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Spectrophotometric modeling and mapping of Ceres

Li, J.-Y and Schröder, Stefan and Mottola, Stefano and Nathues, A. and Castillo-Rogez, J. and Schorghofer, Norbert and Williams, David A. and Ciarniello, M. and Longobardo, Andrea and Raymond, C.A. and Russell, C.T. (2019) Spectrophotometric modeling and mapping of Ceres. Icarus, 322, pp. 144-167. Elsevier. DOI: 10.1016/j.icarus.2018.12.038 ISSN 0019-1035

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Official URL: http://dx.doi.org/10.1016/j.icarus.2018.12.038

Abstract

We report a comprehensive analysis of the global spectrophotometric properties of Ceres using the images collected by the Dawn Framing Camera through seven color filters from April to June 2015 during the RC3 (rotational characterization 3) and Survey mission phases. We derived the Hapke model parameters for all color filters. The single-scattering albedo of Ceres at 555nm wavelength is 0.14 ± 0.04, the geometric albedo is 0.096 ± 0.006, and the bolometric Bond albedo is 0.037 ± 0.002. The asymmetry factors calculated from the best-fit two-term Henyey-Greenstein (HG) single-particle phase functions (SPPFs) show a weak wavelength dependence from −0.04 at 438nm increasing to 0.002 at> 900nm, suggesting that the phase reddening of Ceres is dominated by single-particle scattering rather than multiple scattering or small-scale surface roughness. The Hapke roughness parameter of Ceres is derived to be 20° ± 6°, with no wavelength dependence. The phase function of Ceres presents appreciably strong scattering around 90° phase angle that cannot be fitted with a single-term HG SPPF, suggesting possible stronger forward scattering component than other asteroids previously analyzed with spacecraft data. We speculate that such a scattering characteristic of Ceres might be related to its ubiquitous distribution of phyllosilicates and high abundance of carbonates on the surface. We further grouped the reflectance data into a 1° latitude-longitude grid over the surface of Ceres, and fitted each grid independently with both empirical models and the Hapke model to study the spatial variations of photometric properties. Our derived albedo maps and color maps are consistent with previous studies [Nathues, A., et al., 2016, Planet. Space Sci. 134, 122–127; Schröder, S.E., et al., 2017, Icarus 288, 201–225]. The SPPF over the surface of Ceres shows an overall correlation with albedo distribution, where lower albedo is mostly associated with stronger back- scattering and vice versa, consistent with the general trend among asteroids. On the other hand, the Hapke roughness parameter does not vary much across the surface of Ceres, except for the ancient Vendimia Planitia region that is associated with a slightly higher roughness. Furthermore, the spatial distributions of the SPPF and the Hapke roughness do not depend on wavelength. Based on the wavelength dependence of the SPPF of Ceres, we hypothesize that the regolith grains on Ceres either contain a considerable fraction of μm-sized or smaller particles, or are strongly affected by internal scatterers of this size.

Item URL in elib:https://elib.dlr.de/126190/
Document Type:Article
Title:Spectrophotometric modeling and mapping of Ceres
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Li, J.-YPlanetary Science Institute, Tucson, Arizona 85719, USAUNSPECIFIED
Schröder, StefanStefanus.Schroeder (at) dlr.dehttps://orcid.org/0000-0003-0323-8324
Mottola, StefanoStefano.Mottola (at) dlr.deUNSPECIFIED
Nathues, A.Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, GermanyUNSPECIFIED
Castillo-Rogez, J.Jet Propulsion Laboratory, California Institute of Technology,UNSPECIFIED
Schorghofer, NorbertPlanetary Science Institute, Tucson, AZ, USAUNSPECIFIED
Williams, David A.Arizona State University, Tempe, AZ, United States.UNSPECIFIED
Ciarniello, M.INAF–IAPS, Istituto di Astrofisica e Planetologia Spaziali, Area di Ricerca di Tor Vergata, via del Fosso del Cavaliere, 100, 00133 Rome, ItalyUNSPECIFIED
Longobardo, AndreaINAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, 00133 Rome, ItalyUNSPECIFIED
Raymond, C.A.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USAUNSPECIFIED
Russell, C.T.Institute of Geophysics, University of California, Los Angeles, Los Angeles, CA 90095UNSPECIFIED
Date:7 January 2019
Journal or Publication Title:Icarus
Refereed publication:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:322
DOI :10.1016/j.icarus.2018.12.038
Page Range:pp. 144-167
Publisher:Elsevier
ISSN:0019-1035
Status:Published
Keywords:Asteroid Ceres Asteroids, surfaces Photometry Spectrophotometry
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt DAWN
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Geology
Institute of Planetary Research > Asteroids and Comets
Deposited By: Schröder, Dr. Stefan
Deposited On:04 Feb 2019 09:46
Last Modified:04 Feb 2019 09:46

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