Author: "Koschny, D." / Publisher: tu braunschweig, inst geophys & extraterr phys, d-38106 braunschweig, germany. - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Koschny, D."' showing total 43 results

Start Over Author "Koschny, D." Publisher tu braunschweig, inst geophys & extraterr phys, d-38106 braunschweig, germany.

43 results on '"Koschny, D."'

1. Opposition effect on comet 67P/Churyumov-Gerasimenko using Rosetta-OSIRIS images

Author: Masoumzadeh, N., Oklay, N., Kolokolova, L., Sierks, H., Fornasier, S., Barucci, M. A., Vincent, J. -B, Tubiana, C., Guettler, C., Preusker, F., Scholten, F., Mottola, S., Hasselmann, P. H., Feller, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, Björn J. R., Debei, S., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Masoumzadeh, N., Oklay, N., Kolokolova, L., Sierks, H., Fornasier, S., Barucci, M. A., Vincent, J. -B, Tubiana, C., Guettler, C., Preusker, F., Scholten, F., Mottola, S., Hasselmann, P. H., Feller, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, Björn J. R., Debei, S., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., and Thomas, N.
Abstract: Aims. We aim to explore the behavior of the opposition effect as an important tool in optical remote sensing on the nucleus of comet 67P/Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in different filters during the approach phase, July-August 2014 and the close flyby images on 14 of February 2015, which contain the spacecraft shadow. Methods. We based our investigation on the global and local brightness from the surface of 67P with respect to the phase angle, also known as phase curve. The local phase curve corresponds to a region that is located at the Imhotep-Ash boundary of 67P. Assuming that the region at the Imhotep-Ash boundary and the entire nucleus have similar albedo, we combined the global and local phase curves to study the opposition-surge morphology and constrain the structure and properties of 67P. The model parameters were furthermore compared with other bodies in the solar system and existing laboratory study. Results. We found that the morphological parameters of the opposition surge decrease monotonically with wavelength, whereas in the case of coherent backscattering this behavior should be the reverse. The results from comparative analysis place 67P in the same category as the two Mars satellites, Phobos and Deimos, which are notably different from all airless bodies in the solar system. The similarity between the surface phase function of 67P and a carbon soot sample at extremely small angles is identified, introducing regolith at the boundary of the Imhotep-Ash region of 67P as a very dark and fluffy layer.
Published: 2017
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2. Detection of exposed H2O ice on the nucleus of comet 67P/Churyumov-Gerasimenko as observed by Rosetta OSIRIS and VIRTIS instruments

Author: Barucci, M. A., Filacchione, G., Fornasier, S., Raponi, A., Deshapriya, J. D. P., Tosi, F., Feller, C., Ciarniello, M., Sierks, H., Capaccioni, F., Pommerol, A., Massironi, M., Oklay, N., Merlin, F., Vincent, J. -B, Fulchignoni, M., Guilbert-Lepoutre, A., Perna, D., Capria, M. T., Hasselmann, P. H., Rousseau, B., Barbieri, C., Bockelee-Morvan, D., Lamy, P. L., De Sanctis, C., Rodrigo, R., Erard, S., Koschny, D., Leyrat, C., Rickman, Hans, Drossart, P., Keller, H. U., A'Hearn, M. F., Arnold, G., Bertaux, J. -L, Bertini, I., Cerroni, P., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., El-Maarry, M. R., Fonti, S., Fulle, M., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Kappel, D., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Moreno, J. J. Lopez, Mancarella, F., Marzari, F., Mottola, S., Naletto, G., Pajola, M., Palomba, E., Quirico, E., Schmitt, B., Thomas, N., Tubiana, C., Barucci, M. A., Filacchione, G., Fornasier, S., Raponi, A., Deshapriya, J. D. P., Tosi, F., Feller, C., Ciarniello, M., Sierks, H., Capaccioni, F., Pommerol, A., Massironi, M., Oklay, N., Merlin, F., Vincent, J. -B, Fulchignoni, M., Guilbert-Lepoutre, A., Perna, D., Capria, M. T., Hasselmann, P. H., Rousseau, B., Barbieri, C., Bockelee-Morvan, D., Lamy, P. L., De Sanctis, C., Rodrigo, R., Erard, S., Koschny, D., Leyrat, C., Rickman, Hans, Drossart, P., Keller, H. U., A'Hearn, M. F., Arnold, G., Bertaux, J. -L, Bertini, I., Cerroni, P., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., El-Maarry, M. R., Fonti, S., Fulle, M., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Kappel, D., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Moreno, J. J. Lopez, Mancarella, F., Marzari, F., Mottola, S., Naletto, G., Pajola, M., Palomba, E., Quirico, E., Schmitt, B., Thomas, N., and Tubiana, C.
Abstract: Context. Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and spectra of the comet's nucleus. Aims. The aim of this work is to search for the presence of H2O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H2O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS. Methods. The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 mu m absorption band of water ice in the VIRTIS spectral cubes. Results. Out of the 13 selected bright spots, eight of them present positive H2O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H2O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H2O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots.
Published: 2016
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3. Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images : The southern hemisphere

