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44 results on '"El-Maarry , M. R."'

1. A Global Dataset of Potential Chloride Deposits on Mars as Identified by TGO CaSSIS

Author: Bickel, V. T., Thomas, N., Pommerol, A., Tornabene, L. L., El-Maarry, M. R., and Rangarajan, V. G.
Published: 2024
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2. Evidence for transient morning water frost deposits on the Tharsis volcanoes of Mars

Author: Valantinas, A., Thomas, N., Pommerol, A., Karatekin, O., Ruiz Lozano, L., Senel, C. B., Temel, O., Hauber, E., Tirsch, D., Bickel, V. T., Munaretto, G., Pajola, M., Oliva, F., Schmidt, F., Thomas, I., McEwen, A. S., Almeida, M., Read, M., Rangarajan, V. G., El-Maarry, M. R., Re, C., Carrozzo, F. G., D’Aversa, E., Daerden, F., Ristic, B., Patel, M. R., Bellucci, G., Lopez-Moreno, J. J., Vandaele, A. C., and Cremonese, G.
Published: 2024
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3. Large Glacier‐Like Forms on Mars: Insights From Crater Morphologies and Crater Retention Ages.

Author: Driver, G., El‐Maarry, M. R., Hubbard, B., and Brough, S.
Subjects: VISCOUS flow, GLACIERS, LANDFORMS, GEOMORPHOLOGY, REGIONAL differences, IMPACT craters
Abstract: Glacier‐Like Forms (GLFs) are a subset of ice‐rich landforms known as Viscous Flow Features that populate Mars' mid‐latitudes. GLFs are morphologically similar to terrestrial valley glaciers and are thought to result from the redistribution of water ice from the Martian poles during periods of high obliquity throughout the Amazonian period. Their ages, formation, and evolutionary processes are poorly constrained. We selected the 100 largest GLFs from the most recent GLF population data set, and by analyzing their superimposing crater morphologies and populations, we calculated their Crater Retention Ages (CRAs) and identified any relationships between CRAs, crater morphologies, and GLF geometries. We also organized the crater morphologies into states of degradation based on the understood erosional sequences. 3,630 craters were mapped, which we classified into 15 different crater morphologies. We calculated 98 CRAs, ranging from ∼2.88 Ma to ∼3.5 Ga. On average, GLFs in the southern hemisphere have younger CRAs, higher average slopes, smaller crater populations, and show less variability in crater morphological development than in the northern hemisphere. GLFs with higher mean slopes display less crater morphology variety, suggesting that shallow GLFs experience less reworking than steeper GLFs. We propose that these regional and hemispheric differences are due to a combination of favorable topography and climate conditions, both during and between high obliquity periods. We present several scenarios for the GLFs observed in this study and suggest that the glacial and erosional processes that affect GLF evolution are likely locale‐dependent. Plain Language Summary: Glacier‐Like Forms (GLFs) are ice‐rich landforms located in the mid‐latitudes of Mars and are similar in appearance to valley glaciers found on Earth. They are thought to be a result of the redistribution of water ice from the Martian poles during periods when Mars' axis tilts to a higher angle, exposing the poles to more heat from the sun. We selected the 100 largest glaciers to estimate the age of their surfaces via impact crater counting, to identify impact crater morphologies, and to compare this data to existing data on GLF geometrics. We mapped 3,630 craters, identified 15 different impact crater morphologies, and determined the surface ages of 98 glaciers, which ranged from 2.88 million years to 3.5 billion years old. Our analysis shows that glaciers with lower than average slopes have impact craters with a wider range of morphologies than glaciers with higher average surface slopes. Overall we find that glaciers in the southern hemisphere of Mars have young surface ages, and fewer and less developed craters compared with the northern hemisphere. We suggest different regional processes are occurring across Mars, with some areas favoring resurfacing processes more than others, and that glacier surface evolution is specific to the local environment. Key Points: The surface ages, crater morphologies, and metrics of the 100 largest Glacier‐Like Forms (GLFs) on Mars were explored to determine any trendsSurface ages range from 3430 to 2.88 Ma with 15 different crater morphologies. Slope exerts a substantial control on crater morphology developmentResurfacing processes occurring in certain regions of Mars have a greater effect on GLF surfaces than in others [ABSTRACT FROM AUTHOR]
Published: 2024
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4. 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, N., Vincent, J.-B., Mottola, S., Pajola, M., Otto, K., Herny, C., and Krasilnikov, S.
Published: 2019
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5. The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter

