THE COMPOSITION OF THE LUNAR CRUST: AN IN-DEPTH REMOTE SENSING VIEW A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAIʻI AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN GEOLOGY AND GEOPHYSICS August 2016 By Myriam Lemelin Dissertation Committee: Paul G. Lucey, Chairperson G. Jeffrey Taylor Jeffrey J. Gillis-Davis Peter Englert Karen Meech Keywords: Moon; Remote sensing; Spectroscopy; Lunar crust; Central peak; Basin ring ii ACKNOWLEDGEMENTS Five years ago I was working at the Lunar and Planetary Institute with amazing colleagues such as Carolyn Eve, David Blair, Kirby Runyon, Stephanie Quintana and Sarah Crites. We were discussing our future on our way back home from work, stopping to see the alligators and armadillos on the way, and they asked me what I wanted do next. If I could do anything, what would it be? I wanted to do a PhD in Hawaii with Paul Lucey. I feel very privileged that it happened, as it has been such a marking moment in my life, both from a science and a personnel perspective. I want to thank many people who contributed in making this experience incredible. I want to thank my advisor, Paul Lucey, for his endless creative ideas, his impressive knowledge and for allowing me to take part in many science meetings and conferences where I learned so much about various aspects of planetary sciences, and where I met numerous space enthusiast scientists. I want to thank my dissertation committee members, Jeff Taylor, Jeff Gillis-Davis, Peter Englert, and Karen Meech for their suggestions and comments. I want to thank my comprehensive exam committee members, Julia Hammer, Scott Rowland, Ed Scott, and Peter Isaacson. I especially enjoyed taking Julia Hammer’s mineralogy class even if it sounded terrifying, I learned so much. I enjoyed taking Scott Rowland’s class where we mapped lava flows and sampled active lava, it was a memorable first trip to Big Island. I thank Ed Scott for teaching me about asteroids and comets. I enjoyed it so much that I will soon embark on the OSIRIS-REx mission to asteroid Bennu. I want to thank collaborators who helped with various aspects of the research presented herein: Greg Neumann, Erwan Mazarico, Ben Greenhagen, Katarina Miljković, Lisa Gaddis, Trent Hare, Mike Barker, Makiko Ohtake, Mark Wood, Jessica Norman, and Ashley Kakazu. iii I thank Ethan Kasner, and Eric Pilger for their previous technical support, Vi Nakahara, Grace Furuya and Rena Lefevre for their help with the massive amount of administrative work involved. This experience would not have been the same without the lunatic friends I made in Hawaii, Sarah Crites, Katie Robinson, David Trang, Laura Corley, Eugenie Song, Tanja Giebner, and Elizabeth Fisher. Thanks for the great discussions. Thanks to my officemates and friends Caroline Caplan, Estelle Bonny, Melissa Adams, Andrea Gabrieli, David Frank, Tayro Acosta, Myriam Telus, and Elise Rumpf. You made every work day feels like just another day in paradise, besides the days I was hiding in my office. Thanks to the GG peeps. You enriched the experience in so many ways, including teaching me precious things such as what a meme is and how to pronounce the word salmon. Thanks to my friends in Canada for always being present, and to those who could visit me in paradise. Thanks to my family who was so supportive, truly tried to understand what I was doing, and made sure I was happy. Last but not the least, thanks to my love Simon (and the fluffiest of all, Paco). It has been extremely difficult to leave home every time, but knowing that you were proud of me and that you were waiting for me to go on the next adventures made it bearable. This work was supported by the financial help from the Hawaii Institute of Geophysics and Planetology, and from the Natural Sciences and Engineering Research Council of Canada (PGSD3 - 442668 - 2013). iv ABSTRACT In this dissertation, we investigate the composition of the lunar crust by conducting a quantitative and comprehensive analysis of the mineralogical composition of the central peak in 61 craters and the innermost ring of 18 impact basins, which expose material originating from various depths, using reflectance data acquired by the Kaguya Multiband Imager and Spectral Profiler in the visible and near infrared wavelengths. We also place constraints on the depth of origin of the material exposed by the innermost ring of impact basins using impact modeling code that tracks the fate of tracer particles in the target site. We find that the central peaks in the Feldspathic Highlands Terrane are composed of anorthositic lithologies. The variability of their mafic assemblage suggests that some of them are sampling intrusions of mafic material into that crust, though no ultramafic material was detected that might suggest fully differentiated plutons. The central peaks in the South Pole-Aitken basin indicate mafic compositions at all depths, consistent with the presence of a large differentiated melt sheet that assimilated anorthositic crust and ultramafic mantle. The central peaks in the thorium rich Procellarum KREEP Terrane are composed of lithologies intermediate between the anorthositic material of the Feldspathic Highlands Terrane and the more mafic South Pole- Aitken Basin Terrane. We find that the most abundant rock type is anorthosite on the innermost ring of most basins, consistent with our impact modeling results suggesting that the innermost rings are dominated by crustal material. Models indicate that most basins excavate mantle material and should expose a small proportion of such on their innermost ring. However, we do not detect ultramafic lithologies, thus mantle exposures should be present at the subpixel scale, or intermixed with crustal component. v We also produced various datasets that are now available to the lunar community, such as maps of olivine, low- and high-calcium pyroxene, plagioclase, iron and optical maturity parameter at 62 meters per pixel (available from the USGS Astropedia website), and maps of the normal albedo measured by the Lunar Orbiter Laser Altimeter at 3 and 1 km per pixel (available on the Planetary Data System website). vi TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................................... iii ABSTRACT .................................................................................................................................... v LIST OF TABLES ......................................................................................................................... xi LIST OF FIGURES ...................................................................................................................... xii LIST OF ABBREVIATIONS AND VARIABLES ..................................................................... xix Chapter 1. Introduction ................................................................................................................... 1 1.1 Our closest celestial neighbor ......................................................................................... 1 1.2 The formation of the primary crust ................................................................................. 1 1.3 The evolution of the primary crust: cratering history and geochemical terranes ............ 2 1.4 The composition of the lunar crust interpreted by the study of lunar samples ................ 3 1.5 The composition of the lunar crust interpreted by the study of impacts features ............ 4 Chapter 2. Lunar central peak mineralogy and iron content using the Kaguya Multiband Imager: Reassessment of the compositional structure of the lunar crust ..................................................... 7 2.1. Introduction .................................................................................................................... 8 2.2. Background................................................................................................................... 10 2.3. Data and Methods ......................................................................................................... 11 2.3.1 Multiband Imager UVVIS/NIR data ................................................................. 11 2.3.2 Hapke radiative transfer model ......................................................................... 13 2.3.3 Depth estimates ................................................................................................. 18 2.4. Results .......................................................................................................................... 19 2.4.1 Mineral abundances .......................................................................................... 19 2.4.2 Exposures of purest anorthosite ........................................................................ 25 2.4.2 The Mafic Mineral Assemblages of Central Peaks ........................................... 28 2.5. Discussion..................................................................................................................... 31 2.6. Conclusion .................................................................................................................... 33 vii Chapter 3. Mineralogy and constraints on the depth of origin of impact basin rings using the Kaguya Multiband Imager: Reassessment of the compositional structure of the lunar crust ....... 35 3.1. Introduction .................................................................................................................