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The great dichotomy of the Solar System: Small terrestrial embryos and massive giant planet cores

Morbidelli, A.; Lambrechts, Michiel LU ; Jacobson, S. and Bitsch, Bertram LU (2015) In Icarus 258. p.418-429
Abstract
The basic structure of the Solar System is set by the presence of low-mass terrestrial planets in its inner part and giant planets in its outer part. This is the result of the formation of a system of multiple embryos with approximately the mass of Mars in the inner disk and of a few multi-Earth-mass cores in the outer disk, within the lifetime of the gaseous component of the protoplanetary disk. What was the origin of this dichotomy in the mass distribution of embryos/cores? We show in this paper that the classic processes of runaway and oligarchic growth from a disk of planetesimals cannot explain this dichotomy, even if the original surface density of solids increased at the snowline. Instead, the accretion of drifting pebbles by... (More)
The basic structure of the Solar System is set by the presence of low-mass terrestrial planets in its inner part and giant planets in its outer part. This is the result of the formation of a system of multiple embryos with approximately the mass of Mars in the inner disk and of a few multi-Earth-mass cores in the outer disk, within the lifetime of the gaseous component of the protoplanetary disk. What was the origin of this dichotomy in the mass distribution of embryos/cores? We show in this paper that the classic processes of runaway and oligarchic growth from a disk of planetesimals cannot explain this dichotomy, even if the original surface density of solids increased at the snowline. Instead, the accretion of drifting pebbles by embryos and cores can explain the dichotomy, provided that some assumptions hold true. We propose that the mass-flow of pebbles is two-times lower and the characteristic size of the pebbles is approximately ten times smaller within the snowline than beyond the snowline (respectively at heliocentric distance r < r(ice) and r > r(ice) where r(ice) is the snowline heliocentric distance), due to ice sublimation and the splitting of icy pebbles into a collection of chondrule-size silicate grains. In this case, objects of original sub-lunar mass would grow at drastically different rates in the two regions of the disk. Within the snowline these bodies would reach approximately the mass of Mars while beyond the snowline they would grow to similar to 20 Earth masses. The results may change quantitatively with changes to the assumed parameters, but the establishment of a clear dichotomy in the mass distribution of protoplanets appears robust provided that there is enough turbulence in the disk to prevent the sedimentation of the silicate grains into a very thin layer. (C) 2015 Elsevier Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Solar System, Origin, Planetary formation, Accretion, Extra-solar, planets
in
Icarus
volume
258
pages
418 - 429
publisher
Academic Press
external identifiers
  • wos:000359095300028
  • scopus:84946141655
ISSN
0019-1035
DOI
10.1016/j.icarus.2015.06.003
language
English
LU publication?
yes
id
ea72d831-53fe-4272-aab5-3d744e5db59d (old id 7975714)
date added to LUP
2015-09-24 16:01:15
date last changed
2017-11-19 03:06:00
@article{ea72d831-53fe-4272-aab5-3d744e5db59d,
  abstract     = {The basic structure of the Solar System is set by the presence of low-mass terrestrial planets in its inner part and giant planets in its outer part. This is the result of the formation of a system of multiple embryos with approximately the mass of Mars in the inner disk and of a few multi-Earth-mass cores in the outer disk, within the lifetime of the gaseous component of the protoplanetary disk. What was the origin of this dichotomy in the mass distribution of embryos/cores? We show in this paper that the classic processes of runaway and oligarchic growth from a disk of planetesimals cannot explain this dichotomy, even if the original surface density of solids increased at the snowline. Instead, the accretion of drifting pebbles by embryos and cores can explain the dichotomy, provided that some assumptions hold true. We propose that the mass-flow of pebbles is two-times lower and the characteristic size of the pebbles is approximately ten times smaller within the snowline than beyond the snowline (respectively at heliocentric distance r &lt; r(ice) and r &gt; r(ice) where r(ice) is the snowline heliocentric distance), due to ice sublimation and the splitting of icy pebbles into a collection of chondrule-size silicate grains. In this case, objects of original sub-lunar mass would grow at drastically different rates in the two regions of the disk. Within the snowline these bodies would reach approximately the mass of Mars while beyond the snowline they would grow to similar to 20 Earth masses. The results may change quantitatively with changes to the assumed parameters, but the establishment of a clear dichotomy in the mass distribution of protoplanets appears robust provided that there is enough turbulence in the disk to prevent the sedimentation of the silicate grains into a very thin layer. (C) 2015 Elsevier Inc. All rights reserved.},
  author       = {Morbidelli, A. and Lambrechts, Michiel and Jacobson, S. and Bitsch, Bertram},
  issn         = {0019-1035},
  keyword      = {Solar System,Origin,Planetary formation,Accretion,Extra-solar,planets},
  language     = {eng},
  pages        = {418--429},
  publisher    = {Academic Press},
  series       = {Icarus},
  title        = {The great dichotomy of the Solar System: Small terrestrial embryos and massive giant planet cores},
  url          = {http://dx.doi.org/10.1016/j.icarus.2015.06.003},
  volume       = {258},
  year         = {2015},
}