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

¹ Physikalisches Institut, Sidlerstr. 5, University of Bern, 3012 Bern, Switzerland
e-mail: mohammed.elmaarry@space.unibe.ch
² Centro di Ateneo di Studi ed Attivitá Spaziali, “Giuseppe Colombo” (CISAS), University of Padova, 35131 Padova, Italy
³ Department of Earth Sciences, National Central University, 32054 Chung-Li, Taiwan
⁴ Dipartimento di Geoscienze, University of Padova, via G. Gradenigo 6, 35131 Padova, Italy
⁵ Jet Propulsion Laboratory, M/S 183-301, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁶ Solar System Exploration Research Virtual Institute, Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA
⁷ Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, 38106 Braunschweig, Germany
⁸ Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Planetenforschung, Rutherfordstraße 2, 12489 Berlin, Germany
⁹ Scientific Support Office, European Space Agency, 2201 Noordwijk, The Netherlands
¹⁰ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg, 3, 37077 Göttingen, Germany
¹¹ INAF–Osservatorio Astronomico, vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹² Aix-Marseille Université, CNRS, LAM, UMR 7326, 38 rue Frédéric Joliot-Curie, 13388 Marseille, France
¹³ International Space Science Institute, Hallerstraße 6, 3012 Bern, Switzerland
¹⁴ Centro de Astrobiología, CSIC-INTA, 28850 Torrejón de Ardoz, Madrid, Spain
¹⁵ Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
¹⁶ PAS Space Research Center, Bartycka 18A, 00716 Warszawa, Poland
¹⁷ Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
¹⁸ LESIA, Obs. de Paris, CNRS, Univ. Paris 06, Univ. Paris-Diderot, 5 place J. Janssen, 92195 Meudon, France
¹⁹ LATMOS, CNRS/UVSQ/IPSL, 11 boulevard d’Alembert, 78280 Guyancourt, France
²⁰ Centro di Ateneo di Studi ed Attivitá Spaziali, “Giuseppe Colombo” (CISAS), University of Padova, 35131 Padova, Italy
²¹ CNR-IFN UOS Padova LUXOR, via Trasea, 7, 35131 Padova, Italy
²² UNITN, Universitá di Trento, via Mesiano, 77, 38100 Trento, Italy
²³ Department of Mechanical Engineering – University of Padova, via Venezia 1, 35131 Padova, Italy
²⁴ INAF–Osservatorio Astronomico, via Tiepolo 11, 34014 Trieste, Italy
²⁵ Instituto de Astrofísica de Andalucía (CSIC), c/ Glorieta de la Astronomía s/n, 18008 Granada, Spain
²⁶ National Central University, Graduate Institute of Astronomy, 300 Chung-Da Rd, 32054 Chung-Li, Taiwan
²⁷ Laboratoire d’Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
²⁸ Scientific Support Office, European Space Astronomy Centre/ESA, PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
²⁹ University of Padova, Department of Information Engineering, via Gradenigo 6/B, 35131 Padova, Italy

Received: 4 April 2016
Accepted: 31 May 2016

Abstract

Aims. 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.