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1. Tensile strength of 67P/Churyumov–Gerasimenko nucleus material from overhangs

Author

Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, Ekkehard, Preusker, Frank, Scholten, Frank, Knollenberg, Jörg, Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A’Hearn, M. F., Auger, A.-T., Barucci, Antonella, Bertaux, J.-L., Bertini, I., Bodewits, Dennis, Boudreault, S., Cremonese, G., Deppo, Vania Da, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutierrez, P.J., Güttler, C., Hviid, Stubbe, Ip, W-H., Kovacs, G., Kramm, J. R., Küppers, M., Lara López, Luisa M., Lazzarin, M., Lopez Moreno, J., Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., Oklay, Nilda, Pajola, M., Toth, I., Tubiana, C., Vincent, Jean-Baptiste, Shi, X., Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Physikalisches Institut [Bern], Universität Bern [Bern], DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Dipartimento di Fisica e Astronomia 'Galileo Galilei', Universita degli Studi di Padova, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), International Space Science Institute [Bern] (ISSI), European Space Agency Advanced Concepts and Science Payloads Office (ESA ESTEC), European Space Agency (ESA), ESA Scientific Support Office, Department of Physics and Astronomy [Uppsala], Uppsala University, Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Institut für Geophysik und Extraterrestrische Physik [Braunschweig] (IGEP), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Astrofisica (INAF), Laboratory for Ultraviolet and X-ray Optical Research [Padova] (LUXOR), CNR Institute for Photonics and Nanotechnologies (IFN), Consiglio Nazionale delle Ricerche [Roma] (CNR)-Consiglio Nazionale delle Ricerche [Roma] (CNR), Department of Industrial Engineering [Padova], University of Trento [Trento], Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institute of Space Science [Taiwan], National Central University [Taiwan] (NCU), Operations Department (ESAC), European Space Astronomy Centre (ESAC), European Space Agency (ESA)-European Space Agency (ESA), Centre for Astrophysics and Planetary Science [Canterbury] (CAPS), University of Kent [Canterbury], Solar System Exploration Research Virtual Institute (SSERVI), Southwest Research Institute [Boulder] (SwRI), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), NASA Ames Research Center (ARC), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Laboratoire d'Astrophysique de Marseille ( LAM ), Aix Marseille Université ( AMU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Deutsches Zentrum für Luft- und Raumfahrt [Berlin] ( DLR ), Max-Planck-Institut für Sonnensystemforschung ( MPS ), IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Centro de Astrobiologia [Madrid] ( CAB ), Instituto Nacional de Técnica Aeroespacial ( INTA ) -Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), International Space Science Institute ( ISSI ), Space Research Centre [Warsaw] ( CBK ), Polska Akademia Nauk ( PAN ), Institut für Geophysik und Extraterrestrische Physik [Braunschweig] ( IGEP ), Technische Universität Braunschweig [Braunschweig], 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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), INAF - Osservatorio Astronomico di Trieste ( OAT ), Istituto Nazionale di Astrofisica ( INAF ), Laboratory for Ultraviolet and X-ray Optical Research [Padova] ( LUXOR ), CNR Institute for Photonics and Nanotechnologies ( IFN ), Consiglio Nazionale delle Ricerche [Roma] ( CNR ) -Consiglio Nazionale delle Ricerche [Roma] ( CNR ), Instituto de Astrofísica de Andalucía ( IAA ), Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), National Central University [Taiwan] ( NCU ), European Space Astronomy Center ( ESAC ), European Space Agency ( ESA ) -European Space Agency ( ESA ), Centre for Astrophysics and Planetary Science [Canterbury] ( CAPS ), Solar System Exploration Research Virtual Institute ( SSERVI ), Southwest Research Institute [Boulder] ( SwRI ), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' ( CISAS ), NASA Ames Research Center ( ARC ), Hungarian Academy of Sciences [Budapest], Universität Bern [Bern] (UNIBE), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Università degli Studi di Padova = University of Padua (Unipd), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Agence Spatiale Européenne = European Space Agency (ESA), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR)-National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), ITA, USA, GBR, FRA, DEU, Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Consejo Superior de Investigaciones Científicas [Spain] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA), Polska Akademia Nauk (PAN), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Consejo Superior de Investigaciones Científicas [Spain] (CSIC) more...

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Comets: individual: Churyumov-Gerasimenko, FOS: Physical sciences, general [comets], Comets: general, Methods: observational, es, individual: Churyumov-Gerasimenko [comets], Astronomi, astrofysik och kosmologi, [SDU]Sciences of the Universe [physics], Astronomy, Astrophysics and Cosmology, observational [Methods], addenda, errata, ComputingMilieux_MISCELLANEOUS, [ SDU ] Sciences of the Universe [physics], Astrophysics - Earth and Planetary Astrophysics
Abstract

We directly measure twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimate the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around one Pa or less (one to five Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and implied previous collapse of another, suggests that they are prone to failure and that true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of 67P's nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties with size, over the $\sim10-100$ m range studied here, or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small (tens of km) body., 13 pages, 11 figures. Accepted for publication in Astronomy & Astrophysics more...

Published
2018
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2. Tensile strength of 67P/Churyumov–Gerasimenko nucleus material from overhangs

