
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - C M Pieters
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - C A Polanskey
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - M D Rayman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - P M Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - F Zambon
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - C T Russell
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
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3
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Park RS, Konopliv AS, Bills BG, Rambaux N, Castillo-Rogez JC, Raymond CA, Vaughan AT, Ermakov AI, Zuber MT, Fu RR, Toplis MJ, Russell CT, Nathues A, Preusker F. A partially differentiated interior for (1) Ceres deduced from its gravity field and shape. Nature 2016; 537:515-517. [PMID: 27487219 DOI: 10.1038/nature18955] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 05/27/2016] [Indexed: 11/09/2022]
Abstract
Remote observations of the asteroid (1) Ceres from ground- and space-based telescopes have provided its approximate density and shape, leading to a range of models for the interior of Ceres, from homogeneous to fully differentiated. A previously missing parameter that can place a strong constraint on the interior of Ceres is its moment of inertia, which requires the measurement of its gravitational variation together with either precession rate or a validated assumption of hydrostatic equilibrium. However, Earth-based remote observations cannot measure gravity variations and the magnitude of the precession rate is too small to be detected. Here we report gravity and shape measurements of Ceres obtained from the Dawn spacecraft, showing that it is in hydrostatic equilibrium with its inferred normalized mean moment of inertia of 0.37. These data show that Ceres is a partially differentiated body, with a rocky core overlaid by a volatile-rich shell, as predicted in some studies. Furthermore, we show that the gravity signal is strongly suppressed compared to that predicted by the topographic variation. This indicates that Ceres is isostatically compensated, such that topographic highs are supported by displacement of a denser interior. In contrast to the asteroid (4) Vesta, this strong compensation points to the presence of a lower-viscosity layer at depth, probably reflecting a thermal rather than compositional gradient. To further investigate the interior structure, we assume a two-layer model for the interior of Ceres with a core density of 2,460-2,900 kilograms per cubic metre (that is, composed of CI and CM chondrites), which yields an outer-shell thickness of 70-190 kilometres. The density of this outer shell is 1,680-1,950 kilograms per cubic metre, indicating a mixture of volatiles and denser materials such as silicates and salts. Although the gravity and shape data confirm that the interior of Ceres evolved thermally, its partially differentiated interior indicates an evolution more complex than has been envisioned for mid-sized (less than 1,000 kilometres across) ice-rich rocky bodies.
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Affiliation(s)
- R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - A S Konopliv
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - B G Bills
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - N Rambaux
- IMCCE, Observatoire de Paris-PSL Research University, Sorbonne Universités-UPMC Université Paris 06, Université Lille 1, CNRS, 77 avenue Denfert-Rochereau, 75014 Paris, France
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - A T Vaughan
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - A I Ermakov
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - M T Zuber
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - R R Fu
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
| | - M J Toplis
- Institut de Recherche en Astrophysique et Planetologie, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - C T Russell
- Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA
| | - A Nathues
- Max Planck Institute for Solar System Research, Goettingen, Germany
| | - F Preusker
- Institute of Planetary Research, DLR, Department of Planetary Geodesy, Rutherfordstrasse 2, 12489 Berlin, Germany
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4
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De Sanctis MC, Ammannito E, Capria MT, Tosi F, Capaccioni F, Zambon F, Carraro F, Fonte S, Frigeri A, Jaumann R, Magni G, Marchi S, McCord TB, McFadden LA, McSween HY, Mittlefehldt DW, Nathues A, Palomba E, Pieters CM, Raymond CA, Russell CT, Toplis MJ, Turrini D. Spectroscopic characterization of mineralogy and its diversity across Vesta. Science 2012; 336:697-700. [PMID: 22582257 DOI: 10.1126/science.1219270] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The mineralogy of Vesta, based on data obtained by the Dawn spacecraft's visible and infrared spectrometer, is consistent with howardite-eucrite-diogenite meteorites. There are considerable regional and local variations across the asteroid: Spectrally distinct regions include the south-polar Rheasilvia basin, which displays a higher diogenitic component, and equatorial regions, which show a higher eucritic component. The lithologic distribution indicates a deeper diogenitic crust, exposed after excavation by the impact that formed Rheasilvia, and an upper eucritic crust. Evidence for mineralogical stratigraphic layering is observed on crater walls and in ejecta. This is broadly consistent with magma-ocean models, but spectral variability highlights local variations, which suggests that the crust can be a complex assemblage of eucritic basalts and pyroxene cumulates. Overall, Vesta mineralogy indicates a complex magmatic evolution that led to a differentiated crust and mantle.
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Affiliation(s)
- M C De Sanctis
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Rome, Italy.
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5
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Russell CT, Raymond CA, Coradini A, McSween HY, Zuber MT, Nathues A, De Sanctis MC, Jaumann R, Konopliv AS, Preusker F, Asmar SW, Park RS, Gaskell R, Keller HU, Mottola S, Roatsch T, Scully JEC, Smith DE, Tricarico P, Toplis MJ, Christensen UR, Feldman WC, Lawrence DJ, McCoy TJ, Prettyman TH, Reedy RC, Sykes ME, Titus TN. Dawn at Vesta: testing the protoplanetary paradigm. Science 2012; 336:684-6. [PMID: 22582253 DOI: 10.1126/science.1219381] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Dawn spacecraft targeted 4 Vesta, believed to be a remnant intact protoplanet from the earliest epoch of solar system formation, based on analyses of howardite-eucrite-diogenite (HED) meteorites that indicate a differentiated parent body. Dawn observations reveal a giant basin at Vesta's south pole, whose excavation was sufficient to produce Vesta-family asteroids (Vestoids) and HED meteorites. The spatially resolved mineralogy of the surface reflects the composition of the HED meteorites, confirming the formation of Vesta's crust by melting of a chondritic parent body. Vesta's mass, volume, and gravitational field are consistent with a core having an average radius of 107 to 113 kilometers, indicating sufficient internal melting to segregate iron. Dawn's results confirm predictions that Vesta differentiated and support its identification as the parent body of the HEDs.
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Affiliation(s)
- C T Russell
- Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, USA.
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