Europa: Effects of rotation and tides on tectonic processes Item Type text; Dissertation-Reproduction (electronic) Authors Hoppa, Gregory Vincent, 1972- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 05/10/2021 10:36:44 Link to Item http://hdl.handle.net/10150/282763 INFORMATION TO USERS This manuscript has been reproduced from the microfihn master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. 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Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zed) Road, Ann Aiiwr MI 48106-1346 USA 313/761-4700 800/521-0600 EUROPA: EFFECTS OF ROTATION AND TIDES ON TECTONIC PROCESSES by Gregory Vincent Hoppa A Dissertation Submitted to the Faculty of the DEPARTMENT OF LUNAR AND PLANETARY SCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY WITH A MAJOR IN PLANETARY SCIENCES In the Graduate College THE UNIVERSITY OF ARIZONA 1998 T3MI Ntmber: 9912056 UMI Microform 9912056 Copyright 1999, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, Ml 48103 THE UNIVERSITY OF ARIZONA ® GRADUATE COLLEGE As members of the Final Examination Committee, we certify that we have read the dissertation prepared by Gregory Vincent Hoppa entitled Europa.- Effects of Rotation and Tides on Tectonic Processes and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy Richard J. Greenberg Henry J. Melosh ( ^ Date ' William B. Rnhha.rdI/l^^^yUi/>^ ^ / Date Randall Richardson Lt g • .c^ly J J ^ f P' Date Terry C. Wallace ^ ? ( I Date Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirei&nt. 2- ^ , Dissertation Director^ Date 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from of reproduction of this manuscript in whole or in part may be granted by the head of the major department of the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however permission must be obtained from the author. SIGNED: 4 ACKNOWLEDGMENTS I would like to thank my advisor, Richard Greenberg, for his support and guidance throughout this entire project. H. J. Melosh, William Hubbard, Randall Richardson, and Terry Wallace for comments and suggestions as faculty members on my dissertation committee. Paul Geissler, Daniel Durda, Randy Tufts, and Terry Hurford for additional comments and suggestions that have come out of weekly discussions. Cynthia Phillips and Moses Milazzo for providing mosaics that were used throughout this work and making suggestions for improvements to image products. The Galileo imaging team, lead by Mike Belton, and their associates for their comments and suggestions. The technical staff of the Galileo project for making this study possible. And finally, my parents, James and Nancy Hoppa, for their love and support throughout my graduate career. DEDICATION To Katfay, my wife and best friend. Thank you for keeping my priorities straight. 6 TABLE OF CONTENTS LIST OF FIGURES .11 LIST OF TABLES .14 ABSTRACT .15 CHAPTER L- Introduction .17 I. The Galilean satellites: A miniature solar system ..17 II. The Laplace resonance and tides .19 III. Non-synchronous rotation .21 IV. Introduction to Europa's geology .22 A. Voyager .22 B. Galileo ..23 V. Rotational and geophysical studies of Europa .29 CHAPTER 2: Rotation of Europa: Constraints from Terminator and Limb Positions ..,.31 I. Introduction .31 II. Measviring the rotation rate from the position of the terminator .32 in. Results .38 rv. Additional Constraints on Europa's Rotation Rate .44 A. Cilix .44 B. Limb Fits .46 V. Other Satellites .48 7 TABLE OF CONTENTS - Continued A. lo 48 B. Ganymede 50 VT. Discussion 51 CHAPTER 3: Global Tidal Stress Fields on Europa 56 I. Introduction 56 II. Previous Calculations 57 A. Tidal Fractures on Europa 57 B. Rotational Tidal Stress on Europa 59 C. Polar Wander on Europa 62 m. Reproduction of stress field for non-synchronous rotation 63 IV. Calculation of the diurnal stress field 73 V. Combined stress fields 85 VI. Polar wander 93 VII. Discussion 96 CHAPTER 4: Comparison of Global Stress Models with Features on Europa 103 I. Introduction 103 II. Astypalaea Linea 103 III. Agenor Linea 107 IV. Libya and Thynia Linea (Gray Bands) 111 8 TABLE OF CONTENTS - Continued V. Rhadamanthys Linea 120 VI. Agave and Asterius region 125 VII. Arcuate Ridges 128 VIII. Wedges region 136 IX. Discussion 140 CHAPTER 5: Evidence of strike slip motion on Europa due to tidal stress 149 I. Introduction 149 II. Astypalaea Linea 149 III. Observations of strike-slip faults 153 A. Astypalaea Linea region 153 B. Wedges region 156 C. Conamara Chaos region 159 D. Northern hemisphere bright plains 159 E. Tyre region 163 F. Summary of observations 163 IV. A closer look at the theory of "walking" 167 V. Comparison of theory with observation 175 V. Discussion 179 9 TABLE OF CONTENTS - Continued CHAPTER 6: Tidal Torque between Satellites in Resonance 182 I. Introduction 182 II. Darwin Tides 182 III. Torque from lo on Europa 185 IV. Enceladus and Dione 188 V. Discussion 189 CHAPTER 7: Stereo Images of the Surface of Europa 191 I. Introduction 191 II. Technique for making stereo pairs 191 III. Wedges region 193 IV. Craters 198 A. Pwyll 200 B. Mannan'an 200 C. Cilix 203 V. Discussion 206 CHAPTER 8: Conclusions 211 I. Rotation of Europa: Constraints from terminator and limb positions 211 II. Global tidal stress fields on Europa 212 III. Comparison of global stress models with geologic features on Europa 214 10 TABLE OF CONTENTS - Continued IV. Evidence of strike-slip motion on Europa due to tidal stress 215 V. Tidal torque between satellites in resonance 216 VI. Galileo stereo images of the surface of Europa 217 VII. Future work 218 REFERENCES 221 11 LIST OF FIGURES Figure 1.1. Linear features on Europa as observed by Voyager 24 Figure 1.2. Six impact features identified by Voyager 25 Figure 1.3. Linear features on Europa based on the Greenberg et al. 1998 taxonomy 27 Figure 1.4. New impact features discovered by Galileo 28 Figure 2.1. Galileo image (s0349875113) of the terminator at 1.6 km/pixel 33 Figure 2.2. Voyager 2 image of the terminator 35 Figure 2.3. Voyager 2 image of Europa's terminator with different linear stretches 35 Figure 2.4. Reflectance curve for an typical row in the Galileo terminator image 36 Figure 2.5. Reflectance curve for an typical row in the Voyager 2 image 37 Figure 2.6. Galileo Image of the terminator 39 Figure 2.7. Geologic map of Europa by Lucchitta et al. 1982 42 Figure 2.8. Cilix and the terminator as viewed by Galileo and Voyager 45 Figure 2.9. Europa's limb as viewed by Galileo and Voyager 47 Figure 3.1. Tidal stress field for 1° non-synchronous rotation 66 Figure 3.2. Tidal stress field for 25° of non-synchronous rotation 67 Figure 3.3. Tidal stress field for 50° of non-synchronous rotation 68 Figure 3.4. Tidal stress field for 1° slower-than-synchronous rotation 69 Figure 3.5. Galileo image of the Cadmus - Minos region (resolution 1.6 km/pixel) 72 Figure 3.6. Europa's diurnal tides at quarter orbit intervals 74 Figure 3.7. Diurnal stress field at apocenter 77 Figure 3.8. Diurnal stress field at 1/8 orbit after apocenter 78 Figure 3.9. Diurnal stress field at 1/4 orbit after apocenter 79 Figure 3.10. Diumal stress field at 3/8 orbit after apocenter 80 Figure 3.11. Diumal stress field at pericenter 81 Figure 3.12.