The Development and Implementation of Numerical Tools for Investigation into the Granular Dynamics of Solid Solar System Bodies

Abstract

The work advanced in this thesis joins together the disciplines of planetary science and granular physics. Grain dynamics have played a prominent role in the evolution of our Solar System from planetesimal formation billions of years ago to the surface processes that take place today on terrestrial planets, moons, and small bodies. Recent spacecraft images of small Solar System bodies provide strong evidence that the majority of these bodies are covered in regolith. This regolith ranges in size from the fine powder found on the Moon to large rocks and boulders, like the 27 m Yoshinodai boulder on the small asteroid, Itokawa. Accordingly, the processes that take place on the solid bodies of the Solar System vary widely based upon the material properties of the regolith and the gravitational environments on their surfaces. An understanding of granular dynamics is also critical for the design and operations of landers, sampling devices and rovers to be included in space missions.

Part of my research is concerned with the development of numerical tools that have the ability to provide explanations for the types of processes that our spacecraft have observed. Granular processes on Earth are incredibly complex and varied, and constitute an enormous field of study on their own, with input taken from across the broad disciplines of engineering and the physical sciences. In micro-gravity, additional forces, which on Earth are relevant only to micron-size particles or smaller, are expected to become important for material up to the size of large rocks, adding further complexity.

The numerical tools developed in this work allow for the simulation of grains using an adaptation of the Soft-Sphere Discrete Element Method (SSDEM) along with implementations of cohesive forces between particles into an existing parallel gravity tree code.