Author: Thomas, N., Cremonese, G., Ziethe, R., Gerber, M., Brändli, M., Bruno, G., Erismann, M., Gambicorti, L., Gerber, T., Ghose, K., Gruber, M., Gubler, P., Mischler, H., Jost, J., Piazza, D., Pommerol, A., Rieder, M., Roloff, V., Servonet, A., Trottmann, W., Uthaicharoenpong, T., Zimmermann, C., Vernani, D., Johnson, M., Pelò, E., Weigel, T., Viertl, J., De Roux, N., Lochmatter, P., Sutter, G., Casciello, A., Hausner, T., Ficai Veltroni, I., Da Deppo, V., Orleanski, P., Nowosielski, W., Zawistowski, T., Szalai, S., Sodor, B., Tulyakov, S., Troznai, G., Banaskiewicz, M., Bridges, J. C., Byrne, S., Debei, S., El-Maarry, M. R., Hauber, E., Hansen, C. J., Ivanov, A., Keszthelyi, L., Kirk, R., Kuzmin, R., Mangold, N., Marinangeli, L., Markiewicz, W. J., Massironi, M., McEwen, A. S., Okubo, C., Tornabene, L. L., Wajer, P., and Wray, J. J.
Published: 2017
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6. The morphological diversity of comet 67P/Churyumov-Gerasimenko

Author: Thomas, N., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Rickman, H., Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Angrilli, F., Auger, A.-T., Barucci, M. A., Bertaux, J.-L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., El-Maarry, M. R., Ferri, F., Fornasier, S., Fulle, M., Giacomini, L., Groussin, O., Gutierrez, P. J., Güttler, C., Hviid, S. F., Ip, W.-H., Jorda, L., Knollenberg, J., Kramm, J.-R., Kührt, E., Küppers, M., La Forgia, F., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Preusker, F., Sabau, L., Scholten, F., Snodgrass, C., Tubiana, C., Vincent, J.-B., and Wenzel, K.-P.
Published: 2015

7. Cometary surface dust layers built out of millimetre-scale aggregates: dependence of modelled cometary gas production on the layer transport properties.

Author: Skorov, Yu, Markkanen, J, Reshetnyk, V, Mottola, S, Küppers, M, Besse, S, El-Maarry, M R, and Hartogh, P
Subjects: THERMAL conductivity, SURFACE properties, STRUCTURAL models, RADIATIVE transfer, ENERGY transfer, DUST
Abstract: The standard approach to obtaining knowledge about the properties of the surface layer of a comet from observations of gas production consists of two stages. First, various thermophysical models are used to calculate gas production for a few sets of parameters. Second, a comparison of observations and theoretical predictions is performed. This approach is complicated because the values of many model characteristics are known only approximately. Therefore, it is necessary to investigate the sensitivity of the simulated outgassing to variations in the properties of the surface layer. This problem was recently considered by us for aggregates up to tens of microns in size. For millimetre-size aggregates, a qualitative extension of the method used to model the structural characteristics of the layer is required. It is also necessary to study the role of radiative thermal conductivity, which may play an important role for such large particles. We investigated layers constructed from large aggregates and having various thicknesses and porosity and evaluated the effective sublimation of water ice at different heliocentric distances. For radiative conductivity, approximate commonly used models and the complicated model based on the dense-medium radiative transfer theory were compared. It was shown that for millimetre-size aggregates careful consideration of the radiative thermal conductivity is required since this mechanism of energy transfer may change the resulting gas productivity by several times. We demonstrate that our model is more realistic for an evolved comet than simple models parameterizing the properties of the cometary surface layer, yet maintains comparable computational complexity. [ABSTRACT FROM AUTHOR]
Published: 2023
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8. 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, Nicholas, Caudill, C. M., Becerra, 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.
Published: 2017
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9. Diurnal Variability in EMIRS Daytime Observations of Water Ice Clouds During Mars Aphelion‐Season.

