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1. Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Author

Luigi Colangeli, Vito Mennella, Federico Tosi, M. Combes, D. Despan, Patrick G. J. Irwin, Andrea Cicchetti, Lydie Bonal, Bernard Schmitt, Nicolas Biver, M. Cartacci, Florence Henry, Th. Encrenaz, Romolo Politi, Michelangelo Formisano, M. A. Barucci, David Kappel, Eric Quirico, Mauro Ciarniello, Roberto Orosei, Ralf Jaumann, Andrea Longobardo, Katrin Stephan, E. Kuehrt, Fabrizio Capaccioni, Yves Langevin, Wing-Huen Ip, Gianrico Filacchione, Michael R. Combi, Gabriele Arnold, Ernesto Palomba, Giovanna Rinaldi, D. Tiphene, Y. Hello, Robert W. Carlson, Ulrich Schade, Gianfranco Magni, Alessandra Migliorini, G. P. Tozzi, Sonia Fornasier, J. Crovisier, Andrea Raponi, Pierre Beck, U. Fink, Pierre Drossart, Stefano Mottola, Enrico Flamini, M. C. De Sanctis, D. Bockelee-Morvan, Marcello Fulchignoni, Kathrin Markus, Giancarlo Bellucci, M. T. Capria, G. Peter, Davide Grassi, F. Merlin, Sergio Fonti, Costanzo Federico, Eleonora Ammannito, M. I. Blecka, Armando Blanco, Raffaella Noschese, Jean-Michel Reess, T. B. McCord, Alessandro Frigeri, C. Leyrat, Giuseppe Piccioni, Priscilla Cerroni, U. Carsenty, F. Mancarella, L. Moroz, Fredric W. Taylor, Jean-Pierre Bibring, Stéphane Erard, Johannes Benkhoff, S. Jacquinod, J. Ph. Combe, M. S. Gudipati, Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Polska Akademia Nauk = Polish Academy of Sciences (PAN), German Aerospace Center (DLR), INAF - Osservatorio Astronomico di Capodimonte (OAC), Department of Physics [Imperial College London], Imperial College London, Instituto de Estudos Avançados (IEAV), Institut, Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Dipartimento di Fisica, Università degli studi di Lecce, Institute of Space Science [Taiwan], National Central University [Taiwan] (NCU), Department of Physics [Oxford], University of Oxford, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Department of Earth and Space Sciences [Seattle], University of Washington [Seattle], INAF - Osservatorio Astrofisico di Arcetri (OAA), Laboratoire de Sciences de la Terre, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Alenia Aerospazio, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Department of Physics [Lecce], Università del Salento [Lecce], JDS Uniphase/Cronos, USA, JDS Uniphase/Cronos, IASI (IASI), Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), Consiglio Nazionale delle Ricerche (CNR), European Space Agency (ESA), University of Oxford [Oxford], Max-Planck-Institut für Sonnensystemforschung (MPS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ITA, USA, GBR, FRA, DEU, TWN, and NLD

Subjects
[PHYS]Physics [physics], Multidisciplinary, 010504 meteorology & atmospheric sciences, Infrared, Atmospheric sciences, 01 natural sciences, Astrobiology, chemistry.chemical_compound, medicine.anatomical_structure, chemistry, 13. Climate action, Comet nucleus, Rosetta, 0103 physical sciences, Carbon dioxide, medicine, Environmental science, Surface layer, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Nucleus, Volatility (chemistry), ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

Rosetta observes sublimating surface icesComets are “dirty snowballs” made of ice and dust, but they are dark because the ice sublimates away, leaving some of the dust behind on the surface. The Rosetta spacecraft has provided a close-up view of the comet 67P/Churyumov-Gerasimenko as it passes through its closest point to the Sun (see the Perspective by Dello Russo). Filacchioneet al.detected the spectral signature of solid CO2(dry ice) in small patches on the surface of the nucleus as they emerged from local winter. By modeling how the CO2sublimates, they constrain the composition of comets and how ices generate the gaseous coma and tail. Fornasieret al.studied images of the comet and discovered bright patches on the surface where ice was exposed, which disappeared as the ice sublimated. They also saw frost emerging from receding shadows. The surface of the comet was noticeably less red just after local dawn, indicating that icy material is removed by sunlight during the local day.Science, this issue p.1563, p.1566; see also p.1536

