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Sulfides and refractory organic matter at the surface of 67P/Churyumov-Gerasimenko: evidence from VIRTIS data and laboratory measurements

Rousseau, Batiste and Erard, S. and Beck, P. and Quirico, E. and Schmitt, B. and Bonal, L. and Montes-Hernandez, German and Moroz, L.V. and Kappel, David and Markus, Kathrin and Arnold, Gabriele and Ciarniello, M. and Raponi, A. and Longobardo, A and Capaccioni, F. and Filacchione, G. and Bockelee-Morvan, D. and Leyrat, C. (2016) Sulfides and refractory organic matter at the surface of 67P/Churyumov-Gerasimenko: evidence from VIRTIS data and laboratory measurements. In: Comets Symposium: A new vision after Rosetta and Philae, p. 119. Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016, 14-18 November 2016, Toulouse.

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Official URL: http://www.comets2016toulouse.com

Abstract

From Aug. 2014 to Sept. 2016, the Rosetta spacecraft has been orbiting comet 67P/CG and has obtained information on the origin and evolution of comets. The imaging spectrometer VIRTIS collected reflectance spectra of the surface within the range 0.25-5.1 μm that revealed a low single scattering albedo (0.06 @ 0.65 μm) and a homogeneous surface (Capaccioni et al., 2015; Ciarniello et al., 2015). The reflectance spectra are also characterized by red slopes in the visible (0.5-0.8 μm) and in the near infrared (1.0-2.7 μm). These properties have been interpreted to be due to the presence of an organic polyaromatic material mixed with opaque minerals, presumably troilite-like sulfides according to the composition of presumed cometary grains (Quirico et al., 2016). In order to test this proposition, we have run series of experimental measurements of granular mixtures of an analog of cometary polyaromatic organic matter (an immature coal) and different sulfides (pyrite, pyrrhotite and troilite). Bi-directional reflectance spectra were obtained at IPAG in the range 0.4-4 μm, and under a range of viewing geometries. For the first time we are performing measurements on materials with sub-micrometer grains relevant to what is expected for cometary grains. Produced with a planetary grinder operating on colloidal solutions, these grains were characterized with scanning electron microscopy, X-ray diffraction and an electronic microprobe. The experiment confirms that the low albedo in the near infrared is controlled by the abundance of pyrrhotite or troilite, while pyrite is not a viable candidate. These sulfides also account very well for the red slopes in the visible and the near infrared ranges. Excellent match with VIRTIS spectra is obtained for coal+pyrrhotite mixtures with a pyrrhotite abundance ranging from 30 to 50 wt%. Although the cometary grains composition include silicates and other organic compounds (see IDPs and Wild2 samples analysis), these results offer another interpretation of the reddish nature of some small bodies’ surfaces, which has been interpreted so far as the presence of red organics or the consequence of space weathering. Finally, the suggestion that sulfides are major contributors to 67P dust might be generalized to other cometary nuclei that have similar VNIR spectra, as well as to P & D type asteroids.

Item URL in elib:https://elib.dlr.de/115314/
Document Type:Conference or Workshop Item (Speech)
Title:Sulfides and refractory organic matter at the surface of 67P/Churyumov-Gerasimenko: evidence from VIRTIS data and laboratory measurements
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Rousseau, BatistelesiaUNSPECIFIED
Erard, S.lesiaUNSPECIFIED
Beck, P.laboratoire de planétologie de grenoble (lpg) - university joseph fourier grenoble, grenboble, franceUNSPECIFIED
Quirico, E.laboratory of planetology, cnrs joseph fourier universityUNSPECIFIED
Schmitt, B.grenoble planetology laboratoryUNSPECIFIED
Bonal, L.université grenoble alpes, cnrs, institut de planétologie et d’astrophysique de grenoble, grenoble, franceUNSPECIFIED
Montes-Hernandez, Germanisterre - universite grenoble alpesUNSPECIFIED
Moroz, L.V.ljuba.moroz (at) dlr.deUNSPECIFIED
Kappel, Daviddavid.kappel (at) dlr.deUNSPECIFIED
Markus, Kathrinwestfälische wilhelms-universität münsterUNSPECIFIED
Arnold, Gabrielegabriele.arnold (at) dlr.deUNSPECIFIED
Ciarniello, M.inaf-iasf, italyUNSPECIFIED
Raponi, A.inaf-iasf, italyUNSPECIFIED
Longobardo, Ainaf-laps, via del fosso del cavaliere 100, i-00133 rome, italyUNSPECIFIED
Capaccioni, F.inaf-iasf, italyUNSPECIFIED
Filacchione, G.inaf-iasf, rome, italyUNSPECIFIED
Bockelee-Morvan, D.observatoire de paris, meudonUNSPECIFIED
Leyrat, C.lesiaUNSPECIFIED
Date:November 2016
Journal or Publication Title:Comets Symposium: A new vision after Rosetta and Philae
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Page Range:p. 119
Status:Published
Keywords:Rosetta, 67P, laboratory, spectra
Event Title:Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016
Event Location:Toulouse
Event Type:international Conference
Event Dates:14-18 November 2016
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt ROSETTA Instrumente
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Institute of Planetary Research > Leitungsbereich PF
Deposited By: Kappel, David
Deposited On:20 Nov 2017 15:07
Last Modified:20 Nov 2017 15:07

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