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

Auger, A.-T. and Groussin, O. and Jorda, L. and El-Maarry, Mohamed Ramy and Bouley, S. and Séjourné, A. and Gaskell, R. and Capanna, C. and Davidsson, B. and Marchi, S. and Höfner, S. and Lamy, P.L. and Sierks, H. and Barbieri, C. and Rodrigo, R. and Koschny, D. and Rickman, H. and Keller, H.U. and Agarwal, J. and A’Hearn, M.F. and Barucci, M.A. and Bertaux, J.-L. and Bertini, I. and Cremonese, G. and Da Deppo, V. and Debei, S. and De Cecco, M. and Fornasier, S. and Fulle, M. and Gutiérrez, P.J. and Güttler, C. and Hviid, S. and Ip, W.-H. and Knollenberg, J. and Kramm, J.-R. and Kührt, E. and Küppers, M. and Lara, L.M. and Lazzarin, M. and Lopez Moreno, J.J. and Marzari, F. and Massironi, M. and Michalik, H. and Naletto, G. and Oklay, N. and Pommerol, A. and Sabau, L. and Thomas, N. and Tubiana, C. and Vincent, J.-B. and Wenzel, K.-P. (2018) Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko. Icarus 301 , pp. 173-188. ISSN 0019-1035.

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Official URL: https://doi.org/10.1016/j.icarus.2017.09.037

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.

Metadata

Item Type:	Article
Keyword(s) / Subject(s):	Comets, Nucleus, Geological processes
School:	Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
Depositing User:	Administrator
Date Deposited:	17 Oct 2018 15:39
Last Modified:	02 Aug 2023 17:45
URI:	https://eprints.bbk.ac.uk/id/eprint/24730

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