Early Giant Planet Migration in the Solar System: Geochemical and Cosmochemical Implications for Terrestrial Planet Formation

A new terrestrial planet formation model (Walsh et al., this meeting) explores the effects of a two-stage, inward-then-outward migration of Jupiter and Saturn, as found in numerous hydrodynamical simulations of giant planet formation (Masset & Snellgrove 2001, Morbidelli & Crida 2007, Pierens & Nelson 2008). Walsh et al. show that the inward migration of Jupiter truncates the disk of planetesimals and embryos in the terrestrial planet region. Subsequent accretion in that region then forms a realistic system of terrestrial planets, in particular giving a low-mass Mars, which has been difficult to reproduce in simulations with a self-consistent set of initial conditions (see, eg. Raymond et al. 2009). Additionally, the outward migration of the giant planets populates the asteroid belt with distinct populations of bodies, with the inner belt filled by bodies originating inside of 3 AU, and the outer belt filled with bodies originating from beyond the giant planets. From a geochemical and cosmochemical point of view, this scenario differs significantly from the "standard model" in which essentially all of the material in the inner Solar System initially formed there. Specifically, the assumption that the current radial distribution of material in the inner Solar System is reflective of the primordial distribution of material in that region is no longer necessary. This is important for understanding the chemical and isotopic diversity of the inner Solar System as inferred from studies of the terrestrial planets, asteroids, and meteorites, as well as for understanding the origin of Earth's water. We will discuss the geochemical and cosmochemical implications of this model in relation to available constraints, as well as to previous models of terrestrial planet formation. Masset & Snellgrove (2001), MNRAS 320, L55. Morbidelli & Crida (2007), Icarus 191, 158. Pierens & Nelson (2008), A&A 482, 333. Raymond et al. (2009), Icarus 203, 644