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1. Spectrophotometric variegation of the layering in comet 67P/Churyumov-Gerasimenko as seen by OSIRIS

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Tognon, G, Ferrari, S., Penasa, L., La Forgia, F., Massironi, M., Naletto, G., Lazzarin, M., Cambianica, P., Lucchetti, A., Pajola, M., Ferri, F., Güttler, C., Davidsson, B., Deshapriya, P, Fornasier, S., Mottola, S., Toth, I., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Barbieri, C, Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Franceschi, M., Frattin, E., Fulle, M., Gutiérrez, Pedro J., Ip, W. H., Keller, H.U., Lara, Luisa María, López-Moreno, José Juan, Marzari, F., Petropoulou, V., Shi, X., Tubiana, C., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Tognon, G, Ferrari, S., Penasa, L., La Forgia, F., Massironi, M., Naletto, G., Lazzarin, M., Cambianica, P., Lucchetti, A., Pajola, M., Ferri, F., Güttler, C., Davidsson, B., Deshapriya, P, Fornasier, S., Mottola, S., Toth, I., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Barbieri, C, Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Franceschi, M., Frattin, E., Fulle, M., Gutiérrez, Pedro J., Ip, W. H., Keller, H.U., Lara, Luisa María, López-Moreno, José Juan, Marzari, F., Petropoulou, V., Shi, X., and Tubiana, C.

Abstract

Between August 2014 and September 2016, the ESA space mission Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P) during its perihelion passage. The onboard OSIRIS Narrow Angle Camera (NAC) acquired high-resolution multispectral images of the cometary surface. These datasets allowed a characterization of the spectrophotometric variegation of the layering of the large lobe, correlated with the layer structural elevation. Aims. We perform a spectrophotometric characterization of the outcropping stratification of the small lobe of 67P as a function of its structural elevation, and consequently, a spectrophotometric comparison of the layered outcrops of the two lobes. Methods. We selected two sequences of post-perihelion OSIRIS NAC images (similar to 2.4 au outbound to the Sun), from which we built up two multispectral images, framing an extended geological section of the onion-like stratification of the small lobe. Then we classified the consolidated areas of the outcropping and the relative coarse deposits that were identified in the multispectral data with a two-class maximum likelihood method. For this, we defined the classes as a function of the structural elevation of the surface. Results. As a result, we identified a brightness variegation of the surface reflectance that is correlated with the structural elevation. The outer class, which is located at higher elevations, appears darker than the inner class. This fits previously obtained results for the large lobe. The reflectance values of the nucleus of 67P tend to decrease with increasing structural elevation. Conclusions. The observed spectrophotometric variegation can be due to a different texture as well as to a different content of volatiles and refractories. We suggest that the outer outcrops appear darker because they have been exposed longer, and the inner outcrops appear brighter because the surface has been more effectively rejuvenated. We interpret this variegation as the result of an evolutionary p

Published
2019

2. Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Fornasier, S., Feller, C., Hasselmann, P.H., Barucci, M.A., Sunshine, J, Vincent, J.B., Shi, X., Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Jorda, L., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lucchetti, A., Marzari, F., Mottola, S., Pajola, M., Toth, I., Tubiana, C., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Fornasier, S., Feller, C., Hasselmann, P.H., Barucci, M.A., Sunshine, J, Vincent, J.B., Shi, X., Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Jorda, L., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lucchetti, A., Marzari, F., Mottola, S., Pajola, M., Toth, I., and Tubiana, C.

