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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. 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: Astrophysics - Earth and Planetary Astrophysics
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 parameterising the properties of the cometary surface layer, yet maintains comparable computational complexity.
Published: 2023
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3. 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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4. Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt Object

Author: Stern, S. A., Weaver, H. A., Spencer, J. R., Olkin, C. B., Gladstone, G. R., Grundy, W. M., Moore, J. M., Cruikshank, D. P., Elliott, H. A., McKinnon, W. B., Parker, J. Wm., Verbiscer, A. J., Young, L. A., Aguilar, D. A., Albers, J. M., Andert, T., Andrews, J. P., Bagenal, F., Banks, M. E., Bauer, B. A., Bauman, J. A., Bechtold, K. E., Beddingfield, C. B., Behrooz, N., Beisser, K. B., Benecchi, S. D., Bernardoni, E., Beyer, R. A., Bhaskaran, S., Bierson, C. J., Binzel, R. P., Birath, E. M., Bird, M. K., Boone, D. R., Bowman, A. F., Bray, V. J., Britt, D. T., Brown, L. E., Buckley, M. R., Buie, M. W., Buratti, B. J., Burke, L. M., Bushman, S. S., Carcich, B., Chaikin, A. L., Chavez, C. L., Cheng, A. F., Colwell, E. J., Conard, S. J., Conner, M. P., Conrad, C. A., Cook, J. C., Cooper, S. B., Custodio, O. S., Ore, C. M. Dalle, Deboy, C. C., Dharmavaram, P., Dhingra, R. D., Dunn, G. F., Earle, A. M., Egan, A. F., Eisig, J., El-Maarry, M. R., Engelbrecht, C., Enke, B. L., Ercol, C. J., Fattig, E. D., Ferrell, C. L., Finley, T. J., Firer, J., Fischetti, J., Folkner, W. M., Fosbury, M. N., Fountain, G. H., Freeze, J. M., Gabasova, L., Glaze, L. S., Green, J. L., Griffith, G. A., Guo, Y., Hahn, M., Hals, D. W., Hamilton, D. P., Hamilton, S. A., Hanley, J. J., Harch, A., Harmon, K. A., Hart, H. M., Hayes, J., Hersman, C. B., Hill, M. E., Hill, T. A., Hofgartner, J. D., Holdridge, M. E., Horányi, M., Hosadurga, A., Howard, A. D., Howett, C. J. A., Jaskulek, S. E., Jennings, D. E., Jensen, J. R., Jones, M. R., Kang, H. K., Katz, D. J., Kaufmann, D. E., Kavelaars, J. J., Keane, J. T., Keleher, G. P., Kinczyk, M., Kochte, M. C., Kollmann, P., Krimigis, S. M., Kruizinga, G. L., Kusnierkiewicz, D. Y., Lahr, M. S., Lauer, T. R., Lawrence, G. B., Lee, J. E., Lessac-Chenen, E. J., Linscott, I. R., Lisse, C. M., Lunsford, A. W., Mages, D. M., Mallder, V. A., Martin, N. P., May, B. H., McComas, D. J., McNutt, R. L., Mehoke, Jr. D. S., Mehoke, T. S., Nelson, D. S., Nguyen, H. D., Núñez, J. I., Ocampo, A. C., Owen, W. M., Oxton, G. K., Parker, A. H., Pätzold, M., Pelgrift, J. Y., Pelletier, F. J., Pineau, J. P., Piquette, M. R., Porter, S. B., Protopapa, S., Quirico, E., Redfern, J. A., Regiec, A. L., Reitsema, H. J., Reuter, D. C., Richardson, D. C., Riedel, J. E., Ritterbush, M. A., Robbins, S. J., Rodgers, D. J., Rogers, G. D., Rose, D. M., Rosendall, P. E., Runyon, K. D., Ryschkewitsch, M. G., Saina, M. M., Salinas, M. J., Schenk, P. M., Scherrer, J. R., Schlei, W. R., Schmitt, B., Schultz, D. J., Schurr, D. C., Scipioni, F., Sepan, R. L., Shelton, R. G., Showalter, M. R., Simon, M., Singer, K. N., Stahlheber, E. W., Stanbridge, D. R., Stansberry, J. A., Steffl, A. J., Strobel, D. F., Stothoff, M. M., Stryk, T., Stuart, J. R., Summers, M. E., Tapley, M. B., Taylor, A., Taylor, H. W., Tedford, R. M., Throop, H. B., Turner, L. S., Umurhan, O. M., Van Eck, J., Velez, D., Versteeg, M. H., Vincent, M. A., Webbert, R. W., Weidner, S. E., Weigle II, G. E., Wendel, J. R., White, O. L., Whittenburg, K. E., Williams, B. G., Williams, K. E., Williams, S. P., Winters, H. L., Zangari, A. M., and Zurbuchen, T. H.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observations. MU69 is a bi-lobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color and compositional heterogeneity. No evidence for satellites, ring or dust structures, gas coma, or solar wind interactions was detected. By origin MU69 appears consistent with pebble cloud collapse followed by a low velocity merger of its two lobes., Comment: 43 pages, 8 figure
Published: 2020
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5. The Geology and Geophysics of Kuiper Belt Object (486958) Arrokoth

Author: Spencer, J. R., Stern, S. A., Moore, J. M., Weaver, H. A., Singer, K. N., Olkin, C. B., Verbiscer, A. J., McKinnon, W. B., Parker, J. Wm., Beyer, R. A., Keane, J. T., Lauer, T. R., Porter, S. B., White, O. L., Buratti, B. J., El-Maarry, M. R., Lisse, C. M., Parker, A. H., Throop, H. B., Robbins, S. J., Umurhan, O. M., Binzel, R. P., Britt, D. T., Buie, M. W., Cheng, A. F., Cruikshank, D. P., Elliott, H. A., Gladstone, G. R., Grundy, W. M., Hill, M. E., Horanyi, M., Jennings, D. E., Kavelaars, J. J., Linscott, I. R., McComas, D. J., McNutt, R. L., Protopapa, S., Reuter, D. C., Schenk, P. M., Showalter, M. R., Young, L. A., Zangari, A. M., Abedin, A. Y., Beddingfield, C. B., Benecchi, S. D., Bernardoni, E., Bierson, C. J., Borncamp, D., Bray, V. J., Chaikin, A. L., Dhingra, R. D., Fuentes, C., Fuse, T., Gay, P. L, Gwyn, S. D. J., Hamilton, D. P., Hofgartner, J. D., Holman, M. J., Howard, A. D., Howett, C. J. A., Karoji, H., Kaufmann, D. E., Kinczyk, M., May, B. H., Mountain, M., Pätzold, M., Petit, J. M., Piquette, M. R., Reid, I. N., Reitsema, H. J., Runyon, K. D., Sheppard, S. S., Stansberry, J. A., Stryk, T., Tanga, P., Tholen, D. J., Trilling, D. E., and Wasserman, L. H.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, are primitive objects preserving information about Solar System formation. The New Horizons spacecraft flew past one of these objects, the 36 km long contact binary (486958) Arrokoth (2014 MU69), in January 2019. Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters diameter) within a radius of 8000 km, and 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.
Published: 2020
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6. Tensile Strength of 67P/Churyumov-Gerasimenko Nucleus Material from Overhangs

