Carl Sagan - Pale Blue Dot

Ballantine Books Edition, September 1997

ISBN: 0-345-37659-5

Scanned: December, 2000 V.1.0

Formatted for viewing in Word 97

CARL SAGAN

PALE BLUE DOT

A V I S I O N O F T H E

H U M A N F U T UR E I N S PA C E

F O R S A M

Another wanderer,

May your generation see

Wonders undreamt.

2

SPACECRAFT EXPLORATION

OF THE SOLAR SYSTEM

NOTABLE EARLY ACHIEVEMENTS

UNITED STATES

1958 First scientific discovery in space-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

(Mariner 9 to Mars)

1973 First flyby of Jupiter

(Pioneer 10)

1974 First dual-planet mission

(Mariner 10 to Venus and Mercury)

1974 First flyby of Mercury

(Mariner 10)

1976 First successful Mars landing; first spacecraft

to search for life on another planet

(Viking 1)

1977 First flybys of Saturn

(Pioneer 11)

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 flyby of Uranus

(Voyager 2)

1989 First flyby of Neptune

(Voyager 2)

1992 First detection of the heliopause

(Voyager)

1992 First encounter with a main-belt asteroid

(Galileo to Gaspra)

3

1994 First detection of a moon of an asteroid

(Galileo to Ida)

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 multi-person space mission

(Voskhod 1)

1965 First space "walk"

(Voskhod 2)

1966 First spacecraft to enter the atmosphere of another planet

(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 a 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 First approximately year-long manned spaceflight

1981 (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)

4

CONTENTS

WANDERERS: AN INTRODUCTION 5

1. YOU ARE HERE 10

2. ABERRATIONS OF LIGHT 14

3. THE GREAT DEMOTIONS 20

4. A UNIVERSE NOT MADE FOR US 29

5. IS THERE INTELLIGENT LIFE ON EARTH? 39

6. THE TRIUMPH OF VOYAGER 46

7. AMONG THE MOONS OF SATURN 54

8. THE FIRST NEW PLANET 62

9. AN AMERICAN SHIP AT THE FRONTIERS OF THE SOLAR SYSTEM 69

10. SACRED BLACK 78

11. EVENING AND MORNING STAR 84

12. THE GROUND MELTS 90

13. THE GIFT OF APOLLO 98

14. EXPLORING OTHER WORLDS AND PROTECTING THIS ONE 103

15. THE GATES OF THE WONDER WORLD OPEN 109

16. SCALING HEAVEN 122

17. ROUTINE INTERPLANETARY VIOLENCE 134

18. THE MARSH OF CAMARINA 143

19. REMAKING THE PLANETS 152

20. DARKNESS 162

21. TO THE SKY! 171

22. TIPTOEING THROUGH THE MILKY WAY 177

ABOUT THE AUTHOR 189

ACKNOWLEDGMENTS 189

REFERENCES 191

5

WANDERERS:

AN INTRODUCTION

But tell me, who are they, these wanderers . . .?

—RAINER MARIA RILKE, "THE FIFTH ELEGY" (1923)

We 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 find 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

officials. 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 fife. 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, unfulfilled. 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-off 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

6

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 first, 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 first 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 Pacific; people from Borneo settled

Madagascar; Egyptians and Libyans circumnavigated Africa; and a great fleet of ocean going

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 fifteenth 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

Pacific. 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 first 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 flee from war, oppression, and famine today than at any other time in

human history. As the Earth's climate changes in the coming decade. 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 flow 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.

* * *

* "As to the fable that there are Antipodes," wrote St. Augustine in the fifth century, "that is to say, men on the opposite side of the

earth, where the sun rises when it sets to us, men who walk with their feet opposite ours, that is on I'll ground credible." Even if some

unknown landmass is there, and not just ocean, "there was only one pair of original ancestors, and it is inconceivable that such distant

regions should have been peopled by Adam's descendants.''

