I am grateful for the support and encouragement of my advisor, Clive R. Neal. Were it not for his longanimity and wonderful personality, I doubt I would have survived graduate school much less finished with a promising career ahead of me. I am also thankful to Bradley L. Jolliff, who served as a second, long-distance advisor. His ideas and patience in explaining them to me was a true inspiration. Both of these men will always serve as the model of a mentor for me. I wish to thank the staff at

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... e Lunar and Planetary Institute for all their help during the two months I spent with them, especially Steve Mackwell for giving me the opportunity, Laurel Kirkland for her guidance, and Brian Fessler for all the time he devoted to teaching me ISIS and ensuring I had all the necessary data for my research. I want to thank my hockey team, the Michiana Sting, for being such great friends and supporting my academic and athletic endeavors. Saving the best for last, I want to thank my husband, James Kramer, for lifting me up in my darkest moments, and making me realize that I really could do this. xiv