Author

Attree , N., Groussin , O., Jorda , L., Nébouy , D., Thomas , N., Brouet , Y., Kührt , E., Preusker , F., Scholten , F., Knollenberg , J., Hartogh , P., Sierks , H., Barbieri , C., Lamy , P., Rodrigo , R., Koschny , D., Rickman , H., Keller , H. U., A'Hearn , M. F., Auger , A.-T., Barucci , M. A., Bertaux , J.-L., Bertini , I., Bodewits , D., Boudreault , S., Cremonese , G., Da Deppo , V., Davidsson , B., Debei , S., De Cecco , M., Deller , J., El-Maarry , M. R., Fornasier , S., Fulle , M., Gutiérrez , P. J., Güttler , C., Hviid , S., Ip , W.-H., Kovacs , G., Kramm , J. R., Küppers , M., Lara , L. M., Lazzarin , M., Lopez Moreno , J. J., Lowry , S., Marchi , S., Marzari , F., Mottola , S., Naletto , G., Oklay , N., Pajola , M., Toth , I., Tubiana , C., Vincent , J.-B., Shi , X., A’Hearn , M., Gutierrez , J., Lara , M., Laboratoire d'Astrophysique de Marseille ( LAM ), Aix Marseille Université ( AMU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Physikalisches Institut [Bern], Universität Bern [Bern], DLR Institute of Planetary Research, German Aerospace Center ( DLR ), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] ( DLR ), Max-Planck-Institut für Sonnensystemforschung ( MPS ), Dipartimento di Fisica e Astronomia 'Galileo Galilei', Universita degli Studi di Padova, Research and Scientific Support Department, ESTEC ( RSSD ), European Space Research and Technology Centre ( ESTEC ), European Space Agency ( ESA ) -European Space Agency ( ESA ), Space Research Centre [Warsaw] ( CBK ), Polska Akademia Nauk ( PAN ), Department of Astronomy [College Park], University of Maryland [College Park], 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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' ( CISAS ), INAF - Osservatorio Astronomico di Padova ( OAPD ), Istituto Nazionale di Astrofisica ( INAF ), CNR Institute for Photonics and Nanotechnologies ( IFN ), Consiglio Nazionale delle Ricerche [Roma] ( CNR ), Department of Physics and Astronomy [Uppsala], Uppsala University, INAF - Osservatorio Astronomico di Trieste ( OAT ), Instituto de Astrofísica de Andalucía ( IAA ), Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), Space Science Institute [Macau] ( SSI ), Macau University of Science and Technology ( MUST ), European Space Astronomy Center ( ESAC ), European Space Agency ( ESA ), Centre for Astrophysics and Planetary Science [Canterbury] ( CAPS ), University of Kent [Canterbury], Solar System Exploration Research Virtual Institute ( SSERVI ), Southwest Research Institute [Boulder] ( SwRI ), Istituto Nazionale di Fisica Nucleare, Sezione di Padova ( INFN, Sezione di Padova ), National Institute for Nuclear Physics ( INFN ), Institut des Sciences Chimiques de Rennes ( ISCR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Ecole Nationale Supérieure de Chimie de Rennes-Institut National des Sciences Appliquées ( INSA ) -Centre National de la Recherche Scientifique ( CNRS ), Institute for Nanoscale Physics and Chemistry ( INPAC ), and Katholieke Universiteit Leuven ( KU Leuven ) more...

Subjects
Methods: observational, comets: general, [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], comets: individual: Churyumov-Gerasimenko
Abstract

International audience; We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features andthe implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the 10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km). more...

Published
2018
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3. Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko

Author

Auger , A.-T., Groussin , O., Jorda , L., El-Maarry , M. R., Bouley , S., Sejourne , A., Gaskell , R., Capanna , C., Davidsson , B., Marchi , S., Höfner , S., Lamy , P. L., Sierks , H., Barbieri , C., Rodrigo , R., Koschny , D., Rickman , H., Keller , H. U., Agarwal , J., A'Hearn , M. F., Barucci , M. A., Bertaux , J.-L., Bertini , I., Cremonese , G., Da Deppo , V., Debei , S., De Cecco , M., Fornasier , S., Fulle , M., Gutiérrez , P. J., Güttler , C., Hviid , S., Ip , W.-H., Knollenberg , J., Kramm , J.-R., Kührt , E., Küppers , M., Lara , L. M., Lazzarin , M., Lopez Moreno , J. J., Marzari , F., Massironi , M., Michalik , H., Naletto , G., Oklay , N., Pommerol , A., Sabau , L., Thomas , N., Tubiana , C., Vincent , J.-B., Wenzel , K.-P., Lamy , L., A’Hearn , M., Barucci , A., BERTAUX , L., Gutierrez , J., Ip , H., Laboratoire d'Astrophysique de Marseille ( LAM ), Aix Marseille Université ( AMU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Physikalisches Institut [Bern], Universität Bern [Bern], Institut de Mécanique Céleste et de Calcul des Ephémérides ( IMCCE ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université de Lille-Centre National de la Recherche Scientifique ( CNRS ), Interactions et dynamique des environnements de surface ( IDES ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Planetary Science Institute [Tucson] ( PSI ), Department of Physics and Astronomy [Uppsala], Uppsala University, Solar System Exploration Research Virtual Institute ( SSERVI ), Southwest Research Institute [Boulder] ( SwRI ), Max-Planck-Institut für Sonnensystemforschung ( MPS ), Dipartimento di Fisica e Astronomia 'Galileo Galilei', Universita degli Studi di Padova, Research and Scientific Support Department, ESTEC ( RSSD ), European Space Research and Technology Centre ( ESTEC ), European Space Agency ( ESA ) -European Space Agency ( ESA ), Space Research Centre [Warsaw] ( CBK ), Polska Akademia Nauk ( PAN ), European Space Agency ( ESA ), Department of Astronomy [College Park], University of Maryland [College Park], 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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' ( CISAS ), INAF - Osservatorio Astronomico di Padova ( OAPD ), Istituto Nazionale di Astrofisica ( INAF ), CNR Institute for Photonics and Nanotechnologies ( IFN ), Consiglio Nazionale delle Ricerche [Roma] ( CNR ), INAF - Osservatorio Astronomico di Trieste ( OAT ), Instituto de Astrofísica de Andalucía ( IAA ), Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), DLR Institute of Planetary Research, German Aerospace Center ( DLR ), Space Science Institute [Macau] ( SSI ), Macau University of Science and Technology ( MUST ), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] ( DLR ), European Space Astronomy Center ( ESAC ), Istituto Nazionale di Fisica Nucleare, Sezione di Padova ( INFN, Sezione di Padova ), National Institute for Nuclear Physics ( INFN ), Dipartimento di Geoscienze [Padova], Institut für Datentechnik und Kommunikationsnetze, Technische Universität Braunschweig [Braunschweig], Instituto Nacional de Técnica Aeroespacial ( INTA ), Institute for Nanoscale Physics and Chemistry ( INPAC ), and Katholieke Universiteit Leuven ( KU Leuven ) more...