Author: Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A'Hearn, M. F., Auger, A. -T., Barucci, M. A., Bertaux, J. -L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, P. J., Güttler, C., Hviid, S., Ip, W. -H, Kovacs, G., Kramm, J. R., Küppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Toth, I., Tubiana, C., Vincen, J. -B., and Shi, X.
Subjects: 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., Comment: 13 pages, 11 figures. Accepted for publication in Astronomy & Astrophysics
Published: 2017
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7. The highly active Anhur-Bes regions in the 67P/Churyumov - Gerasimenko comet: results from OSIRIS/ROSETTA observations

Author: Fornasier, S., Feller, C., Lee, J. C., Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P, Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. H., Lin, Z. Y., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J ., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since March 2015. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rate, thus exposing the subsurface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits, and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur/Bes boundary during/after the perihelion passage, close to the area where exposed CO$_2$ and H$_2$O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit, and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers., Comment: 16 pages, 15 figures, published online on 24 May 2017 on Mon. Not. R. Astron. Soc. stx1275, https://doi.org/10.1093/mnras/stx1275
Published: 2017
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8. 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: 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
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9. Summer fireworks on comet 67P

Author: Vincent, J. -B., A'Hearn, M. F., Lin, Z. -Y., El-Maarry, M. R., Pajola, M., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., Guettler, C., Hoefner, S., Hofmann, M., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: During its two years 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 to 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 three months surrounding the comet's perihelion passage in August 2015. We detected and characterized 34 outbursts with the Rosetta cameras, one every 2.4 nucleus rotation. We identified 3 main dust plume morphologies associated to 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 correlates 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., Comment: MNRAS (2016)
Published: 2016
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10. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras onboard Rosetta

Author: Gicquel, A., Vincent, J. -B., Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., 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., Cremonese, G., Da Deppo, V., Davidsson, B., 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., Guettler, C., Hoefner, S., Hofmann, M., Hu, X., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kuehrt, E., Kueppers, 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., Pommerol, A., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: Beginning in March 2014, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analyzed the dust monitoring observations shortly after the southern vernal equinox on May 30 and 31, 2015 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this article was that through the sublimation of the aggregates of dirty grains (radius a between 5 microm and 50 microm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data we needed to inject a number of aggregates between 8.5 x $10^{13}$ and 8.5 x $10^{10}$ for a = 5 microm and 50 microm respectively, or an initial mass of $H_2O$ ice around 22kg., Comment: 11 pages, 7 figures, 3 tables, special issue "The ESLAB 50 Symposium - spacecraft at comets from 1P/Halley to 67P/Churyumov-Gerasimenko" in the Monthly Notices of the Royal Astronomical Society
Published: 2016
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11. Are fractured cliffs the source of cometary dust jets ? Insights from OSIRIS/Rosetta at 67P

Author: Vincent, J. -B., Oklay, N., Pajola, M., Höfner, S., Sierks, H., Hu, X., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P. J., Gutiérrez-Marquez, P., Güttler, C., Hofmann, M., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y., Moreno, J. J. Lopez, Lowry, S., Marzari, F., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: Dust jets, i.e. fuzzy collimated streams of cometary material arising from the nucleus, have been observed in-situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986. Yet their formation mechanism remains unknown. Several solutions have been proposed, from localized physical mechanisms on the surface/sub-surface (see review in Belton (2010)) to purely dynamical processes involving the focusing of gas flows by the local topography (Crifo et al. 2002). While the latter seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller features (a few meters wide) that connect directly to the nucleus surface. We monitored these jets at high resolution and over several months to understand what are the physical processes driving their formation, and how this affects the surface. Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets, and linked them precisely to their sources on the nucleus. Results.We show here observational evidence that the Northern hemisphere jets of comet 67P arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features, and therefore the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets., Comment: Accepted by Astronomy & Astrophysics on 4 December 2015
Published: 2015
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12. Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

Author: Groussin, O., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Hearn, M. F. A, Auger, A. -T., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, P. J., Güttler, C., Hviid, S., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Lowry, S., Marchi, S., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, in the smooth terrains of the Imhotep region. We use images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015. The morphological changes observed on the surface are visible in the form of roundish features, which are growing in size from a given location in a preferential direction, at a rate of 5.6 - 8.1$\times$10$^{-5}$ m s$^{-1}$ during the observational period. The location where changes started and the contours of the expanding features are bluer than the surroundings, suggesting the presence of ices (H$_2$O and/or CO$_2$) exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes., Comment: 4 pages, 3 figures; Letter for Astronomy and Astrophysics: accepted
Published: 2015
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13. Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Author: Groussin, O., Jorda, L., Auger, A. -T., Kührt, E., Gaskell, R., Capanna, C., Scholten, F., Preusker, F., Lamy, P., Hviid, S., Knollenberg, J., Keller, U., Huettig, C., Sierks, H., Barbieri, C., Rodrigo, R., Koschny, D., Rickman, H., Hearn, M. F. A, Agarwal, J., Barucci, M. A., Bertaux, J. -L., Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, P. J., Güttler, C., Ip, W. -H, Kramm, J. -R., Küppers, M., Lazzarin, M., Lara, L. M., Moreno, J. J. Lopez, Marchi, S., Marzari, F., Massironi, M., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Pajola, M., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material. We computed the gravitational slopes for five regions on the nucleus that are representative of the different morphologies observed on the surface, using two shape models computed from OSIRIS images by the stereo-photoclinometry (SPC) and stereo-photogrammetry (SPG) techniques. We estimated the tensile, shear, and compressive strengths using different surface morphologies and mechanical considerations. The different regions show a similar general pattern in terms of the relation between gravitational slopes and terrain morphology: i) low-slope terrains (0-20 deg) are covered by a fine material and contain a few large ($>$10 m) and isolated boulders, ii) intermediate-slope terrains (20-45 deg) are mainly fallen consolidated materials and debris fields, with numerous intermediate-size boulders from $<$1 m to 10 m for the majority of them, and iii) high-slope terrains (45-90 deg) are cliffs that expose a consolidated material and do not show boulders or fine materials. The best range for the tensile strength of overhangs is 3-15 Pa (upper limit of 150 Pa), 4-30 Pa for the shear strength of fine surface materials and boulders, and 30-150 Pa for the compressive strength of overhangs (upper limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P and weak rocks on Earth. As a result of the low compressive strength, the interior of the nucleus may have been compressed sufficiently to initiate diagenesis, which could have contributed to the formation of layers. Our value for the tensile strength is comparable to that of dust aggregates formed by gravitational instability and tends to favor a formation of comets by the accrection of pebbles at low velocities., Comment: 18 pages, 15 figures, 1 table; Astronomy and Astrophysics, in press
Published: 2015
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14. Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations

