Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko

Anne-Thérèse Auger 1, 2 Olivier Groussin 1 Laurent Jorda 3 Mohamed Ramy El-Maarry 4 Sylvain Bouley 2, 5 Antoine Séjourné 2 Robert Gaskell 6 Claire Capanna 1 Björn Davidsson 7 Simone Marchi 8 Sebastian Höfner 9 Philippe Lamy 1 Holger Sierks 9 Cesare Barbieri 10 Rafael Rodrigo 11, 12 Detlef Koschny 13 Hans Rickman 14, 7 Horst Uwe Keller 15 Jessica Agarwal 9 Michael F. A'Hearn 16 Maria Antonella Barucci 17 Jean-Loup Bertaux 18 Ivano Bertini 19 Gabriele Cremonese 20 Vania Da Deppo 21 Stefano Debei 20 Mariolino De Cecco 22 Sonia Fornasier 17 Marco Fulle 23 Pedro J. Gutierrez 24 Carsten Güttler 9 Stubbe Hviid 25 Wing-Huen Ip 26 Jörg Knollenberg 27 Jörg-Rainer Kramm 9 Ekkerhard Kührt 25 Michael Küppers 28 Luisa-Maria Lara 24 Monica Lazzarin 10 Josè J. Lopez-Moreno 24 Francesco Marzari 10 Matteo Massironi 19, 29 Harald Michalik 30 Giampiero Naletto 19, 21, 31 Nilda Oklay 27 Antoine Pommerol 4 Lola Sabau 32 Nicolas Thomas 4 Cécilia Tubiana 9 Jean-Baptiste Vincent 9 Klaus-Peter Wenzel 33
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (from North to South) and longitudes (head, neck, and body), sometimes on pit walls or following lineaments. About 1.5% of the observed surface is covered by polygons. Polygons have an homogeneous size across the nucleus, with 90% of them in the size range 1 – 5 m and a mean size of 3.0 ± 1.4 m. They show different morphologies, depending on the width and depth of their trough. They are found in networks with 3- or 4-crack intersection nodes. The polygons observed on 67P are consistent with thermal contraction crack polygons formed by the diurnal or seasonal temperature variations in a hard (MPa) and consolidated sintered layer of water ice, located a few centimeters below the surface. Our thermal analysis shows an evolution of thermal contraction crack polygons according to the local thermal environment, with more evolved polygons (i.e. deeper and larger troughs) where the temperature and the diurnal and seasonal temperature range are the highest. Thermal contraction crack polygons are young surface morphologies that probably formed after the injection of 67P in the inner solar system, typically 100 000 years ago, and could be as young as a few orbital periods, following the decreasing of its perihelion distance in 1959 from 2.7 to 1.3 a.u. Meter scale thermal contraction crack polygons should be common features on the nucleus of Jupiter family comets.
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Soumis le : mercredi 4 octobre 2017 - 15:22:07
Dernière modification le : lundi 22 janvier 2018 - 10:50:03



Anne-Thérèse Auger, Olivier Groussin, Laurent Jorda, Mohamed Ramy El-Maarry, Sylvain Bouley, et al.. Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko. Icarus, Elsevier, 2018, (in press). 〈10.1016/j.icarus.2017.09.037〉. 〈insu-01610197〉



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