Subjects
Comets, Geological processes, [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Nucleus, [ SDU ] Sciences of the Universe [physics], [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (from North to South) and longitudes (head, neck, and body), sometimes on pit walls or following lineaments. About 1.5% of the observed surface is covered by polygons. Polygons have an homogeneous size across the nucleus, with 90% of them in the size range 1 - 5 m and a mean size of 3.0 ± 1.4 m. They show different morphologies, depending on the width and depth of their trough. They are found in networks with 3- or 4-crack intersection nodes. The polygons observed on 67P are consistent with thermal contraction crack polygons formed by the diurnal or seasonal temperature variations in a hard (MPa) and consolidated sintered layer of water ice, located a few centimeters below the surface. Our thermal analysis shows an evolution of thermal contraction crack polygons according to the local thermal environment, with more evolved polygons (i.e. deeper and larger troughs) where the temperature and the diurnal and seasonal temperature range are the highest. Thermal contraction crack polygons are young surface morphologies that probably formed after the injection of 67P in the inner solar system, typically 100,000 years ago, and could be as young as a few orbital periods, following the decreasing of its perihelion distance in 1959 from 2.7 to 1.3 a.u. Meter scale thermal contraction crack polygons should be common features on the nucleus of Jupiter family comets. more...

Published
2018
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4. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, and Swedish National Space Agency more...

Subjects
Comets: general, Comets: individual: 67P/Churyumov-Gerasimenko, Methods: observational, individual: 67P/Churyumov-Gerasimenko [Comets], general [Comets], observational [Methods]
Abstract

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km)., his project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 686709. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2. The opinions expressed and arguments employed herein do not necessarily reflect the official view of the Swiss Government. OSIRIS was built by a consortium of the Max-Planck-Institut fur Sonnensystemforschung, Gottingen, Germany; the CISAS University of Padova, Italy; the Laboratoire d'Astrophysique de Marseille, France; the Instituto de Astrofisica de Andalucia, CSIC, Granada, the Universidad Politechnica de Madrid, Spain; the Department of Physics and Astronomy of Uppsala University, Sweden; and the Institut fur Datentechnik und Kommunikationsnetze der Technischen Universitat Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Operations Centre and the Rosetta Mission Operations Centre for the successful rendezvous with comet 67P/Churyumov-Gerasimenko. more...

Published
2018

5. Corrigendum: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs (Astronomy and Astrophysics (2018) 611 (A33) DOI: 10.1051/0004-6361/201732155)

Author

Attree, N., Groussin, O., Jorda, L., Nebouy, D., Thomas, N., Brouet, Y., Kuhrt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A'Hearn, M. F., Auger, A. -T., Barucci, M. A., Bertaux, J. -L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Deppo, V. D., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutierrez, P. J., Guttler, C., Hviid, S., W. -H., Ip, Kovacs, G., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Toth, I., Tubiana, C., Vincent, J. -B., and Shi, X. more...

Subjects
comets: general, methods: observational, addenda, comets: individual: Churyumov-Gerasimenko, errata, errata, addenda
Published
2018

6. Modeling of the outburst on July 29th, 2015 observed with OSIRIS cameras in the southern hemisphere of comet 67P/Churyumov-Gerasimenko

Author

Gicquel, A., Rose, M., Vincent, J. -B., Davidsson, B., Bodewits, D., Hearn, M. F. A, Agarwal, J., Fougere, N., Sierks, H., Bertini, I., Lin, Z. -Y., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Barucci, M. A., Bertaux, J. -L., Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., Guttler, C., Hofner, S., Hofmann, M., Hu, X., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Lowry, S., Marzari, F., Masoumzadeh, N., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C. more...

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras since March 2014 using both the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC). We use images from the NAC camera to study a bright outburst observed in the southern hemisphere on July 29, 2015. The high spatial resolution of the NAC is needed to localize the source point of the outburst on the surface of the nucleus. The heliocentric distance is 1.25 au and the spacecraft-comet distance is 186 km. Aiming to better understand the physics that led to the outgassing, we used the Direct Simulation Monte Carlo (DSMC) method to study the gas flow close to the nucleus and the dust trajectories. The goal is to understand the mechanisms producing the outburst. We reproduce the opening angle of the outburst in the model and constrain the outgassing ratio between the outburst source and the local region. The outburst is in fact a combination of both gas and dust, in which the active surface is approximately 10 times more active than the average rate found in the surrounding areas. We need a number of dust particles 7.83 $\times$ 10$^{11}$ - 6.90 $\times$ 10$^{15}$ (radius 1.97 - 185 {\mu}m), which corresponds to a mass of dust 220 - 21 $\times$ 10$^{3}$kg., Comment: 8 pages, 9 figures more...

Published
2017

7. Analysis of polygonal cracking patterns in chloride-bearing terrains on Mars: Indicators of ancient playa settings

Author

El-Maarry M. R., Pommerol A., and Thomas N.

Abstract

The ancient southern highlands on Mars (similar to 3.5 Gyr old) contain>600 regions that display spectral evidence in the infrared for the presence of chloride bearing materials. Many of these locations were previously reported to display polygonal cracking patterns. We studied more than 80 of the chloride bearing terrains using high resolution (0.25 0.5 m/pixel) images as well as near infrared spectral data to characterize the surface textures and the associated cracking patterns and mineralogies. Our study indicates that similar to 75 of the studied locations display polygonal cracks that resemble desiccation cracks while some resemble salt expansion/thrust polygons. Furthermore we detect spectrally the presence of smectites in association with similar to 30 of the studied fractured terrains. We note that smectites are a special class of swelling clay minerals that can induce formation of large desiccation cracks. As such we suggest that the cracking patterns are indicative of the presence of smectite phyllosilicates even in the absence of spectral confirmation. Our results suggest that many chloride bearing terrains have a lacustrine origin and a geologic setting similar to playas on Earth. Such locations would have contained ephemeral lakes that may have undergone repeated cycles of desiccation and recharging by a near surface fluctuating water table in order to account for the salt phyllosilicates associations. These results have notable implications for the ancient hydrology of Mars. We propose that the morphologies and sizes of the polygonal cracks can be used as paleoenvironmental as well as lithological indicators that could be helpful in planning future missions. more...

Published
2014
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8. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars: Results from Geomorphological Investigations and Morphometry

Author

Diot X., El-Maarry M. R., Schlunegger E., Norton K. P., Thomas N., and Grindrod P. M.

