[Previous] | [Session 23] | [Next]
C. B. Agnor (University of Colorado/SwRI), W. R. Ward (Southwest Research Institute)
The current model of planetary accretion is divided into three stages: km-sized planetesimal formation, planetary embryo formation, and the collisional accumulation of embryos into planets. This model has been generally successful in demonstrating that planetary bodies grossly similar to the terrestrial planets can be formed with an accretion timescale of 5 x106 - 108 years (e.g. Wetherill 1990, Canup & Agnor 2000). Despite these successes, recent numerical integrations of late stage accretion in the inner solar system have tended to produce planets with eccentricities a factor of 2 or more greater than their terrestrial counterparts (Chambers and Wetherill 1998, Agnor, Canup and Levison 1999, Chambers 2000). However, these late stage models have included only gravitational and collisional interactions between embryos and have largely neglected interactions with other possible constituents of the protoplanetary disk (i.e. smaller planetesimals or gas).
Recent direct observations of substantial reserviors of hydrogen in disks surrounding young (~2x107 years in age) A stars (Thi et al. 2001) suggest that the lifetime of gas in the solar nebula could have been longer than previously believed (a few x106 years). If a small remnant of the original solar nebula persisted for periods comparable to the formation time of the terrestrial planets, gravitational interactions with this disk could significantly influence the final configuration of the planetary system. Here we consider how a long-lived remnant gas disk might have affected the eccentricities of the terrestrial planets.