Published
2016
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2. Exposed water ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Author

Giancarlo Bellucci, Katrin Stephan, Yves Langevin, Sergio Fonti, G. Peter, Gianrico Filacchione, Ulrich Schade, G. P. Tozzi, Jacques Crovisier, Costanzo Federico, Eleonora Ammannito, M. I. Blecka, S. Jacquinod, Jean-Michel Reess, M. Cartacci, Michael R. Combi, Vito Mennella, Federico Tosi, Marcello Fulchignoni, Armando Blanco, Giuseppe Piccioni, Roberto Orosei, Bernard Schmitt, Andrea Longobardo, Giovanna Rinaldi, Ralf Jaumann, Vincenzo Orofino, Alessandra Migliorini, Andrea Raponi, Pierre Drossart, M. Combes, David Kappel, Mauro Ciarniello, D. Despan, Murthy S. Gudipati, C. Leyrat, T. Encrenaz, Ernesto Palomba, Andrea Cicchetti, Fabrizio Capaccioni, Michelangelo Formisano, Maria Teresa Capria, Romolo Politi, Dominique Bockelée-Morvan, Stefano Mottola, Enrico Flamini, Pierre Beck, L. Moroz, Gianfranco Magni, U. Fink, Eric Quirico, Fredric W. Taylor, Sonia Fornasier, J-Ph. Combe, F. Merlin, Jean-Pierre Bibring, N. Biver, M. C. De Sanctis, Florence Henry, Uri Carsenty, M. A. Barucci, Gabriele Arnold, Y. Hello, Patrick G. J. Irwin, R. W. Carlson, Wing-Huen Ip, E. Kuehrt, Kathrin Markus, Davide Grassi, S. Giuppi, Raffaella Noschese, Alessandro Frigeri, F. Mancarella, Stéphane Erard, Luigi Colangeli, Lydie Bonal, T. B. McCord, J. Benkhoff, D. Tiphene, Priscilla Cerroni, G., Filacchione, M. C., De Sancti, F., Capaccioni, A., Raponi, F., Tosi, M., Ciarniello, P., Cerroni, G., Piccioni, M. T., Capria, E., Palomba, G., Bellucci, S., Erard, D., Bockelee Morvan, C., Leyrat, G., Arnold, M. A., Barucci, M., Fulchignoni, B., Schmitt, E., Quirico, R., Jaumann, K., Stephan, A., Longobardo, V., Mennella, A., Migliorini, E., Ammannito, J., Benkhoff, J. P., Bibring, Blanco, Armando, M. I., Blecka, R., Carlson, U., Carsenty, L., Colangeli, M., Combe, M., Combi, J., Crovisier, P., Drossart, T., Encrenaz, C., Federico, U., Fink, Fonti, Sergio, W. H., Ip, P., Irwin, E., Kuehrt, Y., Langevin, G., Magni, T., Mccord, L., Moroz, S., Mottola, Orofino, Vincenzo, U., Schade, F., Taylor, D., Tiphene, G. P., Tozzi, P., Beck, N., Biver, L., Bonal, Combe, J. P. h., D., Despan, E., Flamini, M., Formisano, S., Fornasier, A., Frigeri, D., Grassi, M. S., Gudipati, D., Kappel, Mancarella, Francesca, K., Marku, F., Merlin, R., Orosei, G., Rinaldi, M., Cartacci, A., Cicchetti, S., Giuppi, Y., Hello, F., Henry, S., Jacquinod, J. M., Ree, R., Noschese, R., Politi, G., Peter, Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Mécanique Textiles (LPMT), Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), German Aerospace Center (DLR), Deutsches Zentrum für Luft- und Raumfahrt (DLR), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), INAF - Osservatorio Astronomico di Capodimonte (OAC), Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Instituto de Estudos Avançados (IEAV), Institut, Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Dipartimento di Fisica, Università degli studi di Lecce, Institute of Space Science [Taiwan], National Central University [Taiwan] (NCU), Department of Physics [Oxford], University of Oxford, Department of Earth and Space Sciences [Seattle], University of Washington [Seattle], DLR Institute of Planetary Research, Department of Physics [Lecce], Università del Salento [Lecce], INAF - Osservatorio Astrofisico di Arcetri (OAA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Alenia Aerospazio, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), JDS Uniphase/Cronos, USA, JDS Uniphase/Cronos, CNR-IASF, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Consiglio Nazionale delle Ricerche (CNR), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-ENSITM-Matériaux et nanosciences d'Alsace, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), European Space Agency (ESA), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Polska Akademia Nauk (PAN), University of Oxford [Oxford], Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Centre National de la Recherche Scientifique (CNRS), Université de Lille-Université du Littoral Côte d'Opale-Centre National de la Recherche Scientifique (CNRS), ENSITM-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, 010504 meteorology & atmospheric sciences, Extraterrestrial Environment, Comet, Mineralogy, comet 67P, 01 natural sciences, water ice, Astrobiology, Diffusion, 0103 physical sciences, Rosetta, medicine, Diffusion (business), 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], Multidisciplinary, Meteoroid, Spectrum Analysis, Ice, food and beverages, Meteoroids, VIRTIS, Debris, Asteroids, Grain growth, medicine.anatomical_structure, 13. Climate action, comets and Kuiper belt Early solar system, Gases, Layering, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Nucleus, Water vapor
Abstract

