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Your search keyword '"Kuppers M."' showing total 42 results

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42 results on '"Kuppers M."'

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

Author: Gicquel, A., Rose, M., Vincent, J. -B., Davidsson, B., Bodewits, D., Hearn, M. F. A, Agarwal, J., Fougere, N., Sierks, H., Bertini, I., Lin, Z. -Y., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Barucci, M. A., Bertaux, J. -L., Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., Guttler, C., Hofner, S., Hofmann, M., Hu, X., Hviid, S. F., Ip, W. -H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Lowry, S., Marzari, F., Masoumzadeh, N., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras since March 2014 using both the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC). We use images from the NAC camera to study a bright outburst observed in the southern hemisphere on July 29, 2015. The high spatial resolution of the NAC is needed to localize the source point of the outburst on the surface of the nucleus. The heliocentric distance is 1.25 au and the spacecraft-comet distance is 186 km. Aiming to better understand the physics that led to the outgassing, we used the Direct Simulation Monte Carlo (DSMC) method to study the gas flow close to the nucleus and the dust trajectories. The goal is to understand the mechanisms producing the outburst. We reproduce the opening angle of the outburst in the model and constrain the outgassing ratio between the outburst source and the local region. The outburst is in fact a combination of both gas and dust, in which the active surface is approximately 10 times more active than the average rate found in the surrounding areas. We need a number of dust particles 7.83 $\times$ 10$^{11}$ - 6.90 $\times$ 10$^{15}$ (radius 1.97 - 185 {\mu}m), which corresponds to a mass of dust 220 - 21 $\times$ 10$^{3}$kg., Comment: 8 pages, 9 figures
Published: 2017
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2. Observations and analysis of a curved jet in the coma of comet 67P/Churyumov-Gerasimenko

Author: Lin, Zhong-Yi, Lai, I. -L., Su, C. -C., Ip, W. -H., Lee, J. -C., Wu, J. -S., Vincent, J. -B., La Forgia, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debet, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guttler, C., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Lowry, S., Marzari, F., Michalik, H., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Rozek, A., Thomas, N., and Tubiana, C.
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: We analyze the physical properties and dynamical origin of a curved jet of comet 67P/Churyumov-Gerasimenko that was observed repeatedly in several nucleus rotations starting on May 30 and persisting until early August, 2015. We simulated the motion of dust grains ejected from the nucleus surface under the influence of the gravity and viscous drag effect of the expanding gas flow from the rotating nucleus. The formation of the curved jet is a combination of the size of the dust particles (~0.1-1 mm) and the location of the source region near the nucleus equator. This enhances the spiral feature of the collimated dust stream after the dust is accelerated to a terminal speed on the order of m/s., Comment: 5pages, 5 figures
Published: 2016
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3. HERA autonomous Guidance, Navigation and Control experiments: enabling better asteroid science future missions

Author: GIL-FERNANDEZ, J., CASASCO, M., CARNELLI, I., MARTINO, P., and KUPPERS, M.
Subjects: AUTONOMOUS NAVIGATION, GUIDANCE, Physics::Space Physics, Astrophysics::Instrumentation and Methods for Astrophysics, GNC, ComputerApplications_COMPUTERSINOTHERSYSTEMS, Astrophysics::Earth and Planetary Astrophysics
Abstract: HERA is a mission of opportunity to validate kinetic impact as planetary defense technique in collaboration with NASA\'s DART mission. As a by-product, asteroid science will be achieved using the needed for deflection. In addition, HERA will demonstrate several Guidance, Navigation and Control (GNC) technologies. These GNC experiments permits the achievement of some deflection and science goals of HERA mission and enable the use of the GNC technologies in future space missions. The design of the GNC experiments considers the balance between mission safety, flight operations, payload characteristics, and spacecraft and schedule constraints.
Published: 2019
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4. Corrigendum: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs (Astronomy and Astrophysics (2018) 611 (A33) DOI: 10.1051/0004-6361/201732155)

Author: Attree, N., Groussin, O., Jorda, L., Nebouy, D., Thomas, N., Brouet, Y., Kuhrt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., A'Hearn, M. F., Auger, A. -T., Barucci, M. A., Bertaux, J. -L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Deppo, V. D., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutierrez, P. J., Guttler, C., Hviid, S., W. -H., Ip, Kovacs, G., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Toth, I., Tubiana, C., Vincent, J. -B., and Shi, X.
Subjects: comets: general, methods: observational, addenda, comets: individual: Churyumov-Gerasimenko, errata, errata, addenda
Published: 2018

5. Archetypes of Country Energy Systems

Author: Kuppers, M., primary, Metzger, M., additional, Huber, M., additional, and Paulus, S., additional
Published: 2019
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6. 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., Guettler, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., 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., Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., Vincent, J. -B, 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., Guettler, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., 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., Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., 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 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 prese
Published: 2018
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7. The phase function and density of the dust observed at comet 67P/Churyumov-Gerasimenko

Author: Fulle, Marco, Bertini, I., Della Corte, V., Guttler, C., Ivanovski, S., La Forgia, F., Lasue, J., Levasseur-Regourd, A. C., Marzari, F., Moreno, F., Mottola, S., Naletto, G., Palumbo, P., Rinaldi, G., Rotundi, A., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Hviid, H. S., Ip, W. H., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuhrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Shi, X., Thomas, N., Tubiana, C., Fulle, Marco, Bertini, I., Della Corte, V., Guttler, C., Ivanovski, S., La Forgia, F., Lasue, J., Levasseur-Regourd, A. C., Marzari, F., Moreno, F., Mottola, S., Naletto, G., Palumbo, P., Rinaldi, G., Rotundi, A., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Barucci, M. A., Bertaux, J. -L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Hviid, H. S., Ip, W. H., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuhrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Shi, X., Thomas, N., and Tubiana, C.
Abstract: The OSIRIS camera onboard Rosetta measured the phase function of both the coma dust and the nucleus. The two functions have a very different slope versus the phase angle. Here, we show that the nucleus phase function should be adopted to convert the brightness to the size of dust particles larger than 2.5 mm only. This makes the dust bursts observed close to Rosetta by OSIRIS, occurring about every hour, consistent with the fragmentation on impact with Rosetta of parent particles, whose flux agrees with the dust flux observed by GIADA. OSIRIS also measured the antisunward acceleration of the fragments, thus providing the first direct measurement of the solar radiation force acting on the dust fragments and thus of their bulk density, excluding any measurable rocket effect by the ice sublimation from the dust. The obtained particle density distribution has a peak matching the bulk density of most COSIMA particles, and represents a subset of the density distribution measured by GIADA. This implies a bias in the elemental abundances measured by COSIMA, which thus are consistent with the 67P dust mass fractions inferred by GIADA, i.e. (38 +/- 8) per cent of hydrocarbons versus the (62 +/- 8) per cent of sulphides and silicates.
Published: 2018
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8. Direct observations of asteroid interior and regolith structure : Science measurement requirements

