1
|
Russell CT, Raymond CA, Ammannito E, Buczkowski DL, De Sanctis MC, Hiesinger H, Jaumann R, Konopliv AS, McSween HY, Nathues A, Park RS, Pieters CM, Prettyman TH, McCord TB, McFadden LA, Mottola S, Zuber MT, Joy SP, Polanskey C, Rayman MD, Castillo-Rogez JC, Chi PJ, Combe JP, Ermakov A, Fu RR, Hoffmann M, Jia YD, King SD, Lawrence DJ, Li JY, Marchi S, Preusker F, Roatsch T, Ruesch O, Schenk P, Villarreal MN, Yamashita N. Dawn arrives at Ceres: Exploration of a small, volatile-rich world. Science 2017; 353:1008-1010. [PMID: 27701107 DOI: 10.1126/science.aaf4219] [Citation(s) in RCA: 161] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 07/13/2016] [Indexed: 11/02/2022]
Abstract
On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres' surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres' dry exterior displays hydroxylated silicates, including ammoniated clays of endogenous origin. The possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits, lobate flows of materials, and a singular mountain that appears to be an extrusive cryovolcanic dome. On one occasion, Ceres temporarily interacted with the solar wind, producing a bow shock accelerating electrons to energies of tens of kilovolts.
Collapse
Affiliation(s)
- C T Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA.
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - E Ammannito
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - D L Buczkowski
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA
| | - M C De Sanctis
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - H Hiesinger
- Institut für Planetologie, 48149 Münster, Germany
| | - R Jaumann
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - A S Konopliv
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - A Nathues
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
| | - R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C M Pieters
- Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912, USA
| | | | - T B McCord
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - L A McFadden
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - S Mottola
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - M T Zuber
- Massachussetts Institute of Technology, Cambridge, MA 02139, USA
| | - S P Joy
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - C Polanskey
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - M D Rayman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - P J Chi
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - J P Combe
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - A Ermakov
- Massachussetts Institute of Technology, Cambridge, MA 02139, USA
| | - R R Fu
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10968, USA
| | - M Hoffmann
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
| | - Y D Jia
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - S D King
- Virginia Tech, Geosciences, Blacksburg, VA 24061, USA
| | - D J Lawrence
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA
| | - J-Y Li
- Planetary Science Institute, Tucson, AZ 85719, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - F Preusker
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - T Roatsch
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - O Ruesch
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - P Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - M N Villarreal
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - N Yamashita
- Planetary Science Institute, Tucson, AZ 85719, USA
| |
Collapse
|
2
|
Hiesinger H, Marchi S, Schmedemann N, Schenk P, Pasckert JH, Neesemann A, O'Brien DP, Kneissl T, Ermakov AI, Fu RR, Bland MT, Nathues A, Platz T, Williams DA, Jaumann R, Castillo-Rogez JC, Ruesch O, Schmidt B, Park RS, Preusker F, Buczkowski DL, Russell CT, Raymond CA. Cratering on Ceres: Implications for its crust and evolution. Science 2016; 353:353/6303/aaf4759. [PMID: 27701089 DOI: 10.1126/science.aaf4759] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 07/29/2016] [Indexed: 11/02/2022]
Abstract
Thermochemical models have predicted that Ceres, is to some extent, differentiated and should have an icy crust with few or no impact craters. We present observations by the Dawn spacecraft that reveal a heavily cratered surface, a heterogeneous crater distribution, and an apparent absence of large craters. The morphology of some impact craters is consistent with ice in the subsurface, which might have favored relaxation, yet large unrelaxed craters are also present. Numerous craters exhibit polygonal shapes, terraces, flowlike features, slumping, smooth deposits, and bright spots. Crater morphology and simple-to-complex crater transition diameters indicate that the crust of Ceres is neither purely icy nor rocky. By dating a smooth region associated with the Kerwan crater, we determined absolute model ages (AMAs) of 550 million and 720 million years, depending on the applied chronology model.
Collapse
Affiliation(s)
- H Hiesinger
- Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany.
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - N Schmedemann
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - P Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - J H Pasckert
- Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - A Neesemann
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - D P O'Brien
- Planetary Science Institute, Tucson, AZ 85719, USA
| | - T Kneissl
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - A I Ermakov
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - R R Fu
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - M T Bland
- U.S. Geological Survey, Astrogeology Science Center, Flagstaff, AZ 86001, USA
| | - A Nathues
- Max-Planck Institute for Solar System Research, Göttingen, Germany
| | - T Platz
- Max-Planck Institute for Solar System Research, Göttingen, Germany
| | | | - R Jaumann
- German Aerospace Center (DLR), Berlin, Germany. Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - O Ruesch
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - B Schmidt
- Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - F Preusker
- German Aerospace Center (DLR), Berlin, Germany
| | - D L Buczkowski
- John Hopkins Applied Physics Laboratory, Laurel, MD 20723, USA
| | - C T Russell
- Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|