Imperial Earth

1. A Shriek In The Night

Duncan McKenzie was ten years old when he found the magic number. It was pure chance; he had intended to call Grandma Ellen, but he had been careless and his fingers must have touched the wrong keys. He knew at once that he had made a mistake, because Grandma’s viddy had a two-second delay, even on Auto/Record. This circuit was live immediately.

Yet there was no ringing tone, and no picture. The screen was completely blank, with not even a speckling of interference. Duncan guessed that he had been switched into an audio-only channel, or had reached a station where the camera was disconnected. In any case, this certainly wasn’t Grandma’s number, and he reached out to break the circuit.

Then he noticed the sound. At first, he thought that someone was breathing quietly into the microphone at the far end, but he quickly realized his mistake. There was a random, inhuman quality about this gentle susurration; it lacked any regular rhythm, and there were long intervals of complete silence.

As he listened, Duncan felt a growing sense of awe. Here was something completely outside his normal, everyday experience, yet he recognized it almost at once. In his ten years of life, the impressions of many worlds had been imprinted on his mind, and no one who had heard this most evocative of sounds could ever forget it. He was listening to the voice of the wind, as it sighed and whispered across the lifeless landscape a hundred meters above his head.

Duncan forgot all about Grandma, and turned the volume up to its highest level. He lay back on the couch, closed his eyes, and tried to project himself into the unknown, hostile world from which he was protected by all the safety devices that three hundred years of space technology could contrive. Someday, when he had passed his survival tests, he would go up into that world and see with his own eyes the lakes and chasms and low-lying orange clouds, lit by the thin, cold rays of the distant sun. He had looked forward to that day with calm anticipation rather than excitement—the Makenzies were noted for their lack of excitement—but now he suddenly realized what he was missing. So might a child of Earth, on some dusty desert far from the ocean, have pressed a shell against his ear and listened with sick longing to the music of the unattainable sea.

There was no mystery about the sound, but how was it reaching him? It could be coming from any of the hundred million square kilometers lying above his head. Somewhere—perhaps in an abandoned construction project or experimental station—a live microphone had been left in circuit, exposed to the freezing, poisonous winds of the world above. It was not likely to remain undetected for long; sooner or later it would be discovered and disconnected. He had better capture this message from the outside while it was still there; even if he knew the number he had accidentally called, he doubted if he could ever establish the circuit again.

The amount of audio-visual material that Duncan had stored under MISC was remarkable, even for an inquisitive ten-year-old. It was not that he lacked organizing ability—that was the most celebrated of all the Makenzie talents—but he was interested in more things than he knew how to index. He had now begun to discover, the hard way, that information not properly classified can be irretrievably lost.

He thought intently for a minute, while the lonely wind sobbed and moaned and brought the chill of space into his warm little cubicle. Then he tapped out ALPHA INDEX* WIND SOUNDS* PERM STORE #.

From the moment he touched the # or EXECUTE key, he had begun to capture that voice from the world above. If all went well, he could call it forth again at any time by using the index heading WIND SOUNDS. Even if he had made a mistake, and the console’s search program failed to locate the recording, it would be somewhere in the machine’s permanent, nonerasable memory. There was always the hope that he might one day find it again by chance, as was happening all the time with information he had filed under MISC.

He decided to let the recording run for another few minutes before completing the interrupted call to Grandma. As luck would have it, the wind must have slackened at about the time he keyed EXECUTE, because there was a long, frustrating silence. Then, out of that silence, came something new.

It was faint and distant, yet conveyed the impression of overwhelming power. First there was a thin scream that mounted second by second in intensity, but somehow never came any closer. The scream rose swiftly to a demonic shriek, with undertones of thunder—then dwindled away as quickly as it had appeared. From beginning to end it lasted less than half a minute. Then there was only the sighing of the wind, even lonelier than before.

For a long, delicious moment, Duncan savored the unique pleasure of fear without danger; then he reacted as he always did when he encountered something new or exciting. He tapped out Karl Helmer’s number, and said: “Listen to this.”

Three kilometers away, at the northern end of Oasis City, Karl waited until the thin scream died into silence. As always, his face gave no hint of his thoughts. Presently he said: “Let’s hear it again.”

Duncan repeated the playback, confident that the mystery would soon be solved. For Karl was fifteen, and therefore knew everything.

Those dazzling blue eyes, apparently so candid yet already so full of secrets, looked straight at Duncan. Karl’s surprise and sincerity were totally convincing as he exclaimed: “You didn’t recognize it?”

Duncan hesitated. He had thought of several obvious possibilities—but if he guessed wrongly, Karl would make fun of him. Better to be on the safe side...

“No,” he answered. “Did you?”

“Of course,” said Karl, in his most superior tone of voice. He paused for effect, then leaned toward the camera so that his face loomed enormous on the screen.

“It’s a Hydrosaurus on the rampage.”

For a fraction of a second, Duncan took him seriously—which was exactly what Karl had intended. He quickly recovered, and laughed back at his friend.

“You’re crazy. So you don’t know what it is?”

