Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Physics

Date of Defense

7-10-2019

Graduate Advisor

Erika Gibb

Co-Advisor

Paul Parris

Committee

Boncho Bonev

Bruce Wilking

Alexei Yamilov

Abstract

Understanding the evolution of the solar system, as well as its current volatile content, requires knowledge of the initial conditions present in the solar nebula. As some of the first objects to accrete in the solar nebula, cometary nuclei are among the most primitive remnants of solar system formation, and their present-day volatile composition likely reflects the composition and conditions where (and when) they formed. As such, the volatile compositions of cometary nuclei may serve as "fossils" of solar system formation. High-resolution near-infrared spectroscopy offers a valuable tool for sampling the primary volatile (i.e., ices subliming directly from the nucleus) composition of comets via analysis of fluorescence emission in cometary comae. Sampling fluorescence emission from a suite of primary volatiles has become possible from state-of-the-art ground-based observatories.

An overarching goal of comet volatile composition studies is determining whether comets can be classified according to their volatile content and what this reveals about the history of the early solar system. Early work produced encouraging results, but recent work has left pressing questions regarding whether a compositional taxonomy based on near-infrared measurements is feasible, as well as how to place such measurements into a meaningful context. These include questions such as: Are observed systematic compositional differences between ecliptic comets and Oort cloud comets the result of evolutionary effects or reflective of formative conditions? Is temporal variability in coma composition a common phenomenon, and if so, how can present-day measurements be related to natal solar system conditions? This work examines these questions in the context of near-infrared measurements of an Oort cloud comet, a Jupiter-family comet, and an ecliptic comet. The interplay between evolutionary effects, formative conditions, and temporal variability is examined in the context of the evolving composition-based taxonomy and the interpretation of the results of comet composition studies.

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