Although water vapour is the main species observed in the coma of comet 67P/Churyumov–Gerasimenko1, 2 and water is the major constituent of cometary nuclei3, 4, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far5, 6. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far7, 8, 9. The nucleus of 67P/Churyumov–Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material10. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations6, 7, 8, 9. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers6, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust10 is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov–Gerasimenko11, 12 is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet’s formation.

Published
2016
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3. The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta

Author

Gabriele Arnold, Maria Teresa Capria, Y. Hello, Kathrin Markus, Vincenzo Orofino, A. Semery, Romolo Politi, Stéphane Erard, Roberto Orosei, Robert W. Carlson, Davide Grassi, M. Combes, J. Crovisier, Gianfranco Magni, Andrea Raponi, Michael R. Combi, Priscilla Cerroni, Yves Langevin, L. Moroz, Pierre Drossart, Ulrich Schade, G. P. Tozzi, Wing-Huen Ip, Luigi Colangeli, Fredric W. Taylor, Angioletta Coradini, J. Ph. Combe, Raffaella Noschese, Enrico Flamini, Giancarlo Bellucci, Ernesto Palomba, Sonia Fornasier, F. Merlin, Lydie Bonal, Andrea Longobardo, G. Peter, M. Cartacci, Alessandro Frigeri, Giuseppe Piccioni, Bernard Schmitt, Uwe Fink, Ralf Jaumann, Mauro Ciarniello, D. Despan, M. A. Barucci, Giovanna Rinaldi, Pierre Beck, M. C. De Sanctis, S. Giuppi, S. Jacquinod, Uri Carsenty, D. Bockelee-Morvan, Eric Quirico, Stefano Mottola, F. Henry, N. Biver, Jean-Pierre Bibring, Patrick G. J. Irwin, T. Encrenaz, Katrin Stephan, Andrea Cicchetti, Johannes Benkhoff, C. Leyrat, Gianrico Filacchione, D. Tiphene, J. M. Reess, T. B. McCord, Sergio Fonti, Costanzo Federico, Eleonora Ammannito, M. I. Blecka, Pasquale Palumbo, Armando Blanco, M. Gudipati, Fabrizio Capaccioni, Vito Mennella, Federico Tosi, E. Kuehrt, F., Capaccioni, A., Coradini, G., Filacchione, S., Erard, G., Arnold, P., Drossart, M. C., De Sancti, D., Bockelee Morvan, M. T., Capria, F., Tosi, C., Leyrat, B., Schmitt, E., Quirico, P., Cerroni, V., Mennella, A., Raponi, M., Ciarniello, T., Mccord, L., Moroz, E., Palomba, E., Ammannito, M. A., Barucci, G., Bellucci, J., Benkhoff, J. P., Bibring, Blanco, Armando, M., Blecka, R., Carlson, U., Carsenty, L., Colangeli, M., Combe, M., Combi, J., Crovisier, T., Encrenaz, C., Federico, U., Fink, Fonti, Sergio, W. H., Ip, P., Irwin, R., Jaumann, E., Kuehrt, Y., Langevin, G., Magni, S., Mottola, Orofino, Vincenzo, P., Palumbo, G., Piccioni, U., Schade, F., Taylor, D., Tiphene, G. P., Tozzi, P., Beck, N., Biver, L., Bonal, Combe, J. P. h., D., Despan, E., Flamini, S., Fornasier, A., Frigeri, D., Grassi, M., Gudipati, A., Longobardo, K., Marku, F., Merlin, R., Orosei, G., Rinaldi, K., Stephan, M., Cartacci, A., Cicchetti, S., Giuppi, Y., Hello, F., Henry, S., Jacquinod, R., Noschese, G., Peter, R., Politi, J. M., Ree, A., Semery, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Department of Earth and Space Sciences [Seattle], University of Washington [Seattle], Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Polska Akademia Nauk (PAN), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, German Aerospace Center (DLR), Department of Physics [Imperial College London], Imperial College London, Instituto de Estudos Avançados (IEAV), Institut, Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Dipartimento di Fisica, Università degli studi di Lecce, Institute of Space Science [Taiwan], National Central University [Taiwan] (NCU), Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), University of Oxford [Oxford], DLR Institute of Planetary Research, Department of Physics [Lecce], Università del Salento [Lecce], INAF - Osservatorio Astrofisico di Arcetri (OAA), Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Alenia Aerospazio, JDS Uniphase/Cronos, USA, JDS Uniphase/Cronos, CNR-IASF, IASI (IASI), Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Agence Spatiale Européenne = European Space Agency (ESA), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Polska Akademia Nauk = Polish Academy of Sciences (PAN), NASA-California Institute of Technology (CALTECH), University of Oxford, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ITA, USA, GBR, FRA, DEU, TWN, NLD, and POL

Subjects
67P/Churyumov-Gerasimenko, 010504 meteorology & atmospheric sciences, Opacity, Rosetta mission, VIRTIS, comets, Infrared, Comet, Imaging spectrometer, Astrophysics, 01 natural sciences, Astrobiology, comet, 0103 physical sciences, Spectral slope, Thermal, Rosetta, Rosetta mission, comets, Absorption (electromagnetic radiation), 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], Multidisciplinary, Chemistry, Albedo, VIRTIS, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], organic-rich
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.