Author: Herique, A., Agnus, B., Asphaug, E., Barucci, A., Beck, P., Bellerose, J., Biele, J., Bonal, L., Bousquet, P., Bruzzone, L., Buck, C., Carnelli, I., Cheng, A., Ciarletti, V., Delbo, M., Du, J., Du, X., Eyraud, C., Fa, W., Fernandez, J. Gil, Gassot, O., Granados-Alfaro, R., Green, S. F., Grieger, B., Grundmann, J. T., Grygorczuk, J., Hahnel, R., Heggy, E., Ho, T-M, Karatekin, O., Kasaba, Y., Kobayashi, T., Kofman, W., Krause, C., Kumamoto, A., Kuppers, M., Laabs, M., Lange, C., Lasue, J., Levasseur-Regourd, A. C., Mallet, A., Michel, P., Mottola, S., Murdoch, N., Muetze, M., Oberst, J., Orosei, R., Plettemeier, D., Rochat, S., RodriguezSuquet, R., Rogez, Y., Schaffer, P., Snodgrass, C., Souyris, J-C, Tokarz, M., Ulamec, S., Wahlund, Jan-Erik, Zine, S., Herique, A., Agnus, B., Asphaug, E., Barucci, A., Beck, P., Bellerose, J., Biele, J., Bonal, L., Bousquet, P., Bruzzone, L., Buck, C., Carnelli, I., Cheng, A., Ciarletti, V., Delbo, M., Du, J., Du, X., Eyraud, C., Fa, W., Fernandez, J. Gil, Gassot, O., Granados-Alfaro, R., Green, S. F., Grieger, B., Grundmann, J. T., Grygorczuk, J., Hahnel, R., Heggy, E., Ho, T-M, Karatekin, O., Kasaba, Y., Kobayashi, T., Kofman, W., Krause, C., Kumamoto, A., Kuppers, M., Laabs, M., Lange, C., Lasue, J., Levasseur-Regourd, A. C., Mallet, A., Michel, P., Mottola, S., Murdoch, N., Muetze, M., Oberst, J., Orosei, R., Plettemeier, D., Rochat, S., RodriguezSuquet, R., Rogez, Y., Schaffer, P., Snodgrass, C., Souyris, J-C, Tokarz, M., Ulamec, S., Wahlund, Jan-Erik, and Zine, S.
Abstract: Our knowledge of the internal structure of asteroids is, so far, indirect - relying entirely on inferences from remote sensing observations of the surface, and theoretical modeling of formation and evolution. What are the bulk properties of the regolith and deep interior? And what are the physical processes that shape asteroid internal structures? Is the composition and size distribution observed on the surface representative of the bulk? These questions are crucial to understand small bodies' history from accretion in the early Solar System to the present, and direct measurements are needed to answer these questions for the benefit of science as well as for planetary defense or exploration. Radar is one of the main instruments capable of sounding asteroids to characterize internal structure from sub-meter to global scale. In this paper, we review the science case for direct observation of the deep internal structure and regolith of a rocky asteroid of kilometer size or smaller. We establish the requirements and model dielectric properties of asteroids to outline a possible instrument suite, and highlight the capabilities of radar instrumentation to achieve these observations. We then review the expected science return including secondary objectives contributing to the determination of the gravitational field, the shape model, and the dynamical state. This work is largely inherited from MarcoPolo-R and AIDA/AIM studies.
Published: 2018
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9. Investigating the physical properties of outbursts on comet 67P/Churyumov-Gerasimenko

Author: Lin, Zhong-Yi, Knollenberg, J., Vincent, J. -B, A'Hearn, M. F., Ip, W-H, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Mottola, S., Bodewits, D., Agarwal, J., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Deller, J., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lai, I. -L, Lara, L. M., Lazzarin, M., Lee, J-C, Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Ott, T., Drolshagen, E., Shi, X., Thomas, N., Tubiana, C., Lin, Zhong-Yi, Knollenberg, J., Vincent, J. -B, A'Hearn, M. F., Ip, W-H, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Mottola, S., Bodewits, D., Agarwal, J., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Deller, J., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lai, I. -L, Lara, L. M., Lazzarin, M., Lee, J-C, Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Ott, T., Drolshagen, E., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Cometary outbursts on several comets have been observed both by ground-based telescopes and by in situ instruments on spacecraft. However, the mechanism behind these phenomena and their physical properties are still unclear. The optical, spectrocopic and infrared remote imaging system (OSIRIS) onboard the Rosetta spacecraft provided first-hand information on the outbursts from comet 67P/Churyumov-Gerasimenko during its perihelion passage in 2015. The physical properties of the outbursts can be investigated by examining the time series of these high-resolution images. An analysis is made of the wide- and narrow-angle images obtained during the monitoring of the outburst sequences, which occurred between July and September in 2015. A ring-masking technique is used to calculate the excess brightness of the outbursts. The ejected mass and expansion velocity of the outbursts is estimated from differences in images made with the same filter (orange filter). The calculated excess brightness from these outburst plumes ranges from a few per cent to 28 per cent. In some major outbursts, the brightness contribution from the outburst plume can be one or two times higher than that of the typical coma jet activities. The strongest event was the perihelion outburst detected just a few hours before perihelion. The mass ejection rate during a generic outburst could reach a few per cent of the steady-state value of the dust coma. Transient events are detected by studying the brightness slope of the outburst plume with continuous streams of outflowing gas and dust triggered by driving mechanisms, as yet not understood, which remain active for several minutes to less than a few hours.
Published: 2017
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10. Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio

Author: Hu, X., Shi, X., Sierks, H., Blum, J., Oberst, J., Fulle, M., Kuehrt, E., Guettler, C., Gundlach, B., Keller, H. U., Mottola, S., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., Buettner, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Gutierrez-Marques, P., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Richards, M. L., Ripken, J., Thomas, N., Tubiana, C., Vincent, J. -B, Hu, X., Shi, X., Sierks, H., Blum, J., Oberst, J., Fulle, M., Kuehrt, E., Guettler, C., Gundlach, B., Keller, H. U., Mottola, S., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., Buettner, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Gutierrez-Marques, P., Hall, I., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Richards, M. L., Ripken, J., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: We perform a thermo-physical analysis on water activity of comet 67P/Churyumov-Gerasimenko (67P). The sublimation of water is assumed to occur from beneath a global, desiccated dust mantle over the irregular-shaped nucleus. The concept of two thermal models, the recipe of model formulation and the strategy of application to comet 67P are described. For an accurate and efficient evaluation of energy input by insolation and self-heating over the nucleus, a Landscape data base is devised based on polyhedral shape models of the nucleus. We apply the thermal models to investigate the impact of certain parameters of nucleus properties on water production. It is found that the measured water production of 67P can be overall attributed to sublimation of water ice with a mass abundance of a few to 10 per cent beneath a uniform dust mantle of several millimetres to one centimetre in thickness. Insofar as 67P is concerned, we argue against the necessity to invoke assumptions on localized water activity, or on the distinction of active/dormant surface areas.
Published: 2017
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11. Long-term monitoring of comet 67P/Churyumov-Gerasimenko's jets with OSIRIS onboard Rosetta