Author: Rickman, H., Marchi, S., A'Hearn, M. F., Barbieri, C., El-Maarry, M. R., Güttler, C., Ip, W. -H., Keller, H. U., Lamy, P., Marzari, F., Massironi, M., Naletto, G., Pajola, M., Sierks, H., and Team, OSIRIS
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: One of the main aims of the ESA Rosetta mission is to study the origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko at close range. In this paper we discuss the origin and evolution of comet 67P/Churyumov-Gerasimenko in relation to that of comets in general and in the framework of current solar system formation models. We use data from the OSIRIS scientific cameras as basic constraints. In particular, we discuss the overall bi-lobate shape and the presence of key geological features, such as layers and fractures. We also treat the problem of collisional evolution of comet nuclei by a particle-in-a-box calculation for an estimate of the probability of survival for 67P/Churyumov-Gerasimenko during the early epochs of the solar system. We argue that the two lobes of the 67P/Churyumov-Gerasimenko nucleus are derived from two distinct objects that have formed a contact binary via a gentle merger. The lobes are separate bodies, though sufficiently similar to have formed in the same environment. An estimate of the collisional rate in the primordial, trans-planetary disk shows that most comets of similar size to 67P/Churyumov-Gerasimenko are likely collisional fragments, although survival of primordial planetesimals cannot be excluded. A collisional origin of the contact binary is suggested, and the low bulk density of the aggregate and abundance of volatile species show that a very gentle merger must have occurred. We thus consider two main scenarios: the primordial accretion of planetesimals, and the re-accretion of fragments after an energetic impact onto a larger parent body. We point to the primordial signatures exhibited by 67P/Churyumov-Gerasimenko and other comet nuclei as critical tests of the collisional evolution., Comment: Accepted, to appear on Astronomy & Astrophysics
Published: 2015
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15. 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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16. 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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17. Cometary surface dust layers built out of millimetre-scale aggregates: dependence of modelled cometary gas production on the layer transport properties

Author: Skorov, Yu, primary, Markkanen, J, additional, Reshetnyk, V, additional, Mottola, S, additional, Küppers, M, additional, Besse, S, additional, El-Maarry, M R, additional, and Hartogh, P, additional
Published: 2023
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18. 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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19. 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

20. Diurnal Variability in EMIRS Daytime Observations of Water Ice Clouds During Mars Aphelion‐Season

Author: Atwood, Samuel A., primary, Smith, Michael D., additional, Badri, Khalid, additional, Edwards, Christopher S., additional, Christensen, Philip R., additional, Wolff, Michael J., additional, Forget, François, additional, Anwar, Saadat, additional, Smith, Nathan, additional, and El‐Maarry, M. R., additional
Published: 2022
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21. 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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22. The geology and geophysics of Kuiper Belt object (486958) Arrokoth

Author: Spencer, J. R., primary, Stern, S. A., additional, Moore, J. M., additional, Weaver, H. A., additional, Singer, K. N., additional, Olkin, C. B, additional, Verbiscer, A. J., additional, McKinnon, W. B., additional, Parker, J. Wm., additional, Beyer, R. A., additional, Keane, J. T., additional, Lauer, T. R., additional, Porter, S. B., additional, White, O. L., additional, Buratti, B. J., additional, El-Maarry, M. R., additional, Lisse, C. M., additional, Parker, A. H., additional, Throop, H. B., additional, Robbins, S. J., additional, Umurhan, O. M., additional, Binzel, R. P., additional, Britt, D. T., additional, Buie, M. W., additional, Cheng, A. F., additional, Cruikshank, D. P., additional, Elliott, H. A., additional, Gladstone, G. R., additional, Grundy, W. M., additional, Hill, M. E., additional, Horanyi, M., additional, Jennings, D. E., additional, Kavelaars, J. J., additional, Linscott, I. R., additional, McComas, D. J., additional, McNutt, R. L., additional, Protopapa, S., additional, Reuter, D. C., additional, Schenk, P. M., additional, Showalter, M. R., additional, Young, L. A., additional, Zangari, A. M., additional, Abedin, A. Y., additional, Beddingfield, C. B., additional, Benecchi, S. D., additional, Bernardoni, E., additional, Bierson, C. J., additional, Borncamp, D., additional, Bray, V. J., additional, Chaikin, A. L., additional, Dhingra, R. D., additional, Fuentes, C., additional, Fuse, T., additional, Gay, P. L, additional, Gwyn, S. D. J., additional, Hamilton, D. P., additional, Hofgartner, J. D., additional, Holman, M. J., additional, Howard, A. D., additional, Howett, C. J. A., additional, Karoji, H., additional, Kaufmann, D. E., additional, Kinczyk, M., additional, May, B. H., additional, Mountain, M., additional, Pätzold, M., additional, Petit, J. M., additional, Piquette, M. R., additional, Reid, I. N., additional, Reitsema, H. J., additional, Runyon, K. D., additional, Sheppard, S. S., additional, Stansberry, J. A., additional, Stryk, T., additional, Tanga, P., additional, Tholen, D. J., additional, Trilling, D. E., additional, and Wasserman, L. H., additional
Published: 2020
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23. 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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24. Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Author: Masoumzadeh, N, primary, Kolokolova, L, additional, Tubiana, C, additional, El-Maarry, M. R., additional, Mottola, S, additional, Güttler, C., additional, Snodgrass, C, additional, Sierks, H., additional, Naletto, G., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D, additional, Davidsson, B, additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I, additional, Bodewits, D., additional, Cremonese, G, additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fornasier, S., additional, Fulle, M, additional, Gutiérrez, P. J., additional, Hasselmann, P. H., additional, Ip, W.-H., additional, Keller, H. U., additional, Lara, L. M., additional, Lazzarin, M, additional, López-Moreno, J. J., additional, Marzari, F, additional, Shi, X, additional, and Toth, I, additional
Published: 2019
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25. Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