Abstract

Hellas basin is a large impact basin situated in the southern highlands of Mars. The north western part of the basin has the lowest elevation ( 7.5 km) on the planet and contains a possibly unique terrain type which we informally call "banded terrain". The banded terrain is made up of smooth looking banded deposits that display signs of viscous behavior and a paucity of superimposed impact craters. In this study we use newly acquired high spatial resolution images from the High Resolution Imaging Science Experiment (HiRISE) in addition to existing datasets to characterize the geomorphology the morphometry and the architecture of the banded terrain. The banded terrain is generally confined to the NW edge of the Alpheus Colles plateau. The individual bands are similar to 3 15 km long similar to 0.3 km wide and are separated by narrow inter band depressions which are similar to 65 m wide and similar to 10 m deep. The bands display several morphologies that vary from linear to concentric forms. Morphometric analysis reveals that the slopes along a given linear or lobate band ranges from 0.5 degrees to 15 degrees (average similar to 6 degrees) whereas the concentric bands are located on flatter terrain (average slope similar to 2 3 degrees). Crater size frequency analysis yields an Amazonian Hesperian boundary crater retention age for the terrain (similar to 3 Gyr) which together with the presence of very few degraded craters either implies a recent emplacement resurfacing or intense erosion. The apparent sensitivity to local topography and preference for concentrating in localized depressions is compatible with deformation as a viscous fluid. In addition the bands display clear signs of degradation and slumping at their margins along with a suite of other features that include fractured mounds polygonal cracks at variable size scales and knobby/hummocky textures. Together these features suggest an ice rich composition for at least the upper layers of the terrain which is currently being heavily modified through loss of ice and intense weathering possibly by wind. more...

Published
2014
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9. Summer fireworks on comet 67P

Author

Vincent , J.-B., A'Hearn , M. F., Lin , Z.-Y., El-Maarry , M. R., Pajola , M., Sierks , H., Barbieri , C., Lamy , P. L., Rodrigo , R., Koschny , D., Rickman , H., Keller , H. U., Agarwal , J., Barucci , M. A., Bertaux , J.-L., Bertini , I., Besse , S., Bodewits , D., Cremonese , G., Da Deppo , V., Davidsson , B., Debei , S., De Cecco , M., Deller , J., Fornasier , S., Fulle , M., Gicquel , A., Groussin , O., Gutiérrez , P. J., Gutiérrez-Marquez , P., Güttler , C., Höfner , S., Hofmann , M., Hviid , S. F., Ip , W.-H., Jorda , L., Knollenberg , J., Kovacs , G., Kramm , J.-R., Kührt , E., Küppers , M., Lara , L. M., Lazzarin , M., Lopez Moreno , J. J., Marzari , F., Massironi , M., Mottola , S., Naletto , G., Oklay , N., Preusker , F., Scholten , F., Shi , X., Thomas , N., Toth , I., Tubiana , C., A'Hearn , F., Lamy , L., Gutierrez , J., Hviid , F., Lara , M., Max-Planck-Institut für Sonnensystemforschung ( MPS ), Department of Astronomy [College Park], University of Maryland [College Park], Institute of Astronomy [Taiwan] ( IANCU ), National Central University [Taiwan] ( NCU ), Physikalisches Institut [Bern], Universität Bern [Bern], Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' ( CISAS ), Universita degli Studi di Padova, Dipartimento di Fisica e Astronomia 'Galileo Galilei', Laboratoire d'Astrophysique de Marseille ( LAM ), Aix Marseille Université ( AMU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Research and Scientific Support Department, ESTEC ( RSSD ), European Space Research and Technology Centre ( ESTEC ), European Space Agency ( ESA ) -European Space Agency ( ESA ), Space Research Centre [Warsaw] ( CBK ), Polska Akademia Nauk ( PAN ), European Space Agency ( ESA ), 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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), INAF - Osservatorio Astronomico di Padova ( OAPD ), Istituto Nazionale di Astrofisica ( INAF ), CNR Institute for Photonics and Nanotechnologies ( IFN ), Consiglio Nazionale delle Ricerche [Roma] ( CNR ), Department of Physics and Astronomy [Uppsala], Uppsala University, INAF - Osservatorio Astronomico di Trieste ( OAT ), Laboratoire des Sciences des Procédés et des Matériaux ( LSPM ), Université Paris 13 ( UP13 ) -Université Sorbonne Paris Cité ( USPC ) -Institut Galilée-Centre National de la Recherche Scientifique ( CNRS ), Instituto de Astrofísica de Andalucía ( IAA ), Consejo Superior de Investigaciones Científicas [Spain] ( CSIC ), Space Science Institute [Macau] ( SSI ), Macau University of Science and Technology ( MUST ), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] ( DLR ), DLR Institute of Planetary Research, German Aerospace Center ( DLR ), European Space Astronomy Center ( ESAC ), Istituto Nazionale di Fisica Nucleare, Sezione di Padova ( INFN, Sezione di Padova ), National Institute for Nuclear Physics ( INFN ), Dipartimento di Geoscienze [Padova], Institut des Sciences Chimiques de Rennes ( ISCR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Ecole Nationale Supérieure de Chimie de Rennes-Institut National des Sciences Appliquées ( INSA ) -Centre National de la Recherche Scientifique ( CNRS ), Institute for Nanoscale Physics and Chemistry ( INPAC ), and Katholieke Universiteit Leuven ( KU Leuven ) more...

Subjects
comets: individual: 67P/Churyumov, [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [ SDU ] Sciences of the Universe [physics], [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], Gerasimenko
Abstract

International audience; During its 2 yr mission around comet 67P/Churyumov-Gerasimenko, ESA's Rosetta spacecraft had the unique opportunity to follow closely a comet in the most active part of its orbit. Many studies have presented the typical features associated with the activity of the nucleus, such as localized dust and gas jets. Here, we report on series of more energetic transient events observed during the 3 months surrounding the comet's perihelion passage in 2015 August. We detected and characterized 34 outbursts with the Rosetta cameras, one every 2.4 nucleus rotations. We identified three main dust plume morphologies associated with these events: a narrow jet, a broad fan, and more complex plumes featuring both previous types together. These plumes are comparable in scale and temporal variation to what has been observed on other comets. We present a map of the outbursts' source locations, and discuss the associated topography. We find that the spatial distribution sources on the nucleus correlate well with morphological region boundaries, especially in areas marked by steep scarps or cliffs. Outbursts occur either in the early morning or shortly after the local noon, indicating two potential processes: morning outbursts may be triggered by thermal stresses linked to the rapid change of temperature; afternoon events are most likely related to the diurnal or seasonal heat wave reaching volatiles buried under the first surface layer. In addition, we propose that some events can be the result of a completely different mechanism, in which most of the dust is released upon the collapse of a cliff. more...

