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    OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

    Pommerol, A. and Thomas, N. and El-Maarry, Mohamed Ramy and Pajola, M. and Groussin, O. and Auger, A.-T. and Oklay, N. and Fornasier, S. and Feller, C. and Davidsson, B. and Gracia-Berná, A. and Jost, B. and Marschall, R. and Poch, O. and Barucci, M.A. and Bertaux, J.-L. and La Forgia, F. and Keller, H.U. and Kührt, E. and Lowry, S.C. and Mottola, S. and Naletto, G. and Sierks, H. and Barbieri, C. and Lamy, P.L. and Rodrigo, R. and Koschny, D. and Rickman, H. and Agarwal, J. and A’Hearn, M.F. and Bertini, I. and Boudreault, S. and Cremonese, G. and Da Deppo, V. and De Cecco, M. and Debei, S. and Güttler, C. and Fulle, M. and Gutierrez, P.J. and Hviid, S.F. and Ip, W.-H. and Jorda, L. and Knollenberg, J. and Kovacs, G. and Kramm, J.-R. and Küppers, E. and Lara, L. and Lazzarin, M. and Lopez Moreno, J.L. and Marzari, F. and Michalik, H. and Preusker, F. and Scholten, F. and Tubiana, C. and Vincent, J.-B. (2015) OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments. Astronomy & Astrophysics 583 , A25. ISSN 0004-6361.

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    Abstract

    Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): comets: general / techniques: image processing / methods: laboratory: solid state
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 20 Nov 2018 14:13
    Last Modified: 20 Nov 2018 14:13
    URI: http://eprints.bbk.ac.uk/id/eprint/25200

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