Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations

Rickman, H.; Marchi, S.; A'Hearn, M. F.; Barbieri, C.; Elmaarry, Mohamed Ramy; Guettler, C.; Ip, W. H.; Keller, H. U.; Lamy, P.; Marzari, F.; Massironi, M.; Naletto, G.; Pajola, M.; Sierks, H.; Koschny, D.; Rodrigo, R.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; ... (2015). Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations. Astronomy and astrophysics, 583(A44), A44. EDP Sciences 10.1051/0004-6361/201526093

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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.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Elmaarry, Mohamed Ramy

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

15 Jun 2016 15:33

Last Modified:

26 Jun 2016 02:16

Publisher DOI:

10.1051/0004-6361/201526093

Web of Science ID:

000365072200053

ArXiv ID:

1505.07021

BORIS DOI:

10.7892/boris.81702

URI:

https://boris.unibe.ch/id/eprint/81702

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