DPS 34th Meeting, October 2002
Session 28. Solar System Origin, Planet and Satellite Formation
Oral, Chair(s): W.R. Ward and G.J. Consolmagno SJ, Thursday, October 10, 2002, 2:00-4:00pm, Room M

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[28.02] Terrestrial Planet Accretion: Dependence on Nebula Surface Density Profile and Giant-Planet Eccentricities.

J.E. Chambers (NASA Ames/SETI Institute)

To date, most models for the accretion of the terrestrial planets have assumed that the surface density of solids in the Sun's protoplanetary disk decreased with distance from the Sun as a power law. In addition, models which included the perturbing effects of Jupiter and Saturn have assumed that these planets moved on orbits similar to their modern ones. However, recent models for the accumulation of solids in an evolving disk indicate that planetesimals followed a surface density profile that was flat or increased with heliocentric distance in the terrestrial region (Cassen 2001, MAPS, 36, 671). Models for the clearing of most of the primordial mass from the asteroid belt imply that the giant planets' orbits were initially more eccentric than they are today (Chambers and Wetherill 2001, MAPS, 36, 381).

I will present results of 32 new N-body simulations of planetary accretion which compare the effect of using standard model parameters with cases using a non-standard surface density profile and/or enhanced initial giant-planet eccentricities. Each simulation begins with about 150 planetary embryos in a disk which spans the terrestrial region and asteroid belt, and continues until a long-lived system of planets is formed. In general, the simulations using a decaying surface density profile and more-eccentric orbits for the giant planets yield planetary systems that most closely resemble the inner Solar System. The composition of the planets produced in the simulations depends sensitively on the giant planets' eccentricities. When these eccentricities are initially enhanced, the amount of (possibly volatile rich?) material from the asteroid belt which is delivered to Earth-like planets is greatly reduced.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.