Author: Atwood, Samuel A., Smith, Michael D., Badri, Khalid, Edwards, Christopher S., Christensen, Philip R., Wolff, Michael J., Forget, François, Anwar, Saadat, Smith, Nathan, and El‐Maarry, M. R.
Subjects: GENERAL circulation model, MARTIAN atmosphere, OROGRAPHIC clouds, MARS (Planet), ICE clouds, IR spectrometers
Abstract: Diurnal analyses of water ice cloud optical depths retrieved from thermal infrared spectra by the Emirates Mars Infrared Spectrometer showed changing cloud abundance throughout the Martian day. Observations began with the start of the Emirates Mars Mission science phase near the beginning of aphelion‐season in Mars Year 36 and included the prominent aphelion cloud belt (ACB) and orographic clouds in the vicinity of volcanoes. A midday minimum with higher morning and afternoon optical depths was typical for the ACB, though with considerable spatial variability in this diurnal pattern. Clouds near volcanoes reached a minimum before local noon and tended to increase in abundance throughout the afternoon. Comparisons against the Laboratoire de Météorologie Dynamique global circulation model showed analogous spatial patterns in the diurnal signal, which suggested thermal tides and topographic effects to be the predominant drivers of ACB variability, while more localized circulations affected volcano clouds. Plain Language Summary: Observations from the Emirates Mars Infrared Spectrometer onboard the Emirates Mars Mission (EMM) spacecraft were used to measure the abundance of clouds in the Martian atmosphere and investigate how they changed throughout the day. Due to the unique nature of EMM's high orbit, the observations provided by EMIRS cover all times of day and provide more detailed information about how clouds change as compared to many previous missions. In these results we present information about this daytime cloud variability for different regions on Mars. A prominent region of clouds that is commonly observed near the equator during Mars' cold season—known as the aphelion cloud belt—was observed to reach a minimum near midday, with more clouds typically observed in both the morning and afternoon. Distinct differences were found in clouds observed near volcanoes, which tended to reach a minimum before local noon and increase throughout the afternoon. These results add detail to our understanding of cloud behavior and help us to validate computer models of the Martian atmosphere. Key Points: Infrared spectra from the Emirates Mars Infrared Spectrometer were used to obtain water ice cloud optical depths throughout the dayThe aphelion cloud belt had a midday minimum with higher optical depths in the morning and afternoonOrographic clouds near volcanoes were observed to increase throughout the afternoon [ABSTRACT FROM AUTHOR]
Published: 2022
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10. 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)
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
Published: 2018
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11. 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 )
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.
Published: 2018
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12. 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.
Subjects: comets: general, methods: observational, addenda, comets: individual: Churyumov-Gerasimenko, errata, errata, addenda
Published: 2018

13. 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.
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
Published: 2017

14. 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 )
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.
Published: 2016
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15. 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.
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}.
Published: 2016

16. 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)
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.
Published: 2015
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17. FIRST LIGHT OF CASSIS - THE STEREO SURFACE IMAGING SYSTEM ONBOARD THE EXOMARS TGO.

Author: Gambicorti, L., Piazza, D., Pommerol, A., Roloff, V., Gerber, M., Ziethe, R., El-Maarry, M. R., Weigel, T., Johnson, M., Vernani, D., Pelo, E., Da Deppo, V., Cremonese, G., Veltroni, I. Ficai, and Thomas, N.
Published: 2017
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18. 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.
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.
Published: 2014

19. 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, Nicholas, Caudill, C. M., Becerra, 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, and Marinangeli, Lucia
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 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. [ABSTRACT FROM AUTHOR]
Published: 2018
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20. Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere.

Author: El-Maarry, M. R., Thomas, N., Gracia-Berná, A., Pajola, M., Lee, J.-C., Massironi, M., Davidsson, B., Marchi, S., Keller, H. U., Hviid, S. F., Besse, S., Sierks, H., Barbieri, C., Lamy, P. L., Koschny, D., Rickman, H., Rodrigo, R., A’Hearn, M. F., Auger, A.-T., and Barucci, M. A.
Abstract: Aims. The OSIRIS camera on board the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)’s nucleus since August 2014. Starting in May 2015, the southern hemisphere gradually became illuminated and was imaged for the first time. Here we present the regional morphology of the southern hemisphere, which serves as a companion to an earlier paper that presented the regional morphology of the northern hemisphere. Methods. We used OSIRIS images that were acquired at orbits ∼45−125 km from the center of the comet (corresponding to spatial resolutions of ∼0.8 to 2.3 m/pixel) coupled with the use of digital terrain models to define the different regions on the surface, and identify structural boundaries accurately. Results. Seven regions have been defined in the southern hemisphere bringing the total number of defined regions on the surface of the nucleus to 26. These classifications are mainly based on morphological and/or topographic boundaries. The southern hemisphere shows a remarkable dichotomy with its northern counterpart mainly because of the absence of wide-scale smooth terrains, dust coatings and large unambiguous depressions. As a result, the southern hemisphere closely resembles previously identified consolidated regions. An assessment of the overall morphology of comet 67P suggests that the comet’s two lobes show surface heterogeneities manifested in different physical/mechanical characteristics, possibly extending to local (i.e., within a single region) scales. [ABSTRACT FROM AUTHOR]
Published: 2016
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21. Aswan site on comet 67P/Churyumov-Gerasimenko: Morphology, boulder evolution, and spectrophotometry.

