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Article

Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres

1
CNRS, Physique Des Interactions Ioniques et Moléculaires, UMR CNRS 7345 and Laboratoire d’Astrophysique de Marseille, UMR CNRS 7326, Aix-Marseille Université, 13013 Marseille, France
2
Istituto di Astrofisica e Planetologia Spaziali- IAPS-INAF, 00133 Roma, Italy
3
INAF—Astrophysical Observatory of Arcetri, 50125 Firenze, Italy
4
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Samintha Perera
Minerals 2021, 11(7), 719; https://doi.org/10.3390/min11070719
Received: 2 June 2021 / Revised: 25 June 2021 / Accepted: 29 June 2021 / Published: 3 July 2021
Organic matter directly observed at the surface of an inner planetary body is quite infrequent due to the usual low abundance of such matter and the limitation of the infrared technique. Fortuitously, the Dawn mission has revealed, thanks to the Visible and InfraRed mapping spectrometer (VIR), large areas rich in organic matter at the surface of Ceres, near Ernutet crater. The origin of the organic matter and its abundance in association with minerals, as indicated by the low altitude VIR data, remains unclear, but multiple lines of evidence support an endogenous origin. Here, we report an experimental investigation to determine the abundance of the aliphatic carbon signature observed on Ceres. We produced relevant analogues containing ammoniated-phyllosilicates, carbonates, aliphatic carbons (coals), and magnetite or amorphous carbon as darkening agents, and measured their reflectance by infrared spectroscopy. Measurements of these organic-rich analogues were directly compared to the VIR spectra taken from different locations around Ernutet crater. We found that the absolute reflectance of our analogues is at least two orders of magnitude higher than Ceres, but the depths of absorption bands match nicely the ones of the organic-rich Ceres spectra. The choices of the different components are discussed in comparison with VIR data. Relative abundances of the components are extrapolated from the spectra and mixture composition, considering that the differences in reflectance level is mainly due to optical effects. Absorption bands of Ceres’ organic-rich spectra are best reproduced by around 20 wt.% of carbon (a third being aliphatic carbons), in association with around 20 wt.% of carbonates, 15 wt.% of ammoniated-phyllosilicate, 20 wt.% of Mg-phyllosilicates, and 25 wt.% of darkening agent. Results also highlight the pertinence to use laboratory analogues in addition to models for planetary surface characterization. Such large quantities of organic materials near Ernutet crater, in addition to the amorphous carbon suspected on a global scale, requires a concentration mechanism whose nature is still unknown but that could potentially be relevant to other large volatile-rich bodies. View Full-Text
Keywords: Ceres organic matter; laboratory analogs; reflectance infrared Ceres organic matter; laboratory analogs; reflectance infrared
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MDPI and ACS Style

Vinogradoff, V.; Poggiali, G.; Raponi, A.; Ciarniello, M.; De Angelis, S.; Ferrari, M.; Castillo-Rogez, J.C.; Brucato, J.; De Sanctis, M.-C. Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres. Minerals 2021, 11, 719. https://doi.org/10.3390/min11070719

AMA Style

Vinogradoff V, Poggiali G, Raponi A, Ciarniello M, De Angelis S, Ferrari M, Castillo-Rogez JC, Brucato J, De Sanctis M-C. Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres. Minerals. 2021; 11(7):719. https://doi.org/10.3390/min11070719

Chicago/Turabian Style

Vinogradoff, Vassilissa, Giovanni Poggiali, Andrea Raponi, Mauro Ciarniello, Simone De Angelis, Marco Ferrari, Julie C. Castillo-Rogez, John Brucato, and Maria-Cristina De Sanctis. 2021. "Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres" Minerals 11, no. 7: 719. https://doi.org/10.3390/min11070719

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