Author: El-Marry, M. R., Thomas, N., Gracia-Berna, A., Pajola, M., Lee, J. -C, Massironi, M., Davidsson, B., Marchi, S., Keller, H. U., Hviid, S. F., Besse, S., Sierks, H., Barbieri, C., Lamy, P. L., Koschny, D., Rickman, Hans, Rodrigo, R., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Gremonese, G., Da Deppo, V., De Cecco, M., Dehei, S., Guettler, C., Fornasier, S., Fulle, M., Giacomini, L., Groussin, O., Gutierrez, P. J., 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, Marschall, R., Marzari, F., Naletto, G., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, El-Marry, M. R., Thomas, N., Gracia-Berna, A., Pajola, M., Lee, J. -C, Massironi, M., Davidsson, B., Marchi, S., Keller, H. U., Hviid, S. F., Besse, S., Sierks, H., Barbieri, C., Lamy, P. L., Koschny, D., Rickman, Hans, Rodrigo, R., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Gremonese, G., Da Deppo, V., De Cecco, M., Dehei, S., Guettler, C., Fornasier, S., Fulle, M., Giacomini, L., Groussin, O., Gutierrez, P. J., 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, Marschall, R., Marzari, F., Naletto, G., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: Aims. The OSIRIS camera on board the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus since August 2014. Starting in May 2015, the southern hemisphere gradually became illuminated and was imaged for the first time. Here we present the regional morphology of the southern hemisphere, which serves as a companion to an earlier paper that presented the regional morphology of the northern hemisphere. Methods. We used OSIRIS images that were acquired at orbits similar to 45-125 km from the center of the comet (corresponding to spatial resolutions of similar to 0.8 to 2.3 m/pixel) coupled with the use of digital terrain models to define the different regions on the surface, and identify structural boundaries accurately. Results. Seven regions have been defined in the southern hemisphere bringing the total number of defined regions on the surface of the nucleus to 26. These classifications are mainly based on morphological and/or topographic boundaries. The southern hemisphere shows a remarkable dichotomy with its northern counterpart mainly because of the absence of wide-scale smooth terrains, dust coatings and large unambiguous depressions. As a result, the southern hemisphere closely resembles previously identified consolidated regions. An assessment of the overall morphology of comet 67P suggests that the comet's two lobes show surface heterogeneities manifested in different physical/mechanical characteristics, possibly extending to local (i.e., within a single region) scales., Carroection in Astronomy and Astrophysics, Volume 596, article number C2. DOI: 10.1051/0004-6361/201628634e
Published: 2016
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4. 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, Hans, 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., 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., 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, Hans, 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., Lopez Moreno, J. J., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: 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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5. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

Author: Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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., Tubiana, C., Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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.
Abstract: Beginning in 2014 March, 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 analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R-h = 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 paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 mu m) 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 and 50 mu m, respectively, or an initial mass of H2O ice around 22 kg.
Published: 2016
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6. The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study