Published
2015
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4. The Surface Composition and Temperature of Asteroid 21 Lutetia As Observed by Rosetta/VIRTIS

Author

Maria Teresa Capria, M. Combes, G. Neukum, Johannes Benkhoff, Stefano Mottola, Pierre Drossart, Uwe Fink, D. Bockelee-Morvan, Vincenzo Orofino, R. W. Carlson, E. T. Encrenaz, M. C. De Sanctis, Davide Grassi, Uri Carsenty, F. Carraro, Michael R. Combi, Luigi Colangeli, M. A. Barucci, Fabrizio Capaccioni, E. Kuehrt, Ralf Jaumann, S. Giuppi, J. Crovisier, Vito Mennella, Federico Tosi, Sergio Fonti, Eleonora Ammannito, D. Tiphene, Wing-Huen Ip, Gianfranco Magni, Fredric W. Taylor, Angioletta Coradini, Gianrico Filacchione, Costanzo Federico, Jean-Pierre Bibring, M. I. Blecka, Pasquale Palumbo, Armando Blanco, G. Arnold, Yves Langevin, Giuseppe Piccioni, Ulrich Schade, G. P. Tozzi, Bernard Schmitt, Lorenza Giacomini, Stéphane Erard, Priscilla Cerroni, Giancarlo Bellucci, T. B. McCord, Coradini, A., Blanco, Armando, Fonti, Sergio, Orofino, Vincenzo, and …., et al

Subjects
Mineral hydration, education.field_of_study, Multidisciplinary, Spectral signature, Materials science, Infrared, Population, Imaging spectrometer, Lutetia, Regolith, Space weathering, Astrobiology, Asteroid, Rosetta, education, Virtis
Abstract

The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.

Published
2011
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5. VIRTIS: An imaging spectrometer for the ROSETTA mission

Author

Wing-Huen Ip, Michael R. Combi, Priscilla Cerroni, Gabriele Arnold, E. Epifani, V. Formisano, Yves Langevin, M. Dami, Fabrizio Capaccioni, Ulrich Schade, S. Fonti, M. Bouyé, E. Ress, G. P. Tozzi, M. Combes, Roberto Orosei, Costanzo Federico, Angioletta Coradini, A. Fave, S. Espinasse, M. I. Blecka, D. Tiphene, Jean-Pierre Bibring, J. Crovisier, D. Stefanovitch, J. M. Reess, A. Stern, Maria Teresa Capria, Maria Antonieta Barucci, Bernard Schmitt, Pasquale Palumbo, G. Mondello, Pierre Drossart, Patrick G. J. Irwin, Bortolino Saggin, Vincenzo Orofino, Vito Mennella, Francesco Angrilli, J. Kachlicki, B. Pforte, A. M. DiLellis, Gerhard Neukum, D. Kouach, Thomas B. McCord, Robert W. Carlson, Fredric W. Taylor, Elisabetta Dotto, R. Bonsignori, G. Bianchini, E. Bussoletti, Uri Carsenty, Dominique Bockelée-Morvan, A. Blanco, H. Hirsch, Harald Michaelis, M. C. Desanctis, Giancarlo Bellucci, G. Peter, A. Semery, R. Knoll, Y. Hello, Uwe Fink, Gerard Huntzinger, Giulio Magni, T. Encrenaz, Stefano Mottola, Luigi Colangeli, Giuseppe Piccioni, and Stéphane Erard

Subjects
Solar System, Comet, Imaging spectrometer, Astronomy, Astronomy and Astrophysics, space missions, Astrobiology, Planetary science, Space and Planetary Science, Asteroid, Comet nucleus, Environmental science, comets, spectrometer, Formation and evolution of the Solar System, Cosmic dust
Abstract

