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Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. PAS Space Res Ctr, PL-00716 Warsaw, Poland..
SW Res Inst, Boulder, CO 80302 USA..
Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
Univ Padua, Dept Phys & Astron G Galilei, I-35122 Padua, Italy..
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2015 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, A44Article in journal (Refereed) PublishedText
Abstract [en]

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.

Place, publisher, year, edition, pages
2015. Vol. 583, A44
Keyword [en]
comets: individual: 67P/Churyumov-Gerasimenko
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-270618DOI: 10.1051/0004-6361/201526093ISI: 000365072200053OAI: oai:DiVA.org:uu-270618DiVA: diva2:890236
Available from: 2016-01-01 Created: 2016-01-01 Last updated: 2016-01-05Bibliographically approved

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Rickman, Hans
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