Author: Pajola, Maurizio, Oklay, Nilda, La Forgia, Fiorangela, Giacomini, Lorenza, Massironi, Matteo, Bertini, Ivano, El-Maarry, M. R., Marzari, Francesco, Preusker, Frank, Scholten, Frank, Höfner, Sebastian, Jui-Chi Lee, Vincent, Jean-Baptiste, Groussin, Olivier, Naletto, Giampiero, Lazzarin, Monica, Barbieri, Cesare, Sierks, Holger, Lamy, Philippe, and Rodrigo, Rafael
Abstract: Aims. We provide a detailed morphological analysis of the Aswan site on comet 67P/Churyumov-Gerasimenko (67P). We derive the size-frequency distribution of boulders ≥2 m and correlate this distribution with the gravitational slopes for the first time on a comet. We perform the spectral analysis of this region to understand if possible surface variegation is related to the different surface textures observable on the different units. Methods. We used two OSIRIS Narrow Angle Camera (NAC) image data sets acquired on September 19 and 22, 2014, with a scale of 0.5 m/px. Gravitational slopes derived from the 3D shape model of 67P were used to identify and interpret the different units of the site. By means of the high-resolution NAC data sets, boulders ≥2.0 m can be unambiguously identified and extracted using the software ArcGIS. Coregistered and photometrically corrected color cubes were used to perform the spectral analyses, and we retrieved the spectral properties of the Aswan units. Results. The high-resolution morphological map of the Aswan site (0.68 km2) shows that this site is characterized by four different units: fine-particle deposits located on layered terrains, gravitational accumulation deposits, taluses, and the outcropping layered terrain. Multiple lineaments are identified on the Aswan cliff, such as fractures, exposed layered outcrops, niches, and terraces. Close to the terrace margin, several arched features observed in plan view suggest that the margin progressively retreats as a result of erosion. The size-frequency of boulders ≥2 m in the entire study area has a power-law index of −3.9 +0.2/−0.3 (1499 boulders ≥2 m/km2), suggesting that the Aswan site is mainly dominated by gravitational events triggered by sublimation and/or thermal insolation weathering causing regressive erosion. The boulder size-frequency distribution versus gravitational slopes indicates that when higher gravitational slope terrains are considered, only boulders ≤10 m are identified, as well as steeper power-slope indices. In addition, no boulders ≥2 m are observed on slopes ≥50◦. This may indicate that larger blocks detached from a sublimating cliff cannot rest at these slopes and consequently fall down. The spectral analysis performed on the site shows that despite different morphologic units, no spectral differences appear in the multiple textures. This may confirm a redistribution of particles across the nucleus as a consequence of airfall, whether coming from Hapi or from the southern hemisphere when it is active during perihelion. [ABSTRACT FROM AUTHOR]
Published: 2016
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22. The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Author: Davidsson, B. J. R., Sierks, H., Güttler, C., Marzari, F., Pajola, M., Rickman, H., A’Hearn, M. F., Auger, A.-T., El-Maarry, M. R., Fornasier, S., Gutiérrez, P. J., Keller, H. U., Massironi, M., Snodgrass, C., Vincent, J.-B., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., and Barucci, M. A.
Abstract: Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods.We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles.We argue that TNOs formed as a result of streaming instabilities at sizes below ~400 km and that ~350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented medium-sized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity to avoid thermal processing by short-lived radionuclides that would lead to loss of supervolatiles, and that allowed comet nuclei to incorporate ~3 Myr old material from the inner solar system. [ABSTRACT FROM AUTHOR]
Published: 2016
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23. Sunset jets observed on comet 67P/Churyumov-Gerasimenko sustained by subsurface thermal lag.