The VIRTIS scientific and technical teams will take advantage of their previous experience in the design and development of spectrometers for space applications. In fact, the various groups contributing to the VIRTIS experiment, from Italy, France and Germany, have been deeply involved in the CASSINI mission, with the experiments VIMS and CIRS. The targets of the ROSETTA mission are the most primi- tive solar system bodies : comets and asteroids. ROSETTA will study in detail a comet nucleus, the prime target of the mission, and will fly by one or two asteroids. The small bodies of the solar system are of great interest for planetary science and their study is crucial to understand the solar system formation. In fact it is believed that comets and, to a lesser extent, asteroids underwent a moderate evolution so that they preserve some pristine solar system material. Comets and asteroids are in close relationship with the plan- etesimals, which formed from the solar nebula 4.6 billion years ago. The global characterisation of one comet nucleus and one or two asteroids will provide basic information on the origin of the solar system and on the interrelation between the solar system and the interstellar dust environment. The ROSETTA mission is designed to obtain the above mentioned scientific goals by : (a) in situ analysis of comet material ; (b) long period of remote sensing of the comet. The combination of remote sensing and in situ measurements will increase the scientific return of the mission. In fact, the “in situ” measurements will give relevant “ground-truth” for the remote sensing information and, in turn, the locally collected data will be interpreted in the appropriate scenario provided by remote sensing investigation. The scientific payload of ROSETTA includes a Visual InfraRed Spectral and Thermal Spectrometer (VIRTIS) among the instrument on board the spacecraft orbiting around the comet. This instrument is fundamental to detect and study the evolution of specific fingerprints—such as the typical spectral bands of minerals and molecules—arising from surface components and from materials dispersed in the coma. Their identification is a primary goal of the ROSETTA mission as it will allow us to identify the nature of the main constituent of the comets. Moreover, the surface thermal evolution during comet approach to Sun is important information that can be obtained by means of spectroscopic observation. The VIRTIS design and its detailed science goals are reported hereafter.

6. The diurnal cycle of water ice on comet 67P/Churyumov-Gerasimenko

Author