Published
2016
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10. The geomorphology of (21) Lutetia: Results from the OSIRIS imaging system onboard ESA's Rosetta spacecraft

Author

Thomas N., Barbieri C., Keller H. U., Lamy P., Rickman H., Rodrigo R., Sierks H., Wenzel K. P., Cremonese G., Jorda L., Kueppers M., Marchi S., Marzari F., Massironi M., Preusker F., Scholten F., Stephan K., Barucci M. A., Besse S., El-Maarry M. R., Fornasier S., Groussin O., Hviid S. F., Koschny D., and Kuehrt E. more...

Abstract

The surface of (21) Lutetia is highly complex with significant interactions between ancient and more recent structures. This work attempts to summarize the surface geomorphology observed using the high resolution images from OSIRIS the imaging system onboard the European Space Agency's Rosetta spacecraft. A wide range of surface morphologies are seen including heavily cratered terrain extensive sets of lineaments young impact craters and a ridge the height of which is more than 1/5th of the mean radius of the body. Very young and very old terrains (as inferred from crater densities) are seen in close proximity. The longest continuous lineament is over 80 km long. The lineaments show regional dependent organization and structure. Several categories of lineament can be described. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent. Although the lineaments may be of seismic origin (and possibly the result of several impact induced events) impacts producing recent large craters place constraints on seismic phenomena. In particular stronger attenuation of shocks than seen on other asteroidal bodies seems to be required. Inhomogeneous energy transport possibly matching observed inhomogeneous ejecta deposition may offer explanations for some of the observed phenomena. Some impact craters show unusual forms which are probably the result of impact into a surface with relief comparable to the resultant crater diameter and/or oblique impact. There is evidence that re surfacing through landslides has occurred at several places on the object. (C) 2011 Elsevier Ltd. All rights reserved. more...

Published
2012

11. First analysis of the size-frequency distribution of boulders ge 7m on comet 67P

Author

PAJOLA, MAURIZIO, Vincent, J. B., Güttler, C., Lee, J. -C., Massironi, M., Bertini, I., SIMIONI, EMANUELE, Marzari, F., GIACOMINI, LIVIA, Barbieri, C., CREMONESE, Gabriele, Naletto, G., Pommerol, A., El Maarry, M. R., Besse, S., Küppers, M., La Forgia, F., Lazzarin, M., Thomas, N., Auger, A. T., Ip, W. -H., Lin, Z. -Y., Sierks, H., OSIRIS Team, A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Ferri, F., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Hviid, S. F., Jorda, L., Keller, H. U., Knollenberg, J., Koschny, D., Kramm, J. -R., Kürt, E., Lamy, P., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Moissl, R., Mottola, S., Oklay, N., Preusker, F., Rickman, H., Rodrigo, R., Scholten, F., and Tubiana, C. more...

Abstract

Images of the surface of comet 67P Churyumov-Gerasimenko taken by the OSIRIS camera on board the Rosetta spacecraft have been used to study the statistical distribution and morphological properties of both cluster and isolated roundish structures ('boulders') scattered all over the surface. We used NAC images taken on Aug 5-6, 2014, at a distance between 131.45 - 109.76 km, with a spatial resolution ranging from 2.44 - 2.03 m/px (Fig. 1). Such data cover a full rotation of 67P, providing the first ever full size frequency distribution coverage of boulders ≥ 7m visible on a cometary illuminated side. Boulders are ubiquitous on the head, neck, and body of 67P \citep{thomas15}. The initial count of 4,976 boulders was reduced to 3,546 for statistical purposes taking into consideration only those with a diameter larger than 7 m \citep{pajola15}. more...

Published
2016

12. Are fractured cliffs the source of cometary dust jets ? Insights from OSIRIS/Rosetta at 67P

Author

Vincent, J. -B., Oklay, N., Pajola, M., Höfner, S., Sierks, H., Hu, X., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P. J., Gutiérrez-Marquez, P., Güttler, C., Hofmann, M., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y., Moreno, J. J. Lopez, Lowry, S., Marzari, F., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C. more...

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

Dust jets, i.e. fuzzy collimated streams of cometary material arising from the nucleus, have been observed in-situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986. Yet their formation mechanism remains unknown. Several solutions have been proposed, from localized physical mechanisms on the surface/sub-surface (see review in Belton (2010)) to purely dynamical processes involving the focusing of gas flows by the local topography (Crifo et al. 2002). While the latter seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller features (a few meters wide) that connect directly to the nucleus surface. We monitored these jets at high resolution and over several months to understand what are the physical processes driving their formation, and how this affects the surface. Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets, and linked them precisely to their sources on the nucleus. Results.We show here observational evidence that the Northern hemisphere jets of comet 67P arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features, and therefore the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets., Comment: Accepted by Astronomy & Astrophysics on 4 December 2015 more...

Published
2015
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13. Fractures on comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS

Author

El-Maarry, M. R., Thomas, N., Gracia-Berna, A., Marschall, R., Auger, A. -T., Groussin, O., Mottola, S., Pajola, M., Massironi, M., Marchi, S., Hofner, S., Preusker, F., Scholten, F., Jorda, L., Kuhrt, E., Keller, H. U., Sierks, H., A'Hearn, M. F., Barbieri, C., Barucci, M. A., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Guttler, C., Fornasier, S., Fulle, M., Gutierrez, P. J., Hofmann, M., Hviid, S. F., W. -H., Ip, Knollenberg, J., Koschny, D., Kovacs, G., Kramm, J. -R., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Rickman, H., Rodrigo, R., Tubiana, C., Vincent, J. -B., Physikalisches Institut [Bern], Universität Bern [Bern] (UNIBE), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), DLR Institute of Planetary Research, German Aerospace Center (DLR), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Università degli Studi di Padova = University of Padua (Unipd), Dipartimento di Geoscienze [Padova], Solar System Exploration Research Virtual Institute (SSERVI), Southwest Research Institute [Boulder] (SwRI), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut für Geophysik und Extraterrestrische Physik [Braunschweig] (IGEP), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Dipartimento di Fisica e Astronomia 'Galileo Galilei', 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), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), CNR Institute for Photonics and Nanotechnologies (IFN), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Department of Physics and Astronomy [Uppsala], Uppsala University, Department of Industrial Engineering [Padova], University of Trento [Trento], INAF - Osservatorio Astronomico di Trieste (OAT), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institute of Astronomy [Taiwan] (IANCU), National Central University [Taiwan] (NCU), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Operations Department (ESAC), European Space Astronomy Centre (ESAC), Institut für Datentechnik und Kommunikationsnetze, Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), International Space Science Institute [Bern] (ISSI), ITA, USA, GBR, FRA, DEU, ESP, Universität Bern [Bern], Universita degli Studi di Padova, Max-Planck-Institut für Sonnensystemforschung (MPS), Consiglio Nazionale delle Ricerche [Roma] (CNR), European Space Agency (ESA)-European Space Agency (ESA), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), and Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA) more...

