Abstract
The NASA/Dawn mission has acquired unprecedented measurements of the surface of the dwarf planet Ceres, the composition of which is a mixture of ultra-carbonaceous material, phyllosilicates, carbonates, organics, Fe-oxides, and volatiles as determined by remote sensing instruments including the VIR imaging spectrometer. We performed a refined analysis merging visible and infrared observations of Ceres’ surface for the first time. The overall shape of the combined spectrum suggests another type of silicate not previously considered, and we confirmed a large abundance of carbon material. More importantly, by analyzing the local spectra of the organic-rich region of the Ernutet crater, we identified a reddening in the visible range, strongly correlated to the aliphatic signature at 3.4 µm. Similar reddening was found in the bright material making up Cerealia Facula in the Occator crater. This implies that organic material might be present in the source of the faculae, where brines and organics are mixed in an environment that may be favorable for prebiotic chemistry.
Highlights
Ceres is the largest object in the asteroid belt
Of carbonaceous chondrites, the large abundance of carbon, which exceeds that of carbonaceous chondrites, found sition:onthe large abundance carbon, exceedsorganic that ofchemistry carbonaceous found a volatile-rich body of implies thatwhich widespread couldchondrites, have ocon a volatile-rich body implies that widespread organicorganic chemistry could have found onCeres
Based on the amount of data returned by the NASA/Dawn spacecraft and its scientific payload, Ceres is recognized as a target of astrobiological significance
Summary
Ceres is the largest object in the asteroid belt. Because of its size (~950 km in diameter) and its spheroidal shape, it has been classified as a dwarf planet. Based on this elemental data, in particular the abundance of C, H, K, and Fe, [12,13] it was established that the dark material that makes up most of Ceres’ surface composition should be rich in carbon and it resembles carbonaceous chondrite material [14,15] which is associated with a thick volatile-rich crust, suggesting a large and diffuse presence of organic material. The resulting VIR data in the visible range, together with the refined calibration in the IR channel provide new constraints on Ceres mineralogy. Using this new capability, we performed spectral analysis and modelling to infer further details on the composition of the dwarf planet. We revise local spectra from the Ernutet and Occator crater regions, where the VIR-IR instrument detected clear signatures of aliphatic organics [18] and a mixture of dry and hydrated salts, respectively, with the possible presence of organics [19]
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