The New Solar System
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The New Solar System FOURTH EDITION TheThe NewSolarSolar SystemSystem EDITED BY J. Kelly Beatty Carolyn Collins Petersen Andrew Chaikin SKY PUBLISHING ® CORPORATION & PUBLISHED BY SKY PUBLISHING CORPORATION 49 Bay State Road, Cambridge, Massachusetts 02138 AND BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK http://www.cup.cam.ac.uk 40 West 20th Street, New York, NY 10011–4211, USA http://www.cup.org 10 Stamford Road, Oakleigh, Melbourne 3166, Australia © 1999 Sky Publishing Corporation All rights reserved. Except for brief passages quoted in a review, no part of this book may be reproduced by any mechanical, photographic, or electronic process, nor may it be stored in an information retrieval system, transmitted, or otherwise copied for public or private use, without the written permission of the publisher. First published 1981 Second edition 1982 Third edition 1990 Fourth edition 1999 Printed in Canada Typeface ITC Galliard 9/12pt System QuarkXPress® [DS] Library of Congress cataloging in publication data The new solar system / edited by J. Kelly Beatty, Carolyn Collins Petersen, Andrew Chaikin. — 4th ed. p. cm. Includes bibliographical references and index. ISBN: 0 933346 86 7 (alk. paper) 1. Solar system. I. Beatty, J. Kelly. II. Petersen, Carolyn Collins. III. Chaikin, Andrew, 1956 – . QB501.N47 1999 523.2 — dc21 98-34472 CIP A catalogue record for this book is available from the British Library ISBN 0-933346-86-7 (Sky edition: softcover) ISBN 0-521-64183-7 (Cambridge Univ. Press edition: hardcover) ISBN 0-521-64587-5 (Cambridge Univ. Press edition: softcover) Contents PAGE Preface vii 1 Exploring the Solar System 1 David Morrison 2 Origin of the Solar System 13 John A. Wood 3 The Sun 23 Kenneth R. Lang 4 Planetary Magnetospheres and the Interplanetary Medium 39 James A. Van Allen & Frances Bagenal 5 Cometary Reservoirs 59 Paul R. Weissman 6 The Role of Collisions 69 Eugene M. Shoemaker & Carolyn S. Shoemaker 7 Mercury 87 Faith Vilas 8 Venus 97 R. Stephen Saunders 9 Planet Earth 111 Don L. Anderson vi PAGE PAGE 10 The Moon 125 21 Triton, Pluto, and Charon 285 Paul D. Spudis Dale P. Cruikshank 11 Mars 141 22 Midsize Icy Satellites 297 Michael H. Carr William B. McKinnon 12 Surfaces and Interiors of the 23 Small Worlds: Patterns and Terrestrial Planets 157 Relationships 311 James W. Head III William K. Hartmann 13 Atmospheres of the Terrestrial Planets 175 24 Comets 321 Bruce M. Jakosky John C. Brandt 14 Interiors of the Giant Planets 193 25 Asteroids 337 William B. Hubbard Clark R. Chapman 15 Atmospheres of the Giant Planets 201 26 Meteorites 351 Andrew P. Ingersoll Harry Y. McSween Jr. 16 Planetary Rings 221 27 Life in the Solar System 365 Joseph A. Burns Gerald A. Soffen 17 Io 241 28 Other Planetary Systems 377 Torrence V. Johnson R. Paul Butler 18 Europa 253 Planet, Satellite, and Small-body Ronald Greeley Characteristics 387 19 Ganymede and Callisto 263 Glossary 399 Robert T. Pappalardo Authors, Suggested Readings, and Illustration Credits 403 20 Titan 277 Index 413 Tobias Owen CONTENTS Preface J. Kelly Beatty Carolyn Collins Petersen & Andrew Chaikin HE STUDY OF our solar system is arguably the oldest branch of astronomy. Thousands of years before the vii invention of the telescope, human eyes looked into the night sky and perceived the steady, purposeful motion of certain “stars” among their neighbors. The wandering Tplanets were seen as physical manifestations of prominent gods, whose Roman and Greek names remain with us to this day. Ancient astronomers became obsessed with deducing how and why the planets move as they do. Early telescopes, too crude to resolve dim galaxies, nonetheless revealed the Moon’s stark craters, Jupiter’s satellites, and the spectacle of Saturn’s rings. Given this legacy, it is hard to believe that 40 years ago — at the dawn of space exploration — planetary science was at its nadir. In the postwar 1940s and 1950s, world-class telescopes like the 5-m Hale reflector on Palomar Mountain were reveal- ing the majesty of the distant universe. In those heady days, planetary research was considered second-rate science, and con- sequently very few professional astronomers observed Mars, Jupiter, or other planets on a regular basis. At many professional facilities, only a small fraction of the available observing time could be used for solar-system studies. By stark contrast, the planets loomed large at the newly formed National Aeronautics and Space Administration, where mission planners had already set their sights on the Moon, Venus, Jupiter appeared as a slender crescent as Voyager 1 departed and Mars. However, even though these worlds were within our the Jovian system on 24 March 1979. technological reach, it soon became obvious that we had little concept of what spacecraft should do once they got there. More- over, NASA managers were shocked