Author: Stern, S. A., primary, Weaver, H. A., additional, Spencer, J. R., additional, Olkin, C. B., additional, Gladstone, G. R., additional, Grundy, W. M., additional, Moore, J. M., additional, Cruikshank, D. P., additional, Elliott, H. A., additional, McKinnon, W. B., additional, Parker, J. Wm., additional, Verbiscer, A. J., additional, Young, L. A., additional, Aguilar, D. A., additional, Albers, J. M., additional, Andert, T., additional, Andrews, J. P., additional, Bagenal, F., additional, Banks, M. E., additional, Bauer, B. A., additional, Bauman, J. A., additional, Bechtold, K. E., additional, Beddingfield, C. B., additional, Behrooz, N., additional, Beisser, K. B., additional, Benecchi, S. D., additional, Bernardoni, E., additional, Beyer, R. A., additional, Bhaskaran, S., additional, Bierson, C. J., additional, Binzel, R. P., additional, Birath, E. M., additional, Bird, M. K., additional, Boone, D. R., additional, Bowman, A. F., additional, Bray, V. J., additional, Britt, D. T., additional, Brown, L. E., additional, Buckley, M. R., additional, Buie, M. W., additional, Buratti, B. J., additional, Burke, L. M., additional, Bushman, S. S., additional, Carcich, B., additional, Chaikin, A. L., additional, Chavez, C. L., additional, Cheng, A. F., additional, Colwell, E. J., additional, Conard, S. J., additional, Conner, M. P., additional, Conrad, C. A., additional, Cook, J. C., additional, Cooper, S. B., additional, Custodio, O. S., additional, Dalle Ore, C. M., additional, Deboy, C. C., additional, Dharmavaram, P., additional, Dhingra, R. D., additional, Dunn, G. F., additional, Earle, A. M., additional, Egan, A. F., additional, Eisig, J., additional, El-Maarry, M. R., additional, Engelbrecht, C., additional, Enke, B. L., additional, Ercol, C. J., additional, Fattig, E. D., additional, Ferrell, C. L., additional, Finley, T. J., additional, Firer, J., additional, Fischetti, J., additional, Folkner, W. M., additional, Fosbury, M. N., additional, Fountain, G. H., additional, Freeze, J. M., additional, Gabasova, L., additional, Glaze, L. S., additional, Green, J. L., additional, Griffith, G. A., additional, Guo, Y., additional, Hahn, M., additional, Hals, D. W., additional, Hamilton, D. P., additional, Hamilton, S. A., additional, Hanley, J. J., additional, Harch, A., additional, Harmon, K. A., additional, Hart, H. M., additional, Hayes, J., additional, Hersman, C. B., additional, Hill, M. E., additional, Hill, T. A., additional, Hofgartner, J. D., additional, Holdridge, M. E., additional, Horányi, M., additional, Hosadurga, A., additional, Howard, A. D., additional, Howett, C. J. A., additional, Jaskulek, S. E., additional, Jennings, D. E., additional, Jensen, J. R., additional, Jones, M. R., additional, Kang, H. K., additional, Katz, D. J., additional, Kaufmann, D. E., additional, Kavelaars, J. J., additional, Keane, J. T., additional, Keleher, G. P., additional, Kinczyk, M., additional, Kochte, M. C., additional, Kollmann, P., additional, Krimigis, S. M., additional, Kruizinga, G. L., additional, Kusnierkiewicz, D. Y., additional, Lahr, M. S., additional, Lauer, T. R., additional, Lawrence, G. B., additional, Lee, J. E., additional, Lessac-Chenen, E. J., additional, Linscott, I. R., additional, Lisse, C. M., additional, Lunsford, A. W., additional, Mages, D. M., additional, Mallder, V. A., additional, Martin, N. P., additional, May, B. H., additional, McComas, D. J., additional, McNutt, R. L., additional, Mehoke, D. S., additional, Mehoke, T. S., additional, Nelson, D. S., additional, Nguyen, H. D., additional, Núñez, J. I., additional, Ocampo, A. C., additional, Owen, W. M., additional, Oxton, G. K., additional, Parker, A. H., additional, Pätzold, M., additional, Pelgrift, J. Y., additional, Pelletier, F. J., additional, Pineau, J. P., additional, Piquette, M. R., additional, Porter, S. B., additional, Protopapa, S., additional, Quirico, E., additional, Redfern, J. A., additional, Regiec, A. L., additional, Reitsema, H. J., additional, Reuter, D. C., additional, Richardson, D. C., additional, Riedel, J. E., additional, Ritterbush, M. A., additional, Robbins, S. J., additional, Rodgers, D. J., additional, Rogers, G. D., additional, Rose, D. M., additional, Rosendall, P. E., additional, Runyon, K. D., additional, Ryschkewitsch, M. G., additional, Saina, M. M., additional, Salinas, M. J., additional, Schenk, P. M., additional, Scherrer, J. R., additional, Schlei, W. R., additional, Schmitt, B., additional, Schultz, D. J., additional, Schurr, D. C., additional, Scipioni, F., additional, Sepan, R. L., additional, Shelton, R. G., additional, Showalter, M. R., additional, Simon, M., additional, Singer, K. N., additional, Stahlheber, E. W., additional, Stanbridge, D. R., additional, Stansberry, J. A., additional, Steffl, A. J., additional, Strobel, D. F., additional, Stothoff, M. M., additional, Stryk, T., additional, Stuart, J. R., additional, Summers, M. E., additional, Tapley, M. B., additional, Taylor, A., additional, Taylor, H. W., additional, Tedford, R. M., additional, Throop, H. B., additional, Turner, L. S., additional, Umurhan, O. M., additional, Van Eck, J., additional, Velez, D., additional, Versteeg, M. H., additional, Vincent, M. A., additional, Webbert, R. W., additional, Weidner, S. E., additional, Weigle, G. E., additional, Wendel, J. R., additional, White, O. L., additional, Whittenburg, K. E., additional, Williams, B. G., additional, Williams, K. E., additional, Williams, S. P., additional, Winters, H. L., additional, Zangari, A. M., additional, and Zurbuchen, T. H., additional
Published: 2019
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26. Multidisciplinary analysis of the Hapi region located on Comet 67P/Churyumov–Gerasimenko

Author: Pajola, M, primary, Lee, J-C, additional, Oklay, N, additional, Hviid, S F, additional, Penasa, L, additional, Mottola, S, additional, Shi, X, additional, Fornasier, S, additional, Davidsson, B, additional, Giacomini, L, additional, Lucchetti, A, additional, Massironi, M, additional, Vincent, J B, additional, Bertini, I, additional, Naletto, G, additional, Ip, W H, additional, Sierks, H, additional, Lamy, P L, additional, Rodrigo, R, additional, Koschny, D, additional, Keller, H U, additional, Agarwal, J, additional, Barucci, M A, additional, Bertaux, J L, additional, Bodewits, D, additional, Cambianica, P, additional, Cremonese, G, additional, Da Deppo, V, additional, Debei, S, additional, De Cecco, M, additional, Deller, J, additional, El Maarry, M R, additional, Feller, C, additional, Ferrari, S, additional, Fulle, M, additional, Gutierrez, P J, additional, Güttler, C, additional, Lara, L M, additional, La Forgia, F, additional, Lazzarin, M, additional, Lin, Z-Y, additional, Lopez Moreno, J J, additional, Marzari, F, additional, Preusker, F, additional, Scholten, F, additional, Toth, I, additional, and Tubiana, C, additional
Published: 2019
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27. Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

