Terrestrial Planet Formation with Strong Dynamical Friction

I will present the results of 8 new N-body simulations of the final stages of terrestrial planet accretion, each of which includes over 5x more gravitationally interacting bodies than any previous N-body simulations. Given the large number of small planetesimals in these simulations, they are able to accurately account for the effects of dynamical friction on the accretion process. Dynamical friction is due to the equipartition of energy between large and small interacting bodies, and results in the damping of the relative velocities of the large bodies. Among other things, dynamical friction is found to significantly lower the timescale for the accretion of the terrestrial planets and leads to systems of terrestrial planets that are much less dynamically excited than in previous simulations with fewer initial bodies. These simulations also explore the effects of the orbits of Jupiter and Saturn on the final planetary systems. Four of the simulations were run with the present, eccentric orbits of Jupiter and Saturn and the other four were run with a nearly circular and co-planar Jupiter and Saturn, as predicted by current models of the formation and evolution of the outer planets [Gomes et al., Nature 435 (2005)]. The orbits of Jupiter and Saturn can have a significant effect on the final terrestrial planets in terms of their number, masses and orbital structure. In addition, they can influence the geochemistry of the final terrestrial planets, such as the amount of water-bearing outer-asteroid-belt material that they accrete and the mass of material that is accreted as a late veneer.

Preprint available: HERE .