Dissertation Defense: Timothy Hahn Jr.

Our understanding of planetary bodies and their surfaces originates from measurements made by spacecraft instruments and laboratory analysis of extraterrestrial materials. Integration of these datasets can significantly advance the field of planetary geochemistry.  The goal of my dissertation research has been to develop novel methods for interrogating extraterrestrial samples and planetary regoliths, with an emphasis on integrating these complementary datasets. Additionally, my research has focused on utilizing ‘big data’ within the geoscience and planetary science communities, whether that data be geospatial or geochemical in nature. My dissertation research involves two separate but related projects: (1) coupling Apollo 17 soil sample analyses with orbital observations from the Lunar Reconnaissance Orbiter Camera; and (2) development of quantitative compositional mapping (QCM) and lithologic mapping (LM) techniques using the electron microprobe, with specific applications demonstrated using vestan and lunar meteorites.  The results from my dissertation projects are used to (1) correlate the photometric properties of the lunar regolith to geologically interpretable information and address outstanding science questions at the Apollo 17 landing site (e.g., identification of impact melts from Tycho crater), and (2) assess the extent of magmatic differentiation in the vestan crust, and by inference early planetesimals. This dissertation offers new methods for investigating small-scale compositional variations on the Moon and provides new, highly effective methods for petrologic investigations of complex samples for which only limited quantities exist (e.g., returned asteroid samples).