Author: Stern, S. A., Weaver, H. A., Spencer, J. R., Olkin, C. B., Gladstone, G. R., Grundy, W. M., Moore, J. M., Cruikshank, D. P., Elliott, H. A., McKinnon, W. B., Parker, J. Wm., Verbiscer, A. J., Young, L. A., Aguilar, D. A., Albers, J. M., Andert, T., Andrews, J. P., Bagenal, F., Banks, M. E., Bauer, B. A., Bauman, J. A., Bechtold, K. E., Beddingfield, C. B., Behrooz, N., Beisser, K. B., Benecchi, S. D., Bernardoni, E., Beyer, R. A., Bhaskaran, S., Bierson, C. J., Binzel, R. P., Birath, E. M., Bird, M. K., Boone, D. R., Bowman, A. F., Bray, V. J., Britt, D. T., Brown, L. E., Buckley, M. R., Buie, M. W., Buratti, B. J., Burke, L. M., Bushman, S. S., Careich, B., Chaikin, A. L., Chavez, C. L., Cheng, A. F., Colwell, E. J., Conard, S. J., Conner, M. P., Conrad, C. A., Cook, J. C., Cooper, S. B., Custodio, O. S., Ore, C. M. Dalle, Deboy, C. C., Dharmavaram, P., Dhingra, R. D., Dunn, G. F., Earle, A. M., Egan, A. F., Eisig, J., El-Maarry, M. R., Engelbrecht, C., Enke, B. L., Ercol, C. J., Fattig, E. D., Ferrell, C. L., Finley, T. J., Firer, J., Fischetti, J., Folkner, W. M., Fosbury, M. N., Fountain, G. H., Freeze, J. M., Gabasova, L., Glaze, L. S., Green, J. L., Griffith, G. A., Guo, Y., Hahn, M., Hals, D. W., Hamilton, D. P., Hamilton, S. A., Hanley, J. J., Harch, A., Harmon, K. A., Hart, H. M., Hayes, J., Hersman, C. B., Hill, M. E., Hill, T. A., Hofgartner, J. D., Holdridge, M. E., Horanyi, M., Hosadurga, A., Howard, A. D., Howett, C. J. A., Jaskulek, S. E., Jennings, D. E., Jensen, J. R., Jones, M. R., Kang, H. K., Katz, D. J., Kaufmann, D. E., Kavelaars, J. J., Keane, J. T., Keleher, G. P., Kinczyk, M., Kochte, M. C., Kolmnann, P., Krimigis, S. M., Kruizinga, G. L., Kusnierkiewicz, D. Y., Lahr, M. S., Lauer, T. R., Lawrence, G. B., Lee, J. E., Lessac-Chenen, E. J., Linscott, I. R., Lisse, C. M., Lunsford, A. W., Mages, D. M., Mallder, V. A., Martin, N. P., May, B. H., McComas, D. J., MeNutt, R. L., Jr., Mehoke, D. S., Mehoke, T. S., Nelson, D. S., Nguyen, H. D., Nunez, J. I., Ocampo, A. C., Owen, W. M., Oxton, G. K., Parker, A. H., Patzold, M., Pelgrift, J. Y., Pelletier, F. J., Pineau, J. P., Piquette, M. R., Porter, S. B., Protopapa, S., Quirico, E., Redfern, J. A., Regiec, A. L., Reitsema, H. J., Reuter, D. C., Richardson, D. C., Riedel, J. E., Ritterbush, M. A., Robbins, S. J., Rodgers, D. J., Rogers, G. D., Rose, D. M., Rosendal, P. E., Runyon, K. D., Ryschkewitsch, M. G., Saina, M. M., Salinas, M. J., Schenk, P. M., Scherrer, J. R., Schlei, W. R., Schmitt, B., Schultz, D. J., Schurr, D. C., Scipioni, F., Sepan, R. L., Shelton, R. G., Showalter, M. R., Simon, M., Singer, K. N., Stahlheber, E. W., Stanbridge, D. R., Stansberry, J. A., Steffi, A. J., Strobel, D. F., Stothoff, M. M., Stryk, T., Stuart, J. M., Summers, M. E., Tapley, M. B., Taylor, A., Taylor, H. W., Tedford, R. M., Throop, H. B., Turner, L. S., Umurhan, O. M., Van Eck, J., Velez, D., Versteeg, M. H., Vincent, M. A., Webbert, R. W., Weidner, S. E., Ii, G. E. Weigle, Wendel, J. R., White, O. L., Whittenburg, K. E., Williams, B. G., Williams, K. E., Williams, S. P., Wimters, H. L., Zangari, A. M., Zurbuchen, T. H., Stern, S. A., Weaver, H. A., Spencer, J. R., Olkin, C. B., Gladstone, G. R., Grundy, W. M., Moore, J. M., Cruikshank, D. P., Elliott, H. A., McKinnon, W. B., Parker, J. Wm., Verbiscer, A. J., Young, L. A., Aguilar, D. A., Albers, J. M., Andert, T., Andrews, J. P., Bagenal, F., Banks, M. E., Bauer, B. A., Bauman, J. A., Bechtold, K. E., Beddingfield, C. B., Behrooz, N., Beisser, K. B., Benecchi, S. D., Bernardoni, E., Beyer, R. A., Bhaskaran, S., Bierson, C. J., Binzel, R. P., Birath, E. M., Bird, M. K., Boone, D. R., Bowman, A. F., Bray, V. J., Britt, D. T., Brown, L. E., Buckley, M. R., Buie, M. W., Buratti, B. J., Burke, L. M., Bushman, S. S., Careich, B., Chaikin, A. L., Chavez, C. L., Cheng, A. F., Colwell, E. J., Conard, S. J., Conner, M. P., Conrad, C. A., Cook, J. C., Cooper, S. B., Custodio, O. S., Ore, C. M. Dalle, Deboy, C. C., Dharmavaram, P., Dhingra, R. D., Dunn, G. F., Earle, A. M., Egan, A. F., Eisig, J., El-Maarry, M. R., Engelbrecht, C., Enke, B. L., Ercol, C. J., Fattig, E. D., Ferrell, C. L., Finley, T. J., Firer, J., Fischetti, J., Folkner, W. M., Fosbury, M. N., Fountain, G. H., Freeze, J. M., Gabasova, L., Glaze, L. S., Green, J. L., Griffith, G. A., Guo, Y., Hahn, M., Hals, D. W., Hamilton, D. P., Hamilton, S. A., Hanley, J. J., Harch, A., Harmon, K. A., Hart, H. M., Hayes, J., Hersman, C. B., Hill, M. E., Hill, T. A., Hofgartner, J. D., Holdridge, M. E., Horanyi, M., Hosadurga, A., Howard, A. D., Howett, C. J. A., Jaskulek, S. E., Jennings, D. E., Jensen, J. R., Jones, M. R., Kang, H. K., Katz, D. J., Kaufmann, D. E., Kavelaars, J. J., Keane, J. T., Keleher, G. P., Kinczyk, M., Kochte, M. C., Kolmnann, P., Krimigis, S. M., Kruizinga, G. L., Kusnierkiewicz, D. Y., Lahr, M. S., Lauer, T. R., Lawrence, G. B., Lee, J. E., Lessac-Chenen, E. J., Linscott, I. R., Lisse, C. M., Lunsford, A. W., Mages, D. M., Mallder, V. A., Martin, N. P., May, B. H., McComas, D. J., MeNutt, R. L., Jr., Mehoke, D. S., Mehoke, T. S., Nelson, D. S., Nguyen, H. D., Nunez, J. I., Ocampo, A. C., Owen, W. M., Oxton, G. K., Parker, A. H., Patzold, M., Pelgrift, J. Y., Pelletier, F. J., Pineau, J. P., Piquette, M. R., Porter, S. B., Protopapa, S., Quirico, E., Redfern, J. A., Regiec, A. L., Reitsema, H. J., Reuter, D. C., Richardson, D. C., Riedel, J. E., Ritterbush, M. A., Robbins, S. J., Rodgers, D. J., Rogers, G. D., Rose, D. M., Rosendal, P. E., Runyon, K. D., Ryschkewitsch, M. G., Saina, M. M., Salinas, M. J., Schenk, P. M., Scherrer, J. R., Schlei, W. R., Schmitt, B., Schultz, D. J., Schurr, D. C., Scipioni, F., Sepan, R. L., Shelton, R. G., Showalter, M. R., Simon, M., Singer, K. N., Stahlheber, E. W., Stanbridge, D. R., Stansberry, J. A., Steffi, A. J., Strobel, D. F., Stothoff, M. M., Stryk, T., Stuart, J. M., Summers, M. E., Tapley, M. B., Taylor, A., Taylor, H. W., Tedford, R. M., Throop, H. B., Turner, L. S., Umurhan, O. M., Van Eck, J., Velez, D., Versteeg, M. H., Vincent, M. A., Webbert, R. W., Weidner, S. E., Ii, G. E. Weigle, Wendel, J. R., White, O. L., Whittenburg, K. E., Williams, B. G., Williams, K. E., Williams, S. P., Wimters, H. L., Zangari, A. M., and Zurbuchen, T. H.
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 MU69, 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. MU69 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. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.
Published: 2019

28. Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Author: Masoumzadeh, N., Kolokolova, L., Tubiana, C., El-Maarry, M. R., Mottola, S., Güttler, C., Snodgrass, C, Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Hasselmann, P.H., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Shi, X., Toth, I., Masoumzadeh, N., Kolokolova, L., Tubiana, C., El-Maarry, M. R., Mottola, S., Güttler, C., Snodgrass, C, Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Hasselmann, P.H., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Shi, X., and Toth, I.
Abstract: The Rosetta-OSIRIS images acquired at small phase angles in three wavelengths during the fly-by of the spacecraft on 9-10 April 2016 provided a unique opportunity to study the opposition effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our goal is to study phase curves of the nucleus at small phase angles for a variety of surface structures to show the differences in their opposition effect and to determine which surface properties cause the differences.© N. Masoumzadeh et al. 2019
Published: 2019

