Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

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题名:	Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations
作者:	葉永烜;Groussin, O.;Jorda, L.;Auger, A.-T.;Kührt, E.;Gaskell, R.;Capanna, C.;Scholten, F.;Preusker, F.;Lamy, P.;Hviid, S.;Knollenberg, J.;Keller, U.;Huettig, C.;Sierks, H.;Barbieri, C.;Rodrigo, R.;Koschny, D.;Rickman, H.;A’Hearn, M. F.;Agarwal, J.;Barucci, M. A.;Bertaux, J.-L.;Bertini, I.;Boudreault, S.;Cremonese, G.;Da Deppo, V.;Davidsson, B.;Debei, S.;De Cecco, M.;El-Maarry, M. R.;Fornasier, S.;Fulle, M.;Gutiérrez, P. J.;Güttler, C.;Ip, W.-H;Kramm, J.-R.;Küppers, M.;Lazzarin, M.;Lara, L. M.;Lopez Moreno, J. J.;Marchi, S.;Marzari, F.;Massironi, M.;Michalik, H.;Naletto, G.;Oklay, N.;Pommerol, A.;Pajola, M.;Thomas, N.;Toth, I.;Tubiana, C.;Vincent, J.-B.
贡献者:	理學院天文研究所
关键词:	accretion;accretion disks;Astrophysics;Comet nuclei;Comets;comets: general;comets: individual: 67P/Churyumov-Gerasimenko;Compressive strength;Computation;Earth and Planetary Astrophysics;Formations;Gravitation;methods: data analysis;Morphology;Sciences of the Universe;Slopes
日期:	2015-11-01
上传时间:	2026-04-21 14:40:16 (UTC+8)
出版者:	EDP Sciences
摘要:	摘要： Aims. We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material (tensile, shear, and compressive strengths). Methods. We computed the gravitational slopes for five regions on the nucleus that are representative of the different morphologies observed on the surface (Imhotep, Ash, Seth, Hathor, and Agilkia), using two shape models computed from OSIRIS images by the stereo-photoclinometry (SPC) and stereo-photogrammetry (SPG) techniques. We estimated the tensile, shear, and compressive strengths using different surface morphologies (overhangs, collapsed structures, boulders, cliffs, and Philae’s footprint) and mechanical considerations. Results. The different regions show a similar general pattern in terms of the relation between gravitational slopes and terrain morphology: i) low-slope terrains (0−20°) are covered by a fine material and contain a few large (>10 m) and isolated boulders; ii) intermediate-slope terrains (20−45°) are mainly fallen consolidated materials and debris fields, with numerous intermediate-size boulders from <1 m to 10 m for the majority of them; and iii) high-slope terrains (45−90°) are cliffs that expose a consolidated material and do not show boulders or fine materials. The best range for the tensile strength of overhangs is 3−15 Pa (upper limit of 150 Pa), 4−30 Pa for the shear strength of fine surface materials and boulders, and 30−150 Pa for the compressive strength of overhangs (upper limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P and weak rocks on Earth. As a result of the low compressive strength, the interior of the nucleus may have been compressed sufficiently to initiate diagenesis, which could have contributed to the formation of layers. Our value for the tensile strength is comparable to that of dust aggregates formed by gravitational instability and tends to favor a formation of comets by the accrection of pebbles at low velocities. 出版者： EDP Sciences 出版日期： 2015-11-01 出處： Astronomy & Astrophysics, 2015-11, Vol.583, p.A32- 資源來源： EDP Sciences 版權： CC0 1.0 - Universal 識別號： ISSN: 0004-6361 識別號： ISSN: 1432-0746 識別號： EISSN: 1432-0746 識別號： DOI: 10.1051/0004-6361/201526379
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