<b>Exploring Volatile Mass Balance Under a Variety of Conditions Through Observations and Modeling on the Moon and Mars</b>

<p dir="ltr">Volatiles (molecules like H₂O and CO₂ that readily vaporize) affect the interior, surface, and atmospheric characteristics of planetary bodies throughout the Solar System. However, the relationship between volatile processes (such as sublimation and deposition) and the evolution of the surface are complex and often poorly understood. To understand the chemical and physical processes occurring on planetary bodies, we first must understand the volatile mass balance on these surfaces. In this dissertation, I use ground-penetrating radar, near-infrared spectroscopy, and numerical modeling approaches to characterize the mass balance of volatiles on the Moon and Mars. In Chapter 2, I map and classify subsurface radar signatures in the northern polar H₂O ice cap related to the migration of surface troughs. These “trough migration paths” are thought to provide a record of H₂O mass balance conditions, and therefore act as a proxy for Mars’ polar paleoclimate. In Chapter 3, I combine the features mapped in Chapter 2 with a phenomenological model to investigate the driving processes and timescales of trough migration to constrain H₂O accumulation and ablation rates at Mars’ north pole over time. In Chapter 4, I quantify the expected contribution of ballistic transport on diurnal timescales of hydroxyl and molecular water to the lunar exosphere and compare to abundances from mass spectrometry data. In Chapter 5, I measure how the diurnal variations of hydroxyl/molecular water are related to illumination and temperature conditions. Each of these studies provides new insight into the processes affecting volatiles and surface evolution across timescales, spatial scales, and planetary body, from individual molecules to massive ice deposits.</p>