For the methane-breathing monster Hydrosaurus rex was their private joke—the product of youthful imaginations, inflamed by pictures of ancient Earth and the wonders it had brought forth near the dawn of creation. Duncan knew perfectly well that nothing lived now, or had ever lived, on the world that he called home; only Man had walked upon its frozen surface. Yet if Hydrosaurus could have existed, that awesome sound might indeed have been its battle cry, as it leaped upon the gentle Carbotherium, wallowing in some ammonia lake...

“Oh. I know what made that noise,” said Karl smugly. “Didn’t you guess? That was a ram-tanker making a scoop. If you call Traffic Control, they’ll tell you where it was heading.”

Karl had had his fun, and the explanation was undoubtedly correct. Duncan had already thought of it, yet he had hoped for something more romantic. Though it was perhaps too much to expect methane monsters, and everyday spaceship was a disappointing anticlimax. He felt a sense of letdown, and was sorry that he had given Karl another chance to deflate his dreams. Karl was rather good at that.

But like all healthy ten-year-olds, Duncan was resilient. The magic had not been destroyed. Though the first ship had lifted from Earth three centuries before he was born, the wonder of space had not yet been exhausted. There was romance enough in that shriek from the edge of the atmosphere, as the orbiting tanker collected hydrogen to power the commerce of the Solar System.

In a few hours, that precious cargo would be falling sunward, past Saturn’s other moons, past giant Jupiter, to make its rendezvous with one of the fueling stations that circled the inner planets. It would take months—even years—to get there, but there was no hurry. As long as cheap hydrogen flowed through the invisible pipeline across the Solar System, the fusion rockets could fly from world to world, as once the ocean liners had plied the seas of Earth.

Duncan understood this better than most boys of his age; the hydrogen economy was also the story of his family, and would dominate his own future when he was old enough to play a part in the affairs of Titan. It was now almost a century since Grandfather Malcolm had realized that Titan was the key to all the planets, and had shrewdly used this knowledge for the benefit of mankind—and of himself.

So Duncan continued to listen to the recording after Karl had switched off. Over and over again he played back that triumphant cry of power, trying to detect the precise moment when it was finally swallowed up in the gulfs of space. For years it would haunt his dreams; he would wake in the night, convinced that he had heard it again through the rock that protected Oasis from the hostile wilderness above.

And when he at last fell back into sleep, he would always dream of Earth.

2. Dynasty

Malcolm Makenzie had been the right man, at the right time. Others before him had looked covetously at Titan, but he was the first to work out all the engineering details and to conceive the total system or orbiting scoops, compressors, and cheap, extendable tanks that could hold their liquid hydrogen with minimum loss as they dropped leisurely sunward.

Back in the 2180’s, Malcolm had been a promising young aerospace designer at Port Lowell, trying to make aircraft that could carry useful payloads in the tenuous Martian atmosphere. In those days he had been Malcolm Mackenzie, for the computer mishap that had irrevocably changed the family name did not occur until he emigrated to Titan. After wasting five years in futile attempts at correction, Malcolm had finally co-operated with the inevitable. It was one of the few battles in which the Makenzies had ever admitted defeat, but now they were quite proud of their unique name.

When he had finished his calculations and stolen enough drafting-computer time to prepare a beautiful set of drawings, young Malcolm had approached the Planning Office of the Martian Department of Transportation. He did not anticipate serious criticism, because he knew that his facts and his logic were impeccable.

A large fusion-powered spaceliner could use ten thousand tons of hydrogen on a single flight, merely as inert working fluid. Ninety-nine percent of it took no part in the nuclear reaction, but was hurled from the jets unchanged, at scores of kilometers per second, imparting momentum to the ships it drove between the planets.

There was plenty of hydrogen on Earth, easily available in the oceans; but the cost of lifting megatons a year into space was horrendous. And the other inhabited worlds—Mars, Mercury, Ganymede, and the Moon—could not help. The had no surplus hydrogen at all.

Of course, Jupiter and the other Gas Giants possessed unlimited quantities of the vital element, but their gravitational fields guarded it more effectively than any unsleeping dragon, coiled round some mythical treasure of the Gods. In all the Solar System, Titan was the only place where Nature had contrived the paradox of low gravity and an atmosphere remarkably rich in hydrogen and its compounds.

Malcolm was right in guessing that no one would challenge his figures, or deny the feasibility of the scheme, but a kindhearted senior administrator took it upon himself to lecture young Makenzie on the political and economic facts of life. He learned, with remarkable speed, about growth curves and forward discounting and interplanetary debts and rates of depreciation and technological obsolescence, and understood for the first time why the solar was backed, not by gold, but by kilowatt-hours.

“It’s an old problem,” his mentor had explained patiently. “In fact, it goes back to the very beginnings of astronautics, in the twentieth century. We couldn’t have commercial space flight until there were flourishing extraterrestrial colonies—and we couldn’t have colonies until there was commercial space transportation. In this sort of bootstrap situation, you have a very slow growth rate until you reach the takeoff point. Then, quite suddenly, the curves start shooting upward, and you’re in business.

“It could be the same with your Titan refueling scheme—but have you any idea of the initial investment required? Only the World Bank could possibly underwrite it...”

