Introduction to Planetary Geomorphology Ronald Greeley Frontmatter More Information

Cambridge University Press 978-0-521-86711-5 - Introduction to Planetary Geomorphology Ronald Greeley Frontmatter More information

Introduction to Planetary Geomorphology

Nearly all major planets and moons in our Solar System have been visited by spacecraft, and the data they have returned have revealed the incredible diversity of planetary surfaces. Featuring a wealth of images, this textbook explores the geologic evolution of the planets and moons. Introductory chapters discuss how information gathered from spacecraft is used to unravel the geologic complexities of our Solar System. Subsequent chapters focus on current understandings of planetary systems. The textbook shows how planetary images and remote sensing data are analyzed through the application of fundamental geologic principles. It draws on results from spacecraft sent throughout the Solar System by NASA and other space agencies. Aimed at undergraduate students in planetary geology, geoscience, astronomy, and Solar System science, it highlights the differences and similarities of planetary surfaces at a level that can be readily understood by non-specialists. Electronic versions of ﬁgures from the book are available at www.cambridge.org/Greeley.

R ONALD G REELEY (1939–2011) was a Regents’ Professor in the School of Earth and Space Exploration, Arizona State University, Director of the NASA–ASU Regional Planetary Image Facility, and Principal Investigator of the Planetary Aeolian Laboratory at NASA- Ames Research Center. He co-authored several well-known books on planetary surfaces, including The Compact NASA Atlas of the Solar System and Planetary Mapping (both available from Cambridge University Press).

Introduction to Planetary Geomorphology

Ronald Greeley

Arizona State University

CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo, Delhi, Mexico City Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK

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First published 2013

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A catalog record for this publication is available from the British Library

Library of Congress Catalog in Publication data Greeley, Ronald. Introduction to planetary geomorphology / Ronald Greeley. p. cm. ISBN 978-0-521-86711-5 (hardback) 1. Planets – Geology – Popular works. 2. Planets – Crust – Popular works. 3. Geomorphology. I. Title. QB603.G46.G74 2013 551.41099902–dc23 2011053270

ISBN 978-0-521-86711-5 Hardback

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For Randall and Lidiette Thomas, Rebecca, and Jennifer

CONTENTS

Foreword by Robert T. Pappalardo page xi 2.6 Geophysical data 25 Preface xiii 2.7 Image processing 26 Acknowledgments xiv 2.8 Resolution 28 2.9 Electronic data records (EDRs) 30 1 Introduction 1 2.10 Cartography 30 1.1 Solar System overview 1 Assignments 33 1.1.1 The terrestrial planets 1 1.1.2 The giant planets 3 3 Planetary morphologic processes 34 1.1.3 Small bodies, Pluto, and 3.1 Introduction 34 “dwarf planets” 4 3.2 Tectonism 34 1.2 Objectives of Solar System exploration 6 3.3 Volcanic processes 37 1.2.1 Planetary geology objectives 6 3.3.1 Volcanic eruptions 38 1.2.2 Astrobiology 7 3.3.2 Volcanic morphology 38 1.3 Strategy for Solar System exploration 7 3.3.3 Volcanic craters 40 1.4 Flight projects 9 3.3.4 Intrusive structures 42 1.5 Planetary data 12 3.4 Impact cratering 43 1.6 Planetary research results 13 3.4.1 Impact cratering mechanics 43 Assignments 14 3.4.2 Impact craters on Earth 44 3.4.3 Impact craters and planetary 2 Planetary geomorphology methods 15 environments 50 2.1 Introduction 15 3.5 Gradation 51 2.2 Approach 15 3.5.1 Weathering 51 2.3 Planetary geologic maps 17 3.5.2 Mass wasting 53 2.4 Geologic time 20 3.5.3 Processes associated with the 2.5 Remote sensing data 22 hydrologic cycle 53 2.5.1 Visible imaging data 23 3.5.4 Aeolian processes 54 2.5.2 Multispectral data 24 3.5.5 Periglacial processes 56 2.5.3 Thermal data 24 3.6 Summary 58 2.5.4 Radar imaging data 24 Assignments 58 2.5.5 Ultraviolet, X-ray, and gamma-ray data 25