Author: Shi, X., Hu, X., Sierks, H., Güttler, C., A'Hearn, M., Blum, J., El-Maarry, M. R., Kührt, E., Mottola, S., Pajola, M., Oklay, N., Fornasier, S., Tubiana, C., Keller, H. U., Vincent, J.-B., Bodewits, D., Höfner, S., Lin, Z.-Y., Gicquel, A., and Hofmann, M.
Subjects: CHURYUMOV-Gerasimenko comet, INTERPLANETARY dust, ASTRONOMICAL observations, THERMOPHYSICAL properties
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 ~1.8AU, clusters of dust jets that originated in the Ma'at region on the comet's small lobe were identified from multiple images 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 6mm and with a low thermal inertia of 50Wm-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. [ABSTRACT FROM AUTHOR]
Published: 2016
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24. Characterization of the Abydos region through OSIRIS high-resolution images in support of CIVA measurements.

Author: Lucchetti, A., Cremonese, G., Jorda, L., Poulet, F., Bibring, J.-P., Pajola, M., La Forgia, F., Massironi, M., El-Maarry, M. R., Oklay, N., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., and Barucci, M. A.
Subjects: COMETS, PHILAE (Space probe), SUBLIMATION (Chemistry), GRAVITATION, EROSION
Abstract: Context. On 12 November 2014, the European mission Rosetta delivered the Philae lander on the nucleus of comet 67P/Churyumov- Gerasimenko (67P). After the first touchdown, the lander bounced three times before finally landing at a site named Abydos. Aims. We provide a morphologically detailed analysis of the Abydos landing site to support Philae's measurements and to give context for the interpretation of the images coming from the Comet Infrared and Visible Analyser (CIVA) camera system onboard the lander. Methods. We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 6 December 2014 to perform the analysis of the Abydos landing site, which provided the geomorphological map, the gravitational slope map, the size-frequency distribution of the boulders. We also computed the albedo and spectral reddening maps. Results. The morphological analysis of the region could suggest that Philae is located on a primordial terrain. The Abydos site is surrounded by two layered and fractured outcrops and presents a 0.02 km2 talus deposit rich in boulders. The boulder size frequency distribution gives a cumulative power-law index of -4:0 + 0:3=-0:4, which is correlated with gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. The average value of the albedo is 5.8% at λ1 = 480:7 nm and 7.4% at λ2 = 649:2 nm, which is similar to the global albedos derived by OSIRIS and CIVA, respectively. [ABSTRACT FROM AUTHOR]
Published: 2016
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25. Field investigation of dried lakes in western United States as an analogue to desiccation fractures on Mars.

Author: El-Maarry, M. R., Watters, W. A., Yoldi, Z., Pommerol, A., Fischer, D., Eggenberger, U., and Thomas, N.
Published: 2015
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26. An ice-rich flow origin for the banded terrain in the Hellas basin, Mars.

Author: Diot, X., El-Maarry, M. R., Guallini, L., Schlunegger, F., Norton, K. P., Thomas, N., Sutton, S., and Grindrod, P. M.
Published: 2015
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27. 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.
Published: 2013
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28. Crater floor polygons: Desiccation patterns of ancient lakes on Mars?

Author: El Maarry, M. R., Markiewicz, W. J., Mellon, M. T., Goetz, W., Dohm, J. M., and Pack, A.
Published: 2010
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29. Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties.

Author: Goetz, W., Pike, W. T., Hviid, S. F., Madsen, M. B., Morris, R. V., Hecht, M. H., Staufer, U., Leer, K., Sykulska, H., Hemmig, E., Marshall, J., Morookian, J. M., Parrat, D., Vijendran, S., Bos, B. J., El Maarry, M. R., Keller, H. U., Kramm, R., Markiewicz, W. J., and Drube, L.
Published: 2010
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30. Chemically striking regions on Mars and Stealth revisited.

Author: Karunatillake, Suniti, Wray, James J., Squyres, Steven W., Taylor, G. Jeffrey, Gasnault, Olivier, McLennan, Scott M., Boynton, William, El Maarry, M. R., and Dohm, James M.
Published: 2009
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31. THE EFFECTS OF PAST AND CURRENT GEOLOGIC PROCESSES OBSERVED BY THE CASSIS IMAGER ONBOARD ESA'S EXOMARS TRACE GAS ORBITER.

