“DOWNRIGHT INSPIRATIONAL.” —People “Elegant and appealing … Jargon-free English buoyed by emotion and humor … Sagan’s optimistic vision … shines through every chapter.” —Time “A practical and poetic argument for expanded space travel and exploration … In typical Sagan fashion, [he] makes his case grandly and eloquently.” —The San Diego Union-Tribune “Enthralling … [Sagan was] a true believer in the wealth of the universe, and he may yet make apostles of us all.” —Entertainment Weekly “Glowingly communicates current wonders and large issues ahead … No recent book has done better at making plain the subtle nature and the fascination of scientific investigation.” —Scientific American “[Pale Blue Dot] has the ambiance of a salon, where Galileo, Einstein, and others hold forth.” —Air & Space “Passionate, eloquent … [Sagan] fires our imagination and turns science into high drama.” —Booklist “Eloquent, impassioned … He builds a cogent argument that our species must venture into this vast realm and establish a space-faring civilization.” —Kirkus Reviews SOME OTHER BOOKS BY CARL SAGAN Intelligent Life in the Universe (with I. S. Shklovskii) The Dragons of Eden Broca’s Brain Cosmos Contact: A Novel Comet (with Ann Druyan) A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race (with Richard Turco) Shadows of Forgotten Ancestors: A Search for Who We Are (with Ann Druyan) The Demon-Haunted World: Science as a Candle in the Dark Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium A Ballantine Book Published by The Random House Publishing Group Copyright © 1994 by Carl Sagan All rights reserved under International and Pan-American Copyright Conventions. Published in the United States by Ballantine Books, an imprint of The Random House Publishing Group, a division of Random House, Inc., New York, and simultaneously in Canada by Random House of Canada Limited, Toronto. Originally published by Random House, Inc., in 1994 Ballantine and colophon are registered trademarks of Random House, Inc. www.ballantinebooks.com Library of Congress Catalog Card Number: 97-94010 eISBN: 978-0-307-80101-2 v3.1 FOR SAM, another wanderer. May your generation see wonders undreamt. SPACECRAFT EXPLORATION OF THE SOLAR SYSTEM NOTABLE EARLY ACHIEVEMENTS SOVIET UNION/RUSSIA 1957 First artificial satellite of the Earth (Sputnik 1) 1957 First animal in space (Sputnik 2) 1959 First spacecraft to escape the Earth’s gravity (Luna 1) 1959 First artificial planet of the Sun (Luna 1) 1959 First spacecraft to impact another world (Luna 2 to the Moon) 1959 First view of the far side of the moon (Luna 3) 1961 First human in space (Vostok 1) 1961 First human to orbit the Earth (Vostok 1) 1961 First spacecraft to fly by other planets (Venera 1 to Venus; 1962 Mars 1 to Mars) 1963 First woman in space (Vostok 6) 1964 First multiperson space mission (Voskhod 1) 1965 First space “walk” (Voskhod 2) First spacecraft to enter the atmosphere of another planet 1966 (Venera 3 to Venus) 1966 First spacecraft to orbit another world (Luna 10 to the Moon) 1966 First successful soft landing on another world (Luna 9 to the Moon) 1970 First robot mission to return α sample from another world (Luna 16 to the Moon) 1970 First roving vehicle on another world (Luna 17 to the Moon) 1971 First soft landing on another planet (Mars 3 to Mars) 1972 First scientifically successful landing on another planet (Venera 8 to Venus) 1980- 1981 First approximately year-long manned spaceflight (comparable to Mars flight time) (Soyuz 35) 1983 First full orbital radar mapping of another planet (Venera 15 to Venus) 1985 First balloon station deployed in the atmosphere of another planet (Vega 1 to Venus) 1986 First close cometary encounter (Vega 1 to Halley’s Comet) 1986 First space station inhabited by rotating crews (Mir) UNITED STATES First scientific discovery in space 1958 —Van Allen radiation belt (Explorer 1) 1959 First television images of the Earth from space (Explorer 6) 1962 First scientific discovery in interplanetary space —direct observation of the solar wind (Mariner 2) 1962 First scientifically successful planetary mission (Mariner 2 to Venus) 1962 First astronomical observatory in space (OSO-1) 1968 First manned orbit of another world (Apollo 8 to the Moon) 1969 First landing of humans on another world (Apollo 11 to the Moon) 1969 First samples returned to Earth from another world (Apollo 11 to the Moon) 1971 First manned roving vehicle on another world (Apollo 15 to the Moon) 1971 First spacecraft to orbit another planet (Manner 9 to Mars) 1974 First dual-planet mission (Mariner 10 to Venus and Mercury) 1976 First successful Mars landing; first spacecraft to search for life on another planet (Viking 1) 1973 First flybys of Jupiter (Pioneer 10), 1974 Mercury (Mariner 10), 1977 Saturn (Pioneer 11), First spacecraft to achieve escape velocity from the Solar System (Pioneers 10 and 11, launched in 1973 and 1974; Voyagers 1 and 2, 1977) 1981 First manned reusable spacecraft (STS-1) 1980 First satellite to be retrieved, repaired, 1984 and redeployed in space (Solar Maximum Mission) 1985 First distant cometary encounter (International Cometary Explorer to Comet Giacobini-Zimmer) 1986 First flybys of Uranus (Voyager 2), 1989 Neptune (Voyager 2) 1992 First detection of the heliopause (Voyager) 1992 First encounter with a main-belt asteroid (Galileo to Gaspra) 1994 First detection of α moon of an asteroid (Galileo to Ida) CONTENTS Cover Other Books by This Author Title Page Copyright Dedication WANDERERS: AN INTRODUCTION 1. YOU ARE HERE 2. ABERRATIONS OF LIGHT 3. THE GREAT DEMOTIONS 4. A UNIVERSE NOT MADE FOR US 5. IS THERE INTELLIGENT LIFE ON EARTH? 