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Contents viii

4 Earth’sMoon 59 7.2 Exploration 126 4.1 Introduction 59 7.3 Interior 129 4.2 Lunar exploration 59 7.4 Surface composition 130 4.2.1 Pre-Apollo studies 59 7.5 Geomorphology 131 4.2.2 The Apollo era 62 7.5.1 Physiography 131 4.2.3 Post-Apollo exploration 65 7.5.2 Impact craters 132 4.3 Interior characteristics 71 7.5.3 Volcanic features 134 4.4 Surface composition 72 7.5.4 Tectonic features 137 4.5 Geomorphology 75 7.5.5 Gradation features 139 4.5.1 Impact craters and basins 75 7.6 Geologic history 145 4.5.2 Highland plains 77 Assignments 146 4.5.3 Mare terrains 77 4.5.4 Sinuous rilles 78 8 The Jupiter system 147 4.5.5 Volcanic constructs 82 8.1 Introduction 147 4.5.6 Tectonic features 82 8.2 Exploration 147 4.5.7 Gradational features 84 8.3 Jupiter 148 4.6 Geologic history of the Moon 85 8.4 Io 149 Assignments 90 8.4.1 Impact features (none!) 152 8.4.2 Volcanic features 152 5 Mercury 91 8.4.3 Tectonic features 155 5.1 Introduction 91 8.4.4 Gradation features 155 5.2 Mercury exploration 91 8.4.5 Io summary 156 5.3 Interior characteristics 92 8.5 Europa 156 5.4 Surface composition 93 8.5.1 Impact features 157 5.5 Geomorphology 94 8.5.2 Tectonic features 158 5.5.1 General physiography 94 8.5.3 Volcanic features 160 5.5.2 Impact craters 95 8.5.4 Gradation features 162 5.5.3 Multi-ring basins 99 8.5.5 Europa summary 162 5.5.4 Volcanic features 102 8.6 Ganymede 162 5.5.5 Tectonic features 103 8.6.1 Physiography 162 5.5.6 Gradation features 104 8.6.2 Impact features 163 5.6 Geologic history 104 8.6.3 Tectonic features 165 Assignments 105 8.6.4 Volcanic features 168 8.6.5 Gradation features 168 6 Venus 106 8.6.6 Ganymede summary 169 6.1 Introduction 106 8.7 Callisto 170 6.2 Venus exploration 106 8.7.1 Physiography 170 6.3 Interior characteristics 112 8.7.2 Impact features 171 6.4 Surface composition 113 8.7.3 Gradation features 173 6.5 Geomorphology 113 8.7.4 Callisto summary 174 6.5.1 General physiography 113 8.8 Small moons and rings 174 6.5.2 Impact craters 114 8.9 Summary 175 6.5.3 Volcanic features 116 Assignments 176 6.5.4 Tectonic features 118 6.5.5 Gradation features 120 9 The Saturn system 177 6.6 Geologic history 124 9.1 Introduction 177 Assignments 125 9.2 Exploration 177 9.3 Saturn 178 7Mars 126 9.4 Satellites 178 7.1 Introduction 126 9.5 Titan 179

Contents ix

9.6 Enceladus 185 10.5 Summary 208 9.7 Intermediate-size satellites 188 Assignments 209 9.7.1 Mimas 188 9.7.2 Tethys 190 11 Planetary geoscience future 210 9.7.3 Dione 192 11.1 Introduction 210 9.7.4 Rhea 193 11.2 Planetary protection 210 9.7.5 Iapetus 194 11.3 Missions in ﬂight and anticipated 9.7.6 Small satellites 197 for launch 211 9.8 The ring system 198 11.4 Extended missions 214 9.9 Summary 199 11.5 Summary 214 Assignments 200 Assignments 215

10 The Uranus and Neptune systems 201 Appendices 216 10.1 Introduction 201 References 221 10.2 Uranus and Neptune 201 Further reading 225 10.3 Uranian moons 202 Index 227 10.4 Neptunian moons 206

FOREWORD

Robert T. Pappalardo

Ron Greeley’s Introduction to Planetary Geomorphology is misunderstanding of his dissertation topic of “lunulitiform the single most outstanding and complete compendium of bryozoans” as somehow related to the geology of the the science of planetary geology that exists. It is a fully Moon! complete and up-to-date synopsis of the science of planetary Greeley trailblazed the burgeoning field of planetary geology, written in Greeley’s characteristically succinct geomorphology at Ames. While the Apollo missions and clear style. This is the ideal primer for an upper under- explored the Moon, Greeley conducted detailed compar- graduate course, and an excellent compendium for the isons of lunar sinuous rilles with terrestrial volcanic land- interested amateur or professional astronomer. The figures forms in Hawaii and the Snake River Plain of Idaho, within are all the “right” ones – the very best for illustrating making important contributions to understanding lunar fundamental concepts and “type examples” of terrestrial processes. Then, as early 1970s Mariner 9 photos began and planetary processes – compiled here in one place. to reveal Mars, Greeley used wind tunnels at Ames to Ron Greeley passed away suddenly in the fall of 2011, simulate how aeolian processes might operate on the Red just a month after submitting this complete book for pub- Planet. His seminal work on terrestrial and planetary lication. It will remain a tribute to his life’s work, encapsu- aeolian processes is being applied anew today to explan- lating his passions both for research and for teaching. ation of dunes on Saturn’s moon Titan, which were Greeley was a scholar and a gentleman, and a pioneer in recently discovered by the Cassini spacecraft. the methods of planetary geology. His Ph.D. research at the Greeley was involved in nearly every major spacecraft University of Missouri at Rolla included field work on the mission flown in the Solar System since Apollo. This Mississippi Barrier Islands, where he studied modern liv- includes the Magellan mission to Venus and the Galileo ing forms of organisms that he was researching in the fossil mission to Jupiter. He contributed to a panoply of rock record. This work laid the foundation for his practical missions to Mars: Mariners 6, 7, and 9, Viking, Mars approach to deciphering the processes that have shaped the Pathfinder, Mars Global Surveyor, the two Mars surfaces of other planets by studying their modern Earth Exploration Rovers, and the European Space Agency’s analogues. In the laboratory and the field, Greeley would (ESA’s) Mars Express. He chaired many NASA and effectively visit other worlds and other times. National Research Council (NRC) panels, including Greeley’s career in planetary geology began in 1967, NASA’s Mars Exploration Program Analysis Group, the when he was called to active military service just a year Mars Reconnaissance Orbiter Science Definition Team, after receiving his Ph.D. Fortunately, he was assigned the NASA–ESA Joint Jupiter Science Definition Team, to NASA’s Ames Research Center to work on Apollo- the NRC’s Committee on Planetary and Lunar related problems. He occasionally mused about whether Exploration, and most recently the Planetary Science this interesting assignment came about by someone’s Subcommittee of the NASA Advisory Council.