Subjects
Comet 67P, comets, fractures, OSIRIS, Rosetta, 530 Physics, 520 Astronomy, Comets, Fractures, Earth and Planetary Sciences (all), Geophysics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 620 Engineering, comet 67P/ Churyumov-Gerasimenko
Abstract

The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard the Rosetta spacecraft currently orbiting comet 67P/Churyumov-Gerasimenko has yielded unprecedented views of a comet's nucleus. We present here the first ever observations of meter-scale fractures on the surface of a comet. Some of these fractures form polygonal networks. We present an initial assessment of their morphology, topology, and regional distribution. Fractures are ubiquitous on the surface of the comet's nucleus. Furthermore, they occur in various settings and show different topologies suggesting numerous formation mechanisms, which include thermal insulation weathering, orbital-induced stresses, and possibly seasonal thermal contraction. However, we conclude that thermal insolation weathering is responsible for creating most of the observed fractures based on their morphology and setting in addition to thermal models that indicate diurnal temperature ranges exceeding 200K and thermal gradients of similar to 15K/min at perihelion are possible. Finally, we suggest that fractures could be a facilitator in surface evolution and long-term erosion. more...

Published
2015
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14. The Colour and Stereo Surface Imaging System (CaSSIS) for ESA's Trace Gas Orbiter

Author

Thomas, N., Gabriele Cremonese, Banaszkiewicz, M., Bridges, J., Byrne, S., Da Deppo, V., Debei, S., El-Maarry, M. R., Hauber, E., Hansen, C. J., Ivanov, A., Kestay, L., Kirk, R., Kuzmin, R., Mangold, N., Marinangeli, L., Markiewicz, W., Massironi, M., Mcewen, A. S., Okubo, C., Orleanski, P., Pommerol, A., Wajer, P., and Wray, J. more...

Subjects
Planetengeologie, Mapping, Trace Gas Orbiter, Mars, Stereo, Camera, ExoMars
Abstract

CaSSIS (Colour and Stereo Surface Imaging System) will be the main imaging system for the ExoMars 2016 Trace Gas Orbiter (TGO) mission. A viable and scientifically compelling instrument is now in the build phase with a target completion date of Sept. 2015 for a launch in Jan. 2016. This abstract describes CaSSIS and its capabilities. more...

Published
2014

15. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

Author

Küppers, M., Bertini, I., Ip, W.-H., Lara, L. M., Sierks, H., Kührt, E., Feller, C., Hasselmann, P. H., Fulchignoni, M., Barbieri, C., Oklay, N., Debei, S., Marzari, F., Knollenberg, J., Hviid, S. F., Kramm, R., Rodrigo, Rafael, Güttler, C., De Cecco, M., Bertaux, J.-L., El-Maarry, M. R., Lazzarin, M., Tubiana, C., Hofmann, M., Thomas, Nicolas, Barucci, M. A., Cremonese, G., Deller, J., Lamy, P. L., Lopez Moreno, J. J., Davidsson, B., A’Hearn, M., Fornasier, S., Keller, H. U., Fulle, M., Jorda, L., Da Deppo, V., Naletto, G., Vincent, J.-B., Deshapriya, J. D. P., Perna, D., Gutierrez, P. J., Groussin, O., Koschny, D., and Rickman, H. more...

Subjects
13. Climate action, 520 Astronomy, 620 Engineering
Abstract

The ESA Rosetta mission explored comet 67P/Churyumov-Gerasimenko in 2014−2016, following its target before and after the perihelion passage on 13 August 2015. The NAC camera of the OSIRIS imaging system allowed to map the nucleus surface acquiring images with different filters in the visible wavelength range. Aims. Here we study the spectrophotometric behaviour of the nucleus by a multivariate statistical analysis, aiming to distinguish homogeneous groups and to constrain the bulk composition. Methods. We applied the G-mode clustering algorithm to 16 OSIRIS data cubes acquired on 5−6 August 2014 (mostly covering the northern hemisphere) and 2 May 2015 (mostly covering the southern hemisphere), selected to have complete coverage of the comet’s surface with similar observing conditions. Results. We found four similar homogeneous groups for each of the analysed cubes. The first group corresponds to the average spectrophotometric behaviour of the nucleus. The second (spectrally redder) and the third (spectrally bluer) groups are found in regions that were already found to deviate from the average terrain of the comet by previous studies. A fourth group (characterised by enhancements of the flux at 700−750 nm and 989 nm, possibly due to H2O + and/or NH2 emissions) seems connected with the cometary activity rather than with the bulk composition. Conclusions. While our aim in this work was to study the spectrophotometric behaviour of the nucleus of 67P/Churyumov-Gerasimenko as a whole, we found that a follow-up application of the G-mode to smaller regions of the surface could be useful in particular to identify and study the temporal evolution of ice patches, as well as to constrain the composition and physical processes behind the emission of dust jets. more...

16. Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Author

Debei, S., Vincent, J.-B., Barbieri, C., Güttler, C., Jorda, L., Besse, S., Knollenberg, J., Sierks, H., Hviid, S. F., Bertaux, J.-L., Boudreault, S., Lowry, S., Lamy, P. L., Pajola, M., Keller, H. U., Rodrigo, R., Marzari, F., Fulle, M., Lazzarin, M., Fornasier, S., Bodewits, D., Kührt, E., Cremonese, G., Lee, J.-C., Tubiana, C., Koschny, D., Li, Y., La Forgia, F., Kramm, J.-R., Bertini, I., Küppers, M., Lin, Z.-Y., Oklay, N., Mottola, S., Toth, E., Ip, W.-H., El-Maarry, M. R., Agarwal, J., Barucci, M. A., López-Moreno, J. J., A’Hearn, M. F., Marchi, S., Da Deppo, V., Davidsson, B., Rickman, H., Cheng, Y.-C., De Cecco, M., Naletto, G., Lara, L. M., Michalik, H., Kovacs, G., Groussin, O., Lai, I.-L., Thomas, Nicolas, and Gutiérrez, P. J. more...

Subjects
13. Climate action, 530 Physics
Abstract

Aims. We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC). Methods. The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other. Results. The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived. Conclusions. The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history. more...

