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Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

Sebastien Höfner 1, 2 Jean-Baptiste Vincent 1 Jürgen Blum 2 Björn J. R. Davidsson 3, 4 Holger Sierks 1 Mohamed Ramy El-Maarry 5 Jakob Deller 1 Marc Hofmann 1 Xuan Hu 1, 2 Maurizio Pajola 6, 7 Cesare Barbieri 7 Philippe Lamy 8 Rafael Rodrigo 9, 10 Detlief Koschny 11 Hans Rickman 12 Horst Uwe Keller 2 Michael A’hearn 1, 13, 14 Anne-Thérèse Auger 8 Maria Antonella Barucci 15 Jean-Loup Bertaux 16 Ivano Bertini 7 Dennis Bodewits 13 Gabriele Cremonese 7 Vania da Deppo 7 Stefano Debei 7 Mariolino de Cecco 7 Sonia Fornasier 15 Marco Fulle 17 Adeline Gicquel 1 O. Groussin 8 Pedro J. Gutierrez 18 Pablo Gutiérrez-Marqués 1 Carsten Güttler 1 Stubbe F. Hviid 19 Wing-Huen Ip 20 Laurent Jorda 8 Jörg Knollenberg 19 Gabor Kovacs 1, 21 Jörg Rainer Kramm 1 Ekkehard Kührt 19 Michael Küppers 22 Florangela La Forgia 7 Monica Lazzarin 7 José J. Lopez-Moreno 18 Francesco Marzari 7 Harald Michalik 2 R. Moissl-Fraund 7 Fernando Moreno 18 Stefano Mottola 19 Giampiero Naletto 6, 7, 23 Nilda Oklay 1 Frank Preusker 19 Frank Scholten 19 Xian Shi 1 Nicolas Thomas 5 Imre Toth 8, 24 Cécilia Tubiana 1 S. Zitzmann 1
Abstract : Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain. Aims. Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods. Methods. We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain. Results. Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P. Conclusions. At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.
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Sebastien Höfner, Jean-Baptiste Vincent, Jürgen Blum, Björn J. R. Davidsson, Holger Sierks, et al.. Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko. Astronomy and Astrophysics - A&A, EDP Sciences, 2017, 608, pp.A121. ⟨10.1051/0004-6361/201628726⟩. ⟨obspm-02190984⟩

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