Foreword xii

For those fortunate enough to have known Ron Greeley As Greeley would say: a journey of a thousand miles ﬁrst-hand, through his teaching, research, committees, or begins with a single step. In your introduction to the friendship, this book will serve as a lasting tribute. For planets and moons of our Solar System, the journey of those learning of him, and from him, for the ﬁrst time, 4.5 billion kilometers begins with a turn of the page. An welcome to this man and his work. adventure awaits.

PREFACE

Planetary geoscience had its inception with the birth of the Uranus and Neptune, because dozens of successful space- Space Age in the early 1960s. In the ensuing decades, it craft have visited our nearest planetary neighbors, in con- has evolved into a discipline that is recognized by sections trast to the limited data returned from “flybys” of the of professional organizations such as the Geological Voyager spacecraft to the planets beyond Saturn. Society of America and the American Geophysical Our journey to explore the geomorphology of the Solar Union, as well as being taught at the university level. System begins with introductory chapters that introduce Much of our understanding of the geology of extra- the planets and other objects of planetary geoscience terrestrial objects is derived from remote sensing data – interest, discuss the methods used in studying extraterres- primarily images that portray planetary surfaces. In fact, trial objects, and review the fundamental geomorphic discoveries such as the dry river beds on Mars, the tectonic processes on Earth that can be compared with what we deformation of Venus, and the actively erupting volcanoes see on other planets and satellites. on Jupiter’s moon Io all came from pictures taken from Key references are given in the text and listed at the spacecraft. Thus, the focus of this book is on the geo- back of the book. The end of this book includes morphology of solid-surface objects in our Solar System additional reading for those who wish to delve into the and the interpretations of the processes that led to the chapter topic in more detail. Because images form the diverse landforms observed. Geomorphology, however, basis of much of planetary geomorphology, figure cap- must be analyzed in the context of broader geoscience; tions generally include the basic NASA or other space consequently, in the chapters on the individual planetary agency data for the frames shown, to enable the use of systems, the geophysics and interior characteristics are various electronic search engines for obtaining additional reviewed along with our current understanding of surface information. compositions and the general geologic histories. Of I hope that you find the exploration of the Solar System course, our knowledge of the Solar System is far from a rewarding experience. While many planets and satellites uniform from one planet to another, dependent upon the show landforms that are quite familiar to geologists, numbers and types of spacecraft that have returned data. others hold surprises that have not yet been explained or Thus, the chapters on the Moon and Mars are more understood. Have fun, and maybe you can solve some of detailed than those on the outermost planet systems, these mysteries!

xiii

ACKNOWLEDGMENTS

I thank the countless graduate and undergraduate students The preparation of this book was facilitated by the from planetary geoscience classes who have provided the talents of Sue Selkirk for illustrations, Amy Zink for stimulus for this book. Students have the marvelous preparation of the final versions of the images, and Dan capacity to ask thought-provoking questions that remind Ball and the NASA Space Photography Laboratory for planetary scientists that there is still a great deal to learn access to the planetary images; I am grateful for their about the Solar System. I also thank my colleagues who are substantial help. I thank Stephanie Holaday for her tireless at the forefront of planetary exploration for their keen word-processing of many draft iterations as well as track- insight into the complexities of geologic surface evolution. ing down permissions for previously published figures. While they have helped me tremendously in understanding Her assistance has been invaluable and is much appreci- these complexities, any errors in fact or interpretation con- ated. Finally, I thank Cindy Greeley for her editing skills tained herein are solely my responsibility. and corrections to my flawed writing!

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