Abstract

The southern hemisphere of comet 67P/Churyumov-Gerasimenko (67P) became observable by the Rosetta mission in March 2015, a few months before cometary southern vernal equinox. The Anhur region in the southern part of the comet's larger lobe was found to be highly eroded, enriched in volatiles, and highly active. Aims. We analyze high-resolution images of the Anhur region pre- and post-perihelion acquired by the OSIRIS imaging system on board the Rosetta mission. The Narrow Angle Camera is particularly useful for studying the evolution in Anhur in terms of morphological changes and color variations. Methods. Radiance factor images processed by the OSIRIS pipeline were coregistered, reprojected onto the 3D shape model of the comet, and corrected for the illumination conditions. Results. We find a number of morphological changes in the Anhur region that are related to formation of new scarps; removal of dust coatings; localized resurfacing in some areas, including boulders displacements; and vanishing structures, which implies localized mass loss that we estimate to be higher than 50 million kg. The strongest changes took place in and nearby the Anhur canyon-like structure, where significant dust cover was removed, an entire structure vanished, and many boulders were rearranged. All such changes are potentially associated with one of the most intense outbursts registered by Rosetta during its observations, which occurred one day before perihelion passage. Moreover, in the niche at the foot of a new observed scarp, we also see evidence of water ice exposure that persisted for at least six months. The abundance of water ice, evaluated from a linear mixing model, is relatively high (>20%). Our results confirm that the Anhur region is volatile-rich and probably is the area on 67P with the most pristine exposures near perihelion.© S. Fornasier et al. 2019

Published
2019

3. Quantitative analysis of isolated boulder fields on comet 67P/Churyumov-Gerasimenko

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Cambianica, P., Cremonese, G., Naletto, G., Lucchetti, A., Pajola, M., Penasa, L., Simioni, E., Massironi, M., Ferrari, S., Bodewits, D., La Forgia, F., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Dayidsson, B, Barucci, M.A., Bertaux, J.L., Bertini, I., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Mottola, S., Shi, X., Scholten, F., Toth, I., Tubiana, C., Vincent, J.B., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Cambianica, P., Cremonese, G., Naletto, G., Lucchetti, A., Pajola, M., Penasa, L., Simioni, E., Massironi, M., Ferrari, S., Bodewits, D., La Forgia, F., Sierks, H., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Dayidsson, B, Barucci, M.A., Bertaux, J.L., Bertini, I., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Mottola, S., Shi, X., Scholten, F., Toth, I., Tubiana, C., and Vincent, J.B.

Abstract

We provide a detailed quantitative analysis of isolated boulder fields situated in three different regions of comet 67P/Churyumov-Gerasimenko: Imhotep, Hapi, and Hatmehit. This is done to supply a useful method for analyzing the morphology of the boulders and to characterize the regions themselves. Methods. We used OSIRIS Narrow Angle Camera images with a spatial scale smaller than 2 mpx(-1) and analyzed the size-frequency distribution and the cumulative fractional area per boulder population. In addition, we correlated shape parameters, such as circularity and solidity, with both the spatial and the size-frequency distribution of the three populations. Results. We identified 11 811 boulders in the Imhotep, Hapi, and Hatmehit regions. We found that the Hatmehit and Imhotep areas show power indices in the range of -2.3/-2.7. These values could represent a transition between gravitational events caused by thermal weathering and sublimation, and material formed during collapses that has undergone sublimation. The Hapi area is characterized by a lower power index (-1.2/-1.7), suggesting that those boulders have a different origin. They can be the result of material formed during gravitational events and collapses that has undergone continuous fragmentation. We calculated the cumulative fractional area (CFA) in order to investigate how the area is covered by boulders as a function of their sizes. The Hatmehit and Imhotep regions show a CFA that is well fit by a power law. In contrast, the Hapi area does not show the same trend. We analyzed the fractal distributions, finding that the populations seem to be fractal at all dimensions, except for the Hapi distribution, which shows a possible fractal behavior for small dimensions only. Finally, the average values of the shape parameters reveal solid and roundish boulders in all populations we studied.© ESO 2019

Published
2019

4. Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Ministry of Science and Technology (Taiwan), Science and Technology Development Fund (Macau), Lai, IL, Ip, W. H., Lee, J.C., Lin, Zhong-Yi, Vincent, J.B., Oklay, N., Sierks, H., Barbieri, C, Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hofmann, M., Hviid, S.F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., Tubiana, C., Thomas, N, German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Ministry of Science and Technology (Taiwan), Science and Technology Development Fund (Macau), Lai, IL, Ip, W. H., Lee, J.C., Lin, Zhong-Yi, Vincent, J.B., Oklay, N., Sierks, H., Barbieri, C, Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hofmann, M., Hviid, S.F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., Tubiana, C., and Thomas, N

