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

Xian Shi (1) , Xuanyu Hu (1) , Sefano Mottola (2) , Holger Sierks (1) , Horst Uwe 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 L. 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 F. 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 J. Lopez-Moreno (19) , Francesco Marzari (9) , Giampiero Naletto (22, 9, 23) , Nilda Oklay (2) , Imre Toth (24) , Jean-Baptiste Vincent (2)

1 MPS - Max-Planck-Institut für Sonnensystemforschung
2 DLR Institut für Planetenforschung
3 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
4 PI-DSMC software package
5 OAT - INAF - Osservatorio Astronomico di Trieste
6 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
7 ARC - NASA Ames Research Center
8 Department of Astronomy [College Park]
9 Dipartimento di Fisica e Astronomia "Galileo Galilei"
10 PLANETO - LATMOS
11 CAB - Centro de Astrobiologia [Madrid]
12 ISSI - International Space Science Institute [Bern]
13 ESTEC - European Space Research and Technology Centre
14 IFN - CNR Institute for Photonics and Nanotechnologies
15 JPL - Jet Propulsion Laboratory
16 Department of Industrial Engineering [Padova]
17 University of Trento [Trento]
18 LAM - Laboratoire d'Astrophysique de Marseille
19 IAA - Instituto de Astrofísica de Andalucía
20 IANCU - Institute of Astronomy [Taiwan]
21 ESAC - European Space Astronomy Centre
22 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
23 POLIMI - Dipartimento di Fisica [Politecnico Milano]
24 Konkoly Observatory

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.

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Xian Shi, Xuanyu Hu, Sefano Mottola, Holger Sierks, Horst Uwe Keller, et al.. Coma morphology of comet 67P controlled by insolation over irregular nucleus. Nature Astronomy, 2018, 2, pp.562-567. ⟨10.1038/s41550-018-0481-5⟩. ⟨insu-01806355⟩