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

    Groussin, O. and Jorda, L. and Auger, A.-T. and Kührt, E. and Gaskell, R. and Capanna, C. and Scholten, F. and Preusker, F. and Lamy, P. and Hviid, S. and Knollenberg, J. and Keller, U. and Huettig, C. and Sierks, H. and Barbieri, C. and Rodrigo, R. and Koschny, D. and Rickman, H. and A’Hearn, M.F. and Agarwal, J. and Barucci, M.A. and Bertaux, J.-L. and Bertini, I. and Boudreault, S. and Cremonese, G. and Da Deppo, V. and Davidsson, B. and Debei, S. and De Cecco, M. and El-Maarry, Mohamed Ramy and Fornasier, S. and Fulle, M. and Gutiérrez, P.J. and Güttler, C. and Ip, W.-H and Kramm, J.-R. and Küppers, M. and Lazzarin, M. and Lara, L.M. and Lopez Moreno, J.J. and Marchi, S. and Marzari, F. and Massironi, M. and Michalik, H. and Naletto, G. and Oklay, N. and Pommerol, A. and Pajola, M. and Thomas, N. and Toth, I. and Tubiana, C. and Vincent, J.-B. (2015) Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations. Astronomy & Astrophysics 583 , A32. ISSN 0004-6361.

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    Abstract

    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.

    Metadata

    Item Type: Article
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 20 Nov 2018 14:04
    Last Modified: 20 Nov 2018 14:04
    URI: http://eprints.bbk.ac.uk/id/eprint/25196

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