6. THE TRIUMPH OF VOYAGER 7. AMONG THE MOONS OF SATURN 8. THE FIRST NEW PLANET 9. AN AMERICAN SHIP AT THE FRONTIERS OF THE SOLAR SYSTEM 10. SACRED BLACK 11. EVENING AND MORNING STAR 12. THE GROUND MELTS 13. THE GIFT OF APOLLO 14. EXPLORING OTHER WORLDS AND PROTECTING THIS ONE 15. THE GATES OF THE WONDER WORLD OPEN 16. SCALING HEAVEN 17. ROUTINE INTERPLANETARY VIOLENCE 18. THE MARSH OF CAMARINA 19. REMAKING THE PLANETS 20. DARKNESS 21. TO THE SKY! 22. TIPTOEING THROUGH THE MILKY WAY REFERENCES ACKNOWLEDGMENTS About the Author W WANDERERS: AN INTRODUCTION But tell me, who are they, these wanderers …? —RAINER MARIA RILKE, “THE FIFTH ELEGY” (1923) e were wanderers from the beginning. We knew every stand of tree for a hundred miles. When the fruits or nuts were ripe, we were there. We followed the herds in their annual migrations. We rejoiced in fresh meat. Through stealth, feint, ambush, and main-force assault, a few of us cooperating accomplished what many of us, each hunting alone, could not. We depended on one another. Making it on our own was as ludicrous to imagine as was settling down. Working together, we protected our children from the lions and the hyenas. We taught them the skills they would need. And the tools. Then, as now, technology was the key to our survival. When the drought was prolonged, or when an unsettling chill lingered in the summer air, our group moved on—sometimes to unknown lands. We sought a better place. And when we couldn’t get on with the others in our little nomadic band, we left to �nd a more friendly bunch somewhere else. We could always begin again. For 99.9 percent of the time since our species came to be, we were hunters and foragers, wanderers on the savannahs and the steppes. There were no border guards then, no customs o�cials. The frontier was everywhere. We were bounded only by the Earth and the ocean and the sky—plus occasional grumpy neighbors. When the climate was congenial, though, when the food was plentiful, we were willing to stay put. Unadventurous. Overweight. Careless. In the last ten thousand years —an instant in our long history—we’ve abandoned the nomadic life. We’ve domesticated the plants and animals. Why chase the food when you can make it come to you? For all its material advantages, the sedentary life has left us edgy, unful�lled. Even after 400 generations in villages and cities, we haven’t forgotten. The open road still softly calls, like a nearly forgotten song of childhood. We invest far-o� places with a certain romance. This appeal, I suspect, has been meticulously crafted by natural selection as an essential element in our survival. Long summers, mild winters, rich harvests, plentiful game—none of them lasts forever. It is beyond our powers to predict the future. Catastrophic events have a way of sneaking up on us, of catching us unaware. Your own life, or your band’s, or even your species’ might be owed to a restless few—drawn, by a craving they can hardly articulate or understand, to undiscovered lands and new worlds. Herman Melville, in Moby Dick, spoke for wanderers in all epochs and meridians: “I am tormented with an everlasting itch for things remote. I love to sail forbidden seas …” To the ancient Greeks and Romans, the known world comprised Europe and an attenuated Asia and Africa, all surrounded by an impassable World Ocean. Travelers might encounter inferior beings called barbarians or superior beings called gods. Every tree had its dryad, every district its legendary hero. But there were not very many gods, at least at �rst, perhaps only a few dozen. They lived on mountains, under the Earth, in the sea, or up there in the sky. They sent messages to people, intervened in human affairs, and interbred with us. As time passed, as the human exploratory capacity hit its stride, there were surprises: Barbarians could be fully as clever as Greeks and Romans. Africa and Asia were larger than anyone had guessed. The World Ocean was not impassable. There were Antipodes.