to learn how few astronomers had any relevant experience in the planetary field. Historian Joseph Tatarewicz describes the agency’s predica- ment in his 1990 book Space Technology and Planetary Astron- omy: “In order to develop lunar and planetary probes, calculate trajectories, and develop scientific instruments, NASA planners viii had hoped to enlist the expertise of a science that had spent lit- belt, thus certifying that the Sun’s dominion extends far beyond erally thousands of years preoccupied with the planets. Yet on Pluto’s orbit. And the final chapter provides a census of the the very eve of planetary exploration astronomers showed little rapidly growing number of known worlds around other stars. interest.” Tatarewicz recalls that NASA officials even “stood In assembling this book, we have attempted, as before, to before groups of astronomers and implored them to enter a bring the fruits of recent planetary exploration to the widest field of study for which there were few inducements.” possible audience. This is neither a textbook nor a “coffee- One of the few astronomers actively — and overtly — pursu- table” volume — it lies somewhere in between. By the same ing solar-system research at that time was Gerard P. Kuiper. token, we have encouraged our authors to avoid both sweeping Having already distinguished himself with research on double generalizations and incomprehensible details. An abiding theme stars and stellar evolution, Kuiper had turned his considerable has been that our solar system is no longer a collection of indi- talent to the planets in the 1940s. Working with the limited vidual bodies that can be addressed in isolation. It is instead an tools of the era, utilizing his skills as an observer and his rigor- interrelated whole, whose parts must be studied comparatively. ous scientific judgment, Kuiper amassed a body of knowledge Above all, we strove to make this enjoyable reading for those that formed the basis for modern planetary science. with either casual or professional interest. In 1961, on the eve of the first interplanetary missions, We have drawn upon the talents of many individuals. Artist Kuiper and Barbara Middlehurst published Planets and Satel- Don Davis and illustrator Sue Lee have imbued these pages lites, the third installment in a four-volume series that surveyed with their colorful vitality and uncompromising attention to the state of knowledge about the entire solar system. In its pref- detail. We thank Richard Tresch Fienberg and Leif Robinson of ace Kuiper argued that, even in the era of planetary exploration, Sky Publishing, and Simon Mitton of Cambridge University telescopic observations from Earth would remain important. Press for editorial direction. Our thanks also go to designer Today, even though our robotic emissaries have surveyed at David Seabourne and CUP production manager Tony Tomlin- close range every one of the known planets except Pluto, it is son, and to Mary Agner, Vanessa Thomas, Tal Mentall, Cheryl clear that he was right. Were it not for the ongoing scrutiny of Beatty, Lynn Sternbergh, and Paul Williams for editorial and the solar system by patient professional and amateur observers design support. Myche McAuley and Susan LaVoie of NASA’s here on Earth, much of what you will read in these pages would Planetary Photojournal ensured that we had the best possible still lie waiting to be discovered. We would know little about the spacecraft images at our disposal. And finally we are deeply potential danger posed by Earth-crossing asteroids and nothing indebted to SPC production manager Sally MacGillivray and about the planets of other stars, to cite but two examples. photo researcher Imelda Joson, whose tireless perseverance and When Gerard Kuiper died in 1973, he left a void not easily dedication were truly inspirational. filled. No single person has yet matched his influence on and This edition has been two years in the making, an interval command of planetary science. In fairness, however, the present- during which, sadly, we mourned the deaths of Carl Sagan and day study of “a planet” can involve a host of scientific disciplines. Gene Shoemaker, singular members of the planetary-science Few scientists today possess a complete working knowledge of community who had served us as contributors and honored us any one world, let alone the entire solar system. Over the years with their close friendship. Also lost were Clyde Tombaugh, the the ranks of traditional planetary astronomers have been forti- discoverer of Pluto, and Jürgen Rahe, who helped manage fied with geologists, physicists, chemists, mathematicians, fluid NASA’s planetary programs for many years. We acknowledge dynamicists, biologists, and others. We suspect Kuiper would be their accomplishments and unflagging spirit in furthering our pleased to know that the study of our solar system now occupies understanding of the solar system.