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

Author: Oklay, N., Mottola, S., Vincent, J. -B, Pajola, M., Fornasier, S., Hviid, S. F., Kappel, D., Kuehrt, E., Keller, H. U., Barucci, M. A., Feller, C., Preusker, F., Scholten, F., Hall, I., Sierks, H., 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., Deshapriya, J. D. P., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hasselmann, P. H., Hofmann, M., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Masoumzadeh, N., Naletto, G., Pommerol, A., Shi, X., Thomas, N., Tubiana, C., Oklay, N., Mottola, S., Vincent, J. -B, Pajola, M., Fornasier, S., Hviid, S. F., Kappel, D., Kuehrt, E., Keller, H. U., Barucci, M. A., Feller, C., Preusker, F., Scholten, F., Hall, I., Sierks, H., 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., Deshapriya, J. D. P., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hasselmann, P. H., Hofmann, M., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Masoumzadeh, N., Naletto, G., Pommerol, A., Shi, X., Thomas, N., and Tubiana, C.
Abstract: Numerous water-ice-rich deposits surviving more than several months on comet 67P/Churyumov-Gerasimenko were observed during the Rosetta mission. We announce the first-time detection of water-ice features surviving up to 2 yr since their first observation via OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) NAC (narrow angle camera). Their existence on the nucleus of comet 67P at the arrival of the Rosetta spacecraft suggests that they were exposed to the surface during the comet's previous orbit. We investigated the temporal variation of large water-ice patches to understand the long-term sustainability of water ice on cometary nuclei on time-scales of months and years. Large clusters are stable over typical periods of 0.5 yr and reduce their size significantly around the comet's perihelion passage, while small exposures disappear. We characterized the temporal variation of their multispectral signatures. In large clusters, dust jets were detected, whereas in large isolated ones no associated activity was detected. Our thermal analysis shows that the long-term sustainability of water-ice-rich features can be explained by the scarce energy input available at their locations over the first half year. However, the situation reverses for the period lasting several months around perihelion passage. Our two end-member mixing analysis estimates a pure water-ice equivalent thickness up to 15 cm within one isolated patch, and up to 2 m for the one still observable through the end of the mission. Our spectral modelling estimates up to 48 per cent water-ice content for one of the large isolated feature, and up to 25 per cent water ice on the large boulders located within clusters.
Published: 2017
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13. The highly active Anhur-Bes regions in the 67P/Churyumov-Gerasimenko comet : results from OSIRIS/ROSETTA observations

Author: Fornasier, S., Feller, C., Lee, J. -C, Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P., Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. -H, Lin, Z. -Y, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B, Fornasier, S., Feller, C., Lee, J. -C, Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P., Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. -H, Lin, Z. -Y, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B
Abstract: The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since 2015 March. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rates, thus exposing the sub-surface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur-Bes boundary during/after the perihelion passage, close to the area where exposed CO2 and H2O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers.
Published: 2017
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14. Modelling of the outburst on 2015 July 29 observed with OSIRIS cameras in the Southern hemisphere of comet 67P/Churyumov-Gerasimenko

Author: Gicquel, A., Rose, M., Vincent, J. -B, Davidsson, B., Bodewits, D., A'Hearn, M. F., Agarwal, J., Fougere, N., Sierks, H., Bertini, I., Lin, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., 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., Kuppers, 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., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., Tubiana, C., Gicquel, A., Rose, M., Vincent, J. -B, Davidsson, B., Bodewits, D., A'Hearn, M. F., Agarwal, J., Fougere, N., Sierks, H., Bertini, I., Lin, Z. -Y, Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., 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., Kuppers, 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., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov-Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) cameras since 2014 March using both the wide-angle camera and the narrow-angle camera (NAC). We use images from the NAC camera to study a bright outburst observed in the Southern hemisphere on 2015 July 29. The high spatial resolution of the NAC is needed to localize the source point of the outburst on the surface of the nucleus. The heliocentric distance is 1.25 au and the spacecraft-comet distance is 186 km. Aiming to better understand the physics that led to the outgassing, we used the Direct Simulation Monte Carlo method to study the gas flow close to the nucleus and the dust trajectories. The goal is to understand the mechanisms producing the outburst. We reproduce the opening angle of the outburst in the model and constrain the outgassing ratio between the outburst source and the local region. The outburst is in fact a combination of both gas and dust, in which the active surface is approximately 10 times more active than the average rate found in the surrounding areas. We need a number of dust particles 7.83 x 10(11) to 6.90 x 10(15) (radius 1.97-185 mu m), which correspond to a mass of dust (220-21) x 10(3) kg.
Published: 2017
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15. Post-perihelion photometry of dust grains in the coma of 67P Churyumov-Gerasimenko

Author: Frattin, E., Cremonese, G., Simioni, E., Bertini, I., Lazzarin, M., Ott, T., Drolshagen, E., La Forgia, F., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Ferri, F., Fornasier, S., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Penasa, L., Shi, X., Thomas, N., Tubiana, C., Vincent, J. -B, Frattin, E., Cremonese, G., Simioni, E., Bertini, I., Lazzarin, M., Ott, T., Drolshagen, E., La Forgia, F., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Deller, J., Ferrari, S., Ferri, F., Fornasier, S., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, L. M., Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Penasa, L., Shi, X., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: We present a photometric analysis of individual dust grains in the coma of comet 67P/Churyumov-Gerasimenko using OSIRIS images taken from 2015 July to 2016 January. We analysed a sample of 555 taken during 18 d at heliocentric distances ranging between 1.25 and 2.04 au and at nucleocentric distances between 80 and 437 km. An automated method to detect the tracks was specifically developed. The images were taken by OSIRIS NAC in four different filters: Near-IR (882 nm), Orange (649 nm), FarOrange (649 nm) and Blue (480 nm). It was not always possible to recognize all the grains in the four filters, hence we measured the spectral slope in two wavelengths ranges: in the interval [480-649] nm, for 1179 grains, and in the interval [649-882] nm, for 746 grains. We studied the evolution of the two populations' average spectral slopes. The data result scattered around the average value in the range [480-649] nm, while in the [649-882] nm we observe a slight decreasing moving away from the Sun as well as a slight increasing with the nucleocentric distance. A spectrophotometric analysis was performed on a subsample of 339 grains. Three major groups were defined, based on the spectral slope between [535-882] nm: (i) the steep spectra that may be related with organic material, (ii) the spectra with an intermediate slope, likely a mixture of silicates and organics and (iii) flat spectra that may be associated with a high abundance of water ice.
Published: 2017
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16. Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

Author: Guettler, C., Hasselmann, P. H., Li, Y., Fulle, M., Tubiana, C., Kovacs, G., Agarwal, J., Sierks, H., Fornasier, S., Hofmann, M., Marques, P. Gutierrez, Ott, T., Drolshagen, E., Bertini, I., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bodewits, D., Bertaux, J. -L, Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Geiger, B., Groussin, O., Gutierrez, P. J., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Vincent, J. -B, Guettler, C., Hasselmann, P. H., Li, Y., Fulle, M., Tubiana, C., Kovacs, G., Agarwal, J., Sierks, H., Fornasier, S., Hofmann, M., Marques, P. Gutierrez, Ott, T., Drolshagen, E., Bertini, I., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bodewits, D., Bertaux, J. -L, Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Geiger, B., Groussin, O., Gutierrez, P. J., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., and Vincent, J. -B
Abstract: In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent.
Published: 2017
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17. Constraints on cometary surface evolution derived from a statistical analysis of 67P's topography

Author: Vincent, J. -B, Hviid, S. F., Mottola, S., Kuehrt, E., Preusker, F., Scholten, F., Keller, H. U., Oklay, N., de Niem, D., Davidsson, B., Fulle, M., Pajola, M., Hofmann, M., Hu, X., Rickman, Hans, Lin, Z. -Y, Feller, C., Gicquel, A., Boudreault, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., Guettler, C., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Penasa, L., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B, Hviid, S. F., Mottola, S., Kuehrt, E., Preusker, F., Scholten, F., Keller, H. U., Oklay, N., de Niem, D., Davidsson, B., Fulle, M., Pajola, M., Hofmann, M., Hu, X., Rickman, Hans, Lin, Z. -Y, Feller, C., Gicquel, A., Boudreault, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutierrez, P. J., Gutierrez-Marquez, P., Guettler, C., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Penasa, L., Shi, X., Thomas, N., Toth, I., and Tubiana, C.
Abstract: We present a statistical analysis of the distribution of large-scale topographic features on comet 67P/Churyumov-Gerasimenko. We observe that the cumulative cliff height distribution across the surface follows a power law with a slope equal to -1.69 +/- 0.02. When this distribution is studied independently for each region, we find a good correlation between the slope of the power law and the orbital erosion rate of the surface. For instance, the Northern hemisphere topography is dominated by structures on the 100 m scale, while the Southern hemisphere topography, illuminated at perihelion, is dominated by 10 m scale terrain features. Our study suggests that the current size of a cliff is controlled not only by material cohesion but also by the dominant erosional process in each region. This observation can be generalized to other comets, where we argue that primitive nuclei are characterized by the presence of large cliffs with a cumulative height-power index equal to or above -1.5, while older, eroded cometary surfaces have a power index equal to or below -2.3. In effect, our model shows that a measure of the topography provides a quantitative assessment of a comet's erosional history, that is, its evolutionary age.
Published: 2017
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18. A three-dimensional modelling of the layered structure of comet 67P/Churyumov-Gerasimenko

