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Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion.

Johansen, Anders LU ; Low, Mordecai-Mark Mac; Lacerda, Pedro and Bizzarro, Martin (2015) In Science advances 1(3).
Abstract
Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of... (More)
Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of millimeter-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and chondrule accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of chondrules destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct chondrule accretion and giant impacts. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Science advances
volume
1
issue
3
publisher
American Association for the Advancement of Science (AAAS)
external identifiers
  • pmid:26601169
ISSN
2375-2548
DOI
10.1126/sciadv.1500109
language
English
LU publication?
yes
id
8b8210dc-e78e-46d2-a039-d2058c62e93d (old id 8234681)
date added to LUP
2015-12-08 22:58:35
date last changed
2016-09-20 04:34:34
@article{8b8210dc-e78e-46d2-a039-d2058c62e93d,
  abstract     = {Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of millimeter-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and chondrule accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of chondrules destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct chondrule accretion and giant impacts.},
  articleno    = {e1500109},
  author       = {Johansen, Anders and Low, Mordecai-Mark Mac and Lacerda, Pedro and Bizzarro, Martin},
  issn         = {2375-2548},
  language     = {eng},
  number       = {3},
  publisher    = {American Association for the Advancement of Science (AAAS)},
  series       = {Science advances},
  title        = {Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion.},
  url          = {http://dx.doi.org/10.1126/sciadv.1500109},
  volume       = {1},
  year         = {2015},
}