OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments
Year: 2015
Type: article
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.
Source: Astronomy and Astrophysics
Authors: A. Pommerol, N. Thomas, M. R. El-Maarry, M. Pajola, O. Groussin, A.-T. Auger, N. Oklay, S. Fornasier, C. Feller, B. Davidsson, A. Gracia-Berná, B. Jost, R. Marschall, O. Poch, M. A. Barucci, J.-L. Bertaux, F. La Forgia, H. U. Keller, E. Kührt, S. C. Lowry, S. Mottola, G. Naletto, H. Sierks, C. Barbieri, P. L. Lamy, R. Rodrigo, D. Koschny, H. Rickman, J. Agarwal, M. F. A’Hearn, I. Bertini, S. Boudreault, G. Cremonese, V. Da Deppo, M. De Cecco, S. Debei, C. Güttler, M. Fulle, P. J. Gutierrez, S. F. Hviid, W.-H. Ip, L. Jorda, J. Knollenberg, G. Kovacs, J.-R. Kramm, E. Küppers, L. Lara, M. Lazzarin, J. L. Lopez Moreno, F. Marzari, H. Michalik, F. Preusker, F. Scholten, C. Tubiana, J.-B. Vincent
Institutions: University of Bern, University of Padua, Centre National de la Recherche Scientifique, Aix-Marseille Université, Laboratoire d’Astrophysique de Marseille, Max Planck Institute for Solar System Research, Laboratoire d’études spatiales et d’instrumentation en astrophysique, Université Paris Diderot, Uppsala University, Université de Versailles Saint-Quentin-en-Yvelines, Institut Pierre-Simon Laplace, Laboratoire atmosphères, milieux, observations spatiales, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), Technische Universität Braunschweig, University of Kent, Consejo Superior de Investigaciones Científicas, Centro de Astrobiología, International Space Science Institute, European Space Agency, Centrum Badań Kosmicznych, University of Maryland, College Park, Osservatorio Astronomico di Padova, National Institute for Astrophysics, University of Trento, Trieste Astronomical Observatory, National Central University, European Space Astronomy Centre, Instituto de Astrofísica de Andalucía
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1848572254