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The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Davidsson, B. and Sierks, H. and Güttler, C. and Marzari, F. and Pajola, M. and Rickman, Hans and A'Hearn, M. F. and Auger, Anne-Therese and El-Maarry, M. R. and Fornasier, S. and Gutierrez, P.J. and Keller, H. U. and Massironi, Matteo and Snodgrass, C. and Vincent, J.B. and Barbieri, C. and Lamy, P. and Rodrigo, Rafael and Koschny, Detlef and Barucci, M. A. and Bertaux, J.-L. and Bertini, I. and Cremonese, G. and Da Deppo, V. and Debei, S. and Cecconi, B. and De Cecco, M. and Feller, Clement and Fulle, M. and Groussin, Olivier and Hviid, Stubbe and Höfner, S. and Ip, W-H. and Jorda, L and Knollenberg, J. and Kovacs, G. and Kramm, J. R. and Kührt, E. and Küppers, Michael and La Forgia, Fiorangela and Lara López, Luisa M. and Lazzarin, M. and Lopez Moreno, J. and Moissl-Fraund, R. and Mottola, S. and Naletto, G. and Oklay, N. and Thomas, N. and Tubiana, C. (2016) The primordial nucleus of comet 67P/Churyumov-Gerasimenko. Astronomy & Astrophysics. EDP Sciences. DOI: 10.1051/0004-6361/201526968 ISSN 0004-6361

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Abstract

Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods. We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ~400 km and that ~350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented medium-sized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity to avoid thermal processing by short-lived radionuclides that would lead to loss of supervolatiles, and that allowed comet nuclei to incorporate ~3 Myr old material from the inner solar system.

Item URL in elib:https://elib.dlr.de/109890/
Document Type:Article
Title:The primordial nucleus of comet 67P/Churyumov-Gerasimenko
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Davidsson, B.astronomiska observatoriet, uppsala, swedenUNSPECIFIED
Sierks, H.max-planck-institut für sonnensystemforschung, katlenburg-lindau, germanyUNSPECIFIED
Güttler, C.max-planck-institut für sonnensystemforschungUNSPECIFIED
Marzari, F.università di padova, departimento di fisica, padova, italyUNSPECIFIED
Pajola, M.cisas - center for studies and activities for space, university of padovaUNSPECIFIED
Rickman, Hansuppsala astronomical observatoryUNSPECIFIED
A'Hearn, M. F.university of maryland, department of astronomy, maryland, usaUNSPECIFIED
Auger, Anne-Thereseaix marseille université, cnrs, laboratoire d’astrophysique de marseille, umr 7326, 38 rue frédéric joliot-curie, 13388 marseille, france.UNSPECIFIED
El-Maarry, M. R.physikalisches institut, sidlerstrasse 5, university of bern, ch-3012 bern, switzerlandUNSPECIFIED
Fornasier, S.observatoire de paris-meudon, franceUNSPECIFIED
Gutierrez, P.J.iaa-csic, granada, spainUNSPECIFIED
Keller, H. U.max-planck-institut für sonnensystemforschung, katlenburg-lindauUNSPECIFIED
Massironi, Matteoinaf, padova, iUNSPECIFIED
Snodgrass, C.max-planck-institut für sonnensystemforschung, göttingen, germanyUNSPECIFIED
Vincent, J.B.max-planck-institut fuer sonnensystemforschung, germanyUNSPECIFIED
Barbieri, C.university of padova, padova, italyUNSPECIFIED
Lamy, P.laboratoire d'astronomie spatiale, marseille, franceUNSPECIFIED
Rodrigo, Rafaelinstituto de astrofisica de andaluciaUNSPECIFIED
Koschny, Detlefestec, the netherlandsUNSPECIFIED
Barucci, M. A.observatoire de paris, meudon, franceUNSPECIFIED
Bertaux, J.-L.laboratoire atmosphères, milieux, observations spatiales, cnrs/uvsq/upmc, 11 boulevard d’alembert, 78280 guyancourt, franceUNSPECIFIED
Bertini, I.dipartimento di astronomia, università di padova, padova, italyUNSPECIFIED
Cremonese, G.osservatorio astronomico, padova, italyUNSPECIFIED
Da Deppo, V.consiglio nazionale delle ricerche-istituto nazionale per la fisica della materia, luxor, padova, italyUNSPECIFIED
Debei, S.università di padova, center of studies and activities of space (cisas) "g.colombo", padova, italyUNSPECIFIED
Cecconi, B.lesia, cnrs-observatoire de paris, meudon, franceUNSPECIFIED
De Cecco, M.università di padova, center of studies and activities of space (cisas) "g.colombo", padova, italyUNSPECIFIED
Feller, Clementlesia, observatoire de paris, cnrs, upmc univ paris 06, univ. paris-diderot, 5 place j. janssen, 92195 meudon pricipal cedex, franceUNSPECIFIED
Fulle, M.inaf – osservatorio astronomico di trieste, via tiepolo 11, 34143 trieste, italyUNSPECIFIED
Groussin, Olivierlab. d'astrophysique de marseille, franceUNSPECIFIED
Hviid, Stubbestubbe.hviid (at) dlr.deUNSPECIFIED
Höfner, S.max-planck-institut für sonnensystemforschung, göttingen, germanyUNSPECIFIED
Ip, W-H.institute for space science, national central university, chung li, taiwanUNSPECIFIED
Jorda, Llam, marseilleUNSPECIFIED
Knollenberg, J.joerg.knollenberg (at) dlr.deUNSPECIFIED
Kovacs, G.max–planck–institut für sonnensystemforschung, justus–von–UNSPECIFIED
Kramm, J. R.max planck institute for solar systems research, katlenburg-lindau, germanyUNSPECIFIED
Kührt, E.ekkehard.kuehrt (at) dlr.deUNSPECIFIED
Küppers, Michaelmax-planck-institut für sonnensystemforschungUNSPECIFIED
La Forgia, Fiorangelauniversity of padova, department of physics and astronomy, vicolo dell'osservatorio 3, 35122 padova, italyUNSPECIFIED
Lara López, Luisa M.iaa-csic granada, spainUNSPECIFIED
Lazzarin, M.department of astronomy, university of paduaUNSPECIFIED
Lopez Moreno, J.instituto de astrofifica de andalucia-consejo superior de investigaciones cientificas, granada, spainUNSPECIFIED
Moissl-Fraund, R.Operations Department, European Space Astronomy Centre/ESA, PO Box 78, 28691 Villanueva de la Canada, Madrid, SpainUNSPECIFIED
Mottola, S.stefano.mottola (at) dlr.deUNSPECIFIED
Naletto, G.università di padova, departimento di elettronica et informatica, padova, italyUNSPECIFIED
Oklay, N.max-planck-institut für sonnensystemforschungUNSPECIFIED
Thomas, N.max-planck-institut für aeronomie, katlenburg-lindauUNSPECIFIED
Tubiana, C.max-planck-institut fuer sonnensystemforschung, germanyUNSPECIFIED
Date:2016
Journal or Publication Title:Astronomy & Astrophysics
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1051/0004-6361/201526968
Publisher:EDP Sciences
ISSN:0004-6361
Status:Published
Keywords:comets: individual: 67P/Churyumov-Gerasimenko / Kuiper belt: general / protoplanetary disks
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt ROSETTA Instrumente, R - Projekt ROSETTA Lander
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Deposited By: Schubert, Renate
Deposited On:21 Dec 2016 08:12
Last Modified:08 Mar 2018 18:23

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