Author: Thomas, N., Cremonese, G., Perry, J., Almeida, M., Banaszkiewicz, M., Bapst, J. N., Becerra, P., Bridges, J. C., Byrne, S., Conway, S., DaDeppo, V., Debei, S., El-Maarry, M. R., Fennema, A., Gwinner, K., Hauber, E., Heyd, R., Hansen, C. J., Ivanov, A., and Keszthelyi, L.
Subjects: TRACE gases, PLANETARY science, EARTH sciences, SPACE exploration, DIGITAL elevation models
Published: 2019

32. MINERALOGY OF FUMAROLIC DEPOSITS FROM ICELAND AS ANALOGS FOR ANCIENT HYDROTHERMAL SYSTEMS ON MARS: ROLE OF TEMPERATURE.

Author: El-Maarry, M. R., Black, S. R., Hynek, B. M., and McHenry, L. J.
Subjects: MINERALOGY, TEMPERATURE, HYDROTHERMAL alteration
Published: 2017

33. REMARKABLE SURFACE CHANGES OF COMET 67P/CHURYUMOV-GERASIMENKO'S NUCLEUS AROUND PERIHELION.

Author: El-Maarry, M. R., Groussin, O., Thomas, N., Pajola, M., Auger, A.-T., Davidsson, B., Hu, X., Hviid, S. F., Knollenberg, J., Güttler, C., Tubiana, C., Bodewits, D., Fornasier, S., and Sierks, H.
Subjects: COMPOUND nucleus, CHURYUMOV-Gerasimenko comet
Published: 2017

34. 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.
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.

35. 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.
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.

36. 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.
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.

37. 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.

38. 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.
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.

39. 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.
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.

40. 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.
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.

41. Correction to 'Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties'.

Author: Goetz, W., Pike, W. T., Hviid, S. F., Madsen, M. B., Morris, R. V., Hecht, M. H., Staufer, U., Leer, K., Sykulska, H., Hemmig, E., Marshall, J., Morookian, J. M., Parrat, D., Vijendran, S., Bos, B. J., El Maarry, M. R., Keller, H. U., Kramm, R., Markiewicz, W. J., and Drube, L.
Published: 2010
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42. The geology and geophysics of Kuiper Belt object (486958) Arrokoth.

Author: Spencer JR, Stern SA, Moore JM, Weaver HA, Singer KN, Olkin CB, Verbiscer AJ, McKinnon WB, Parker JW, Beyer RA, Keane JT, Lauer TR, Porter SB, White OL, Buratti BJ, El-Maarry MR, Lisse CM, Parker AH, Throop HB, Robbins SJ, Umurhan OM, Binzel RP, Britt DT, Buie MW, Cheng AF, Cruikshank DP, Elliott HA, Gladstone GR, Grundy WM, Hill ME, Horanyi M, Jennings DE, Kavelaars JJ, Linscott IR, McComas DJ, McNutt RL Jr, Protopapa S, Reuter DC, Schenk PM, Showalter MR, Young LA, Zangari AM, Abedin AY, Beddingfield CB, Benecchi SD, Bernardoni E, Bierson CJ, Borncamp D, Bray VJ, Chaikin AL, Dhingra RD, Fuentes C, Fuse T, Gay PL, Gwyn SDJ, Hamilton DP, Hofgartner JD, Holman MJ, Howard AD, Howett CJA, Karoji H, Kaufmann DE, Kinczyk M, May BH, Mountain M, Pätzold M, Petit JM, Piquette MR, Reid IN, Reitsema HJ, Runyon KD, Sheppard SS, Stansberry JA, Stryk T, Tanga P, Tholen DJ, Trilling DE, and Wasserman LH
Abstract: The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU 69 ). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)
Published: 2020
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43. Initial results from the New Horizons exploration of 2014 MU 69 , a small Kuiper Belt object.

