Clouds and Hazes in Planetary Atmospheres Thesis by Peter Gao In Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2017 Defended September 8th, 2016 ii © 2017 Peter Gao ORCID: 0000-0002-8518-9601 All rights reserved iii Live Long and Prosper iv TABLE OF CONTENTS Table of Contents . iv Acknowledgements . vi Abstract . xi List of Illustrations . xii List of Tables . xx Published Content and Contributions . xxii Chapter I: Space: The Final Frontier . 1 Chapter II: Bimodal Distribution of Sulfuric Acid Aerosols in the Upper Haze of Venus . 8 2.1 Abstract . 8 2.2 Introduction . 9 2.3 Model . 12 2.3.1 Model Setup . 12 2.3.2 Thermodynamics of H2SO4 . 19 2.3.3 Water Vapor Profile . 20 2.3.4 Eddy Diffusion . 21 2.3.5 Meteoric Dust . 22 2.3.6 Winds . 24 2.4 Results & Discussion . 26 2.4.1 Nominal Results . 26 2.4.2 Periodic Behavior and Precipitation on Venus . 36 2.4.3 Variations in the Sulfur Production Rate . 39 2.4.4 Transient Wind Results . 42 2.5 Summary & Conclusions . 45 Chapter III: Constraints on the Microphysics of Pluto’s Photochemical Haze from New Horizons Observations . 54 3.1 Abstract . 54 3.2 Introduction . 55 3.3 Model . 55 3.4 Results & Discussion . 62 3.4.1 Comparison to Data . 62 3.4.2 Effects of Condensation . 67 Chapter IV: Aggregate Particles in the Plumes of Enceladus . 75 4.1 Abstract . 75 4.2 Introduction . 75 4.3 Aggregate Model . 77 4.4 Observations and Model Setup . 78 4.5 Fitting to Data . 81 4.6 Results . 83 v 4.7 Discussion . 91 Chapter V: Microphysics of KCl and ZnS Clouds on GJ 1214 b . 102 5.1 Abstract . 102 5.2 Introduction . 102 5.3 Model . 106 5.3.1 Model Description & Setup . 106 5.3.2 Microphysical Properties of KCl & ZnS . 108 5.4 Results . 110 5.4.1 The Lack of Pure ZnS Clouds . 110 5.4.2 Variations with Kzz . 110 5.4.3 Variations with Metallicity . 116 5.4.4 Mixed Clouds . 121 5.5 Discussion . 123 5.6 Conclusions . 127 Chapter VI: Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Re- flected Light Spectra . 134 6.1 Abstract . 134 6.2 Introduction . 135 6.3 Sulfur in Giant Exoplanets . 136 6.4 Methods . 140 6.4.1 Model Atmosphere . 140 6.4.2 Cloud Model and Haze Treatment . 142 6.4.3 Geometric Albedo Model . 143 6.4.4 WFIRST Noise Model . 144 6.5 Results . 145 6.6 Discussion . 150 Appendix A: CARMA Overview . 158 A.1 A Brief History of CARMA . 158 A.2 CARMA Machinery . 158 A.3 Nucleation . 159 A.4 Condensation/Evaporation . 162 A.5 Coagulation/Coalescence . 164 A.6 Vertical Transport . 165 vi ACKNOWLEDGEMENTS Here we are at last. It’s hard to believe that it has almost been six years since I crossed the border between Canada and the United States to start my journey at Caltech. These past six years have been an extraordinary time in my life, filled with both the highest of highs, and the lowest of lows. There were lots of struggles and tough times, but also incredible experiences that I will cherish forever. None of this would’ve mattered though, if it were not for the people here, those who shared in my experiences, those who helped me with my problems, who listened to both my complaints and my good news, and above all, those who cared. It’s tough to be away from family, and that’s why many here have become a second one for me. I would like to begin by thanking the unsung heroes of the office, the admin and tech staff. I thank Irma Black, Margaret Carlos, and Ulrika Terrones for helping me deal with the simplest of bureaucratic nightmares that would drive me up the wall. I have always said that they keep us alive, and I maintain that. I also thank Mike Black, Scott Dungan, and Ken Ou for keeping our science machines running, our data safe, and our brains from exploding whenever we need to do anything remotely tech-related. I would also like to thank my distant (and not so distant) collaborators. David Crisp advised me on my second paper (Chapter 2 of this thesis), and I thank him for his unending knowledge of Venus and radiative transfer, which he is able to rattle off at no less than 10% the speed of light. I thank Ty Robinson, who helped me with my third paper about exoplanet photochemistry, for his calm demeanor, patience with my ignorance, and unlimited skill set. I thank Vikki Meadows and the VPL team for their support, both financially and academically, and for their encouragements throughout the years. I thank Danie “from Taiwan” Liang for his