Author: Penasa, L., Massironi, M., Naletto, G., Simioni, E., Ferrari, S., Pajola, M., Lucchetti, A., Preusker, F., Scholten, F., Jorda, L., Gaskell, R., Ferri, F., Marzari, F., Davidsson, B., Mottola, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Feller, C., Fornasier, S., Frattin, E., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. H., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lazzarin, M., Lee, J. -C, Lopez Moreno, J. J., Oklay, N., Shi, X., Thomas, N., Tubiana, C., Vincent, J. B., Penasa, L., Massironi, M., Naletto, G., Simioni, E., Ferrari, S., Pajola, M., Lucchetti, A., Preusker, F., Scholten, F., Jorda, L., Gaskell, R., Ferri, F., Marzari, F., Davidsson, B., Mottola, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Feller, C., Fornasier, S., Frattin, E., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. H., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lazzarin, M., Lee, J. -C, Lopez Moreno, J. J., Oklay, N., Shi, X., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: We provide a three-dimensional model of the inner layered structure of comet 67P based on the hypothesis of an extended layering independently wrapping each lobe. A large set of terrace orientations was collected on the latest shape model and then used as a proxy for the local orientation of the surfaces of discontinuity which defines the layers. We modelled the terraces as a family of concentric ellipsoidal shells with fixed axis ratios, producing a model that is completely defined by just eight free parameters. Each lobe of 67P has been modelled independently, and the two sets of parameters have been estimated by means of non-linear optimization of the measured terrace orientations. The proposed model is able to predict the orientation of terraces, the elongation of cliffs, the linear traces observed in the Wosret and Hathor regions and the peculiar alignment of boulder-like features which has been observed in the Hapi region, which appears to be related to the inner layering of the big lobe. Our analysis allowed us to identify a plane of junction between the two lobes, further confirming the independent nature of the lobes. Our layering models differ from the best-fitting topographic ellipsoids of the surface, demonstrating that the terraces are aligned to an internal structure of discontinuities, which is unevenly exposed on the surface, suggesting a complex history of localized material removal from the nucleus.
Published: 2017
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19. The opposition effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images

Author: Hasselmann, P. H., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Fulchignoni, M., Jost, B., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gaskell, R. W., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Hasselmann, P. H., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Fulchignoni, M., Jost, B., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gaskell, R. W., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of 2016 April 9-10 show, at large scale, an opposition effect (OE) spot sweeping across Imhotep as the phase angle ranges from 0 degrees to 17 degrees. In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both the linear-exponential and Hapke models. These features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemblage of bright spots, going from red to blue colours. Both the Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet a very broad nonlinear phase curve is verified and no sign of sharp OE associated with a coherent-backscattering mechanism is observed. We estimate that the 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent with surfaces becoming slightly brighter as they are enriched by high-albedo ice grains. We also report the estimation of normal albedo for all cometary regions observed throughout the image sequence. Comparison to pre-perihelion results indicates that far better insolation of northern brighter regions, i.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the photometric parameters. However, metre-scale photometric analysis of the Imhotep-Ash boundary area advocates for mild darkening (<7 per cent) of the surface at local scale.
Published: 2017
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20. Dust mass distribution around comet 67P/Churyumov-Gerasimenko determined via parallax measurements using Rosetta's OSIRIS cameras

Author: Ott, T., Drolshagen, E., Koschny, D., Guettler, C., Tubiana, C., Frattin, E., Agarwal, J., Sierks, H., Bertini, I., Barbieri, C., Lamy, P. I., Rodrigo, R., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Feller, C., Fornasier, S., Fulle, M., Geiger, B., Gicquel, A., Groussin, O., Gutierrez, P. J., 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., Lin, Z. -Y, Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Vincent, J. -B, Poppe, B., Ott, T., Drolshagen, E., Koschny, D., Guettler, C., Tubiana, C., Frattin, E., Agarwal, J., Sierks, H., Bertini, I., Barbieri, C., Lamy, P. I., Rodrigo, R., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Feller, C., Fornasier, S., Fulle, M., Geiger, B., Gicquel, A., Groussin, O., Gutierrez, P. J., 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., Lin, Z. -Y, Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Vincent, J. -B, and Poppe, B.
Abstract: The OSIRIS (optical, spectroscopic and infrared remote imaging system) instrument on board the ESA Rosetta spacecraft collected data of 67P/Churyumov-Gerasimenko for over 2 yr. OSIRIS consists of two cameras, a Narrow Angle Camera and a Wide Angle Camera. For specific imaging sequences related to the observation of dust aggregates in 67P's coma, the two cameras were operating simultaneously. The two cameras are mounted 0.7 m apart from each other, as a result this baseline yields a parallax shift of the apparent particle trails on the analysed images directly proportional to their distance. Thanks to such shifts, the distance between observed dust aggregates and the spacecraft was determined. This method works for particles closer than 6000 m to the spacecraft and requires very few assumptions. We found over 250 particles in a suitable distance range with sizes of some centimetres, masses in the range of 10(-6)-10(2) kg and a mean velocity of about 2.4 m s(-1) relative to the nucleus. Furthermore, the spectral slope was analysed showing a decrease in the median spectral slope of the particles with time. The further a particle is from the spacecraft the fainter is its signal. For this reason, this was counterbalanced by a debiasing. Moreover, the dust mass-loss rate of the nucleus could be computed as well as the Af rho of the comet around perihelion. The summed-up dust mass-loss rate for the mass bins 10(-4)-10(2) kg is almost 8300 kg s(-1).
Published: 2017
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21. Seasonal mass transfer on the nucleus of comet 67P/Chuyumov-Gerasimenko

Author: Keller, H. U., Mottola, S., Hviid, S. F., Agarwal, J., Kuehrt, E., Skorov, Y., Otto, K., Vincent, J. -B, Oklay, N., Schroeder, S. E., Davidsson, Björn, Pajola, M., Shi, X., Bodewits, D., Toth, I., Preusker, F., Scholten, F., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. R., Kuppers, M., Lara, L. -M, Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Tubiana, C., Thomas, N., Keller, H. U., Mottola, S., Hviid, S. F., Agarwal, J., Kuehrt, E., Skorov, Y., Otto, K., Vincent, J. -B, Oklay, N., Schroeder, S. E., Davidsson, Björn, Pajola, M., Shi, X., Bodewits, D., Toth, I., Preusker, F., Scholten, F., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. R., Kuppers, M., Lara, L. -M, Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Tubiana, C., and Thomas, N.
Abstract: We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov-Gerasimenko. The obliquity of the rotation axis of 67P causes strong seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an antisolar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of traveltime. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO2 or CO. This causes a north-south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are 'shock frozen' and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, i.e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements.
Published: 2017
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22. Geomorphological and spectrophotometric analysis of Seth's circular niches on comet 67P/Churyumov-Gerasimenko using OSIRIS images