17. Sunset jets observed on comet 67P/Churyumov-Gerasimenko sustained by subsurface thermal lag

Author

Hu, X., Thomas, Nicolas, A’Hearn, M., Lara, L. M., Pajola, M., Oklay, N., Kovacs, G., Koschny, D., Knollenberg, J., Güttler, C., Bertaux, J.-L., Lamy, P. L., Barbieri, C., Tubiana, C., Shi, X., Bertini, I., Hofmann, M., Bodewits, D., Sierks, H., Kührt, E., Keller, H. U., Mottola, S., Rodrigo, R., Gutiérrez, P. J., Cremonese, G., Jorda, L., Lin, Z.-Y., Hviid, S. F., Lopez-Moreno, J. J., Blum, J., Vincent, J.-B., Naletto, G., Fornasier, S., De Cecco, M., Küppers, M., Ip, W.-H., Kramm, J.-R., Höfner, S., Gicquel, A., Da Deppo, V., Fulle, M., Debei, S., Groussin, O., Lazzarin, M., Barucci, M. A., Davidsson, B., Marzari, F., Rickman, H., and El-Maarry, M. R. more...

Subjects
13. Climate action, 530 Physics, 520 Astronomy, 620 Engineering
Abstract

We present observations of sunset jets on comet 67P/Churyumov-Gerasimenko by Rosetta/OSIRIS camera. In late April 2015, when the comet was at a heliocentric distance of ~1.8 AU, clusters of dust jets that originated in the Ma’at region on the comet’s small lobe were identified from multipleimages and were apparently sustained for about an hour beyond local sunset. Emanating from the shadowed nucleus, these jets became visible by solar illumination at their apparent sources up to only a few tens of meters above the nucleus surface. We investigate the plausibility of these jets as having been triggered by water ice sublimation and sustained by thermal lag in the subsurface beyond sunset. A general thermo-physical model was parameterized such that the thermal lag in the subsurface is consistent with the elapsed time of observation after sunset. It is found that the sublimation of water ice from a depth of 6 mm and with a low thermal inertia of 50 W m-2 K-1 s1/2 could explain the spatial pattern and evolution of the apparent sources, particularly their disappearance due to the eventual cooling of the subsurface. Our analysis suggests that these sunset jets were essentially day-side dust activities that continued after sunset. Specific observational conditions for the sunset jets constrain their possible sources to mostly within the less abrupt, dusty terrains. The uneven distribution of these jets is possibly related to subsurface inhomogeneities in the dusty area. more...

18. Surface Morphology of Comets and Associated Evolutionary Processes: A Review of Rosetta’s Observations of 67P/Churyumov–Gerasimenko

Author

El-Maarry, M. R., Groussin, O., Keller, H. U., Thomas, Nicolas, Vincent, J.-B., Mottola, S., Pajola, M., Otto, K., Herny, Clémence Emilie Lucile, and Krasilnikov, S.

Subjects
13. Climate action, 520 Astronomy, 620 Engineering, 7. Clean energy
Abstract

Comets can be regarded as active planetary bodies because they display evidence for nearly all fundamental geological processes, which include impact cratering, tectonism, and erosion. Comets also display sublimation-driven outgassing, which is comparable to volcanism on larger planetary bodies in that it provides a conduit for delivering materials from the interior to the surface. However, in the domain of active geological bodies, comets occupy a special niche since their geologic activity is almost exclusively driven by externally supplied energy (i.e. solar energy) as opposed to an internal heat source, which makes them “seasonally-active” geological bodies. During their active phase approaching the Sun, comets also develop a transient atmosphere that interacts with the surface and contributes to its evolution, particularly by transporting materials across the surface. Variations in solar energy input on diurnal and seasonal scale cause buildup of thermal stresses within consolidated materials that lead to weathering through fracturing, and eventually mass-wasting. The commonly irregular shapes of comets also play a major role in their evolution by leading to (1) non-uniform gravitational forces that affect material movement across the surface, and (2) spatially heterogeneous outgassing patterns that affect the comet’s orbital dynamics and lead to tidal stresses that can further fracture the nucleus. In this chapter, we review the surface morphology of comet 67P/Churyumov–Gerasimenko as well as its seasonal evolution as viewed by Rosetta from August 2014 to September 2016, their link to various processes, and the forces that drive surface evolution. more...

19. Modelling of the outburst on 2015 July 29 observed with OSIRIS cameras in the Southern hemisphere of comet 67P/Churyumov–Gerasimenko

Author

De Cecco, M., Debei, S., Gutiérrez, P. J., Rodrigo, Rafael, Moreno, F., Groussin, O., Sierks, H., Keller, H. U., Barbieri, C., Da Deppo, V., Bertaux, J.-L., Lamy, P. L., Mottola, S., Hu, X., Kührt, E., Kramm, J.-R., Rickman, H., Agarwal, J., Lin, Z.-Y., Davidsson, B., Lazzarin, M., Gutiérrez-Marquez, P., Höfner, S., Oklay, N., Gicquel, A., Shi, X., Massironi, M., Jorda, L., Deller, J., Güttler, C., Ip, W.-H., Cremonese, G., Rose, M., Toth, I., Hofmann, M., Küppers, M., Lara, L. M., Kovacs, G., Fulle, M., Masoumzadeh, N., Knollenberg, J., El-Maarry, M. R., Vincent, J.-B., Fornasier, S., Fougere, N., Thomas, Nicolas, Scholten, F., Boudreault, S., Hviid, S. F., Lowry, S., Tubiana, C., Frattin, E., Pajola, M., A’Hearn, M. F., Koschny, D., Bertini, I., Marzari, F., Bodewits, D., Preusker, F., Barucci, M. A., Naletto, G., Moreno, J. J. Lopez, and Besse, S. more...

Subjects
13. Climate action, 520 Astronomy, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 620 Engineering, Astrophysics::Galaxy Astrophysics
Abstract

Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov– Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) cameras since 2014 March using both the wide-angle camera and the narrow-angle camera (NAC). We use images from the NAC camera to study a bright outburst observed in the Southern hemisphere on 2015 July 29. The high spatial resolution of the NAC is needed to localize the source point of the outburst on the surface of the nucleus. The heliocentric distance is 1.25 au and the spacecraft–comet distance is 186 km. Aiming to better understand the physics that led to the outgassing, we used the Direct Simulation Monte Carlo method to study the gas flow close to the nucleus and the dust trajectories. The goal is to understand the mechanisms producing the outburst. We reproduce the opening angle of the outburst in the model and constrain the outgassing ratio between the outburst source and the local region. The outburst is in fact a combination of both gas and dust, in which the active surface is approximately 10 times more active than the average rate found in the surrounding areas. We need a number of dust particles 7.83 × 1011 to 6.90 × 1015 (radius 1.97–185 μm), which correspond to a mass of dust (220–21) × 103 kg. more...