7

LATE IN THE NINETEENTH CENTURY, Leib Gruber was growing up 111 Central Europe, in an

obscure town in the immense, polyglot, ancient Austro-Hungarian Empire. His father sold fish

when he could. But times were often hard. As a young man, the only honest employment Leib

could find 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 different from his tiny back-water hamlet the great German port cities must have seemed,

how vast the ocean, how strange the lofty skyscrapers and endless hub-bub 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 firstborn, a son, after the mother she never knew.

OUR DISTANT ANCESTORS, watching the stars, noted five that did more than rise and set in stolid

procession, as the so-called "fixed" stars did. These five 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 recognize it as one

world among an uncounted multitude of others, circling the Sun or orbiting the other stars that

make up the Milky Way galaxy. Our planet and our solar system are surrounded by a new world

ocean the depths of space. It is no more impassable than the last.

Maybe it's a little early. Maybe the time is not quite yet. But those other worlds—

promising untold opportunities—beckon.

In the last few decades, the United States and the former Soviet Union have

accomplished something stunning and historic—the close-up examination of all those points of

light, from Mercury to Saturn, that moved our ancestors to wonder and to science. Since the

advent of successful interplanetary flight in 1962, our machines have flown by, orbited, or landed

8

on more than seventy new worlds. We have wandered among the wanderers. We have found vast

volcanic eminences that dwarf the highest mountain on Earth; ancient river valleys on two planets

enigmatically one too cold and the other too hot for running water; a giant planet with an interior

of liquid metallic hydrogen into which a thousand Earths would fit; whole moons that have

melted; a cloud-covered place with an atmosphere of corrosive raids, where even the high

plateaus are above the melting point of lead ancient surfaces on which a faithful record of the

violent formation of the Solar System is engraved; refugee ice worlds from the transplutonian

depths; exquisitely patterned ring systems, marking the subtle harmonies of gravity; and a world

surrounded by clouds of complex organic molecules like those that m the earliest history of our

planet led to the origin of life. Silently, they orbit the Sun, waiting.

We have uncovered wonders undreamt by our ancestors who first speculated on the

nature of those wandering lights in the night sky. We have probed the origins of our planet and

ourselves. By discovering what else is possible, by coming face to face with alternative fates of

worlds more or less like our own, we have begun to better understand the Earth. Every one of

these worlds is lovely and instructive. But, so far as we know, they are also, every one of them,

desolate and barren. Out there, there are no "better places." So far, at least.

During the Viking robotic mission, beginning in July 1976, in a certain sense I spent a

year on Mars. I examined the boulders and sand dunes, the sky red even at high noon, the ancient

river valleys, the soaring volcanic mountains, the fierce wind erosion, the laminated polar terrain,

the two dark potato-shaped moons. But there was no life—not a cricket or a blade of grass, or

even, so far as we can tell for sure, a microbe. These worlds have not been graced, as ours has, by

life. Life is a comparative rarity. You can survey dozens of worlds and find that on only one of

them does life arise and evolve and persist.

Having in all their lives till then crossed nothing wider than a layer, Leib and Chaiya

graduated to crossing oceans. They had one great advantage: On the other side of the waters there

would be-invested with outlandish customs, it is true—other human beings speaking their

language and sharing at least some of their values, even people to whom they were closely

related.

In our time we've crossed the Solar System and sent four ships to the stars. Neptune lies a

million times farther from Earth than New York City is from the banks of the Bug. But there are

no distant relatives, no humans, and apparently no life waiting for us on those other worlds. No

letters conveyed by recent émigrés help us to understand the new land— only digital data

transmitted at the speed of light by unfeeling, precise robot emissaries. They tell us that these new

worlds are not much like home. But we continue to search for inhabitants. We can't help it. Life

looks for life.

No one on Earth, not the richest among us, can afford the passage; so we can't pick up

and leave for Mars or Titan on a whim, or because we're bored, or out of work, or drafted into the

army, or oppressed, or because, justly or unjustly, we've been accused of a crime. There does not

seem to be sufficient short-term profit to motivate private industry. If we humans ever go to these

worlds, then, it will be because a nation or a consortium of them believes it to be to its

advantage—or to the advantage of the human species. Just now, there are a great many matters

pressing in on us that compete for the money it takes to send people to other worlds.