Abstract

We investigate the surface distribution of the source regions of dust jets on comet 67P/Churyumov-Gerasimenko as a function of time. Methods. The dust jet source regions were traced by the comprehensive imaging data set provided by the OSIRIS scientific camera. Results. We show in detail how the projected footpoints of the dust jets and hence the outgassing zone would move in consonance with the sunlit belt. Furthermore, a number of source regions characterized by repeated jet activity might be the result of local topographical variations or compositional heterogeneities. Conclusions. The spatial and temporal variations in source regions of the dust jets are influenced significantly by the seasonal effect. The strong dependence on the solar zenith angle and local time could be related to the gas sublimation process driven by solar insolation on a surface layer of low thermal inertia.© ESO 2019

Published
2019

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

Author

Masoumzadeh, N., Kolokolova, L., Tubiana, C., El-Maarry, M. R., Mottola, S., Güttler, C., Snodgrass, C, Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Hasselmann, P.H., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Shi, X., Toth, I., Masoumzadeh, N., Kolokolova, L., Tubiana, C., El-Maarry, M. R., Mottola, S., Güttler, C., Snodgrass, C, Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Hasselmann, P.H., Ip, W. H., Keller, H.U., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Shi, X., and Toth, I.

Abstract

The Rosetta-OSIRIS images acquired at small phase angles in three wavelengths during the fly-by of the spacecraft on 9-10 April 2016 provided a unique opportunity to study the opposition effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our goal is to study phase curves of the nucleus at small phase angles for a variety of surface structures to show the differences in their opposition effect and to determine which surface properties cause the differences.© N. Masoumzadeh et al. 2019

Published
2019

6. Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Author

Agenzia Spaziale Italiana, German Research Foundation, Centre National de la Recherche Scientifique (France), Ministerio de Economía y Competitividad (España), Government of Sweden, European Space Agency, l'Observatoire de Paris, Science and Technology Facilities Council (UK), Tubiana, C., Rinaldi, G., Güttler, C., Snodgrass, C, Shi, X., Hu, X., Marschall, R., Fulle, M., Bockelée-Morvan, D., Naletto, G., Capaccioni, F, Sierks, H., Arnold, G., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Capria, MT, Ciarniello, M, Cremonese, G., Crovisier, J, Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., De Sanctis, MC, Davidsson, B., Doose, L, Erard, S, Filacchione, G., Fink, U, Formisano, M, Fornasier, S., Gutiérrez, Pedro J., Ip, W. H., Ivanovski, S., Kappel, D, Keller, H.U., Kolokolova, L., Koschny, D., Krueger, H, La Forgia, F., Lamy, P.L., Lara, Luisa María, Lazzarin, M., Levasseur-Regourd, A. C., Lin, Zhong-Yi, Longobardo, A, López-Moreno, José Juan, Marzari, F., Migliorini, A, Mottola, S., Rodrigo Montero, Rafael, Taylor, F, Toth, I., Zakharov, V, Agenzia Spaziale Italiana, German Research Foundation, Centre National de la Recherche Scientifique (France), Ministerio de Economía y Competitividad (España), Government of Sweden, European Space Agency, l'Observatoire de Paris, Science and Technology Facilities Council (UK), Tubiana, C., Rinaldi, G., Güttler, C., Snodgrass, C, Shi, X., Hu, X., Marschall, R., Fulle, M., Bockelée-Morvan, D., Naletto, G., Capaccioni, F, Sierks, H., Arnold, G., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Capria, MT, Ciarniello, M, Cremonese, G., Crovisier, J, Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., De Sanctis, MC, Davidsson, B., Doose, L, Erard, S, Filacchione, G., Fink, U, Formisano, M, Fornasier, S., Gutiérrez, Pedro J., Ip, W. H., Ivanovski, S., Kappel, D, Keller, H.U., Kolokolova, L., Koschny, D., Krueger, H, La Forgia, F., Lamy, P.L., Lara, Luisa María, Lazzarin, M., Levasseur-Regourd, A. C., Lin, Zhong-Yi, Longobardo, A, López-Moreno, José Juan, Marzari, F., Migliorini, A, Mottola, S., Rodrigo Montero, Rafael, Taylor, F, Toth, I., and Zakharov, V