Author: Stern SA, Weaver HA, Spencer JR, Olkin CB, Gladstone GR, Grundy WM, Moore JM, Cruikshank DP, Elliott HA, McKinnon WB, Parker JW, Verbiscer AJ, Young LA, Aguilar DA, Albers JM, Andert T, Andrews JP, Bagenal F, Banks ME, Bauer BA, Bauman JA, Bechtold KE, Beddingfield CB, Behrooz N, Beisser KB, Benecchi SD, Bernardoni E, Beyer RA, Bhaskaran S, Bierson CJ, Binzel RP, Birath EM, Bird MK, Boone DR, Bowman AF, Bray VJ, Britt DT, Brown LE, Buckley MR, Buie MW, Buratti BJ, Burke LM, Bushman SS, Carcich B, Chaikin AL, Chavez CL, Cheng AF, Colwell EJ, Conard SJ, Conner MP, Conrad CA, Cook JC, Cooper SB, Custodio OS, Dalle Ore CM, Deboy CC, Dharmavaram P, Dhingra RD, Dunn GF, Earle AM, Egan AF, Eisig J, El-Maarry MR, Engelbrecht C, Enke BL, Ercol CJ, Fattig ED, Ferrell CL, Finley TJ, Firer J, Fischetti J, Folkner WM, Fosbury MN, Fountain GH, Freeze JM, Gabasova L, Glaze LS, Green JL, Griffith GA, Guo Y, Hahn M, Hals DW, Hamilton DP, Hamilton SA, Hanley JJ, Harch A, Harmon KA, Hart HM, Hayes J, Hersman CB, Hill ME, Hill TA, Hofgartner JD, Holdridge ME, Horányi M, Hosadurga A, Howard AD, Howett CJA, Jaskulek SE, Jennings DE, Jensen JR, Jones MR, Kang HK, Katz DJ, Kaufmann DE, Kavelaars JJ, Keane JT, Keleher GP, Kinczyk M, Kochte MC, Kollmann P, Krimigis SM, Kruizinga GL, Kusnierkiewicz DY, Lahr MS, Lauer TR, Lawrence GB, Lee JE, Lessac-Chenen EJ, Linscott IR, Lisse CM, Lunsford AW, Mages DM, Mallder VA, Martin NP, May BH, McComas DJ, McNutt RL Jr, Mehoke DS, Mehoke TS, Nelson DS, Nguyen HD, Núñez JI, Ocampo AC, Owen WM, Oxton GK, Parker AH, Pätzold M, Pelgrift JY, Pelletier FJ, Pineau JP, Piquette MR, Porter SB, Protopapa S, Quirico E, Redfern JA, Regiec AL, Reitsema HJ, Reuter DC, Richardson DC, Riedel JE, Ritterbush MA, Robbins SJ, Rodgers DJ, Rogers GD, Rose DM, Rosendall PE, Runyon KD, Ryschkewitsch MG, Saina MM, Salinas MJ, Schenk PM, Scherrer JR, Schlei WR, Schmitt B, Schultz DJ, Schurr DC, Scipioni F, Sepan RL, Shelton RG, Showalter MR, Simon M, Singer KN, Stahlheber EW, Stanbridge DR, Stansberry JA, Steffl AJ, Strobel DF, Stothoff MM, Stryk T, Stuart JR, Summers ME, Tapley MB, Taylor A, Taylor HW, Tedford RM, Throop HB, Turner LS, Umurhan OM, Van Eck J, Velez D, Versteeg MH, Vincent MA, Webbert RW, Weidner SE, Weigle GE 2nd, Wendel JR, White OL, Whittenburg KE, Williams BG, Williams KE, Williams SP, Winters HL, Zangari AM, and Zurbuchen TH
Abstract: The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU 69 , a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU 69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU 69 's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)
Published: 2019
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44. Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature.

Author: Fornasier S, Mottola S, Keller HU, Barucci MA, Davidsson B, Feller C, Deshapriya JD, Sierks H, Barbieri C, Lamy PL, Rodrigo R, Koschny D, Rickman H, A'Hearn M, Agarwal J, Bertaux JL, Bertini I, Besse S, Cremonese G, Da Deppo V, Debei S, De Cecco M, Deller J, El-Maarry MR, Fulle M, Groussin O, Gutierrez PJ, Güttler C, Hofmann M, Hviid SF, Ip WH, Jorda L, Knollenberg J, Kovacs G, Kramm R, Kührt E, Küppers M, Lara ML, Lazzarin M, Moreno JJ, Marzari F, Massironi M, Naletto G, Oklay N, Pajola M, Pommerol A, Preusker F, Scholten F, Shi X, Thomas N, Toth I, Tubiana C, and Vincent JB
Abstract: The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 square meters) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color are seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties., (Copyright © 2016, American Association for the Advancement of Science.)
Published: 2016
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