29. Multidisciplinary analysis of the Hapi region located on Comet 67P/Churyumov-Gerasimenko

Author: European Space Agency, Swedish National Space Board, Ministerio de Educación y Ciencia (España), Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, German Centre for Air and Space Travel, Pajola, M., Lee, J.C., Oklay, N., Hviid, S.F., Penasa, L., Mottola, S., Shi, X., Fornasier, S., Davidsson, B., Giacomini, L., Lucchetti, A., Massironi, M., Vincent, J.B., Bertini, I., Naletto, G., Ip, W. H., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bodewits, D., Cambianica, P., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Lara, Luisa María, La Forgia, F., Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Preusker, F., Scholten, F., Toth, I., Tubiana, C., European Space Agency, Swedish National Space Board, Ministerio de Educación y Ciencia (España), Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, German Centre for Air and Space Travel, Pajola, M., Lee, J.C., Oklay, N., Hviid, S.F., Penasa, L., Mottola, S., Shi, X., Fornasier, S., Davidsson, B., Giacomini, L., Lucchetti, A., Massironi, M., Vincent, J.B., Bertini, I., Naletto, G., Ip, W. H., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bodewits, D., Cambianica, P., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Lara, Luisa María, La Forgia, F., Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Preusker, F., Scholten, F., Toth, I., and Tubiana, C.
Abstract: By using the Rosetta/OSIRIS-NAC data set taken in 2014 August, we focus on the neck region, called Hapi, located on 67P Churyumov-Gerasimenko's Northern hemisphere. The gravitational potential and slopes of Hapi, coupled with the geological unit identification and the boulder size-frequency distributions, support the interpretation that both taluses and gravitational accumulation deposits observable on Hapi are the result of multiple cliff collapses that occurred at different times. By contrast, the fine-particle deposits observable in the central part of the study area are made of aggregates coming from the Southern hemisphere and deposited during each perihelion passage. Both the consolidated terrains on the western part of Hapi, as well as the centrally aligned ridge made of boulder-like features, suggest that Hapi is in structural continuity with the onion-like structure of the main lobe of 67P. Despite the dusty blanket observable on Hapi, its terrains are characterized by water-ice-rich components that, once repeatedly and rapidly illuminated, sublimate, hence resulting in the strong jet activity observed in 2014 August.© 2019 The Author(s).
Published: 2019

30. 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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31. 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

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

Author: El-Maarry M. R., Pommerol A., and Thomas N.
Abstract: The ancient southern highlands on Mars (similar to 3.5 Gyr old) contain>600 regions that display spectral evidence in the infrared for the presence of chloride bearing materials. Many of these locations were previously reported to display polygonal cracking patterns. We studied more than 80 of the chloride bearing terrains using high resolution (0.25 0.5 m/pixel) images as well as near infrared spectral data to characterize the surface textures and the associated cracking patterns and mineralogies. Our study indicates that similar to 75 of the studied locations display polygonal cracks that resemble desiccation cracks while some resemble salt expansion/thrust polygons. Furthermore we detect spectrally the presence of smectites in association with similar to 30 of the studied fractured terrains. We note that smectites are a special class of swelling clay minerals that can induce formation of large desiccation cracks. As such we suggest that the cracking patterns are indicative of the presence of smectite phyllosilicates even in the absence of spectral confirmation. Our results suggest that many chloride bearing terrains have a lacustrine origin and a geologic setting similar to playas on Earth. Such locations would have contained ephemeral lakes that may have undergone repeated cycles of desiccation and recharging by a near surface fluctuating water table in order to account for the salt phyllosilicates associations. These results have notable implications for the ancient hydrology of Mars. We propose that the morphologies and sizes of the polygonal cracks can be used as paleoenvironmental as well as lithological indicators that could be helpful in planning future missions.
Published: 2014
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33. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars: Results from Geomorphological Investigations and Morphometry

Author: Diot X., El-Maarry M. R., Schlunegger E., Norton K. P., Thomas N., and Grindrod P. M.
Abstract: Hellas basin is a large impact basin situated in the southern highlands of Mars. The north western part of the basin has the lowest elevation ( 7.5 km) on the planet and contains a possibly unique terrain type which we informally call "banded terrain". The banded terrain is made up of smooth looking banded deposits that display signs of viscous behavior and a paucity of superimposed impact craters. In this study we use newly acquired high spatial resolution images from the High Resolution Imaging Science Experiment (HiRISE) in addition to existing datasets to characterize the geomorphology the morphometry and the architecture of the banded terrain. The banded terrain is generally confined to the NW edge of the Alpheus Colles plateau. The individual bands are similar to 3 15 km long similar to 0.3 km wide and are separated by narrow inter band depressions which are similar to 65 m wide and similar to 10 m deep. The bands display several morphologies that vary from linear to concentric forms. Morphometric analysis reveals that the slopes along a given linear or lobate band ranges from 0.5 degrees to 15 degrees (average similar to 6 degrees) whereas the concentric bands are located on flatter terrain (average slope similar to 2 3 degrees). Crater size frequency analysis yields an Amazonian Hesperian boundary crater retention age for the terrain (similar to 3 Gyr) which together with the presence of very few degraded craters either implies a recent emplacement resurfacing or intense erosion. The apparent sensitivity to local topography and preference for concentrating in localized depressions is compatible with deformation as a viscous fluid. In addition the bands display clear signs of degradation and slumping at their margins along with a suite of other features that include fractured mounds polygonal cracks at variable size scales and knobby/hummocky textures. Together these features suggest an ice rich composition for at least the upper layers of the terrain which is currently being heavily modified through loss of ice and intense weathering possibly by wind.
Published: 2014
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34. Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

Author: Swiss National Science Foundation, European Commission, State Secretariat for Education, Research and Innovation (Switzerland), Thomas, N., El Maarry, M. R., Theologou, P., Preusker, F., Scholten, F., Jorda, L., Hviid, S.F., Marschall, R., Kührt, E., Naletto, G., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Knollenberg, J., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Tubiana, C., Vincent, J.B., Swiss National Science Foundation, European Commission, State Secretariat for Education, Research and Innovation (Switzerland), Thomas, N., El Maarry, M. R., Theologou, P., Preusker, F., Scholten, F., Jorda, L., Hviid, S.F., Marschall, R., Kührt, E., Naletto, G., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Knollenberg, J., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Tubiana, C., and Vincent, J.B.
Abstract: The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified.© 2018 The Authors
Published: 2018

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

Author: German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Auger, A.T., Groussin, O., Jorda, L., El-Maarry, M. R., Bouley, S., Séjourné, A., Gaskell, R., Capanna, C., Davidsson, B., Marchi, S., Höfner, S., Lamy, P.L., Sierks, H., Barbieri, C., Rodrigo Montero, Rafael, 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, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Massironi, M., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Sabau, L., Thomas, N., Tubiana, C., Vincent, J.B., Wenzel, K. -P., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Auger, A.T., Groussin, O., Jorda, L., El-Maarry, M. R., Bouley, S., Séjourné, A., Gaskell, R., Capanna, C., Davidsson, B., Marchi, S., Höfner, S., Lamy, P.L., Sierks, H., Barbieri, C., Rodrigo Montero, Rafael, 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, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Massironi, M., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Sabau, L., Thomas, N., Tubiana, C., Vincent, J.B., and Wenzel, K. -P.
Abstract: 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.© 2017 Elsevier Inc.
Published: 2018

36. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author: European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., and Naletto, G.
Abstract: We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km).
Published: 2018

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

Author: Thomas N., Barbieri C., Keller H. U., Lamy P., Rickman H., Rodrigo R., Sierks H., Wenzel K. P., Cremonese G., Jorda L., Kueppers M., Marchi S., Marzari F., Massironi M., Preusker F., Scholten F., Stephan K., Barucci M. A., Besse S., El-Maarry M. R., Fornasier S., Groussin O., Hviid S. F., Koschny D., and Kuehrt E.
Abstract: The surface of (21) Lutetia is highly complex with significant interactions between ancient and more recent structures. This work attempts to summarize the surface geomorphology observed using the high resolution images from OSIRIS the imaging system onboard the European Space Agency's Rosetta spacecraft. A wide range of surface morphologies are seen including heavily cratered terrain extensive sets of lineaments young impact craters and a ridge the height of which is more than 1/5th of the mean radius of the body. Very young and very old terrains (as inferred from crater densities) are seen in close proximity. The longest continuous lineament is over 80 km long. The lineaments show regional dependent organization and structure. Several categories of lineament can be described. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent. Although the lineaments may be of seismic origin (and possibly the result of several impact induced events) impacts producing recent large craters place constraints on seismic phenomena. In particular stronger attenuation of shocks than seen on other asteroidal bodies seems to be required. Inhomogeneous energy transport possibly matching observed inhomogeneous ejecta deposition may offer explanations for some of the observed phenomena. Some impact craters show unusual forms which are probably the result of impact into a surface with relief comparable to the resultant crater diameter and/or oblique impact. There is evidence that re surfacing through landslides has occurred at several places on the object. (C) 2011 Elsevier Ltd. All rights reserved.
Published: 2012

39. 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

40. Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

Author: Höfner, S., primary, Vincent, J.-B., additional, Blum, J., additional, Davidsson, B. J. R., additional, Sierks, H., additional, El-Maarry, M. R., additional, Deller, J., additional, Hofmann, M., additional, Hu, X., additional, Pajola, M., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, A’Hearn, M. F., additional, Auger, A.-T., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Fornasier, S., additional, Fulle, M., additional, Gicquel, A., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Gutiérrez-Marqués, P., additional, Güttler, C., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, La Forgia, F., additional, Lazzarin, M., additional, Lopez-Moreno, J. J., additional, Marzari, F., additional, Michalik, H., additional, Moissl-Fraund, R., additional, Moreno, F., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Preusker, F., additional, Scholten, F., additional, Shi, X., additional, Thomas, N., additional, Toth, I., additional, Tubiana, C., additional, and Zitzmann, S., additional
Published: 2017
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41. First light of Cassis: the stereo surface imaging system onboard the exomars TGO

Author: Pommerol, A., primary, Ziethe, R., primary, El-Maarry, M. R., primary, Weigel, T., primary, Vernani, D., primary, Pelo, E., primary, Da Deppo, V., primary, Cremonese, G., primary, Thomas, N., primary, Gambicorti, L., primary, Piazza, D., primary, Roloff, V., primary, Gerber, M., primary, Johnson, M., primary, and Ficai Veltroni, I., primary
Published: 2017
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42. Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta

Author: Hu, X., primary, Shi, X., additional, Sierks, H., additional, Fulle, M., additional, Blum, J., additional, Keller, H. U., additional, Kührt, E., additional, Davidsson, B., additional, Güttler, C., additional, Gundlach, B., additional, Pajola, M., additional, Bodewits, D., additional, Vincent, J.-B., additional, Oklay, N., additional, Massironi, M., additional, Fornasier, S., additional, Tubiana, C., additional, Groussin, O., additional, Boudreault, S., additional, Höfner, S., additional, Mottola, S., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, A’Hearn, M., additional, Agarwal, J., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, El-Maarry, M. R., additional, Gicquel, A., additional, Gutierrez-Marques, P., additional, Gutiérrez, P. J., additional, Hofmann, M., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Lopez-Moreno, J. J., additional, Marzari, F., additional, Naletto, G., additional, and Thomas, N., additional
Published: 2017
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43. Long-term monitoring of comet 67P/Churyumov–Gerasimenko’s jets with OSIRIS onboard Rosetta

Author: Schmitt, M. I., primary, Tubiana, C., additional, Güttler, C., additional, Sierks, H., additional, Vincent, J.-B., additional, El-Maarry, M. R., additional, Bodewits, D., additional, Mottola, S., additional, Fornasier, S., additional, Hofmann, M., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, A’Hearn, M. F., additional, Agarwal, J., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fulle, M., additional, Gicquel, A., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Keller, H. U., additional, Knollenberg, J., additional, Kramm, J. R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, López-Moreno, J. J., additional, Marzari, F., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Prasanna, D., additional, Shi, X., additional, Scholten, F., additional, Toth, I., additional, and Thomas, N., additional
Published: 2017
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44. The pebbles/boulders size distributions on Sais: Rosetta’s final landing site on comet 67P/Churyumov–Gerasimenko

Author: Pajola, M., primary, Lucchetti, A., additional, Fulle, M., additional, Mottola, S., additional, Hamm, M., additional, Da Deppo, V., additional, Penasa, L., additional, Kovacs, G., additional, Massironi, M., additional, Shi, X., additional, Tubiana, C., additional, Güttler, C., additional, Oklay, N., additional, Vincent, J. B., additional, Toth, I., additional, Davidsson, B., additional, Naletto, G., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J. L., additional, Bertini, I., additional, Cremonese, G., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, El Maarry, M. R., additional, Fornasier, S., additional, Frattin, E., additional, Gicquel, A., additional, Groussin, O., additional, Gutierrez, P. J., additional, Höfner, S., additional, Hofmann, M., additional, Hviid, S. F., additional, Ip, W. H., additional, Jorda, L., additional, Knollenberg, J., additional, Kramm, J. R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Moreno, J. J. Lopez, additional, Marzari, F., additional, Michalik, H., additional, Preusker, F., additional, Scholten, F., additional, and Thomas, N., additional
Published: 2017
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45. Modelling of the outburst on 2015 July 29 observed with OSIRIS cameras in the Southern hemisphere of comet 67P/Churyumov–Gerasimenko

Author: Gicquel, A., primary, Rose, M., additional, Vincent, J.-B., additional, Davidsson, B., additional, Bodewits, D., additional, A’Hearn, M. F., additional, Agarwal, J., additional, Fougere, N., additional, Sierks, H., additional, Bertini, I., additional, Lin, Z.-Y., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Besse, S., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, Deller, J., additional, De Cecco, M., additional, Frattin, E., additional, El-Maarry, M. R., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Gutiérrez-Marquez, P., additional, Güttler, C., additional, Höfner, S., additional, Hofmann, M., additional, Hu, X., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Moreno, J. J. Lopez, additional, Lowry, S., additional, Marzari, F., additional, Masoumzadeh, N., additional, Massironi, M., additional, Moreno, F., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Preusker, F., additional, Scholten, F., additional, Shi, X., additional, Thomas, N., additional, Toth, I., additional, and Tubiana, C., additional
Published: 2017
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46. The highly active Anhur–Bes regions in the 67P/Churyumov–Gerasimenko comet: results from OSIRIS/ROSETTA observations