20. Image Simulation and Assessment of the Colour and Spatial Capabilities of the Colour and Stereo Surface Imaging System (CaSSIS) on the ExoMars Trace Gas Orbiter

Author

Tornabene, Livio L., Seelos, Frank P., Pommerol, Antoine, Thomas, Nicolas, Caudill, C. M., Becerra Valdes, Patricio, Bridges, John C., Byrne, Shane, Cardinale, Marco, Chojnacki, Matthew, Conway, Susan J., Cremonese, Gabriele, Dundas, Colin M., El-Maarry, M. R., Fernando, Jennifer, Hansen, Candice J., Hansen, Kayle, Harrison, Tanya N., Henson, Rachel, Marinangeli, Lucia, McEwen, Alfred S., Pajola, Maurizio, Sutton, Sarah S., and Wray, James J. more...

Subjects
13. Climate action, 520 Astronomy, 620 Engineering
Abstract

This study aims to assess the spatial and visible/near-infrared (VNIR) colour/spectral capabilities of the 4-band Colour and Stereo Surface Imaging System (CaSSIS) aboard the ExoMars 2016 Trace Grace Orbiter (TGO). The instrument response functions for the CaSSIS imager was used to resample spectral libraries, modelled spectra and to construct spectrally (i.e., in I/F space) and spatially consistent simulated CaSSIS image cubes of various key sites of interest and for ongoing scientific investigations on Mars. Coordinated datasets from Mars Reconnaissance Orbiter (MRO) are ideal, and specifically used for simulating CaSSIS. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provides colour information, while the Context Imager (CTX), and in a few cases the High-Resolution Imaging Science Experiment (HiRISE), provides the complementary spatial information at the resampled CaSSIS unbinned/unsummed pixel resolution (4.6 m/pixel from a 400-km altitude). The methodology used herein employs a Gram-Schmidt spectral sharpening algorithm to combine the ∼18–36 m/pixel CRISM-derived CaSSIS colours with I/F images primarily derived from oversampled CTX images. One hundred and eighty-one simulated CaSSIS 4-colour image cubes (at 18–36 m/pixel) were generated (including one of Phobos) based on CRISM data. From these, thirty-three “fully”-simulated image cubes of thirty unique locations on Mars (i.e., with 4 colour bands at 4.6 m/pixel) were made. All simulated image cubes were used to test both the colour capabilities of CaSSIS by producing standard colour RGB images, colour band ratio composites (CBRCs) and spectral parameters. Simulated CaSSIS CBRCs demonstrated that CaSSIS will be able to readily isolate signatures related to ferrous (Fe2+) iron- and ferric (Fe3+) iron-bearing deposits on the surface of Mars, ices and atmospheric phenomena. Despite the lower spatial resolution of CaSSIS when compared to HiRISE, the results of this work demonstrate that CaSSIS will not only compliment HiRISE-scale studies of various geological and seasonal phenomena, it will also enhance them by providing additional colour and geologic context through its wider and longer full-colour coverage (∼9.4×50 ∼9.4×50 km), and its increased sensitivity to iron-bearing materials from its two IR bands (RED and NIR). In a few examples, subtle surface changes that were not easily detected by HiRISE were identified in the simulated CaSSIS images. This study also demonstrates the utility of the Gram-Schmidt spectral pan-sharpening technique to extend VNIR colour/spectral capabilities from a lower spatial resolution colour/spectral dataset to a single-band or panchromatic image greyscale image with higher resolution. These higher resolution colour products (simulated CaSSIS or otherwise) are useful as means to extend both geologic context and mapping of datasets with coarser spatial resolutions. The results of this study indicate that the TGO mission objectives, as well as the instrument-specific mission objectives, will be achievable with CaSSIS. more...

21. The Agilkia boulders/pebbles size–frequency distributions: OSIRIS and ROLIS joint observations of 67P surface

Author

Thomas, Nicolas, Kramm, J. R., Rodrigo, R., Bertaux, J. L., Barbieri, C., Keller, H. U., Agarwal, J., Boudreault, S., Lin, Z. Y., Michalik, H., Koschny, D., Küppers, M., Lopez Moreno, J. J., Michaelis, H., Fulle, M., Preusker, F., Rickman, H., Jaumann, R., Feller, C., Barucci, M. A., Lara, L. M., Kührt, E., Mottola, S., Ip, W. H., Grothues, H.-G., Naletto, G., Lamy, P. L., El Maarry, M. R., Davidsson, B., Oklay, N., Hamm, M., Groussin, O., Scholten, F., Cremonese, G., Hofmann, M., Güttler, C., Lucchetti, A., Pajola, M., Marzari, F., Debei, S., De Cecco, M., Lazzarin, M., Bibring, J. P., Da Deppo, V., La Forgia, F., Massironi, M., Arnold, G., Fornasier, S., Knollenberg, J., Deller, J., Pommerol, Antoine, Bertini, I., Gutierrez, P. J., Jorda, L., A'Hearn, M. F., Gicquel, A., Sierks, H., Vincent, J. B., Hviid, S. F., and Tubiana, C. more...

Subjects
530 Physics, 520 Astronomy, 14. Life underwater, 620 Engineering
Abstract

By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size– frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05– 30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders ‘peek through’ the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD. more...

22. OSIRIS observations of metre-size bright exposures of H2O ice at the surface of comet 67P/C-G

Author

Pommerol, A., Fornasier, S., Thomas, N., El-Maarry, M. R., Pajola, M., Groussin, O., Auger, A. -T, Oklay, N., Feller, C., Davidsson, B., Gracia, A., Jost, B., Raphael Marschall, Poch, O., Barucci, M. A., Bertaux, J. L., La Forgia, F., Keller, H. U., Kührt, E., Lowry, S. C., ITA, USA, GBR, FRA, and DEU more...

Abstract

Since the beginning of Rosetta's orbital observations, over a hundred small bright spots have been identified in images returned by its OSIRIS NAC camera, in all types of morphological regions on the nucleus. This abstract focuses on such analysis. more...