Abstract

On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and VIRTIS-M instruments on board the Rosetta spacecraft simultaneously observed the evolving dust and gas coma during a complete rotation of the comet.© C. Tubiana et al. 2019

Published
2019

7. Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko

Author

Federal Ministry of Education and Research (Germany), Agence Nationale de la Recherche (France), Agenzia Spaziale Italiana, Ministerio de Ciencia, Innovación y Universidades (España), Government of Sweden, Fornasier, S., Hoang, VH, Hasselmann, P.H., Feller, C., Barucci, M.A., Deshapriya, J.D.P., Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Agarwal, J., Barbieri, C, Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Küppers, M., La Forgia, F., Lara, Luisa María, Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Mottola, S., Pajola, M., Shi, X., Toth, I., Tubiana, C., Federal Ministry of Education and Research (Germany), Agence Nationale de la Recherche (France), Agenzia Spaziale Italiana, Ministerio de Ciencia, Innovación y Universidades (España), Government of Sweden, Fornasier, S., Hoang, VH, Hasselmann, P.H., Feller, C., Barucci, M.A., Deshapriya, J.D.P., Sierks, H., Naletto, G., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Davidsson, B., Agarwal, J., Barbieri, C, Bertaux, J.L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Ip, W. H., Keller, H.U., Küppers, M., La Forgia, F., Lara, Luisa María, Lazzarin, M., Lin, Zhong-Yi, López-Moreno, José Juan, Marzari, F., Mottola, S., Pajola, M., Shi, X., Toth, I., and Tubiana, C.

Abstract

The Rosetta space probe accompanied comet 67P/Churyumov-Gerasimenko for more than two years, obtaining an unprecedented amount of unique data of the comet nucleus and inner coma. This has enabled us to study its activity almost continuously from 4 au inbound to 3.6 au outbound, including the perihelion passage at 1.24 au. This work focuses identifying the source regions of faint jets and outbursts and on studying the spectrophotometric properties of some outbursts. We use observations acquired with the OSIRIS/NAC camera during July-October 2015, that is, close to perihelion. Methods. We analyzed more than 2000 images from NAC color sequences acquired with 7-11 filters covering the 250-1000 nm wavelength range. The OSIRIS images were processed with the OSIRIS standard pipeline up to level 3, that is, converted in radiance factor, then corrected for the illumination conditions. For each color sequence, color cubes were produced by stacking registered and illumination-corrected images. Results. More than 200 jets of different intensities were identified directly on the nucleus. Some of the more intense outbursts appear spectrally bluer than the comet dark terrain in the visible-to-near-infrared region. We attribute this spectral behavior to icy grains mixed with the ejected dust. Some of the jets have an extremely short lifetime. They appear on the cometary surface during the color sequence observations, and vanish in less than some few minutes after reaching their peak. We also report a resolved dust plume observed in May 2016 at a resolution of 55 cm pixel(-1), which allowed us to estimate an optical depth of similar to 0.65 and an ejected mass of similar to 2200 kg, assuming a grain bulk density of similar to 800 kg m(-3). We present the results on the location, duration, and colors of active sources on the nucleus of 67P from the medium-resolution (i.e., 6-10 m pixel(-1)) images acquired close to perihelion passage. The observed jets are mainly located close to bou

Published
2019

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

Author

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

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

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

Published
2018

9. Quantitative analysis of isolated boulder fields on comet 67P/Churyumov-Gerasimenko

Author

Cambianica, P., primary, Cremonese, G., additional, Naletto, G., additional, Lucchetti, A., additional, Pajola, M., additional, Penasa, L., additional, Simioni, E., additional, Massironi, M., additional, Ferrari, S., additional, Bodewits, D., additional, La Forgia, F., additional, Sierks, H., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Davidsson, B., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fornasier, S., additional, Fulle, M., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Ip, W.-H., additional, Keller, H. U., additional, Lara, L. M., additional, Lazzarin, M., additional, Lin, Z.-Y., additional, López-Moreno, J. J., additional, Marzari, F., additional, Mottola, S., additional, Shi, X., additional, Scholten, F., additional, Toth, I., additional, Tubiana, C., additional, and Vincent, J.-B., additional