Author: Fornasier, S, primary, Feller, C, additional, Lee, J-C, additional, Ferrari, S, additional, Massironi, M, additional, Hasselmann, P H, additional, Deshapriya, J D P, additional, Barucci, M A, additional, El-Maarry, M R, additional, Giacomini, L, additional, Mottola, S, additional, Keller, H U, additional, Ip, W-H, additional, Lin, Z-Y, additional, Sierks, H, additional, Barbieri, C, additional, Lamy, P L, additional, Rodrigo, R, additional, Koschny, D, additional, Rickman, H, additional, Agarwal, J, additional, A'Hearn, M, additional, Bertaux, J-L, additional, Bertini, I, additional, Cremonese, G, additional, Da Deppo, V, additional, Davidsson, B, additional, Debei, S, additional, De Cecco, M, additional, Deller, J, additional, Fulle, M, additional, Groussin, O, additional, Gutierrez, P J, additional, Güttler, C, additional, Hofmann, M, additional, Hviid, S F, additional, Jorda, L, additional, Knollenberg, J, additional, Kovacs, G, additional, Kramm, R, additional, Kührt, E, additional, Küppers, M, additional, Lara, M L, additional, Lazzarin, M, additional, Lopez Moreno, J J, additional, Marzari, F, additional, Naletto, G, additional, Oklay, N, additional, Pajola, M, additional, Shi, X, additional, Thomas, N, additional, Toth, I, additional, Tubiana, C, additional, and Vincent, J-B, additional
Published: 2017
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47. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

Author: Perna, D., primary, Fulchignoni, M., additional, Barucci, M. A., additional, Fornasier, S., additional, Feller, C., additional, Deshapriya, J. D. P., additional, Hasselmann, P. H., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, A’Hearn, M., additional, Bertaux, J.-L., additional, Bertini, I., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, Deller, J., additional, De Cecco, M., additional, El-Maarry, M. R., additional, Fulle, M., additional, Groussin, O., additional, Gutierrez, P. J., additional, Güttler, C., additional, Hofmann, M., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Keller, H. U., additional, Knollenberg, J., additional, Kramm, R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Naletto, G., additional, Oklay, N., additional, Thomas, N., additional, Tubiana, C., additional, and Vincent, J.-B., additional
Published: 2017
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48. The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse

Author: Pajola, M., primary, Höfner, S., additional, Vincent, J. B., additional, Oklay, N., additional, Scholten, F., additional, Preusker, F., additional, Mottola, S., additional, Naletto, G., additional, Fornasier, S., additional, Lowry, S., additional, Feller, C., additional, Hasselmann, P. H., additional, Güttler, C., additional, Tubiana, C., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Besse, S., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Deshapriya, J. D. P., additional, El-Maarry, M. R., additional, Ferrari, S., additional, Ferri, F., additional, Fulle, M., additional, Groussin, O., additional, Gutierrez, P., additional, Hofmann, M., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J. R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lin, Z.-Y., additional, Lazzarin, M., additional, Lucchetti, A., additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Massironi, M., additional, Michalik, H., additional, Penasa, L., additional, Pommerol, A., additional, Simioni, E., additional, Thomas, N., additional, Toth, I., additional, and Baratti, E., additional
Published: 2017
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49. The pebbles/boulders size distributions on Sais : Rosetta's final landing site on comet 67P/Churyumov-Gerasimenko

Author: Pajola, M., Lucchetti, A., Fulle, M., Mottola, S., Hamm, M., Da Deppo, V., Penasa, L., Kovacs, G., Massironi, M., Shi, X., Tubiana, C., Güttler, C., Oklay, N., Vincent, J. B., Toth, I., Davidsson, B., Naletto, G., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Fornasier, S., Frattin, E., Gicquel, A., Groussin, O., Gutierrez, P. J., Höfner, S., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Michalik, H., Preusker, F., Scholten, F., Thomas, N., Pajola, M., Lucchetti, A., Fulle, M., Mottola, S., Hamm, M., Da Deppo, V., Penasa, L., Kovacs, G., Massironi, M., Shi, X., Tubiana, C., Güttler, C., Oklay, N., Vincent, J. B., Toth, I., Davidsson, B., Naletto, G., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Fornasier, S., Frattin, E., Gicquel, A., Groussin, O., Gutierrez, P. J., Höfner, S., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Michalik, H., Preusker, F., Scholten, F., and Thomas, N.
Abstract: By using the imagery acquired by the Optical, Spectroscopic, and Infrared Remote Imaging System Wide-Angle Camera (OSIRISWAC), we prepare a high-resolution morphological map of the Rosetta Sais final landing site, characterized by an outcropping consolidated terrain unit, a coarse boulder deposit and a fine particle deposit. Thanks to the 0.014 m resolution images, we derive the pebbles/boulders size-frequency distribution (SFD) of the area in the size range of 0.07-0.70 m. Sais' SFD is best fitted with a two-segment differential power law: the first segment is in the range 0.07-0.26 m, with an index of -1.7 ± 0.1, while the second is in the range 0.26-0.50 m, with an index of -4.2 +0.4/-0.8. The 'knee' of the SFD, located at 0.26 m, is evident both in the coarse and fine deposits. When compared to the Agilkia Rosetta Lander Imaging System images, Sais surface is almost entirely free of the ubiquitous, cm-sized debris blanket observed by Philae. None the less, a similar SFD behaviour of Agilkia, with a steeper distribution above ~0.3 m, and a flatter trend below that, is observed. The activity evolution of 67P along its orbit provides a coherent scenario of how these deposits were formed. Indeed, different lift pressure values occurring on the two locations and at different heliocentric distances explain the presence of the cm-sized debris blanket on Agilkia observed at 3.0 au inbound. Contrarily, Sais activity after 2.1 au outbound has almost completely eroded the fine deposits fallen during perihelion, resulting in an almost dust-free surface observed at 3.8 au.
Published: 2017
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50. Long-term monitoring of comet 67P/Churyumov-Gerasimenko's jets with OSIRIS onboard Rosetta

Author: Schmitt, M. I., Tubiana, C., Guettler, C., Sierks, H., Vincent, J. -B, El-Maarry, M. R., Bodewits, D., Mottola, S., Fornasier, S., Hofmann, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Agarwal, J., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Prasanna, D., Shi, X., Scholten, F., Toth, I., Thomas, N., Schmitt, M. I., Tubiana, C., Guettler, C., Sierks, H., Vincent, J. -B, El-Maarry, M. R., Bodewits, D., Mottola, S., Fornasier, S., Hofmann, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Agarwal, J., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Prasanna, D., Shi, X., Scholten, F., Toth, I., and Thomas, N.
Abstract: We used the OSIRIS camera system onboard the Rosetta spacecraft to monitor jet activity of comet 67P/Churyumov-Gerasimenko. With a monthly cadence, we covered an epoch from 2014 December to 2015 October, thereby including the first equinox and the perihelion passage. Jet features were measured in individual images, which were used to perform a statistical inversion. The study provides maps for the locations of likeliest sources of jet activity on the comet's surface as a function of time. The sources follow the subsolar latitude, show clustering and a broadening of the activity band with time in the Northern hemisphere. In the Southern hemisphere, they are not clustered but show a broader spread over all longitudes which is either related to the north-south dichotomy of the comet's topography or due to a higher insolation during southern summer.
Published: 2017
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