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C. B. Agnor (University of Colorado, Southwest Research Institute), R. M. Canup (Southwest Research Institute)
Multiple studies have demonstrated that dynamical friction fosters the runaway growth of lunar to Mars-sized planetary embryos from a disk of planetesimals on time scales of ~ 105 years (e.g. Wetherill and Stewart 1993, Kokubo and Ida 1996). Simulations of the formation of embryos are typically terminated when a few tens of embryos contain approximately one third of the system mass, although one work has followed the system evolution until nearly 90% of the system mass is contained in the embryos (Weidenschilling et al. 1997). Recent N-body simulations of the final stages of terrestrial accretion have considered only interactions among the embryos, ignoring the possible dynamical effects a co-existing population of smaller planetesimal material (e.g. Chambers and Wetherill 1998; Agnor et al. 1999). However such studies have generally yielded terrestrial planets with overly high eccentricities and inclinations. Here we report on progress in an investigation of potential effects of small background material on the dynamical evolution of planetary embryos.