@article{79f11e05028641278755662dd2850bd7,
title = "Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations",
abstract = "Context. One of the main aims of the ESA Rosetta mission is to study the origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko at close range. Aims. In this paper we discuss the origin and evolution of comet 67P/Churyumov-Gerasimenko in relation to that of comets in general and in the framework of current solar system formation models. Methods. We use data from the OSIRIS scientific cameras as basic constraints. In particular, we discuss the overall bi-lobate shape and the presence of key geological features, such as layers and fractures. We also treat the problem of collisional evolution of comet nuclei by a particle-in-a-box calculation for an estimate of the probability of survival for 67P/Churyumov-Gerasimenko during the early epochs of the solar system. Results. We argue that the two lobes of the 67P/Churyumov-Gerasimenko nucleus are derived from two distinct objects that have formed a contact binary via a gentle merger. The lobes are separate bodies, though sufficiently similar to have formed in the same environment. An estimate of the collisional rate in the primordial, trans-planetary disk shows that most comets of similar size to 67P/Churyumov-Gerasimenko are likely collisional fragments, although survival of primordial planetesimals cannot be excluded. Conclusions. A collisional origin of the contact binary is suggested, and the low bulk density of the aggregate and abundance of volatile species show that a very gentle merger must have occurred. We thus consider two main scenarios: the primordial accretion of planetesimals, and the re-accretion of fragments after an energetic impact onto a larger parent body. We point to the primordial signatures exhibited by 67P/Churyumov-Gerasimenko and other comet nuclei as critical tests of the collisional evolution.",
keywords = "Comets: individual: 67P/Churyumov-Gerasimenko",
author = "H. Rickman and S. Marchi and A'Hearn, \{M. F.\} and C. Barbieri and El-Maarry, \{M. R.\} and C. G{\"u}ttler and Ip, \{W. H.\} and Keller, \{H. U.\} and P. Lamy and F. Marzari and M. Massironi and G. Naletto and M. Pajola and H. Sierks and D. Koschny and R. Rodrigo and Barucci, \{M. A.\} and Bertaux, \{J. L.\} and I. Bertini and G. Cremonese and \{Da Deppo\}, V. and S. Debei and \{De Cecco\}, M. and S. Fornasier and M. Fulle and O. Groussin and Guti{\'e}rrez, \{P. J.\} and Hviid, \{S. F.\} and L. Jorda and J. Knollenberg and Kramm, \{J. R.\} and E. K{\"u}hrt and M. K{\"u}ppers and Lara, \{L. M.\} and M. Lazzarin and \{Lopez Moreno\}, \{J. J.\} and H. Michalik and L. Sabau and N. Thomas and Vincent, \{J. B.\} and Wenzel, \{K. P.\}",
note = "Funding Information: The authors wish to thank Hal Levison, Alessandro Morbidelli, Katherine Kretke, David Nesvorn{\'y}, Alex Parker, Robert Grimm, Anders Johansen for interesting discussions. We also thank the referee, David O{\textquoteright}Brien, for helpful suggestions. OSIRIS was built by a consortium led by the Max-Planck-Institut f{\"u}r Sonnensystemforschung, G{\"o}ttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d{\textquoteright}Astrophysique de Marseille, France, the Instituto de Astrof{\'i}sica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, Netherlands, the Instituto Nacional de T{\'e}cnica Aeroespacial, Madrid, Spain, the Universidad Polit{\'e}chnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut f{\"u}r Datentechnik und Kommunikationsnetze der Technischen Universit{\"a}t Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the ESA teams at European Space Astronomy Center, European Space Operations Center, and European Space Research and Technology Center for their work in support of the Rosetta mission. Special thanks are due to Ryszard Gabryszewski (PAS Space Research Center, Warsaw) for permission to use the plot in Fig. 1. S.M. was supported by NASA Jet Propulsion Laboratory Subcontract No. 1336850 to the Southwest Research Institute. H.R. was supported by Grant No. 2011/01/B/ST9/05442 of the Polish National Science Center. Publisher Copyright: {\textcopyright} ESO, 2015.",
year = "2015",
month = nov,
day = "1",
doi = "10.1051/0004-6361/201526093",
language = "British English",
volume = "583",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}