Characteristics of organic matter on Ceres from VIR/Dawn high spatial resolution spectra. Issue 2 (17th October 2018)

• Record Type: Journal Article
• Authors: De Sanctis, M C; Vinogradoff, V; Raponi, A; Ammannito, E; Ciarniello, M; Carrozzo, F G; De Angelis, S; Raymond, C A; Russell, C T
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 482:Issue 2(2019)
• Page Start: 2407
• Page End: 2421
• Publication Date: 2018-10-17
• Subjects: astrochemistry -- techniques: imaging spectroscopy -- minor planet: Ceres; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2772
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Ceres is the largest object in the main belt and is a wet body with a complex geological and chemical history. Its surface is composed of opaque materials, phyllosilicates, ammoniated-bearing minerals, carbonates, water ice, and salts. Recently, aliphatic organics, whose origin is still uncertain, have also been detected on the Ceres surface by the imaging spectrometer Visible and Infrared Spectrometer (VIR) on board Dawn. Here, using VIR spectra, acquired with a high spatial resolution (< 100 m), we have analysed the organic-rich areas, their spectral characteristics, and the associated mineralogy. The new VIR spectra in the 3.2–3.6 µm spectral range have been compared to organic standard compounds measured in the laboratory, to investigate more deeply the nature of the organic matter on Ceres. The mineralogy appears quite complex, and the organic matter is often associated with a larger amount of ammoniated phases and carbonates. The detailed spectral analysis, as well as the laboratory comparison, reveal the presence of a band at 2.99–3 μm, likely associated with organic or inorganic NH-compounds (amine or salts), and the organic matter may be characterized by a rather low abundance of oxygen atoms. Spectral models of the organic material indicate that hundreds of meters-size areas can be very rich in aliphatic organics, with an estimated organic amount larger than the quantity normally found in CC meteorites. The mineralogical context and the retrieved amounts suggest that the aliphatic organic is likely a Ceres' endogenous product, and we formulate a hypothesis for the formation and evolution of the organic matter inside Ceres.