Article Dans Une Revue Astronomy & Astrophysics - A&A Année : 2015

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

1 CBK - Space Research Centre of Polish Academy of Sciences
2 Department of Physics and Astronomy [Uppsala]
3 SSERVI - Solar System Exploration Research Virtual Institute
4 Department of Astronomy [College Park]
5 Dipartimento di Fisica e Astronomia "Galileo Galilei"
6 Physikalisches Institut [Bern]
7 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
8 IANCU - Institute of Astronomy [Taiwan]
9 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
10 LAM - Laboratoire d'Astrophysique de Marseille
11 Dipartimento di Geoscienze [Padova]
12 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
13 Department of Industrial Engineering [University of Padua]
14 IFN - CNR Institute for Photonics and Nanotechnologies
15 RSSD - Research and Scientific Support Department, ESTEC
16 CAB - Centro de Astrobiologia [Madrid]
17 ISSI - International Space Science Institute [Bern]
18 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
19 PLANETO - LATMOS
20 OAPD - INAF - Osservatorio Astronomico di Padova
21 UNITN - Università degli Studi di Trento = University of Trento
22 OAT - INAF - Osservatorio Astronomico di Trieste
23 IAA-CSIC - Instituto de Astrofísica de Andalucía = Institute of Astrophysics of Andalusia
24 DLR Institute of Planetary Research
25 Operations Department (ESAC)
26 Institut für Datentechnik und Kommunikationsnetze
27 INTA - Instituto Nacional de Técnica Aeroespacial
Jean-Loup Bertaux
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L. Jorda

Résumé

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.

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insu-01200792 , version 1 (20-11-2020)

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H. Rickman, S. Marchi, Michael F. A'Hearn, C. Barbieri, M. R. El-Maarry, et al.. Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations. Astronomy & Astrophysics - A&A, 2015, 583, pp.A44. ⟨10.1051/0004-6361/201526093⟩. ⟨insu-01200792⟩
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