Author: Lucchetti, A., Pajola, M., Fornasier, S., Mottola, S., Penasa, L., Jorda, L., Cremonese, G., Feller, C., Hasselmann, P. H., Massironi, M., Ferrari, S., Naletto, G., Oklay, N., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Boudreault, S., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hoffman, M., Hviid, S. F., Ip, W. H., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., La Forgia, F., Lin, L. Z., Lopez Moreno, J. J., Marzari, F., Preusker, F., Scholten, F., Shi, X., Thomas, N., Tubiana, C., Vincent, J. B., Lucchetti, A., Pajola, M., Fornasier, S., Mottola, S., Penasa, L., Jorda, L., Cremonese, G., Feller, C., Hasselmann, P. H., Massironi, M., Ferrari, S., Naletto, G., Oklay, N., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Boudreault, S., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hoffman, M., Hviid, S. F., Ip, W. H., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., La Forgia, F., Lin, L. Z., Lopez Moreno, J. J., Marzari, F., Preusker, F., Scholten, F., Shi, X., Thomas, N., Tubiana, C., and Vincent, J. B.
Abstract: We provide a detailed geomorphological and spectrophotometric analysis of the circular niches located on the Seth region of 67P using OSIRIS images. The features can be related to landslide events that occurred on 67P and shaped its surface, as the recent Aswan cliff collapse detected in the same region. We therefore provide an analysis of the area pre -and post-perihelion suggesting that no specific changes have been observed. To assess this, after performing a geomorphological map of the area that allows us to identify different terrain units, we computed the boulders cumulative size frequency distribution (SFD) of the niches, before and after the perihelion passage. The niches SFDs are characterized by a similar trend with two different power-law indices within the same deposit: lower power-law value (between -2.3 and -2.7) for boulders smaller than 5 m and steeper power-law value (between -4.7 and -5.0) for boulders larger than 5 m. These trends suggest that smaller boulders have evolved and progressively have been depleted (lower power-law index), while bigger boulders are more representative of the event that generated the deposit and are less degraded. Then, we perform the spectrophotometric analysis of this region comparing pre-and post-perihelion results. We found colour changes within the area, in particular brighter patches related to the presence of exposed water ice mixed to the refractory materials have been detected in the post-perihelion images.
Published: 2017
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23. The scattering phase function of comet 67P/Churyumov-Gerasimenko coma as seen from the Rosetta/OSIRIS instrument

Author: Bertini, I., La Forgia, F., Tubiana, C., Guettler, C., Fulle, M., Moreno, F., Frattin, E., Kovacs, G., Pajola, M., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J-L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Drolshagen, E., Ferrari, S., Ferri, F., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hasselmann, P. H., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Ott, T., Penasa, L., Thomas, N., Vincent, J. -B, Bertini, I., La Forgia, F., Tubiana, C., Guettler, C., Fulle, M., Moreno, F., Frattin, E., Kovacs, G., Pajola, M., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J-L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Drolshagen, E., Ferrari, S., Ferri, F., Fornasier, S., Gicquel, A., Groussin, O., Gutierrez, P. J., Hasselmann, P. H., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lin, Z. -Y, Lopez Moreno, J. J., Lucchetti, A., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Ott, T., Penasa, L., Thomas, N., and Vincent, J. -B
Abstract: The study of dust, the most abundant material in cometary nuclei, is pivotal in understanding the original materials forming the Solar system. Measuring the coma phase function provides a tool to investigate the nature of cometary dust. Rosetta/OSIRIS sampled the coma phase function of comet 67P/Churyumov-Gerasimenko, covering a large phase angle range in a small amount of time. Twelve series were acquired in the period from 2015 March to 2016 February for this scientific purpose. These data allowed, after stray light removal, measuring the phase function shape, its reddening, and phase reddening while varying heliocentric and nucleocentric distances. Despite small dissimilarities within different series, we found a constant overall shape. The reflectance has a u-shape with minimum at intermediate phase angles, reaching similar values at the smallest and largest phase angle sampled. The comparison with cometary phase functions in literature indicates OSIRIS curves being consistent with the ones found in many other single comets. The dust has a negligible phase reddening at alpha < 90 degrees, indicating a coma dominated by single scattering. We measured a reddening of [11-14] %/100 nm between 376 and 744 nm. No trend with heliocentric or nucleocentric distance was found, indicating the coma doesn't change its spectrum with time. These results are consistent with single coma grains and close-nucleus coma photometric results. Comparison with nucleus photometry indicates a different backscattering phase function shape and similar reddening values only at alpha < 30 degrees. At larger phase angles, the nucleus becomes significantly redder than the coma.
Published: 2017
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24. Distance determination method of dust particles using Rosetta OSIRIS NAC and WAC data

Author: Drolshagen, E., Ott, T., Koschny, D., Guetler, C., Tubiana, C., Agarwal, J., Sierks, H., Barbieri, C., Lamy, P. I., Rodrigo, R., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Feller, C., 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., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., Poppe, B., Drolshagen, E., Ott, T., Koschny, D., Guetler, C., Tubiana, C., Agarwal, J., Sierks, H., Barbieri, C., Lamy, P. I., Rodrigo, R., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Feller, C., 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., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., and Poppe, B.
Abstract: The ESA Rosetta spacecraft has been tracking its target, the Jupiter-family comet 67P/Churyumov-Gerasimenko, in close vicinity for over two years. It hosts the OSIRIS instruments: the Optical, Spectroscopic, and Infrared Remote Imaging System composed of two cameras, see e.g. Keller et al. (2007). In some imaging sequences dedicated to observe dust particles in the comet's coma, the two cameras took images at the same time. The aim of this work is to use these simultaneous double camera observations to calculate the dust particles' distance to the spacecraft. As the two cameras are mounted on the spacecraft with an offset of 70 cm, the distance of particles observed by both cameras can be determined by a shift of the particles' apparent trails on the images. This paper presents first results of the ongoing work, introducing the distance determination method for the OSIRIS instrument and the analysis of an example particle. We note that this method works for particles in the range of about 500-6000 m from the spacecraft.
Published: 2017
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25. 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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26. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

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

Author: Pajola, M., Hoefner, S., Vincent, J. B., Oklay, N., Scholten, F., Preusker, F., Mottola, S., Naletto, G., Fornasier, S., Lowry, S., Feller, C., Hasselmann, P. H., Guettler, C., Tubiana, C., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Deshapriya, J. D. P., El-Maarry, M. R., Ferrari, S., Ferri, F., Fulle, M., Groussin, O., Gutierrez, P., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lin, Z. -Y, Lazzarin, M., Lucchetti, A., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Michalik, H., Penasa, L., Pommerol, A., Simioni, E., Thomas, N., Toth, I., Baratti, E., Pajola, M., Hoefner, S., Vincent, J. B., Oklay, N., Scholten, F., Preusker, F., Mottola, S., Naletto, G., Fornasier, S., Lowry, S., Feller, C., Hasselmann, P. H., Guettler, C., Tubiana, C., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Besse, S., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Deshapriya, J. D. P., El-Maarry, M. R., Ferrari, S., Ferri, F., Fulle, M., Groussin, O., Gutierrez, P., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. R., Kuehrt, E., Kuppers, M., Lara, L. M., Lin, Z. -Y, Lazzarin, M., Lucchetti, A., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Michalik, H., Penasa, L., Pommerol, A., Simioni, E., Thomas, N., Toth, I., and Baratti, E.
Abstract: Outbursts occur commonly on comets(1) with different frequencies and scales(2,3). Despite multiple observations suggesting various triggering processes(4,5), the driving mechanism of such outbursts is still poorly understood. Landslides have been invoked(6) to explain some outbursts on comet 103P/Hartley (2), although the process required a pre-existing dust layer on the verge of failure. The Rosetta mission observed several outbursts from its target comet 67P/ChuryumovGerasimenko, which were attributed to dust generated by the crumbling of materials from collapsing cliffs(7,8). However, none of the aforementioned works included definitive evidence that landslides occur on comets. Amongst the many features observed by Rosetta on the nucleus of the comet, one peculiar fracture, 70 m long and 1 m wide, was identified on images obtained in September 2014 at the edge of a cliff named Aswan(9). On 10 July 2015, the Rosetta Navigation Camera captured a large plume of dust that could be traced back to an area encompassing the Aswan escarpment(7). Five days later, the OSIRIS camera observed a fresh, sharp and bright edge on the Aswan cliff. Here we report the first unambiguous link between an outburst and a cliff collapse on a comet. We establish a new dust-plume formation mechanism that does not necessarily require the breakup of pressurized crust or the presence of supervolatile material, as suggested by previous studies(7). Moreover, the collapse revealed the fresh icy interior of the comet, which is characterized by an albedo > 0.4, and provided the opportunity to study how the crumbling wall settled down to form a new talus.
Published: 2017
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28. Fractures on comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS

Author: El-Maarry, M. R., Thomas, N., Gracia-Berna, A., Marschall, R., Auger, A. -T., Groussin, O., Mottola, S., Pajola, M., Massironi, M., Marchi, S., Hofner, S., Preusker, F., Scholten, F., Jorda, L., Kuhrt, E., Keller, H. U., Sierks, H., A'Hearn, M. F., Barbieri, C., Barucci, M. A., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Guttler, C., Fornasier, S., Fulle, M., Gutierrez, P. J., Hofmann, M., Hviid, S. F., W. -H., Ip, Knollenberg, J., Koschny, D., Kovacs, G., Kramm, J. -R., Kuppers, M., Lamy, P. L., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Rickman, H., Rodrigo, R., Tubiana, C., Vincent, J. -B., Physikalisches Institut [Bern], Universität Bern [Bern] (UNIBE), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), DLR Institute of Planetary Research, German Aerospace Center (DLR), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Università degli Studi di Padova = University of Padua (Unipd), Dipartimento di Geoscienze [Padova], Solar System Exploration Research Virtual Institute (SSERVI), Southwest Research Institute [Boulder] (SwRI), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut für Geophysik und Extraterrestrische Physik [Braunschweig] (IGEP), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Dipartimento di Fisica e Astronomia 'Galileo Galilei', Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), CNR Institute for Photonics and Nanotechnologies (IFN), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Department of Physics and Astronomy [Uppsala], Uppsala University, Department of Industrial Engineering [Padova], University of Trento [Trento], INAF - Osservatorio Astronomico di Trieste (OAT), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institute of Astronomy [Taiwan] (IANCU), National Central University [Taiwan] (NCU), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Operations Department (ESAC), European Space Astronomy Centre (ESAC), Institut für Datentechnik und Kommunikationsnetze, Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), International Space Science Institute [Bern] (ISSI), ITA, USA, GBR, FRA, DEU, ESP, Universität Bern [Bern], Universita degli Studi di Padova, Max-Planck-Institut für Sonnensystemforschung (MPS), Consiglio Nazionale delle Ricerche [Roma] (CNR), European Space Agency (ESA)-European Space Agency (ESA), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), and Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA)
Subjects: Comet 67P, comets, fractures, OSIRIS, Rosetta, 530 Physics, 520 Astronomy, Comets, Fractures, Earth and Planetary Sciences (all), Geophysics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 620 Engineering, comet 67P/ Churyumov-Gerasimenko
Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard the Rosetta spacecraft currently orbiting comet 67P/Churyumov-Gerasimenko has yielded unprecedented views of a comet's nucleus. We present here the first ever observations of meter-scale fractures on the surface of a comet. Some of these fractures form polygonal networks. We present an initial assessment of their morphology, topology, and regional distribution. Fractures are ubiquitous on the surface of the comet's nucleus. Furthermore, they occur in various settings and show different topologies suggesting numerous formation mechanisms, which include thermal insulation weathering, orbital-induced stresses, and possibly seasonal thermal contraction. However, we conclude that thermal insolation weathering is responsible for creating most of the observed fractures based on their morphology and setting in addition to thermal models that indicate diurnal temperature ranges exceeding 200K and thermal gradients of similar to 15K/min at perihelion are possible. Finally, we suggest that fractures could be a facilitator in surface evolution and long-term erosion.
Published: 2015

29. Possible interpretation of the precession of comet 67P/Churyumov-Gerasimenko

Author: Gutierrez, P. J., Jorda, L., Gaskell, R. W., Davidsson, Björn J. R., Capanna, C., Hviid, S. F., Keller, H. U., Maquet, L., Mottola, S., Preusker, F., Scholten, F., Lara, L. M., Moreno, F., Rodrigo, R., Sierks, H., Barbieri, C., Lamy, P., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Auger, A. T., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez-Marques, P., Guettler, C., Ip, W. H., Knollenberg, J., Kramm, J. R., Kueht, E., Kuppers, M., La Forgia, F., Lazzarin, M., Lopez-Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Sabau, D., Thomas, N., Toth, I., Tubiana, C., Vincent, J. B., Gutierrez, P. J., Jorda, L., Gaskell, R. W., Davidsson, Björn J. R., Capanna, C., Hviid, S. F., Keller, H. U., Maquet, L., Mottola, S., Preusker, F., Scholten, F., Lara, L. M., Moreno, F., Rodrigo, R., Sierks, H., Barbieri, C., Lamy, P., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Auger, A. T., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez-Marques, P., Guettler, C., Ip, W. H., Knollenberg, J., Kramm, J. R., Kueht, E., Kuppers, M., La Forgia, F., Lazzarin, M., Lopez-Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Sabau, D., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. B.
Abstract: Context. Data derived from the reconstruction of the nucleus shape of comet 67P/Churyumov-Gerasimenko (67P) from images of the OSIRIS camera onboard ROSETTA show evidence that the nucleus rotates in complex mode. First, the orientation of the spin axis is not fixed in an inertial reference frame, which suggests a precessing motion around the angular momentum vector with a periodicity of approximately 257 h +/- 12 h. Second, periodograms of the right ascension and declination (RA/Dec) coordinates of the body-frame Z axis show a very significant (higher than 99.99%) periodicity at 276 h +/- 12 h, different from the rotational period of 12.40 h as previously determined from light-curve analysis. Aims. The main goal is to interpret the data and associated periodicities of the spin axis orientation in space. Methods. We analyzed the spin axis orientation in space and associated periodicities and compared them with solutions of Euler equations under the assumption that the body rotates in torque-free conditions. Statistical tests comparing the observationally derived spin axis orientation with the outcome from simulations were applied to determine the most likely inertia moments, excitation level, and periods. Results. Under the assumption that the body is solid-rigid and rotates in torque-free conditions, the most likely interpretation is that 67P is spinning around the principal axis with the highest inertia moment with a period of about 13 h. At the same time, the comet precesses around the angular momentum vector with a period of about 6.35 h. While the rotating period of such a body would be about 12.4 h, RA/Dec coordinates of the spin axis would have a periodicity of about 270 h as a result of the combination of the two aforementioned motions. Conclusions. The most direct and simple interpretation of the complex rotation of 67P requires a ratio of inertia moments significantly higher than that of a homogeneous body.
Published: 2016
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30. Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Author: Ip, W. -H, Lai, I. -L, Lee, J. -C, Cheng, Y. -C, Li, Y., Lin, Z. -Y, Vincent, J. -B, Besse, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Lowry, S., Marchi, S., Marzari, F., Michalik, H., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Thomas, N., Toth, E., Tubiana, C., Ip, W. -H, Lai, I. -L, Lee, J. -C, Cheng, Y. -C, Li, Y., Lin, Z. -Y, Vincent, J. -B, Besse, S., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., La Forgia, F., Lara, L. M., Lazzarin, M., Lopez-Moreno, J. J., Lowry, S., Marchi, S., Marzari, F., Michalik, H., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Thomas, N., Toth, E., and Tubiana, C.
Abstract: Aims. We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC). Methods. The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other. Results. The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived. Conclusions. The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history.
Published: 2016
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31. 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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32. Changes in the physical environment of the inner coma of 67p/churyumov-gerasimenko with decreasing heliocentric distance

Author: Bodewits, D., Lara, L. M., A'Hearn, M. F., La Forgia, F., Gicquel, A., Kovacs, G., Knollenberg, J., Lazzarin, M., Lin, Z. -Y, Shi, X., Snodgrass, C., Tubiana, C., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Thomas, N., Toth, I., Vincent, J. -B, Bodewits, D., Lara, L. M., A'Hearn, M. F., La Forgia, F., Gicquel, A., Kovacs, G., Knollenberg, J., Lazzarin, M., Lin, Z. -Y, Shi, X., Snodgrass, C., Tubiana, C., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Barucci, M. A., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hviid, S. F., Ip, W. -H, Jorda, L., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lopez-Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Thomas, N., Toth, I., and Vincent, J. -B
Abstract: The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, OI, CN, NH, and NH2 filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO2 rather than H2O is a significant source of the [OI] 630 nm emission. A strong plume-like feature observed in the CN and OI filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO2/H2O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus.
Published: 2016
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33. 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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34. 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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35. 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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36. 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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37. Decimetre-scaled spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Author: Feller, C., Fornasier, S., Hasselmann, P. H., Barucci, A., Preusker, F., Scholten, F., Jorda, L., Pommerol, A., Jost, B., Poch, O., ElMaary, M. R., Thomas, N., Belskaya, I., Pajola, M., Sierks, H., Barbieri, C., Lamy, P. L., Koschny, D., Rickman, Hans, Rodrigo, R., Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Giquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Keller, H., Ip, W. -H, Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Leyrat, C., Moreno, J. J. Lopez, Marzari, F., Masoumzadeh, N., Mottola, S., Naletto, G., Perna, D., Oklay, N., Shi, X., Tubiana, C., Vincent, J. -B, Feller, C., Fornasier, S., Hasselmann, P. H., Barucci, A., Preusker, F., Scholten, F., Jorda, L., Pommerol, A., Jost, B., Poch, O., ElMaary, M. R., Thomas, N., Belskaya, I., Pajola, M., Sierks, H., Barbieri, C., Lamy, P. L., Koschny, D., Rickman, Hans, Rodrigo, R., Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Giquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Keller, H., Ip, W. -H, Knollenberg, J., Kovacs, G., Kramm, J. -R, Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Leyrat, C., Moreno, J. J. Lopez, Marzari, F., Masoumzadeh, N., Mottola, S., Naletto, G., Perna, D., Oklay, N., Shi, X., Tubiana, C., and Vincent, J. -B
Abstract: We present the results of the photometric and spectrophotometric properties of the 67P/Churyumov-Gerasimenko nucleus derived with the Optical, Spectroscopic and Infrared Remote Imaging System instrument during the closest fly-by over the comet, which took place on 2015 February 14 at a distance of similar to 6 km from the surface. Several images covering the 0 degrees-33 degrees. phase angle range were acquired, and the spatial resolution achieved was 11 cm pixel(-1). The flown-by region is located on the big lobe of the comet, near the borders of the Ash, Apis and Imhotep regions. Our analysis shows that this region features local heterogeneities at the decimetre scale. We observed difference of reflectance up to 40 per cent between bright spots and sombre regions, and spectral slope variations up to 50 per cent. The spectral reddening effect observed globally on the comet surface by Fornasier et al. (2015) is also observed locally on this region, but with a less steep behaviour. We note that numerous metre-sized boulders, which exhibit a smaller opposition effect, also appear spectrally redder than their surroundings. In this region, we found no evidence linking observed bright spots to exposed water-ice-rich material. We fitted our data set using the Hapke 2008 photometric model. The region overflown is globally as dark as the whole nucleus (geometric albedo of 6.8 per cent) and it has a high porosity value in the uppermost layers (86 per cent). These results of the photometric analysis at a decimetre scale indicate that the photometric properties of the flown-by region are similar to those previously found for the whole nucleus.
Published: 2016
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38. A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta

Author: Knollenberg, J., Lin, Z. Y., Hviid, S. F., Oklay, N., Vincent, J. -B, Bodewits, D., Mottola, S., Pajola, M., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Davidsson, Björn, Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Ip, W. -H, Jorda, L., Keller, H. U., Kuehrt, E., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Thomas, N., Guettler, C., Preusker, F., Scholten, F., Tubiana, C., Knollenberg, J., Lin, Z. Y., Hviid, S. F., Oklay, N., Vincent, J. -B, Bodewits, D., Mottola, S., Pajola, M., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M. F., Barucci, M. A., Bertaux, J. L., Bertini, I., Cremonese, G., Davidsson, Björn, Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P. J., Ip, W. -H, Jorda, L., Keller, H. U., Kuehrt, E., Kramm, J. R., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Thomas, N., Guettler, C., Preusker, F., Scholten, F., and Tubiana, C.
Abstract: Context. On 12 March 2015 the OSIRIS WAC camera onboard the ESA Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed a small outburst originating from the Imhotep region at the foot of the big lobe of the comet. These measurements are unique since it was the first time that the initial phase of a transient outburst event could be directly observed. Aims. We investigate the evolution of the dust jet in order to derive clues about the outburst source mechanism and the ejected dust particles, in particular the dust mass, dust-to-gas ratio and the particle size distribution. Methods. Analysis of the images and of the observation geometry using comet shape models in combination with gasdynamic modeling of the transient dust jet were the main tools used in this study. Synthetic images were computed for comparison with the observations. Results. Analysis of the geometry revealed that the source region was not illuminated until 1.5 h after the event implying true nightside activity was observed. The outburst lasted for less than one hour and the average dust production rate during the initial four minutes was of the order of 1 kg/s. During this time the outburst dust production rate was approximately constant, no sign for an initial explosion could be detected. For dust grains between 0.01-1 mm a power law size distribution characterized by an index of about 2.6 provides the best fit to the observed radiance profiles. The dust-to-gas ratio of the outburst jet is in the range 0.6-1.8.
Published: 2016
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39. Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature

Author: Fornasier, S., Mottola, S., Keller, H. U., Barucci, M. A., Davidsson, B., Feller, C., Deshapriya, J. D. P., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Agarwal, J., Bertaux, J. -L, Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B, Fornasier, S., Mottola, S., Keller, H. U., Barucci, M. A., Davidsson, B., Feller, C., Deshapriya, J. D. P., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Agarwal, J., Bertaux, J. -L, Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B
Abstract: The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 square meters) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color are seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties.
Published: 2016
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40. 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., Lin, Z.-Y., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Barucci, M. A., Bertaux, J.-L., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P. J., Gutiérrez-Marquez, P., Guttler, C., Hofner, S., Hofmann, M., Hu, X., Hviid, S. F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Lowry, S. C., Marzari, F., Masoumzadeh, N., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommero, 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., Lin, Z.-Y., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Barucci, M. A., Bertaux, J.-L., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., Deller, J., De Cecco, M., Frattin, E., El-Maarry, M. R., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P. J., Gutiérrez-Marquez, P., Guttler, C., Hofner, S., Hofmann, M., Hu, X., Hviid, S. F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Lopez Moreno, J. J., Lowry, S. C., Marzari, F., Masoumzadeh, N., Massironi, M., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommero, 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 theWAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 Œºm) 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 ?ó 1013 and 8.5 ?ó 1010 for a = 5 and 50 Œºm, respectively, or an initial mass of H2O ice around 22 kg. ¬© 2016 The Authors.
Published: 2016

41. Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko

Author: Davidsson, B.J.R., Gutierrez, P.J., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Guttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., La Forgia, F., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Naletto, G., Oklay, N., Pajola, M., Snodgrass, C., Thomas, N., Tubiana, C., Vincent, J.-B., Davidsson, B.J.R., Gutierrez, P.J., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Guttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., La Forgia, F., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Naletto, G., Oklay, N., Pajola, M., Snodgrass, C., Thomas, N., Tubiana, C., and Vincent, J.-B.
Abstract: We investigate the dust coma within the Hill sphere of comet 67P/Churyumov-Gerasimenko. We aim to determine osculating orbital elements for individual distinguishable but unresolved slow-moving grains in the vicinity of the nucleus. In addition, we perform photometry and constrain grain sizes. Methods. We performed astrometry and photometry using images acquired by the OSIRIS Wide Angle Camera on the European Space Agency spacecraft Rosetta. Based on these measurements, we employed standard orbit determination and orbit improvement techniques. Results. Orbital elements and effective diameters of four grains were constrained, but we were unable to uniquely determine them. Two of the grains have light curves that indicate grain rotation. Conclusions. The four grains have diameters nominally in the range 0.14-0.50 m. For three of the grains, we found elliptic orbits, which is consistent with a cloud of bound particles around the nucleus. However, hyperbolic escape trajectories cannot be excluded for any of the grains, and for one grain this is the only known option. One grain may have originated from the surface shortly before observation. These results have possible implications for the understanding of the dispersal of the cloud of bound debris around comet nuclei, as well as for understanding the ejection of large grains far from the Sun.
Published: 2015

42. The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos

Author: Patrick Michel, Michael Küppers, Adriano Campo Bagatin, Benoit Carry, Sébastien Charnoz, Julia de Leon, Alan Fitzsimmons, Paulo Gordo, Simon F. Green, Alain Hérique, Martin Juzi, Özgür Karatekin, Tomas Kohout, Monica Lazzarin, Naomi Murdoch, Tatsuaki Okada, Ernesto Palomba, Petr Pravec, Colin Snodgrass, Paolo Tortora, Kleomenis Tsiganis, Stephan Ulamec, Jean-Baptiste Vincent, Kai Wünnemann, Yun Zhang, Sabina D. Raducan, Elisabetta Dotto, Nancy Chabot, Andy F. Cheng, Andy Rivkin, Olivier Barnouin, Carolyn Ernst, Angela Stickle, Derek C. Richardson, Cristina Thomas, Masahiko Arakawa, Hirdy Miyamoto, Akiko Nakamura, Seiji Sugita, Makoto Yoshikawa, Paul Abell, Erik Asphaug, Ronald-Louis Ballouz, William F. Bottke, Dante S. Lauretta, Kevin J. Walsh, Paolo Martino, Ian Carnelli, Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE), Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Astronomía y Astrofísica, Department of Geosciences and Geography, Geology and Geophysics, Department of Physics, Planetary-system research, Michel P., Kuppers M., Bagatin A.C., Carry B., Charnoz S., de Leon J., Fitzsimmons A., Gordo P., Green S.F., Herique A., Juzi M., Karatekin O., Kohout T., Lazzarin M., Murdoch N., Okada T., Palomba E., Pravec P., Snodgrass C., Tortora P., Tsiganis K., Ulamec S., Vincent J.-B., Wunnemann K., Zhang Y., Raducan S.D., Dotto E., Chabot N., Cheng A.F., Rivkin A., Barnouin O., Ernst C., Stickle A., Richardson D.C., Thomas C., Arakawa M., Miyamoto H., Nakamura A., Sugita S., Yoshikawa M., Abell P., Asphaug E., Ballouz R.-L., Bottke W.F., Lauretta D.S., Walsh K.J., Martino P., and Carnelli I.
Subjects: 1171 Geosciences, Asteroid surfaces, Impact phenomena, Impact phenomena (779), Mission, Near-Earth objects, 114 Physical sciences, Asteroid dynamic, Autre, Asteroid satellites, Earth and Planetary Sciences (miscellaneous), Binary, Near-Earth objects (1092), Near-Earth object, 520 Astronomy, Asteroid dynamics, Asteroid, Astronomy and Astrophysics, 620 Engineering, 115 Astronomy, Space science, Asteroid satellites (2207), Asteroid satellite, Asteroid surfaces (2209), Geophysics, Space and Planetary Science, Asteroid dynamics (2210), Planetary defense
Abstract: Funding Information: To achieve these objectives, Milani is carrying two scientific payloads, the ASPECT visual and near-infrared (Vis-NIR) imaging spectrometer and the VISTA thermogravimeter aimed at collecting and characterizing volatiles and dust particles below 10 μm. Additionally, navigation payloads include a visible navigation camera and lidar. The Milani consortium is composed of entities and institutions from Italy, the Czech Republic, and Finland. The consortium Prime is Tyvak International, responsible for the whole program management and platform design, development, integration, testing, and final delivery to the customer. Politecnico di Torino is tasked with defining requirements and performing thermal, radiation, and debris analysis. Politecnico di Milano is responsible for mission analysis and GNC. Altec will support the Ground Segment architecture and interface definition. Centro Italiano per la Ricerca Aerospaziale (CIRA) is responsible for the execution of the vehicle environmental campaign. HULD contributes to developing the mission-specific software. VTT is the main payload (ASPECT hyperspectral imager) provider and is supported by the following entities dealing with ASPECT-related development: University of Helsinki (ASPECT calibration); Reaktor Space Lab (ASPECT Data Processing Unit development), Institute of Geology of the Czech Academy of Sciences (ASPECT scientific algorithms requirements and testing); and Brno University of Technology (ASPECT scientific algorithms development). INAF-IAPS is the secondary Payload (VISTA, dust detector) provider. Funding Information: The Mission PI is appointed by ESA and is the primary interface to ESA. The Hera SMB consists of the ESA Hera Project Scientist (ESA PS), the Mission PI, and the Hera Advisory Board, consisting of four mission advisors. The Mission PI chairs the HIT and is supported by the Hera Advisory Board. The tasks of the Hera SMB are 1. advising the Hera mission project team on all aspects related to the Hera mission objectives; 2. ensuring that the WGs’ activities cover the needs of the Hera mission; 3. providing recommendations to ESA concerning the membership in the HIT; and 4. implementing the Publication Policy. Funding Information: Hera is the ESA contribution to the AIDA collaboration. Hera, Juventas, Milani, and their instruments are developed under ESA contract supported by national agencies. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP), the CNRS through the MITI interdisciplinary programs, ASI, CNES, JAXA, the Academy of Finland project no. 335595, and was conducted with institutional support RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences. M.L., E.P., P.T .and E.D. are grateful to the Italian Space Agency (ASI) for financial support through Agreement No. 2022-8-HH.0 in the context of ESA’s Hera mission. We are grateful to the whole Hera team, including Working Group core members and other contributors for their continuous efforts and support. Their names can be found on the following website: https:// www.heramission.space/team. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society. Hera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science.
Published: 2022

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