Published
2019
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10. Pronounced morphological changes in a southern active zone on comet 67P/Churyumov-Gerasimenko

Author

Hasselmann, P. H., primary, Barucci, M. A., additional, Fornasier, S., additional, Bockelée-Morvan, D., additional, Deshapriya, J. D. P., additional, Feller, C., additional, Sunshine, J., additional, Hoang, V., additional, Sierks, H., additional, Naletto, G., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Davidsson, B., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, Fulle, M., additional, Gutierrez, P. J., additional, Güttler, C., additional, Deller, J., additional, Ip, W.-H., additional, Keller, H. U., additional, Lara, L. M., additional, De Cecco, M., additional, Lazzarin, M., additional, López-Moreno, J. J. L., additional, Marzari, F., additional, Shi, X., additional, and Tubiana, C., additional

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2019
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11. Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko

Author

Lai, I.-L., primary, Ip, W.-H., additional, Lee, J.-C., additional, Lin, Z.-Y., additional, Vincent, J.-B., additional, Oklay, N., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hofmann, M., additional, Hviid, S. F., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, López-Moreno, J. J., additional, Marzari, F., additional, Naletto, G., additional, Shi, X., additional, Tubiana, C., additional, and Thomas, N., additional

Published
2019
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12. Spectrophotometric variegation of the layering in comet 67P/Churyumov-Gerasimenko as seen by OSIRIS

Author

Tognon, G., primary, Ferrari, S., additional, Penasa, L., additional, La Forgia, F., additional, Massironi, M., additional, Naletto, G., additional, Lazzarin, M., additional, Cambianica, P., additional, Lucchetti, A., additional, Pajola, M., additional, Ferri, F., additional, Güttler, C., additional, Davidsson, B., additional, Deshapriya, P., additional, Fornasier, S., additional, Mottola, S., additional, Tóth, I., additional, Sierks, H., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Barbieri, C., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Franceschi, M., additional, Frattin, E., additional, Fulle, M., additional, Gutiérrez, P. J., additional, Ip, W.-H., additional, Keller, H. U., additional, Lara, L. M., additional, López-Moreno, J. J., additional, Marzari, F., additional, Petropoulou, V., additional, Shi, X., additional, and Tubiana, C., additional

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2019
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13. Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Author

Masoumzadeh, N, primary, Kolokolova, L, additional, Tubiana, C, additional, El-Maarry, M. R., additional, Mottola, S, additional, Güttler, C., additional, Snodgrass, C, additional, Sierks, H., additional, Naletto, G., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D, additional, Davidsson, B, additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I, additional, Bodewits, D., additional, Cremonese, G, additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fornasier, S., additional, Fulle, M, additional, Gutiérrez, P. J., additional, Hasselmann, P. H., additional, Ip, W.-H., additional, Keller, H. U., additional, Lara, L. M., additional, Lazzarin, M, additional, López-Moreno, J. J., additional, Marzari, F, additional, Shi, X, additional, and Toth, I, additional

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2019
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14. Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Author

Fornasier, S., primary, Feller, C., additional, Hasselmann, P. H., additional, Barucci, M. A., additional, Sunshine, J., additional, Vincent, J.-B., additional, Shi, X., additional, Sierks, H., additional, Naletto, G., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Davidsson, B., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Ferrari, S., additional, Fulle, M., additional, Gutierrez, P. J., additional, Güttler, C., additional, Ip, W.-H., additional, Jorda, L., additional, Keller, H. U., additional, Lara, M. L., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Lucchetti, A., additional, Marzari, F., additional, Mottola, S., additional, Pajola, M., additional, Toth, I., additional, and Tubiana, C., additional

Published
2019
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15. Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Author