Author: Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., Zakharov, V. V., Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., and Zakharov, V. V.
Abstract: On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
Published: 2016
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7. Comparative study of water ice exposures on cometary nuclei using multispectral imaging data

Author: Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus.
Published: 2016
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8. The Agilkia boulders/pebbles size-frequency distributions : OSIRIS and ROLIS joint observations of 67P surface

Author: Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., Vincent, J. B., Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.
Published: 2016
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9. Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere

Author: Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel(-1). Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.
Published: 2016
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10. Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko

Author: Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., and Thomas, N.
Abstract: We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.
Published: 2016
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11. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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12. 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, Hans, 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., 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., 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, Hans, 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., Lopez Moreno, J. J., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: 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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13. 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, Hans, 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., 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., 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, Hans, 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., Lopez Moreno, J. J., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: 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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14. Comparative study of water ice exposures on cometary nuclei using multispectral imaging data

Author: Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus.
Published: 2016
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15. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

Author: Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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., Tubiana, C., Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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.
Abstract: Beginning in 2014 March, 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 analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R-h = 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 paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 mu m) 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 and 50 mu m, respectively, or an initial mass of H2O ice around 22 kg.
Published: 2016
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16. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

Author: Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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., Tubiana, C., Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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.
Abstract: Beginning in 2014 March, 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 analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R-h = 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 paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 mu m) 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 and 50 mu m, respectively, or an initial mass of H2O ice around 22 kg.
Published: 2016
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17. The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study

Author: Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., Zakharov, V. V., Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., and Zakharov, V. V.
Abstract: On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
Published: 2016
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18. The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study

Author: Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., Zakharov, V. V., Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., and Zakharov, V. V.
Abstract: On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
Published: 2016
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19. Comparative study of water ice exposures on cometary nuclei using multispectral imaging data

Author: Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus.
Published: 2016
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20. The Agilkia boulders/pebbles size-frequency distributions : OSIRIS and ROLIS joint observations of 67P surface

Author: Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., Vincent, J. B., Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.
Published: 2016
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21. Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko

Author: Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., and Thomas, N.
Abstract: We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.
Published: 2016
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22. Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko

Author: Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., and Thomas, N.
Abstract: We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.
Published: 2016
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23. The Agilkia boulders/pebbles size-frequency distributions : OSIRIS and ROLIS joint observations of 67P surface

Author: Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., Vincent, J. B., Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.
Published: 2016
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24. Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere

Author: Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel(-1). Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.
Published: 2016
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25. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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26. Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere

Author: Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel(-1). Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.
Published: 2016
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27. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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28. 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, Hans, 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., 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., 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, Hans, 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., Lopez Moreno, J. J., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: 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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29. Comparative study of water ice exposures on cometary nuclei using multispectral imaging data

Author: Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus.
Published: 2016
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30. The Agilkia boulders/pebbles size-frequency distributions : OSIRIS and ROLIS joint observations of 67P surface

Author: Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., Vincent, J. B., Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.
Published: 2016
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31. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

Author: Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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., Tubiana, C., Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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.
Abstract: Beginning in 2014 March, 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 analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R-h = 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 paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 mu m) 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 and 50 mu m, respectively, or an initial mass of H2O ice around 22 kg.
Published: 2016
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32. The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study

Author: Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., Zakharov, V. V., Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., and Zakharov, V. V.
Abstract: On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
Published: 2016
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33. Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko

Author: Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., and Thomas, N.
Abstract: We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.
Published: 2016
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34. Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere

Author: Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel(-1). Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.
Published: 2016
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35. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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36. 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, Hans, 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., 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., 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, Hans, 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., Lopez Moreno, J. J., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: 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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37. Comparative study of water ice exposures on cometary nuclei using multispectral imaging data

Author: Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Sunshine, J. M., Pajola, M., Pommerol, A., Vincent, J. -B, Mottola, S., Sierks, H., Fornasier, S., Barucci, M. A., Preusker, F., Scholten, F., Lara, L. M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus.
Published: 2016
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38. Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko

Author: Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Agarwal, Jessica, A'Hearn, M. F., Vincent, J. -B, Guettler, C., Hoefner, S., Sierks, H., Tubiana, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., 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., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kueppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., and Thomas, N.
Abstract: We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.
Published: 2016
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39. The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study

Author: Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., Zakharov, V. V., Grun, E., Agarwal, J., Altobelli, N., Altwegg, K., Bentley, M. S., Biver, N., Della Corte, V., Edberg, Niklas J. T., Feldman, P. D., Galand, M., Geiger, B., Goetz, C., Grieger, B., Guettler, C., Henri, P., Hofstadter, M., Horanyi, M., Jehin, E., Krueger, H., Lee, S., Mannel, T., Morales, E., Mousis, O., Mueller, M., Opitom, C., Rotundi, A., Schmied, R., Schmidt, F., Sierks, H., Snodgrass, C., Soja, R. H., Sommer, M., Srama, R., Tzou, C. -Y, Vincent, J. -B, Yanamandra-Fisher, P., A'Hearn, M. F., Eriksson, Anders, Barbieri, C., Barucci, M. A., Bertaux, J. -L, Bertini, I., Burch, J., Colangeli, L., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Feaga, L. M., Ferrari, M., Fornasier, S., Fulle, M., Gicquel, A., Gillon, M., Green, S. F., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. -H, Ivanovski, S., Jorda, L., Keller, H. U., Knight, M. M., Knollenberg, J., Koschny, D., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Manfroid, J., Epifani, E. Mazzotta, Marzari, F., Naletto, G., Oklay, N., Palumbo, P., Parker, J. Wm., Rickman, Hans, Rodrigo, R., Rodriguez, J., Schindhelm, E., Shi, X., Sordini, R., Steffl, A. J., Stern, S. A., Thomas, N., Tubiana, C., Weaver, H. A., Weissman, P., and Zakharov, V. V.
Abstract: On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
Published: 2016
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40. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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41. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

Author: Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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., Tubiana, C., Gicquel, A., Vincent, J. -B, Agarwal, J., A'Hearn, M. F., Bertini, I., Bodewits, D., Sierks, H., Li, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, 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., Lopez Moreno, J. J., 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.
Abstract: Beginning in 2014 March, 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 analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance R-h = 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 paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 mu m) 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 and 50 mu m, respectively, or an initial mass of H2O ice around 22 kg.
Published: 2016
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42. Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere

Author: Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., Vincent, J. -B, Giacomini, L., Massironi, M., El-Maarry, M. R., Penasa, L., Pajola, M., Thomas, N., Lowry, S. C., Barbieri, C., Cremonese, G., Ferri, F., Naletto, G., Bertini, I., La Forgia, F., Lazzarin, M., Marzari, F., Sierks, H., Lamy, P. L., Rodrigo, R., Rickman, Hans, Koschny, D., Keller, H. U., Agarwal, J., A'Hearn, M. F., Auger, A. -T, Barucci, M. A., Bertaux, J. -L, Besse, S., Bodewits, D., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Magrin, S., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J. -B
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel(-1). Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.
Published: 2016
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43. The Agilkia boulders/pebbles size-frequency distributions : OSIRIS and ROLIS joint observations of 67P surface

Author: Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., Vincent, J. B., Pajola, M., Mottola, S., Hamm, M., Fulle, M., Davidsson, B., Guettler, C., Sierks, H., Naletto, G., Arnold, G., Grothues, H. -G, Jaumann, R., Michaelis, H., Bibring, J. P., 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., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El Maarry, M. R., Feller, C., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hofmann, M., Hviid, S. F., Ip, W. H., Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lin, Z. Y., Lazzarin, M., Moreno, J. J. Lopez, Lucchetti, A., Marzari, F., Massironi, M., Michalik, H., Oklay, N., Pommerol, A., Preusker, F., Scholten, F., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.
Published: 2016
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