Coma morphology of comet 67P controlled by insolation over irregular nucleus

Xian Shi 1 Xuanyu Hu 1 Sefano Mottola 2 Holger Sierks 1 Horst Keller 3, 2 Martin Rose 4 Carsten Guttler 1 Marco Fulle 5 Sonia Fornasier 6 Jessica Agarwal 1 Maurizio Pajola 7 Cécilia Tubiana 1 Dennis Bodewits 8 Cesare Barbieri 9 Philippe Lamy 10 Rafael Rodrigo 11, 12 Detlef Koschny 13 Maria Antonella Barucci 6 Jean-Loup Bertaux 10 Ivano Bertini 9 S. Boudreault 1 Gabriele Cremonese 5 Vania Da deppo 14 Björn Davidsson 15 Stefano Debei 16 Mariolino de Cecco 17 Jakob Deller 1 Olivier Groussin 18 Pedro J. Gutiérrez 19 Stubbe Hviid 2 Wing-Huen Ip 20 Laurent Jorda 18 Jörg Knollenberg 2 Gabor Kovacs 1 J.-Rainer Kramm 1 Ekkehard Kührt 2 Michael Küppers 21 Luisa-Maria Lara 19 Monica Lazzarin 9 Josè Lopez-Moreno 19 Francesco Marzari 9 Giampiero Naletto 22, 9, 23 Nilda Oklay 2 Imre Toth 24 Jean-Baptiste Vincent 2
Abstract : While the structural complexity of cometary comae is already recognizable from telescopic observations1, the innermost region, within a few radii of the nucleus, was not resolved until spacecraft exploration became a reality2,3. The dust coma displays jet-like features of enhanced brightness superposed on a diffuse background1,4,5. Some features can be traced to specific areas on the nucleus, and result conceivably from locally enhanced outgassing and/or dust emission6-8. However, diffuse or even uniform activity over topographic concavity can converge to produce jet-like features9,10. Therefore, linking observed coma morphology to the distribution of activity on the nucleus is difficult11,12. Here, we study the emergence of dust activity at sunrise on comet 67P/Churyumov-Gerasimenko using high-resolution, stereo images from the OSIRIS camera onboard the Rosetta spacecraft, where the sources and formation of the jet-like features are resolved. We perform numerical simulations to show that the ambient dust coma is driven by pervasive but non-uniform water outgassing from the homogeneous surface layer. Physical collimations of gas and dust flows occur at local maxima of insolation and also via topographic focusing. Coma structures are projected to exhibit jet-like features that vary with the perspective of the observer. For an irregular comet such as 67P/Churyumov-Gerasimenko, near-nucleus coma structures can be concealed in the shadow of the nucleus, which further complicates the picture.
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Xian Shi, Xuanyu Hu, Sefano Mottola, Holger Sierks, Horst Keller, et al.. Coma morphology of comet 67P controlled by insolation over irregular nucleus. Nature Astronomy, Nature Publishing Group, 2018, 2, pp.562-567. ⟨10.1038/s41550-018-0481-5⟩. ⟨insu-01806355⟩

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