The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta

Capaccioni F; Coradini A; Filacchione G; Erard S; Arnold G; Drossart P; De Sanctis M; Bockelee-Morvan D; Capria M; Tosi F; Leyrat C; Schmitt B; Quirico E; Cerroni P; Mennella V; Raponi A; Ciarniello M; McCord T; Moroz L; Palomba E; Ammannito E; Barucci M; Bellucci G; Benkhoff J; Bibring J; Blanco A; Blecka M; Carlson R; Carsenty U; Colangeli L; Combes M; Combi M; Crovisier J; Encrenaz T; Federico C; Fink U; Fonti S; Ip W; Irwin P; Jaumann R; Kuehrt E; Langevin Y; Magni G; Mottola S; Orofino V; Palumbo P; Piccioni G; Schade U; Taylor F; Tiphene D; Tozzi G; Beck P; Biver N; Bonal L; Combe J; Despan D; Flamini E; Fornasier S; Frigeri A; Grassi D; Gudipati M; Longobardo A; Markus K; Merlin F; Orosei R; Rinaldi G; Stephan K; Cartacci M; Cicchetti A; Giuppi S; Hello Y; Henry F; Jacquinod S; Noschese R; Peter G; Politi R; Reess J; Semery A

Abstract

The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kÅ−1), and the broad absorption feature in the 2.9-to-3.6–micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun.