5 results on '"Michalik , H."'
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2. A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2
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Snodgrass, C., Tubiana, C., Vincent, J.-B., Sierks, H., Hviid, S., Moissl, R., Boehnhardt, H., Barbieri, C., Koschny, D., Lamy, P., Rickman, H., Rodrigo, R., Carry, B., Lowry, S.C., Laird, R.J.M., Weissman, P.R., Fitzsimmons, A., Marchi, S., A'Hearn, M., Angrilli, F., Barucci, A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fornasier, S., Gutiérrez, P., Ip, W.-H., Keller, H.U., Knollenberg, J., Kramm, J.R., Kuehrt, E., Kueppers, M., Lara, L.M., Lazzarin, M., López-Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., Wenzel, K.P., Snodgrass, C., Tubiana, C., Vincent, J.-B., Sierks, H., Hviid, S., Moissl, R., Boehnhardt, H., Barbieri, C., Koschny, D., Lamy, P., Rickman, H., Rodrigo, R., Carry, B., Lowry, S.C., Laird, R.J.M., Weissman, P.R., Fitzsimmons, A., Marchi, S., A'Hearn, M., Angrilli, F., Barucci, A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fornasier, S., Gutiérrez, P., Ip, W.-H., Keller, H.U., Knollenberg, J., Kramm, J.R., Kuehrt, E., Kueppers, M., Lara, L.M., Lazzarin, M., López-Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., and Wenzel, K.P.
- Abstract
The peculiar object P/2010 A2 was discovered1 in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized2 class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010 A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results3. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009. © 2010 Macmillan Publishers Limited. All rights reserved.
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- 2010
3. The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse
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Michalik, H., Simioni, E., Koschny, D., De Cecco, M., Deller, J., Gutierrez, P., Rodrigo, Rafael, Naletto, G., Feller, C., Lamy, P., Groussin, O., Mottola, S., Jorda, L., Ferrari, S., Toth, I., Knollenberg, J., Besse, S., Agarwal, J., Lowry, S., Preusker, F., Da Deppo, V., Thomas, Nicolas, Davidsson, B., Boudreault, S., A’Hearn, M. F., Küppers, M., Ferri, F., Elmaarry, Mohamed Ramy, Hasselmann, P. H., Massironi, M., Hofmann, M., Hviid, S. F., Baratti, E., Tubiana, C., Scholten, F., Fulle, M., Lucchetti, A., Rickman, H., Güttler, C., Höfner, S., Debei, S., Lin, Z.-Y., Keller, H. U., Lopez Moreno, J. J., Kovacs, G., Deshapriya, J. D. P., Lara, L. M., Bertini, I., Sierks, H., Kramm, J. R., Pommerol, Antoine, Pajola, M., Fornasier, S., Barbieri, C., Marzari, F., Oklay, N., Bertaux, J.-L., Penasa, L., Vincent, J. B., Cremonese, G., Lazzarin, M., Kührt, E., Ip, W.-H., and Barucci, M. A.
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13. Climate action ,520 Astronomy ,620 Engineering - 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 is still poorly understood. Landslides have been invoked to explain some outbursts on comet 103P/Hartley 2 [6], 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/Churyumov-Gerasimenko, which were attributed to dust generated by 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 dustplume formation mechanism that does not necessarily require the breakup of pressurised crust or the presence of super volatile material, as suggested by previous studies [7]. Moreover, the collapse revealed the fresh icy interior of the comet, which is characterised by an albedo > 0.4, and provided the opportunity to study how the crumbling wall settled down forming a new talus.
4. Two independent and primitive envelopes of the bilobate nucleus of comet 67P.
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Massironi M, Simioni E, Marzari F, Cremonese G, Giacomini L, Pajola M, Jorda L, Naletto G, Lowry S, El-Maarry MR, Preusker F, Scholten F, Sierks H, Barbieri C, Lamy P, Rodrigo R, Koschny D, Rickman H, Keller HU, A'Hearn MF, Agarwal J, Auger AT, Barucci MA, Bertaux JL, Bertini I, Besse S, Bodewits D, Capanna C, Da Deppo V, Davidsson B, Debei S, De Cecco M, Ferri F, Fornasier S, Fulle M, Gaskell R, Groussin O, Gutiérrez PJ, Güttler C, Hviid SF, Ip WH, Knollenberg J, Kovacs G, Kramm R, Kührt E, Küppers M, La Forgia F, Lara LM, Lazzarin M, Lin ZY, Lopez Moreno JJ, Magrin S, Michalik H, Mottola S, Oklay N, Pommerol A, Thomas N, Tubiana C, and Vincent JB
- Abstract
The factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with 'onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently.
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- 2015
- Full Text
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5. Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse.
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Vincent JB, Bodewits D, Besse S, Sierks H, Barbieri C, Lamy P, Rodrigo R, Koschny D, Rickman H, Keller HU, Agarwal J, A'Hearn MF, Auger AT, Barucci MA, Bertaux JL, Bertini I, Capanna C, Cremonese G, Da Deppo V, Davidsson B, Debei S, De Cecco M, El-Maarry MR, Ferri F, Fornasier S, Fulle M, Gaskell R, Giacomini L, Groussin O, Guilbert-Lepoutre A, Gutierrez-Marques P, Gutiérrez PJ, Güttler C, Hoekzema N, Höfner S, Hviid SF, Ip WH, Jorda L, Knollenberg J, Kovacs G, Kramm R, Kührt E, Küppers M, La Forgia F, Lara LM, Lazzarin M, Lee V, Leyrat C, Lin ZY, Lopez Moreno JJ, Lowry S, Magrin S, Maquet L, Marchi S, Marzari F, Massironi M, Michalik H, Moissl R, Mottola S, Naletto G, Oklay N, Pajola M, Preusker F, Scholten F, Thomas N, Toth I, and Tubiana C
- Abstract
Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface.
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- 2015
- Full Text
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