OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments
Journal
Date Issued
2015
Author(s)
Pommerol, A.
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Thomas, N.
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El-Maarry, M. R.
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•
Groussin, O.
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Auger, A. -T.
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Oklay, N.
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Fornasier, S.
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Feller, C.
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Davidsson, B.
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Gracia-Berná, A.
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Jost, B.
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Marschall, R.
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Poch, O.
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Barucci, M. A.
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Bertaux, J. -L.
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La Forgia, F.
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Keller, H. U.
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Kührt, E.
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Lowry, S. C.
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Mottola, S.
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Naletto, G.
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Sierks, H.
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Barbieri, C.
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Lamy, P. L.
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Rodrigo, R.
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Koschny, D.
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Rickman, H.
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Agarwal, J.
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A'Hearn, M. F.
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Bertini, I.
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Boudreault, S.
•
•
Da Deppo, V.
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De Cecco, M.
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Debei, S.
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Güttler, C.
•
•
Gutierrez, P. J.
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Hviid, S. F.
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Ip, W. -H.
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Jorda, L.
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Knollenberg, J.
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Kovacs, G.
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Kramm, J. -R.
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Küppers, E.
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Lara, L.
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Lazzarin, M.
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Lopez Moreno, J. L.
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Marzari, F.
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Michalik, H.
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Preusker, F.
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Scholten, F.
•
•
Vincent, J. -B.
Description
OSIRIS was built by a consortium of the Max-Planck-Institut für Sonnensystemforschung, in Göttingen, Germany, CISAS-University of Padova, Italy, the Laboratoire d’Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Research and Scientific Support Department of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politećhnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the ESA teams at ESAC, ESOC and ESTEC for their work in support of the Rosetta mission. We acknowledge an anonymous referee for a detailed and constructive review.
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.
Volume
583
Start page
A25
Issn Identifier
0004-6361
Ads BibCode
2015A&A...583A..25P
Rights
open.access
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