DE SANCTIS, MARIA CRISTINA, CAPACCIONI, FABRIZIO, CIARNIELLO, Mauro, FILACCHIONE, GIANRICO, FORMISANO, Michelangelo, Mottola, S., RAPONI, Andrea, TOSI, Federico, Bockelée-Morvan, D., Erard, S., Leyrat, C., Schmitt, B., Ammannito, E., Arnold, G., Barucci, M. A., Combi, M., Capria, M. T., Cerroni, P., Ip, W. -H., Kuehrt, E., McCord, T. B., PALOMBA, Ernesto, Beck, P., Quirico, E., VIRTIS Team, PICCIONI, GIUSEPPE, BELLUCCI, Giancarlo, Fulchignoni, M., Jaumann, R., Stephan, K., Longobardo, A., MENNELLA, Vito, MIGLIORINI, Alessandra, Benkhoff, J., Bibring, J. P., Blanco, A., Blecka, M., Carlson, R., Carsenty, U., Colangeli, L., Combes, M., Crovisier, J., Drossart, P., Encrenaz, T., Federico, C., Fink, U., Fonti, S., Irwin, P., Langevin, Y., Magni, G., Moroz, L., Orofino, V., Schade, U., Taylor, F., Tiphene, D., Tozzi, G. P., Biver, N., Bonal, L., Combe, J. -Ph., Despan, D., Flamini, E., Fornasier, S., FRIGERI, ALESSANDRO, GRASSI, Davide, Gudipati, M. S., Mancarella, F., Markus, K., Merlin, F., OROSEI, ROBERTO, RINALDI, GIOVANNA, CARTACCI, MARCO, Cicchetti, A., GIUPPI, Stefano, Hello, Y., Henry, F., Jacquinod, S., Rees, J. M., NOSCHESE, RAFFAELLA, POLITI, ROMOLO, Peter, G., M. C., De Sancti, F., Capaccioni, M., Ciarniello, G., Filacchione, M., Formisano, S., Mottola, A., Raponi, F., Tosi, D., Bockele´e Morvan, S., Erard, C., Leyrat, B., Schmitt, E., Ammannito, G., Arnold, M. A., Barucci, M., Combi, M. T., Capria, P., Cerroni, W. H., Ip, E., Kuehrt, T. B., Mccord, E., Palomba, P., Beck, E., Quirico, G., Piccioni, G., Bellucci, M., Fulchignoni, R., Jaumann, K., Stephan, A., Longobardo, V., Mennella, A., Migliorini, J., Benkhoff, J. P., Bibring, Blanco, Armando, M., Blecka, R., Carlson, U., Carsenty, L., Colangeli, M., Combe, J., Crovisier, P., Drossart, T., Encrenaz, C., Federico, U., Fink, Fonti, Sergio, P., Irwin, Y., Langevin, G., Magni, L., Moroz, Orofino, Vincenzo, U., Schade, F., Taylor, D., Tiphene, G. P., Tozzi, N., Biver, L., Bonal, Combe, J. P. h., D., Despan, E., Flamini, S., Fornasier, A., Frigeri, D., Grassi, M. S., Gudipati, Mancarella, Francesca, K., Marku, F., Merlin, R., Orosei, G., Rinaldi, M., Cartacci, A., Cicchetti, S., Giuppi, Y., Hello, F., Henry, S., Jacquinod, J. M., Ree, R., Noschese, R., Politi, G., Peter, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), DLR Institute of Planetary Research, German Aerospace Center (DLR), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Institute of Astronomy [Taiwan] (IANCU), National Central University [Taiwan] (NCU), Department of Earth and Space Sciences [Seattle], University of Washington [Seattle], Laboratoire de Sciences de la Terre, ITA, USA, GBR, FRA, DEU, TWN, NLD, POL, and National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR)

