Ceres's global and localized mineralogical composition determined by Dawn's Visible and Infrared Spectrometer (VIR)

Abstract

The Visible and Infrared Spectrometer (VIR) instrument on the Dawn mission observed Ceres's surface at different spatial resolutions, revealing a nearly uniform global distribution of surface mineralogy. Clearly, Ceres experienced extensive water-related processes and chemical differentiation. The surface is mainly composed of a dark component (carbon, magnetite?), Mg-phyllosilicates, ammoniated clays, carbonates, and salts. The observed species suggest endogenous, global-scale aqueous alteration. While mostly uniform at regional scale, Ceres's surface shows small localized areas with different species and/or variations in abundances. Few local exposures of water ice are seen, especially at higher latitudes. Sodium carbonates have been identified in several areas on the surface, notably in Occator bright faculae. Organic matter has also been discovered in several places, most conspicuously in a large area close to the Ernutet crater. The observed mineralogies, with the presence of ammoniated species and sodium salts, have a strong resemblance to materials found on other bodies of the outer solar system, such as Enceladus. This poses some questions about the original material from which Ceres accreted, suggesting a colder environment for such material with respect to Ceres's present position.

Mineralogy and temperature of crater Haulani on Ceres

“…These endmembers were chosen so as to be representative of the average mineralogy of Ceres (De Sanctis et al. , ; Ammannito et al. ) and of specific surface features known to be enriched in sodium carbonates and NH 4 ‐salts (De Sanctis et al.…”

“…Furthermore, aliphatic organic matter was found to be mainly localized on a broad region of ~1000 km 2 close to the ~50 km Ernutet crater (De Sanctis et al. , ; Pieters et al. ).…”

High Thermal Inertia Zones on Ceres From Dawn Data

“…The surface of Ceres is dark, with an average modeled geometric albedo of 0.094 ± 0.007 (Ciarniello et al, ), and is dominated by a dark, spectrally featureless and yet unidentified component, mixed with magnesium phyllosilicates, ammoniated phyllosilicates, and magnesium carbonates at global/broadly regional scale (Ammannito et al, ; De Sanctis et al, ; Carrozzo et al, ), with calcium and sodium carbonates showing up at specific locations (Carrozzo et al, ). Ceres appears to be icy (De Sanctis et al, ; De Sanctis et al, ); Dawn detected water ice in about 10 specific locations (e.g., Combes et al, ; Platz et al, ) but did not find endogenic sources (e.g., vapor plumes) that could explain the transient behavior of the atmosphere.…”

Asymmetric Craters on the Dwarf Planet Ceres—Results of Second Extended Mission Data Analysis

“…Impact craters are the most prevalent geomorphologic features on Ceres. Craters on Ceres show a large variety of crater morphologies [24,25], including bowl-shaped craters, polygonal craters [25,26], floor-fractured craters [25,27], secondary craters, crater chains, and craters with terraces, central peaks, smooth crater floors [25], flow-like features [25,[28][29][30][31], and bright spots [25,[32][33][34].…”

“…Additionally, Ceres consists of a shell, dominated by an ice-rock mixture [37][38][39] and ammoniated phyllosilicates [32,40,41]. The volatile-rich outer layer is supposed to have an average thickness of about 41.0 + 3.2-4.7 km [42,43].…”