Tubiana, C., primary, Rinaldi, G., additional, Güttler, C., additional, Snodgrass, C., additional, Shi, X., additional, Hu, X., additional, Marschall, R., additional, Fulle, M., additional, Bockelée-Morvan, D., additional, Naletto, G., additional, Capaccioni, F., additional, Sierks, H., additional, Arnold, G., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Capria, M. T., additional, Ciarniello, M., additional, Cremonese, G., additional, Crovisier, J., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, De Sanctis, M. C., additional, Davidsson, B., additional, Doose, L., additional, Erard, S., additional, Filacchione, G., additional, Fink, U., additional, Formisano, M., additional, Fornasier, S., additional, Gutiérrez, P. J., additional, Ip, W.-H., additional, Ivanovski, S., additional, Kappel, D., additional, Keller, H. U., additional, Kolokolova, L., additional, Koschny, D., additional, Krueger, H., additional, La Forgia, F., additional, Lamy, P. L., additional, Lara, L. M., additional, Lazzarin, M., additional, Levasseur-Regourd, A. C., additional, Lin, Z.-Y., additional, Longobardo, A., additional, López-Moreno, J. J., additional, Marzari, F., additional, Migliorini, A., additional, Mottola, S., additional, Rodrigo, R., additional, Taylor, F., additional, Toth, I., additional, and Zakharov, V., additional

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2019
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16. Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko

Author

Fornasier, S., primary, Hoang, V. H., additional, Hasselmann, P. H., additional, Feller, C., additional, Barucci, M. A., additional, Deshapriya, J. D. P., additional, Sierks, H., additional, Naletto, G., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Davidsson, B., additional, Agarwal, J., additional, Barbieri, C., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Ferrari, S., additional, Fulle, M., additional, Gutierrez, P. J., additional, Güttler, C., additional, Ip, W.-H., additional, Keller, H. U., additional, Küppers, M., additional, La Forgia, F., additional, Lara, M. L., additional, Lazzarin, M., additional, Lin, Z-Y, additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Mottola, S., additional, Pajola, M., additional, Shi, X., additional, Toth, I., additional, and Tubiana, C., additional

Published
2019
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17. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

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

Abstract

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

Published
2018

18. Exposed bright features on the comet 67P/Churyumov-Gerasimenko: Distribution and evolution

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Ministerio de Educación y Ciencia (España), European Space Agency, Swedish National Space Board, Deshapriya, J.D.P., Barucci, M.A., Fornasier, S., Hasselmann, P.H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Güttler, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., Cecco, M.D., Deller, J., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Hoang, H. V., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., Vincent, J.B., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Ministerio de Educación y Ciencia (España), European Space Agency, Swedish National Space Board, Deshapriya, J.D.P., Barucci, M.A., Fornasier, S., Hasselmann, P.H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Güttler, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., Cecco, M.D., Deller, J., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Hoang, H. V., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., and Vincent, J.B.

Abstract

Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims. We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods. We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results. We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of HO ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions. Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised HO ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated HO ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated HO ice that is preserved

Published
2018

19. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs (Corrigendum)

Author

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

Published
2018
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20. Exposed bright features on the comet 67P/Churyumov–Gerasimenko: distribution and evolution

Author

Deshapriya, J. D. P., primary, Barucci, M. A., additional, Fornasier, S., additional, Hasselmann, P. H., additional, Feller, C., additional, Sierks, H., additional, Lucchetti, A., additional, Pajola, M., additional, Oklay, N., additional, Mottola, S., additional, Masoumzadeh, N., additional, Tubiana, C., additional, Güttler, C., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B. J. R., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, Fulle, M., additional, Groussin, O., additional, Gutierrez, P. J., additional, Hoang, H. V., additional, Hviid, S. F., additional, Ip, W., additional, Jorda, L., additional, Keller, H. U., additional, Knollenberg, J., additional, Kramm, R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Naletto, G., additional, Preusker, F., additional, Shi, X., additional, Thomas, N., additional, and Vincent, J.-B., additional

Published
2018
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21. Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

Author

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

Published
2017
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22. Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta

