From icy planetesimals to outer planets and comets

Richard J. Greenberg, Stuart J. Weidenschilling, Clark R. Chapman, Donald R. Davis

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Numerical simulations of planet growth in the outer solar system shows thatgrwoth of Uranus and Neptune occurs in reasonably short time, well below the actual age of the system, without the need for ad hoc assumptions about excess mass or artificially low relative velocities among the icy planetesimals. Low velocities, which speed accretion, are a natural consequence of the non-power-law size distribution of planetesimals, just as in our earlier simulations of terrestial planet growth. Initial planetesimals of size ∼ 100 km, predicted by formal expressions for gravitational instability in a thin disk of solid material, failed to produce sufficient debris in the size range 1 to 10 km to account for population of the Oort cloud with comet-sized bodies. However, our model of nonhomologous settling of grains to the midplane of the solar system shows that gravitational clumping did not wait until all solid material had settled to the midplane, as had been assumed in earlier models. Rather, the clumping occurred in successive portions of the material that reached the midplane, producing "initial" planetesimals probably of comet-like sizes. Models of subsequent collisional evolution show that such an initial size distribution, similar to known comets, would have been required in order to have an adequate comet-like size distribution available to feed the Oort cloud as the other planets reach full size. Comets are probably unaltered remnants of the initial population of planetesimals in the outer solar system, not fragments of larger bodies.

Original languageEnglish (US)
Pages (from-to)87-113
Number of pages27
JournalIcarus
Volume59
Issue number1
DOIs
StatePublished - 1984

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protoplanets
planetesimal
comets
comet
planets
planet
solar system
Oort cloud
Uranus (planet)
gravitational instability
Uranus
Neptune (planet)
Neptune
settling
debris
range size
low speed
simulation
accretion
fragments

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Greenberg, R. J., Weidenschilling, S. J., Chapman, C. R., & Davis, D. R. (1984). From icy planetesimals to outer planets and comets. Icarus, 59(1), 87-113. https://doi.org/10.1016/0019-1035(84)90058-7

From icy planetesimals to outer planets and comets. / Greenberg, Richard J.; Weidenschilling, Stuart J.; Chapman, Clark R.; Davis, Donald R.

In: Icarus, Vol. 59, No. 1, 1984, p. 87-113.

Research output: Contribution to journalArticle

Greenberg, RJ, Weidenschilling, SJ, Chapman, CR & Davis, DR 1984, 'From icy planetesimals to outer planets and comets', Icarus, vol. 59, no. 1, pp. 87-113. https://doi.org/10.1016/0019-1035(84)90058-7
Greenberg, Richard J. ; Weidenschilling, Stuart J. ; Chapman, Clark R. ; Davis, Donald R. / From icy planetesimals to outer planets and comets. In: Icarus. 1984 ; Vol. 59, No. 1. pp. 87-113.
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