1. Comet 67P/Churyumov–Gerasimenko preserved the pebbles that formed planetesimals
- Author
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M. Ferrari, Stavro Ivanovski, Mario Accolla, Roberto Sordini, F. J. M. Rietmeijer, Marco Fulle, J. J. López-Moreno, Luigi Colangeli, E. Mazzotta Epifani, J. E. Rodriguez, Pasquale Palumbo, V. V. Zakharov, Jose Luis Ortiz, R. Morales, Alessandra Rotundi, P. Weissman, Simon F. Green, Ernesto Palomba, V. Della Corte, INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), British Geological Survey [Edinburgh], British Geological Survey (BGS), Planetary Science Institute [Tucson] (PSI), INAF - Osservatorio Astrofisico di Catania (OACT), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), INAF - Osservatorio Astronomico di Capodimonte (OAC), Instituto de Astrofsica de Andalucia, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Waves and Solitons LLC, 918 W. Windsong Dr., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Space Agency (ESA), and Agenzia Spaziale Italiana
- Subjects
Planetesimal ,010504 meteorology & atmospheric sciences ,Comets: general ,Comets: individual: 67P/Churyumov ,Gerasimenko ,Space vehicles ,Astronomy and Astrophysics ,Space and Planetary Science ,Astrophysics ,01 natural sciences ,individual: 67P/Churyumov [Comets] ,0103 physical sciences ,10. No inequality ,Porosity ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Physics ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,comets: general ,general [Comets] ,comets: individual: 67P/Churyumov-Gerasimenko ,Mass ratio ,Bulk density ,Amorphous solid ,Volume filling ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,space vehicles ,Formation and evolution of the Solar System - Abstract
Solar system formation models predict that the building blocks of planetesimals were mm- to cm-sized pebbles, aggregates of ices and non-volatile materials, consistent with the compact particles ejected by comet 67P/Churyumov-Gerasimenko (67P hereafter) and detected by GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta spacecraft. Planetesimals were formed by the gentle gravitational accretion of pebbles, so that they have an internal macroporosity of 40 per cent. We measure the average dust bulk density ¿D = 795+840 -65 kg m-3 that, coupled to the nucleus bulk density, provides the average dust-toices mass ratio ¿ = 8.5. We find that the measured densities of the 67P pebbles are consistent with a mixture of (15 ± 6) per cent of ices, (5 ± 2) per cent of Fe-sulphides, (28 ± 5) per cent of silicates, and (52 ± 12) per cent of hydrocarbons, in average volume abundances. This composition matches both the solar and CI-chondritic chemical abundances, thus showing that GIADA has sampled the typical non-volatile composition of the pebbles that formed all planetesimals. The GIADA data do not constrain the abundance of amorphous silicates versus crystalline Mg, Fe-olivines and pyroxenes. We find that the pebbles have a microporosity of (52 ± 8) per cent (internal volume filling factor ¿P = 0.48 ± 0.08), implying an average porosity for the 67P nucleus of (71 ± 8) per cent, lower than previously estimated. © 2016 The Authors., This research was supported by the Italian Space Agency (ASI) within the INAF-ASI agreements I/032/05/0 and I/024/12/0.
- Published
- 2016
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