Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Engineering Physics

First Advisor

Mihàly Horànyi

Second Advisor

Xu Wang

Third Advisor

Tobin Munsat

Fourth Advisor

Todd Murray

Abstract

As airless planetary bodies are directly exposed to solar ultraviolet radiation and plasma, an environment that fosters dust charging within planetary regolith will result, producing dust mobilization and transport. A multitude of unsolved in-situ planetary observations linked to electrostatic processes exist, ranging from dust ponds on the asteroid Eros, to intermittently appearing radial spokes in Saturn’s rings, and even to the lunar horizon glow. Available charging models could not adequately explain any of these phenomena. Through careful experimentation a new “Patched Charge Model” has been developed at the NASA/SSERVI’s Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado at Boulder. Experiments have proven that emission and re-absorption of photoelectrons and/or secondary electrons at the walls of dust microcavities generate large negative charge patches and particle-particle repulsive forces which mobilize dust particles. Experimentation focused on micron sized particles under conditions of ultraviolet illumination, electron-beam, and plasma with electron-beam. Dust was lofted to heights exceeding 2.5 cm, which translates to lofting heights of the same order of magnitude required to produce the lunar horizon glow. Contrary to previous charging models and consistent with the patched charge model, dust under all three conditions were measured as having large negative net charges. Surface mobilization characterizing experiments are underway, investigating magnetic field interaction and surface morphology changes. Greater understanding of electrostatic dust mobilization and transport will enhance current understanding of surface evolution of airless bodies and is expected to assist in explaining unconsidered surface processes.

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