Feb 02, 2017 4:00 pm -
Nielsen Hall 170 -
Kevin Walsh - Southwest Research Institute
Terrestrial Planet Formation with Fragmentation and a Dissipating Nebula
Models of each stage of planet growth have largely been successful atidentifying the important physics in different regions of space atdifferent times. The earliest stages are dominated by small-bodyinteractions, where km-size bodies collide with each other but alsointeract with the gaseous solar nebula. Later, the gravitationalinteraction between planetary embryos on long timescales becomes moreimportant. However, splitting the problem into different stages, eachmodeling subsets of the total physics, has an inherit weakness -planet growth does not progress at the same speed at alllocations. Rather the inner regions of the Solar System may have manygravitationally interacting planetary embryos, while outer regions arestill dominated by small-body collisions.Using a particle-based code that models the fragmentation, accretionand dynamical evolution of a large number of planetesimals through theentire growth process, one can avoid the pitfalls of the classicalpiece-wise approaches. This technique finds that growth timescalesthat are far more dependent on distance from the Sun than previouslyexpected. This leads to giant collisions between Mars-size planetaryembryos at 1 AU before Ceres-size embryos have formed beyond 2 AU. Weuse these results to test classical models of Terrestrial Planetformation and some of the fundamental assumptions built into mostmodern models.