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A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

Kurokawa, H. and Ehlmann, B. L. and De Sanctis, M. C. and Lapôtre, M. G. A. and Usui, T. and Stein, N. T. and Prettyman, T. H. and Raponi, A. and Ciarniello, M. (2020) A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data. Journal of Geophysical Research. Planets, 125 (12). Art. No. e2020JE006606. ISSN 2169-9097. https://resolver.caltech.edu/CaltechAUTHORS:20210113-083950523

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Abstract

The Visible‐Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft revealed that aqueous secondary minerals—Mg‐phyllosilicates, NH4‐bearing phases, and Mg/Ca carbonates—are ubiquitous on Ceres. Ceres' low reflectance requires dark phases, which were assumed to be amorphous carbon and/or magnetite (∼80 wt.%). In contrast, the Gamma Ray and Neutron Detector (GRaND) constrained the abundances of C (8–14 wt.%) and Fe (15–17 wt.%). Here, we reconcile the VIR‐derived mineral composition with the GRaND‐derived elemental composition. First, we model mineral abundances from VIR data, including either meteorite‐derived insoluble organic matter (IOM), amorphous carbon, magnetite, or combination as the darkening agent and provide statistically rigorous error bars from a Bayesian algorithm combined with a radiative‐transfer model. Elemental abundances of C and Fe are much higher than is suggested by the GRaND observations for all models satisfying VIR data. We then show that radiative transfer modeling predicts higher reflectance from a carbonaceous chondrite of known composition than its measured reflectance. Consequently, our second models use multiple carbonaceous chondrite endmembers, allowing for the possibility that their specific textures or minerals other than carbon or magnetite act as darkening agents, including sulfides and tochilinite. Unmixing models with carbonaceous chondrites eliminate the discrepancy in elemental abundances of C and Fe. Ceres' average reflectance spectrum and elemental abundances are best reproduced by carbonaceous‐chondrite‐like materials (40–70 wt.%), IOM or amorphous carbon (10 wt.%), magnetite (3–8 wt.%), serpentine (10–25 wt.%), carbonates (4–12 wt.%), and NH4‐bearing phyllosilicates (1–11 wt.%).


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2020je006606DOIArticle
https://arxiv.org/abs/2011.00157arXivDiscussion Paper
https://doi.org/10.22002/D1.1628DOIData
http://resolver.caltech.edu/CaltechAUTHORS:20170302-115016869Related ItemMATLAB scripts for MCMC computation
ORCID:
AuthorORCID
Kurokawa, H.0000-0003-1965-1586
Ehlmann, B. L.0000-0002-2745-3240
De Sanctis, M. C.0000-0002-3463-4437
Lapôtre, M. G. A.0000-0001-9941-1552
Usui, T.0000-0002-4653-293X
Stein, N. T.0000-0003-3385-9957
Prettyman, T. H.0000-0003-0072-2831
Raponi, A.0000-0003-4996-0099
Ciarniello, M.0000-0002-7498-5207
Alternate Title:A probabilistic approach to determination of Ceres' average surface composition from Dawn VIR and GRaND data
Additional Information:© 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue Online: 14 December 2020; Version of Record online: 14 December 2020; Accepted manuscript online: 05 November 2020; Manuscript accepted: 30 October 2020; Manuscript revised: 26 October 2020; Manuscript received: 07 July 2020. We thank the editor and two anonymous reviewers for comments which improved this manuscript. We thank Driss Takir and Hannah Kaplan for sharing meteorite and organics reflectance data. We also thank to Alexis Templeton for discussing her early analyses of iron speciation and sulfidization in the serpentinized Oman Drilling Program ophiolite core. This work was supported by the JSPS Core‐to‐Core Program “International Network of Planetary Sciences.” H. Kurokawa was supported by JSPS KAKENHI Grant number 17H01175, 17H06457, 18K13602, 19H01960, and 19H05072. B. L. Ehlmann thanks the Dawn team for welcoming her as a Science Affiliate to collaborate on data analysis during the mission's Ceres phase. Data Availability Statement: All data from this work can be downloaded at https://doi.org/10.22002/D1.1628. MATLAB scripts for MCMC computation are available at http://resolver.caltech.edu/CaltechAUTHORS:20170302-115016869. Laboratory spectra presented in this study are available from the RELAB spectral library and the authors of corresponding publications.
Funders:
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)17H01175
Japan Society for the Promotion of Science (JSPS)17H06457
Japan Society for the Promotion of Science (JSPS)18K13602
Japan Society for the Promotion of Science (JSPS)19H01960
Japan Society for the Promotion of Science (JSPS)19H05072
Subject Keywords:carbonaceous chondrites; Ceres; elemental chemistry; infrared spectra; mineralogy
Issue or Number:12
Record Number:CaltechAUTHORS:20210113-083950523
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210113-083950523
Official Citation:Kurokawa, H., Ehlmann, B. L., De Sanctis, M. C., Lapôtre, M. G. A., Usui, T., Stein, N. T., et al. (2020). A probabilistic approach to determination of Ceres' average surface composition from dawn visible‐infrared mapping Spectrometer and Gamma Ray and Neutron Detector data. Journal of Geophysical Research: Planets, 125, e2020JE006606. https://doi.org/10.1029/2020JE006606
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107450
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Jan 2021 17:30
Last Modified:13 Jan 2021 17:30

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