* Three new continents existed, had been settled by Asians in ages past, and the news had never reached Europe. Also the gods were disappointingly hard to find. The �rst large-scale human migration from the Old World to the New happened during the last ice age, around 11,500 years ago, when the growing polar ice caps shallowed the oceans and made it possible to walk on dry land from Siberia to Alaska. A thousand years later, we were in Tierra del Fuego, the southern tip of South America. Long before Columbus, Indonesian argonauts in outrigger canoes explored the western Paci�c; people from Borneo settled Madagascar; Egyptians and Libyans circumnavigated Africa; and a great �eet of oceangoing junks from Ming Dynasty China crisscrossed the Indian Ocean, established a base in Zanzibar, rounded the Cape of Good Hope, and entered the Atlantic Ocean. In the �fteenth through seventeenth centuries, European sailing ships discovered new continents (new, at any rate, to Europeans) and circumnavigated the planet. In the eighteenth and nineteenth centuries, American and Russian explorers, traders, and settlers raced west and east across two vast continents to the Paci�c. This zest to explore and exploit, however thoughtless its agents may have been, has clear survival value. It is not restricted to any one nation or ethnic group. It is an endowment that all members of the human species hold in common. Since we �rst emerged, a few million years ago in East Africa, we have meandered our way around the planet. There are now people on every continent and the remotest islands, from pole to pole, from Mount Everest to the Dead Sea, on the ocean bottoms and even, occasionally, in residence 200 miles up—humans, like the gods of old, living in the sky. These days there seems to be nowhere left to explore, at least on the land area of the Earth. Victims of their very success, the explorers now pretty much stay home. Vast migrations of people—some voluntary, most not—have shaped the human condition. More of us �ee from war, oppression, and famine today than at any other time in human history. As the Earth’s climate changes in the coming decades, there are likely to be far greater numbers of environmental refugees. Better places will always call to us. Tides of people will continue to ebb and �ow across the planet. But the lands we run to now have already been settled. Other people, often unsympathetic to our plight, are there before us. * * * LATE IN THE NINETEENTH CENTURY, Leib Gruber was growing up in Central Europe, in an obscure town in the immense, polyglot, ancient Austro-Hungarian Empire. His father sold �sh when he could. But times were often hard. As a young man, the only honest employment Leib could �nd was carrying people across the nearby river Bug. The customer, male or female, would mount Leib’s back; in his prized boots, the tools of his trade, he would wade out in a shallow stretch of the river and deliver his passenger to the opposite bank. Sometimes the water reached his waist. There were no bridges here, no ferryboats. Horses might have served the purpose, but they had other uses. That left Leib, and a few other young men like him. They had no other uses. No other work was available. They would lounge about the riverbank, calling out their prices, boasting to potential customers about the superiority of their drayage. They hired themselves out like four-footed animals. My grandfather was a beast of burden. I don’t think that in all his young manhood Leib had ventured more than a hundred kilometers from his little hometown of Sassow. But then, in 1904, he suddenly ran away to the New World—to avoid a murder rap, according to one family legend. He left his young wife behind. How di�erent from his tiny backwater hamlet the great German port cities must have seemed, how vast the ocean, how strange the lofty skyscrapers and endless hubbub of his new land. We know nothing of his crossing, but have found the ship’s manifest for the journey undertaken later by his wife, Chaiya—joining Leib after he had saved enough to bring her over. She traveled in the cheapest class on the Batavia, a vessel of Hamburg registry. There’s something heartbreakingly terse about the document: Can she read or write? No. Can she speak English? No. How much money does she have? I can imagine her vulnerability and her shame as she replies, “One dollar.” She disembarked in New York, was reunited with Leib, lived just long enough to give birth to my mother and her sister, and then died from “complications” of childbirth. In those few years in America, her name had sometimes been anglicized to Clara. A quarter century later, my mother named her own �rstborn, a son, after the mother she never knew. OUR DISTANT ANCESTORS, watching the stars, noted �ve that did more than rise and set in stolid procession, as the so-called “�xed” stars did. These �ve had a curious and complex motion. Over the months they seemed to wander slowly among the stars. Sometimes they did loops. Today we call them planets, the Greek word for wanderers. It was, I imagine, a peculiarity our ancestors could relate to. We know now that the planets are not stars, but other worlds, gravitationally lashed to the Sun. Just as the exploration of the Earth was being completed, we began to