Variations and spatial distributions of bright and dark material on dwarf planet Ceres play a key role for the understanding of the processes that have led to its present surface composition. We define limits for "bright" and "dark" material in order to distinguish them consistently, based on the reflectance with respect to the average surface using Dawn Framing Camera data. A systematic classification of four types of bright material is presented based on their spectral properties, composition, spatial distribution, and association with specific geomorphological features. We found obvious correlations of reflectance with spectral shape (slopes) and age; however, this is not unique throughout the bright spots. Although impact features show generally more extreme reflectance variations, several areas can only be understood in terms of inhomogeneous distribution of composition as inferred from Dawn Visible and Infrared Spectrometer data. Additional materials with anomalous composition and spectral properties are rare. The identification of the origin of the dark, and particularly the darkest, material remains to be explored. The spectral properties and the morphology of the dark sites suggest an endogenic origin, but it is not clear whether they are more or less primitive surficial exposures or excavated sub-surface but localized material. The reflectance, spectral properties, inferred composition, and geologic context collectively suggest that the bright and dark materials tend to gradually change towards the average surface over time. This could be because of multiple processes, i.e., impact gardening/space weathering, and lateral mixing, including thermal and aqueous alteration, accompanied with changes in composition and physical properties such as grain size, surface temperature, porosity (compaction).
|Publication status||Published - Dec 14 2017|
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