Detection of exposed H<SUB>2</SUB>O ice on the nucleus of comet 67P/Churyumov-Gerasimenko. as observed by Rosetta OSIRIS and VIRTIS instruments

Publication date: 
Main author: 
Barucci, M. A.
IAA authors: 
Lara, L.;Lopez Moreno, J. J.
Barucci, M. A.;Filacchione, G.;Fornasier, S.;Raponi, A.;Deshapriya, J. D. P.;Tosi, F.;Feller, C.;Ciarniello, M.;Sierks, H.;Capaccioni, F.;Pommerol, A.;Massironi, M.;Oklay, N.;Merlin, F.;Vincent, J. -B.;Fulchignoni, M.;Guilbert-Lepoutre, A.;Perna, D.;Capria, M. T.;Hasselmann, P. H.;Rousseau, B.;Barbieri, C.;Bockelée-Morvan, D.;Lamy, P. L.;De Sanctis, C.;Rodrigo, R.;Erard, S.;Koschny, D.;Leyrat, C.;Rickman, H.;Drossart, P.;Keller, H. U.;A'Hearn, M. F.;Arnold, G.;Bertaux, J. -L.;Bertini, I.;Cerroni, P.;Cremonese, G.;Da Deppo, V.;Davidsson, B. J. R.;El-Maarry, M. R.;Fonti, S.;Fulle, M.;Groussin, O.;Güttler, C.;Hviid, S. F.;Ip, W.;Jorda, L.;Kappel, D.;Knollenberg, J.;Kramm, J. -R.;Kührt, E.;Küppers, M.;Lara, L.;Lazzarin, M.;Lopez Moreno, J. J.;Mancarella, F.;Marzari, F.;Mottola, S.;Naletto, G.;Pajola, M.;Palomba, E.;Quirico, E.;Schmitt, B.;Thomas, N.;Tubiana, C.
Astronomy and Astrophysics
Publication type: 
Context. Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and spectra of the comet's nucleus. <BR /> Aims: The aim of this work is to search for the presence of H<SUB>2</SUB>O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H<SUB>2</SUB>O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS. <BR /> Methods: The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 μm absorption band of water ice in the VIRTIS spectral cubes. <BR /> Results: Out of the 13 selected bright spots, eight of them present positive H<SUB>2</SUB>O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H<SUB>2</SUB>O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H<SUB>2</SUB>O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots.
ADS Bibcode: 
comets: individual: 67P/Churyumov-Gerasimenko;techniques: imaging spectroscopy;techniques: photometric;techniques: image processing;methods: data analysis