Western University Scholarship@Western Electronic Thesis and Dissertation Repository 8-3-2018 2:00 PM Impact Craters on Titan: Finalizing Titan's Crater Population Joshua E. Hedgepeth The University of Western Ontario Supervisor Neish, Catherine D. The University of Western Ontario Graduate Program in Geophysics A thesis submitted in partial fulfillment of the equirr ements for the degree in Master of Science © Joshua E. Hedgepeth 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Geology Commons, Geomorphology Commons, and the Geophysics and Seismology Commons Recommended Citation Hedgepeth, Joshua E., "Impact Craters on Titan: Finalizing Titan's Crater Population" (2018). Electronic Thesis and Dissertation Repository. 5618. https://ir.lib.uwo.ca/etd/5618 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Titan is one of the most dynamic moons in the solar system. It is smaller than Earth and much colder, yet Titan is eerily similar to Earth, with rivers, rain, and seas, as well as sand seas that wrap around the equator. However, the rivers are made of hydrocarbons rather than water and the sand made of organics rather rock. We can use Titan’s impact craters to study how these processes modify the surface by comparing the craters depths, diameters and rim heights of Titan’s craters with fresh craters. Therefore, we have used the complete data set from NASA’s Cassini mission to update Titan’s crater population finding 30 new craters (90 total). We find that Titan’s craters are statistically shallower than those observed on similarly sized icy moons (e.g. Ganymede). We suggest this is due to sand and sediment infilling into the crater and fluvial erosion of the rims. Keywords Titan, Cassini-Huygens, Impact Cratering, Dragonfly, Geomorphology, Fluvial, Aeolian, Radar, i Co-Authorship Statement Chapter 1 and 3 were written by J. Hedgepeth with edits and suggestions from Dr. C. Neish. Chapter 1 is a literature review of previous work. Chapter 3 is a review of the work presented here along with limitations, assumptions, and future work. Chapter 2 is a modified article set to be submitted to Icarus for a publication tentatively titled “Impact Craters on Titan: Finalizing Titan's Crater Population”. Co-authors are Dr. Catherine Neish, Dr. Elizabeth Turtle, and Dr. Bryan Stiles and the Cassini RADAR Team. Dr. B. Stiles produced the SARTopo data. All RADAR data was collected by J. Hedgepeth, and all the data processing and results were produced by J. Hedgepeth. Dr. C. Neish, Dr. E. Turtle, and Dr. B. Stiles contributed to the interpretations and structure of the article as well as editorial suggestions. ii Acknowledgments Thank you to Dr. Catherine Neish for her great guidance and advice throughout this project. Thanks also for your patience and your encouragement for a healthy work life balance. Thank you to everyone in the Neish research group for all your support and aid. Thanks particularly to Alyssa Werynski, as the only other student in the group in the Titan field. Thanks to Dr Elizabeth Turtle for the guidance and for welcoming me into the wonderful Titan community. Thanks to Dr. Brittany Schmidt for suggesting I apply to Western, and thanks for your continual support as I grow as a young scientist. Without you I probably would not have made it this far. Thanks to my friends for the emotional support. Thanks to Bryan Stiles for the awesome topography data that, while frustrating at times, has been the basis for the most interesting part of my research. Thank you to the Technologies for Exo-Planetary Science (TEPS) CREATE program for the funding and opportunities to broaden my background to include exoplanetary research and for the opportunities to network in this early stage of my career. Thank you to my committee for reviewing and critiquing my work. Thank you to my department and particularly to Dr. Gordon Osinski for two awesome classes that gave me the opportunity to study multiple terrestrial analogs that we see on Titan. iii Table of Contents Abstract ........................................................................................................................... i Co-Authorship Statement ............................................................................................... ii Acknowledgments ......................................................................................................... iii Table of Contents .......................................................................................................... iv List of Tables ................................................................................................................ vii List of Figures ............................................................................................................. viii List of Appendices ....................................................................................................... xiii Chapter 1 .........................................................................................................................1 1 Introduction ................................................................................................................1 1.1 The Saturnian System ..........................................................................................1 1.2 Titan ....................................................................................................................4 1.2.1 Titan’s Atmosphere and Origin .................................................................6 1.2.2 Titan’s Surface ....................................................................................... 10 1.3 Impact Cratering ................................................................................................ 13 1.3.1 Formation ............................................................................................... 13 1.3.2 Crater Morphology ................................................................................. 15 1.3.3 Crater Morphometry ............................................................................... 16 1.3.4 Titan Craters ........................................................................................... 19 1.3.5 Crater Degradation ................................................................................. 23 1.3.6 Significance ............................................................................................ 24 1.4 Radar Remote Sensing ....................................................................................... 24 1.4.1 Surface Properties................................................................................... 25 1.4.2 Cassini RADAR and Related Data Products ........................................... 26 1.4.3 Cassini VIMS and ISS Instruments ......................................................... 28 iv 1.5 Summary ........................................................................................................... 29 1.6 References ......................................................................................................... 30 Chapter 2 ....................................................................................................................... 41 2 Identifying Impact Craters on Titan and Constraining their Morphology (i.e. Diameter, Depths, and Rim Heights) ......................................................................................... 41 2.1 Introduction ....................................................................................................... 41 2.2 Methodology ...................................................................................................... 43 2.2.1 Data Gathering and Processing ............................................................... 43 2.2.2 Crater Mapping ...................................................................................... 43 2.2.3 Crater Topography ................................................................................. 47 2.3 Results ............................................................................................................... 53 2.3.1 Final Crater Population ........................................................................... 53 2.3.2 Crater Counts ......................................................................................... 61 2.3.3 Crater Topography ................................................................................. 63 2.4 Conclusion ......................................................................................................... 71 2.5 References ......................................................................................................... 73 Chapter 3 ...................................................................................................................... 78 3 Conclusions .............................................................................................................. 78 3.1 Titan’s Craters ................................................................................................... 78 3.2 Limitations ......................................................................................................... 80 3.2.1 Assumptions in Crater Mapping ............................................................