Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images

M.R. El-Maarry (1) , Nicholas Thomas (1) , L. Giacomini (2) , M. Massironi (2) , M. Pajola (3) , R. Marschall (1) , A. Gracia-Berná (1) , H. Sierks (4) , C. Barbieri (5) , Philippe L. Lamy (6) , R. Rodrigo (7, 8) , H. Rickman (9, 10) , Detlef Koschny (11) , H. U. Keller (12) , J. Agarwal (4) , Michael F. A'Hearn (13) , A-T. Auger (6) , Maria A. Barucci (14) , Jean-Loup Bertaux (15) , I. Bertini (3) , S. Besse (11) , Dennis Bodewits (13) , Gabriele Cremonese (16) , V. da Deppo (17) , B. Davidsson (9) , M. de Cecco (18) , S. Debei (19) , Carsten Güttler (4) , Sonia Fornasier (14, 20) , M. Fulle (21) , Olivier Groussin (6) , Pedro J. Gutiérrez (22) , S. F. Hviid (23) , W-H. Ip (24) , Laurent Jorda (6) , Jörg Knollenberg (23) , G. Kovacs (4) , J.-R. Kramm (4) , Ekkehard Kührt (23) , M. Küppers (25) , Florangela La Forgia (16) , Luisa M. Lara (22) , M. Lazzarin (5) , José J. Lopez Moreno (22) , S. Marchi (26) , F. Marzari (5) , H. Michalik (27) , Giampiero Naletto (28) , Nilda Oklay (4) , A. Pommerol (1) , F. Preusker (23) , F. Scholten (23) , Cécilia Tubiana (4) , Jean-Baptiste Vincent (4)

1 Physikalisches Institut [Bern]
2 Dipartimento di Geoscienze [Padova]
3 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
4 MPS - Max-Planck-Institut für Sonnensystemforschung
5 Dipartimento di Fisica e Astronomia "Galileo Galilei"
6 LAM - Laboratoire d'Astrophysique de Marseille
7 CAB - Centro de Astrobiologia [Madrid]
8 ISSI - International Space Science Institute [Bern]
9 Department of Physics and Astronomy [Uppsala]
10 CBK - Space Research Centre of Polish Academy of Sciences
11 RSSD - Research and Scientific Support Department, ESTEC
12 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
13 Department of Astronomy [College Park]
14 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
15 PLANETO - LATMOS
16 OAPD - INAF - Osservatorio Astronomico di Padova
17 IFN - CNR Institute for Photonics and Nanotechnologies
18 University of Trento [Trento]
19 Department of Industrial Engineering [Padova]
20 UPD7 - Université Paris Diderot - Paris 7
21 OAT - INAF - Osservatorio Astronomico di Trieste
22 IAA - Instituto de Astrofísica de Andalucía
23 DLR Institute of Planetary Research
24 Institute of Space Science [Taiwan]
25 Operations Department (ESAC)
26 SSERVI - Solar System Exploration Research Virtual Institute
27 Institut für Datentechnik und Kommunikationsnetze
28 DEI - Department of Information Engineering [Padova]

The OSIRIS camera onboard the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P/C-G)’s nucleus at spatial resolutions down to ~0.17 m/px ever since Aug 2014. These images have yielded unprecedented insight into the morphological diversity of the comet’s surface. This paper presents an overview of the regional morphology of comet 67P/C-G. Methods. We used the images that were acquired at orbits ~20–30 km from the center of the comet to distinguish different regions on the surface and introduce the basic regional nomenclature adopted by all papers in this issue that address the comet’s morphology and surface processes. We used anaglyphs to detect subtle regional and topographical boundaries and images from close orbit (~10 km from the comet’s center) to investigate the fine texture of the surface. Results. Nineteen regions have currently been defined on the nucleus based on morphological and/or structural boundaries, and they can be grouped into distinctive region types. Consolidated, fractured regions are the most common region type. Some of these regions enclose smooth units that appear to settle in gravitational sinks or topographically low areas. Both comet lobes have a significant portion of their surface covered by a dusty coating that appears to be recently placed and shows signs of mobilization by aeolian- like processes. The dusty coatings cover most of the regions on the surface but are notably absent from a couple of irregular large depressions that show sharp contacts with their surroundings and talus-like deposits in their interiors, which suggests that short- term explosive activity may play a significant role in shaping the comet’s surface in addition to long-term sublimation loss. Finally, the presence of layered brittle units showing signs of mechanical failure predominantly in one of the comet’s lobes can indicate a compositional heterogeneity between the two lobes.

Keywords: 67P/Churyumov-Gerasimenko; observational method; comets

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]; Earth and Planetary Astrophysics [astro-ph.EP]

M.R. El-Maarry, Nicholas Thomas, L. Giacomini, M. Massironi, M. Pajola, et al.. Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images. Astronomy and Astrophysics - A&A, 2015, 583, A26 (28 p.). ⟨10.1051/0004-6361/201525723⟩. ⟨insu-01205653⟩