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Published March 1, 2019 | Supplemental Material + Published
Journal Article Open

The formation and evolution of bright spots on Ceres


The otherwise homogeneous surface of Ceres is dotted with hundreds of anomalously bright, predominantly carbonate-bearing areas, termed "faculae," with Bond albedos ranging from ∼0.02 to >0.5. Here, we classify and map faculae globally to characterize their geological setting, assess potential mechanisms for their formation and destruction, and gain insight into the processes affecting the Ceres surface and near-surface. Faculae were found to occur in four distinct geological settings, associated predominantly with impact craters: (1) crater pits, peaks, or floor fractures (floor faculae), (2) crater rims or walls (rim/wall faculae), (3) bright ejecta blankets, and (4) the mountain Ahuna Mons. Floor faculae were identified in eight large, deep, and geologically young (asteroid-derived model (ADM) ages of <420 ± 60 Ma) craters: Occator, Haulani, Dantu, Ikapati, Urvara, Gaue, Ernutet, and Azacca. The geometry and geomorphic features of the eight craters with floor faculae are consistent with facula formation via impact-induced heating and upwelling of volatile-rich materials, upwelling/excavation of heterogeneously distributed subsurface brines or their precipitation products, or a combination of both processes. Rim/wall faculae and bright ejecta occur in and around hundreds of relatively young craters of all sizes, and the geometry of exposures is consistent with facula formation via the excavation of subsurface bright material, possibly from floor faculae that were previously emplaced and buried. A negative correlation between rim/wall facula albedo and crater age indicates that faculae darken over time. Models using the Ceres crater production function suggest initial production or exposure of faculae by large impacts, subsequent dissemination of facula materials to form additional small faculae, and then burial by impact-induced lateral mixing, which destroys faculae over timescales of less than 1.25 Gyr. Cumulatively, these models and the observation of faculae limited to geologically young craters indicate relatively modern formation or exposure of faculae, indicating that Ceres' surface remains active and that the near surface may support brines in the present day.

Additional Information

© 2017 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license. (http://creativecommons.org/licenses/by/4.0/). Received 12 May 2017, Revised 27 September 2017, Accepted 12 October 2017, Available online 6 November 2017. We are indebted to the Dawn mission team for their efforts in collecting the data used in this paper, as well as to members of the FC and VIR teams for their helpful discussions. Thanks to M. Landis and V. Reddy for reviews that improved this manuscript. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Grant no. DGE-1144469. VIR is funded by the Italian Space Agency and was developed under the leadership of INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy. The instrument was built by Selex-Galileo, Florence, Italy. This work was supported by the Italian Space Agency grant. Data used are available in the supplementary material or archived in the Planetary Data System (pds.nasa.gov).

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