David O'Brien

NASA Planetary Geology and Geophysics

Collisional and Dynamical Processes in the Solar System

This proposed work focuses on two main areas -- the collisional and dynamical evolution of the asteroid belt and NEAs, and the formation of the terrestrial planets.

First, we will use new constraints on the main-belt size distribution (such as the sub-Kilometer Asteroid Diameter Survey) to update our models of the collisional and dynamical evolution of the main-belt and NEA populations. In addition, our collisional and dynamical evolution model for the asteroid belt will be extended to treat multiple interacting populations. We will use this model to help explain the origin of size distribution differences between different sub-populations of asteroids (eg. low- and high-inclination bodies), incorporating new observational constraints and new experimental and numerical estimates of the strength of asteroidal material.

Secondly, we will continue our work on high-resolution n-body modeling of terrestrial planet formation with the goal of matching numerous constraints, such as the low dynamical excitation of the terrestrial planets, the abundance of water on Earth, and the small mass of Mars. This will focus on two specific areas: The effects of nebular gas and secular resonance sweeping on terrestrial planet formation, and the effects that periapse libration between Jupiter and Saturn can have on terrestrial planet formation.

This work is relevant to the goals and science objectives of NASA in general and to those of the PG&G program in particular, in that it seeks to study the planets and small solar system bodies in order to better understand "the origin and evolution of the solar system".