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Seasonal Mass Transfer on the Nucleus of Comet 67P/Chuyumov-Gerasimenko

Horst Uwe Keller 1, 2 Stefano Mottola 1 Stubbe F. Hviid 1 Jessica Agarwal 3 Ekkehard Kührt 1 Yuri Skorov 2 Katharina Otto 1 Jean-Baptiste Vincent 1 Nilda Oklay 1 Stephan E. Schröder 1 Björn Davidsson 4 Maurizio Pajola 5, 6 Xian Shi 3 Dennis Bodewits 7 Imre Toth 8 Frank Preusker 1 Frank Scholten 1 Holger Sierks 3 Cesare Barbieri 9 Philippe Lamy 10 Rafael Rodrigo 11, 12 Detlef Koschny 13 Hans Rickman 4, 14 Michael F. A'Hearn 7 Maria Antonella Barucci 15 Jean-Loup Bertaux 16 Ivano Bertini 6 Gabriele Cremonese 17 Vania da Deppo 18 Stefano Debei 19 Mariolino de Cecco 20 Jakob Deller 3 Sonia Fornasier 15 Marco Fulle 17 Olivier Groussin 10 Pedro J. Gutiérrez 21 Carsten Güttler 3 Marc Hofmann 3 Wing-Huen Ip 22 Laurent Jorda 10 Jörg Knollenberg 1 Jörg Rainer Kramm 3 Michael Küppers 23 Luisa M. Lara 21 Monica Lazzarin 9 José J. Lopez Moreno 21 Francesco Marzari 9 Giampiero Naletto 24, 6, 18 Cécilia Tubiana 3 Ncolas Thomas 25, 26 
Abstract : We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov-Gerasimenko. The obliquity of the rotation axis of 67P causes strong seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an anti-solar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of travel time. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO2 or CO. This causes a north-south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are ‘shock frozen’ and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, i. e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements.
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Horst Uwe Keller, Stefano Mottola, Stubbe F. Hviid, Jessica Agarwal, Ekkehard Kührt, et al.. Seasonal Mass Transfer on the Nucleus of Comet 67P/Chuyumov-Gerasimenko. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2017, 469 (Suppl_2), pp.S357-S371. ⟨10.1093/mnras/stx1726⟩. ⟨insu-01574799⟩



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