Growth of asteroids, planetary embryos and Kuiper belt objects by chondrule accretion
Anders Johansen (Lund University), Mordecai-Mark Mac Low (American Museum of Natural History), Pedro Lacerda (Max Planck Institute for Solar System Research), Martin Bizzarro (University of Copenhagen)
(Submitted on 25 Mar 2015)
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 run-away accretion of chondrules within ~3 Myr, forming planetary embryos up to Mars sizes 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 mm-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disk life time 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 for 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.
Comments:Accepted for publication in Science Advances (new AAAS journal)
Subjects:Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:arXiv:1503.07347 [astro-ph.EP] (or arXiv:1503.07347v1 [astro-ph.EP] for this version)
Submission history
From: Anders Johansen [view email]
[v1] Wed, 25 Mar 2015 11:44:51 GMT (731kb,D)