Subjects
67P/Churyumov-Gerasimenko, Time Factors, Extraterrestrial Environment, 010504 meteorology & atmospheric sciences, Comet, 01 natural sciences, water ice, Astrobiology, comet, Diurnal cycle, 0103 physical sciences, Sunrise, Water cycle, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], Multidisciplinary, Meteoroid, Ice, Diurnal temperature variation, Temperature, food and beverages, Meteoroids, Environmental science, Volatilization, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Surface water, cycle of water ice, Water vapor
Abstract

Observations of cometary nuclei have revealed a very limited amount of surface water ice, which is insufficient to explain the observed water outgassing. This was clearly demonstrated on comet 9P/Tempel 1, where the dust jets (driven by volatiles) were only partially correlated with the exposed ice regions. The observations of 67P/Churyumov-Gerasimenko have revealed that activity has a diurnal variation in intensity arising from changing insolation conditions. It was previously concluded that water vapour was generated in ice-rich subsurface layers with a transport mechanism linked to solar illumination, but that has not hitherto been observed. Periodic condensations of water vapour very close to, or on, the surface were suggested to explain short-lived outbursts seen near sunrise on comet 9P/Tempel 1. Here we report observations of water ice on the surface of comet 67P/Churyumov-Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface.

Published
2015
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7. Exposed water ice on the nucleus of comet 67P/Churyumov-Gerasimenko.

Author

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

Subjects
Diffusion, Gases analysis, Gases chemistry, Spectrum Analysis, Extraterrestrial Environment chemistry, Ice analysis, Meteoroids
Abstract

Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov-Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet's formation.

Published
2016
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8. The surface composition and temperature of asteroid 21 Lutetia as observed by Rosetta/VIRTIS.

Author

Coradini A, Capaccioni F, Erard S, Arnold G, De Sanctis MC, Filacchione G, Tosi F, Barucci MA, Capria MT, Ammannito E, Grassi D, Piccioni G, Giuppi S, Bellucci G, Benkhoff J, Bibring JP, Blanco A, Blecka M, Bockelee-Morvan D, Carraro F, Carlson R, Carsenty U, Cerroni P, Colangeli L, Combes M, Combi M, Crovisier J, Drossart P, Encrenaz ET, Federico C, Fink U, Fonti S, Giacomini L, Ip WH, Jaumann R, Kuehrt E, Langevin Y, Magni G, McCord T, Mennella V, Mottola S, Neukum G, Orofino V, Palumbo P, Schade U, Schmitt B, Taylor F, Tiphene D, and Tozzi G

Abstract

The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.

Published
2011
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