David O'Brien

 NASA Origins

Chemical and Dynamical Modeling of Terrestrial Planet Formation

We will undertake the first study to combine dynamical models of terrestrial planet formation with chemical equilibrium condensation models of solids in the solar nebula and around other stars. First, we will calculate the theoretical bulk compositions of the terrestrial planets formed in n-body accretion simulations and compare them to the actual bulk compositions of the terrestrial planets in the Solar System. Additionally, we will examine how the composition of accreted material changes with time, especially with regards to the delivery of volatiles and a 'late veneer' of siderophile material. Finally, this same method will be applied to specific extrasolar planetary systems to obtain the first predictions of the bulk chemical composition of terrestrial planets that may exist in those systems.

To perform this work, we will run n-body dynamical simulations of terrestrial planet accretion for both the Solar System and for extrasolar planetary systems. Chemical models of these systems will be produced using a chemical equilibrium code and the spectroscopically-determined elemental abundances for the Sun or the host star of the extrasolar system. The dynamical and chemical models will then be combined together, assuming that each embryo and planetesimal that accretes onto a given planet retains the composition of the solid material in the nebula at the location where the embryo or planetesimal first formed. The combination of chemical and dynamical models will allow us to determine the bulk chemical composition of the terrestrial planets formed in the dynamical simulations, and also to trace their bulk chemical evolution throughout formation.

This work represents a major step forward in understanding the development and diversity of planetary systems, and thus this work is relevant to the Origins program. With regards to NASA's strategic goals and objectives, it fits with strategic sub-goal 3C in that it seeks to advance scientific knowledge of the origin and history of the Solar System and the potential for life elsewhere.