9

That's what this book is about: other worlds, what awaits us on them, what they tell us about

ourselves, and—given the urgent problems our species now faces—whether it makes sense to go.

Should we solve those problems first? Or are they a reason for going?

This book is, in many ways, optimistic about the human prospect. The earliest chapters may at

first sight seem to revel overmuch in our imperfections. But they lay an essential spiritual and

logical foundation for the development of my argument.

I have tried to present more than one facet of an issue. There will be places where I seem

to be arguing with myself. I am. Seeing some merit to more than one side, I often argue with

myself. I hope by the last chapter it will be clear where I come out.

The plan of the book is roughly this: We first examine the widespread claims made over

all of human history that our world and our species are unique, and even central to the workings

and purpose of the Cosmos. We venture through the Solar System in the footsteps of the latest

voyages of exploration and discovery, and then assess the reasons commonly offered for sending

humans into space. In the last and most speculative part of the book, I trace how I imagine that

our long-term future in space will work itself out.

Pale Blue Dot is about a new recognition, still slowly overtaking us, of our coordinates,

our place in the Universe and how, even if the call of the open road is muted in our time, a central

element of the human future lies far beyond the Earth.

10

C H A P T E R 1

YOU ARE HERE

The entire Earth is but a point, and the place of

our own habitation but a minute corner of it.

—MARCUS AURELIUS, ROMAN EMPEROR,

MEDITATIONS, BOOK 4 (CA. 170)

As the astronomers unanimously teach, the circuit of the whole earth,

which to us seems endless, compared with the greatness of the universe

has the likeness of a mere tiny point.

—AMMIANUS MARCELLINUS ACA. 330-395,

THE LAST MAJOR ROMAN HISTORIAN,

IN THE CHRONICLE OF EVENTS

The spacecraft was a long way from home, beyond the orbit of the outermost planet and high

above the ecliptic plane—which is an imaginary flat surface that we can think of as something

like a racetrack in which the orbits of the planets are mainly confined. The ship was speeding

away from the Sun at 40,000 miles per hour. But in early February of 1990, it was overtaken by

an urgent message from Earth.

Obediently, it turned its cameras back toward the now-distant planets. Slewing its scan

platform from one spot in the sky to another, it snapped 60 pictures and stored them in digital

form on its tape recorder. Then, slowly, in March, April, and May, it radioed the data back to

Earth. Each image was composed of 640,000 individual picture elements ("pixels"), like the dots

in a newspaper wire-photo or a pointillist painting. The spacecraft was 3.7 billion miles away

from Earth, so far away that it took etch pixel 5½ hours, traveling at the speed of light, to reach

us. The pictures might have been returned earlier, but the big radio telescopes in California,

Spain, and Australia that receive these whispers from the edge of the Solar System had

responsibilities to other ships that ply the sea of space among them, Magellan, bound for Venus,

and Galileo on its tortuous passage to Jupiter.

Voyager 1 was so high above the ecliptic plane because, in 1981, it had made a close pass

by Titan, the giant moon of Saturn. Its sister ship, Voyager 2, was dispatched on a different

trajectory, within the ecliptic plane, and so she was able to perform her celebrated explorations of

Uranus and Neptune The two Voyager robots have explored four planets and nearly sixty moons.

They are triumphs of human engineering an. one of the glories of the American space program.

They will he in the history books when much else about our time forgotten.

The Voyagers were guaranteed to work only until the Saturn encounter. I thought it might

be a good idea, just after Saturn, to have them take one last glance homeward. From Saturn, I

knew the Earth would appear too small for Voyager to make out any detail. Our planet would be

just a point of light, a lonely pixel, hardly distinguishable from the many other points of light

Voyager could see, nearby planets and far-off suns. But precise because of the obscurity of our

world thus revealed, such picture might be worth having.

Carl Sagan - Pale Blue Dot

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