insights into my ideas, and his dedication to his old research group. Finally, I thank my current collaborator, Bj’orn´ Benneke, for being the most patient man alive. I want to especially thank Peter Plavchan, Jonathan Gagné, and Elise Furlan for their guidance and help on the NIR RV project, which has lasted longer than any project in this thesis. I started working with Peter in early 2011, and our relationship since then has been extremely helpful for my professional career. I thank Peter for his patience, perseverance, mentorship, and calm in the face of a limitless number vii of coding issues and data problems. I thank Jonathan and Elise for breaking Peter and I out of our endless struggle for answers with fresh views and skillful solutions; if it weren’t for them I would not have been able to publish. The funny thing about being in a small department is that you can end up “working” with everyone. This can range from actual advising, to being in the same reading class. Thus, I would like to thank the Professors, postdocs, and research staff of the Planetary Science option. I thank Mike Brown for putting up with my loudness, for always being open to questions as long as his door is open, and for putting together a very interesting class for me to TA. I thank Bethany Ehlmann for answering some of my dumb Mars questions, for leading a very informative Mars reading class, and for being one of the architects of the amazing Iceland trip. I thank Andy Ingersoll for always asking the best questions during any seminar, for indulging my attempts at doing Enceladus research (see Chapter 4 of this thesis), and for his pure Awe- someness. Although he is not Planetary, I thank Paul Asimow for being just an incredible Professor, orchestra conductor, evil mustache wearer, and all around fun dude. I thank my thesis committee, Geoff Blake, Heather Knutson, Dave Stevenson, and Yuk Yung. I thank Geoff for always wearing a smile in the hallway and for always giving out sound advice. I thank Heather for being extraordinarily patient with me when I attempted to analyze that one phase curve that I just didn’t have time for, and for being totally ok with me switching to another project when it seemed right. I also thank Heather for teaching me the importance of when to say “enough” when the project doesn’t seem to be working out. I thank Dave for his unrelenting dedication to Planetary Science. He intimidated me at first, and though that still may be true sometimes, I know that Dave is just a big teddy bear with a heart of metallic hydrogen (in a good way). Though we did not continue publishing papers together after our first, I thank Dave for always having the patience to entertain my questions, for always answering questions precisely, and for critiquing questions that aren’t asked correctly. Yuk. What I can I say. Yuk Yung has his own style, #yukyungstyle, if you will. There are not enough words for me to truly spell out the ways that I have appreciated his support and help as my advisor. I’ll try anyway though. Yuk’s style is unique, and it may not be everyone’s tea. It was mine, though. It was good tea. It is still good tea. I thank Yuk for his absolute dedication to his students. I thank him for the way he is willing to set aside his nights to make sure that we are on the right track. viii I thank him for his high standards for us; it’s no secret that working with Yuk is like doing 2 (or more) PhD’s. I thank Yuk for his rambling thoughts on poetry, politics, and life. I thank him for his tireless efforts in writing proposals so that we can all have food to eat. I thank him for trying his hardest to send all of us to conferences so that we may all get a chance to become famous. I thank him for treating me like a colleague as I near the end of my PhD. I thank him for being Yuk. Beyond Yuk, there is the Yuk Army. I thank Dr. Run-Lie Shia for being the best problem solver, for always entertaining my questions, and for his tireless dedication to keeping our models intact and running. I thank Dr. Sally Newman for her work in trying to save the planet, and for helping my fiancée when she needed work. I will never forget what she and Yuk did for us in our time of need. Finally, I thank Dr. Renyu Hu for his advising on my third paper, for his great insights on photochemistry, and his and his wife’s friendship.