During the first stages of planet formation small particles (~0.1 – 1 µm) in the protoplanetary disk collide at low relative velocities (less than 1 m/s) and tend to aggregate into cm-size "pebbles" through a combination of electrostatic interactions and gravitational streaming instabilities. Particles in this size regime also compose a layer of regolith on small, airless bodies that evolves under conditions very different than those on Earth. Characterizing the response of regolith to low-energy impacts in a microgravity environment is therefore critical to our understanding of the processes that lead to the formation of these objects and our ability to develop safe operation procedures on their surfaces. Flight-based microgravity experiments investigating low-velocity collisions of cm-size projectiles into regolith have revealed that certain impact events result in mass transfer from the target regolith onto the surface of the projectile. Characterizing the key parameters and their interactions that produce these events have important implications for the role of energy dissipation and accretion in planet formation processes and understanding the mechanical behavior of granular media composing the surfaces of small bodies. I carried out experimental and numerical campaigns designed to investigate these mass transfer events and found that accretion outcomes differ significantly depending on whether the projectile is launched into granular material or initially at rest before pulling away from the granular bed. I found that interaction effects between various parameters and the balance of the experiment design significantly influence mass transfer outcomes and must be taken into account for future experiment designs. I also present my contributions to a CubeSat mission that will provide the opportunity to observe tens of thousands of collisions between particles in the velocity and size regime relevant to the earliest stages of planet formation.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Physics; Planetary Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Jarmak, Stephanie, "Experimental and Numerical Investigations of Granular Dynamics in Microgravity" (2020). Electronic Theses and Dissertations, 2020-. 63.