Author

European Space Agency, Centre National de la Recherche Scientifique (France), Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), International Max Planck Research Schools, German Centre for Air and Space Travel, Hu, X., Shi, X., Sierks, H., Fulle, M., Blum, J., Keller, H.U., Kührt, E., Davidsson, B., Güttler, C., Gundlach, B., Pajola, M., Bodewits, D., Vincent, J.B., Oklay, N., Massironi, M., Fornasier, S., Tubiana, C., Groussin, O., Boudreault, S., Höfner, S., Mottola, S., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Gicquel, A., Gutierrez-Marques, P., Gutiérrez, Pedro J., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, López-Moreno, José Juan, European Space Agency, Centre National de la Recherche Scientifique (France), Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), International Max Planck Research Schools, German Centre for Air and Space Travel, Hu, X., Shi, X., Sierks, H., Fulle, M., Blum, J., Keller, H.U., Kührt, E., Davidsson, B., Güttler, C., Gundlach, B., Pajola, M., Bodewits, D., Vincent, J.B., Oklay, N., Massironi, M., Fornasier, S., Tubiana, C., Groussin, O., Boudreault, S., Höfner, S., Mottola, S., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Gicquel, A., Gutierrez-Marques, P., Gutiérrez, Pedro J., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, and López-Moreno, José Juan

Abstract

Context. Dust deposits or dust cover are a prevalent morphology in the northern hemi-nucleus of comet 67P/Churyumov-Gerasimenko (67P). The evolution of the dust deposits was captured by the OSIRIS camera system onboard the Rosetta spacecraft having escorted the comet for over two years. The observations shed light on the fundamental role of cometary activity in shaping and transforming the surface morphology. Aims. We aim to present OSIRIS observations of surface changes over the dust deposits before and after perihelion. The distribution of changes and a timeline of their occurrence are provided. We perform a data analysis to quantify the surface changes and investigate their correlation to water activity from the dust deposits. We further discuss how the results of our investigation are related to other findings from the Rosetta mission. Methods. Surface changes were detected via systematic comparison of images, and quantified using shape-from-shading technique. Thermal models were applied to estimate the erosion of water ice in response to the increasing insolation over the areas where surface changes occurred. Modeling results were used for the interpretation of the observed surface changes. Results. Surface changes discussed here were concentrated at mid-latitudes, between about 20â-N and 40â-N, marking a global transition from the dust-covered to rugged terrains. The changes were distributed in open areas exposed to ample solar illumination and likely subject to enhanced surface erosion before perihelion. The occurrence of changes followed the southward migration of the sub-solar point across the latitudes of their distribution. The erosion at locations of most changes was at least about 0.5 m, but most likely did not exceed several meters. The erosive features before perihelion had given way to a fresh, smooth cover of dust deposits after perihelion, suggesting that the dust deposits had been globally restored by at least about 1 m with ejecta from the intens

Published
2017

23. Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta

Author

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

Published
2017
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24. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

Author

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

Published
2017
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25. Continued activity in P/2013 P5 PANSTARRS

Author

Hainaut, O. R., primary, Boehnhardt, H., additional, Snodgrass, C., additional, Meech, K. J., additional, Deller, J., additional, Gillon, M., additional, Jehin, E., additional, Kuehrt, E., additional, Lowry, S. C., additional, Manfroid, J., additional, Micheli, M., additional, Mottola, S., additional, Opitom, C., additional, Vincent, J.-B., additional, and Wainscoat, R., additional

Published
2014
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27. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

