Comet 67P/Churyumov-Gerasimenko preserved the pebbles that formed planetesimals

DOI: 
10.1093/mnras/stw2299
Publication date: 
01/09/2016
Main author: 
Fulle, Marco
IAA authors: 
Lopez-Moreno, J. J.;Morales, R.;Ortiz, J. L.;Rodriguez, J.
Authors: 
Fulle, Marco;Della Corte, V.;Rotundi, A.;Rietmeijer, F. J. M.;Green, S. F.;Weissman, P.;Accolla, M.;Colangeli, L.;Ferrari, M.;Ivanovski, S.;Lopez-Moreno, J. J.;Epifani, E. Mazzotta;Morales, R.;Ortiz, J. L.;Palomba, E.;Palumbo, P.;Rodriguez, J.;Sordini, R.;Zakharov, V.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Pages: 
S132-S137
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%. We measure the average dust bulk density ρ _D = 795_{-65}^{+840} kg m<SUP>-3</SUP> that, coupled to the 67P nucleus bulk density, provides the average dust-to-ices mass ratio δ = 8.5. We find that the measured densities of the 67P pebbles are consistent with a mixture of (15 ± 6)% of ices, (5 ± 2)% of Fe-sulfides, (28 ± 5)% of silicates, and (52 ± 12)% 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 vs. crystalline Mg,Fe-olivines and pyroxenes. We find that the pebbles have a microporosity of (52 ± 8)% (internal volume filling factor φ<SUB>P</SUB> = 0.48 ± 0.08), implying an average porosity for the 67P nucleus of (71 ± 8)%, lower than previously estimated.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2016MNRAS.tmp.1405F/abstract
ADS Bibcode: 
2016MNRAS.tmp.1405F
Keywords: 
comets: general;comets: individual: 67P/Churyumov-Gerasimenko;space vehicles