Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere

M. R. El-Maarry (1) , N. Thomas (1) , A. Gracia-Berná (1) , M. Pajola (2) , J. -C. Lee (3) , M. Massironi (4) , B. Davidsson (5) , S. Marchi (6) , H. U. Keller (7) , S. F. Hviid (8) , S. Besse (9) , H. Sierks (10) , C. Barbieri (11) , Philippe Lamy (12) , D. Koschny (9) , H. Rickman (13, 14) , R. Rodrigo (13, 15) , M. F. A'Hearn (16) , A. -T. Auger (12) , M. A. Barucci (17) , Jean-Loup Bertaux (18) , I. Bertini (2) , D. Bodewits (16) , G. Cremonese (11) , V. da Deppo (19) , M. de Cecco (20) , S. Debei (21) , C. Güttler (10) , S. Fornasier (22) , M. Fulle (23) , L. Giacomini (4) , O. Groussin (12) , P. J. Gutierrez (24) , W. -H. Ip (3) , L. Jorda (12) , J. Knollenberg (8) , G. Kovacs (10) , J. -R. Kramm (10) , E. Kührt (8) , M. Küppers (9) , L. M. Lara (24) , M. Lazzarin (11) , J. J. Lopez Moreno (24) , R. Marschall (1) , F. Marzari (11) , G. Naletto (2, 19, 25) , N. Oklay (10) , A. Pommerol (1) , F. Preusker (8) , F. Scholten (8) , C. Tubiana (10) , J. -B. Vincent (10)

1 Physikalisches Institut [Bern]
2 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
3 NCU - National Central University [Taiwan]
4 Dipartimento di Geoscienze [Padova]
5 JPL - Jet Propulsion Laboratory
6 SSERVI - Solar System Exploration Research Virtual Institute
7 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
8 DLR Institut für Planetenforschung
9 ESA Scientific Support Office
10 MPS - Max-Planck-Institut für Sonnensystemforschung
11 OAPD - INAF - Osservatorio Astronomico di Padova
12 LAM - Laboratoire d'Astrophysique de Marseille
13 CAB - Centro de Astrobiologia [Madrid]
14 Department of Physics and Astronomy [Uppsala]
15 ISSI - International Space Science Institute [Bern]
16 Department of Astronomy [College Park]
17 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
18 PLANETO - LATMOS
19 IFN - CNR Istituto di Fotonica e Nanotecnologie [Padova]
20 UNITN - Università degli Studi di Trento
21 Department of Mechanical Engineering [Padova]
22 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
23 OAT - INAF - Osservatorio Astronomico di Trieste
24 IAA - Instituto de Astrofísica de Andalucía
25 DEI - Department of Information Engineering [Padova]

The OSIRIS camera on board the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus since August 2014. Starting in May 2015, the southern hemisphere gradually became illuminated and was imaged for the first time. Here we present the regional morphology of the southern hemisphere, which serves as a companion to an earlier paper that presented the regional morphology of the northern hemisphere.
Methods: We used OSIRIS images that were acquired at orbits ~45-125 km from the center of the comet (corresponding to spatial resolutions of ~0.8 to 2.3 m/pixel) coupled with the use of digital terrain models to define the different regions on the surface, and identify structural boundaries accurately.
Results: Seven regions have been defined in the southern hemisphere bringing the total number of defined regions on the surface of the nucleus to 26. These classifications are mainly based on morphological and/or topographic boundaries. The southern hemisphere shows a remarkable dichotomy with its northern counterpart mainly because of the absence of wide-scale smooth terrains, dust coatings and large unambiguous depressions. As a result, the southern hemisphere closely resembles previously identified consolidated regions. An assessment of the overall morphology of comet 67P suggests that the comet's two lobes show surface heterogeneities manifested in different physical/mechanical characteristics, possibly extending to local (I.e., within a single region) scales.

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

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

M. R. El-Maarry, N. Thomas, A. Gracia-Berná, M. Pajola, J. -C. Lee, et al.. Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere. Astronomy and Astrophysics - A&A, 2016, 593, A110 (20pp). ⟨10.1051/0004-6361/201628634⟩. ⟨insu-03668054⟩