Author

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

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

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

28. Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta

Author

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

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

Context. Dust deposits or dust cover are a prevalent morphology in the northern hemi-nucleus of comet 67P/Churyumov-Gerasimenko (67P). The evolution of the dust deposits was captured by the OSIRIS camera system onboard the Rosetta spacecraft having escorted the comet for over two years. The observations shed light on the fundamental role of cometary activity in shaping and transforming the surface morphology. Aims. We aim to present OSIRIS observations of surface changes over the dust deposits before and after perihelion. The distribution of changes and a timeline of their occurrence are provided. We perform a data analysis to quantify the surface changes and investigate their correlation to water activity from the dust deposits. We further discuss how the results of our investigation are related to other findings from the Rosetta mission. Methods. Surface changes were detected via systematic comparison of images, and quantified using shape-from-shading technique. Thermal models were applied to estimate the erosion of water ice in response to the increasing insolation over the areas where surface changes occurred. Modeling results were used for the interpretation of the observed surface changes. Results. Surface changes discussed here were concentrated at mid-latitudes, between about 20◦N and 40◦N, marking a global transition from the dust-covered to rugged terrains. The changes were distributed in open areas exposed to ample solar illumination and likely subject to enhanced surface erosion before perihelion. The occurrence of changes followed the southward migration of the sub-solar point across the latitudes of their distribution. The erosion at locations of most changes was at least about 0.5 m, but most likely did not exceed several meters. The erosive features before perihelion had given way to a fresh, smooth cover of dust deposits after perihelion, suggesting that the dust deposits had been globally restored by at least about 1 m with ejecta from the intensely illuminated southern hemi-nucleus around perihelion, when the north was inactive during polar night. Conclusions. The erosion and restoration of the northern dust deposits are morphological expressions of seasonality on 67P. Based on observations and thermal modeling results, it is inferred that the dust deposits contained a few percent of water ice in mass on average. Local inhomogeneity in water abundance at spatial scales below tens of meters is likely. We suspect that dust ejected from the deposits may not have escaped the comet in bulk. That is, at least half of the ejected mass was afloat in the inner-coma or/and redeposited over other areas of the nucleus.

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

Author

Höfner, S., Vincent, J.-B., Blum, J., Davidsson, B. J. R., Sierks, H., Elmaarry, Mohamed Ramy, Deller, J., Hofmann, M., Hu, X., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A’Hearn, M. F., Auger, A.-T., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Gicquel, A., Groussin, O., Gutiérrez, P. J., Gutiérrez-Marqués, P., Güttler, C., Hviid, S. F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kührt, E., Küppers, M., La Forgia, F., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Michalik, H., Moissl-Fraund, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Preusker, F., Scholten, F., Shi, X., Thomas, Nicolas, Toth, I., Tubiana, C., and Zitzmann, S.

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

Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain. Aims. Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods. Methods. We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain. Results. Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P. Conclusions. At 3.5AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50W=m² and trigger dust activity that can be related mainly to H₂O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.

30. Exposed bright features on the comet 67P/Churyumov–Gerasimenko: distribution and evolution

Author

Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Hasselmann, P. H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Güttler, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Bertaux, J.-L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Cecco, M. De, Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Hoang, H. V., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, Nicolas, and Vincent, J.-B.

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

Context. Since its arrival at the comet 67P/Churyumov–Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims. We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods. We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel–Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results. We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of H2O ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions. Although the nucleus of 67P/Churyumov–Gerasimenko appears to be dark in general, there are localised H2O ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated H2O ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet’s return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated H2O ice that is preserved with consolidated cometary material, as observed on exposed patches resting on boulders. This is corroborated by our albedo calculations that attribute higher albedos for bright features with formations related to outbursts.

31. Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko

Author

Lai, I.-L., Ip, W.-H., Lee, J.-C., Lin, Z.-Y., Vincent, J.-B., Oklay, N., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P. J., Güttler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kührt, E., Küppers, M., Lara, L. M., Lazzarin, M., López-Moreno, J. J., Marzari, F., Naletto, G., Shi, X., Tubiana, C., and Thomas, Nicolas

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

Aims. We investigate the surface distribution of the source regions of dust jets on comet 67P/Churyumov-Gerasimenko as a function of time. Methods. The dust jet source regions were traced by the comprehensive imaging data set provided by the OSIRIS scientific camera. Results. We show in detail how the projected footpoints of the dust jets and hence the out gassing zone would move in consonance with the sunlit belt. Furthermore, a number of source regions characterized by repeated jet activity might be the result of local topographical variations or compositional heterogeneities. Conclusions. The spatial and temporal variations in source regions of the dust jets are influenced significantly by the seasonal effect. The strong dependence on the solar zenit hangle and local time could be related to the gas sublimation process driven by solar insolation on a surface layer of low thermal inertia.

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