“What about the Bank of Selene? Isn’t it supposed to be more adventurous?”

“Don’t believe all you’ve read about the Gnomes of Aristarchus; they’re as careful as anyone else. They have to be. Bankers on Earth can still go on breathing if they make a bad investment...”

But it was the Bank of Selene, three years later, that put up the five megasols for the initial feasibility study Then Mercury became interested—and finally Mars. By this time, of course, Malcolm was no longer an aerospace engineer. He had become, not necessarily in this order, a financial expert, a public-relations adviser, a media manipulator, and a shrewd politician. In the incredibly short time of twenty years, the first hydrogen shipments were falling sunward from Titan.

Malcolm’s achievement had been an extraordinary one, now well documented in dozens of scholarly studies, all respectful, though some of them far from flattering. What made it so remarkable—even unique—was the way in which he had converted his hard-won expertise from technology to administration. The process had been so imperceptible that no one realized what was happening. Malcolm was not the first engineer to became a head of state; but he was the first, his critics pointed out, to establish a dynasty. And he had done so against odds that would have daunted lesser men.

In 2195, at the age of forty-four, he had married Ellen Killner, recently emigrated from Earth. Their daughter, Anitra, was the first child to be born in the little frontier community of Oasis, then the only permanent base on Titan, and it was several years before the devoted parents realized the cruel jest that Nature had played upon them.

Even as a baby, Anitra was beautiful, and it was confidently predicted that when she grew up she would be completely spoiled. Needless to say, there were as yet no child psychologists on Titan; so no one noticed that the little girl was too docile, too well behaved—and too silent. Not until she was almost four years old did Malcolm and Ellen finally accept the fact that Anitra would never be able to speak, and that there was really no one at home in the lovely shell their bodies had fashioned.

The fault lay in Malcolm’s genes, not Ellen’s. Sometime during his shuttling back and forth between Earth and Mars, a stray photon that had been cruising through space since cosmic dawn had blasted his hopes for the future. The damage was irreparable, as Malcolm discovered when he consulted the best genetic surgeons of four worlds. It was a chilling thought that he had actually been lucky with Anitra; the results could have been far, far worse...

To the mingled sorrow and relief of an entire world, Anitra had died before she was six years old, and the Makenzie marriage died with her in a flurry of grief and recrimination. Ellen threw herself into her work, and Malcolm departed on what was to be his last visit to Earth. He was gone for almost two years, and in that time he achieved much.

He consolidated his political position and set the pattern of economic development on Titan for the next half-century. And he acquired the son he had now set his heart upon.

Human cloning—the creation of exact replicas of another individual from any cell in the body except the sex cells—had been achieved early in the twenty-first century. Even when the technology had been perfected, it had never become widespread , partly because there were few circumstances that could ever justify it.

Malcolm was not a rich man—there had been no large personal fortunes for a hundred years—but he was certainly not poor. He used a skillful combination of money, flattery, and more subtle pressures to attain his goal. When he returned to Titan, he brought with him the baby who was his identical twin—but a half a century younger.

When Colin grew up, there was no way in which he could be distinguished from his clone father at the same age. Physically, he was an exact duplicate in every respect. But Malcolm was no Narcissus, interested in creating a mere carbon copy of himself; he wanted a partner as well as a successor. So Colin’s educational program concentrated on the weak points of Malcolm’s. Though he had a good grounding in science, he specialized in history, law, and economics. Whereas Malcolm was an engineer-administrator, Colin was an administrator-engineer. While still in his twenties, he was acting as his father’s deputy wherever it was legally admissible, and sometimes where it was not. Together, the two Makenzies formed an unbeatable combination, and trying to draw subtle distinctions between their psychologies was a favorite Titanian pastime.

Perhaps because he had never been compelled to fight for any great objective, and had had all his goals formulated before his birth, Colin was more gentle and easygoing than Malcolm—and therefore more popular. No one outside the Makenzie family ever called the older man by his first name; few called Colin anything else. He had no real enemies, and there was only one person on Titan who disliked him. At least, it was assumed that Malcolm’s estranged wife, Ellen, did so, for she refused to acknowledge his existence.

Perhaps she regarded Colin as a usurper, an unacceptable substitute for the son who could never be born to her. If so, it was indeed strange that she was so fond of Duncan.

But Duncan had been cloned from Colin almost forty years later and by that time Ellen had passed through a second tragedy—one that had nothing to do with the Makenzies. To Duncan, she was always Grandma Ellen, but he was now old enough to realize in his heart she combined two generations, and filled a void that earlier ages would have found it impossible to imagine or believe.

If Grandma had any real genetic relationship with him, all trace of it had been lost centuries ago on another world. And yet, by some strange quirk of chance and personality, she had become for him the phantom mother who had never even existed.

3. Invitation To A Centennial

“And who the hell is George Washington?” asked Malcolm Makenzie.

“Middle-aged Virginia farmer, runs a place called Mount Vernon—”

“You’re joking.”

“I’m not. No relation, of course—old George was childless—but that’s his real name, and he’s perfectly genuine.”

“I suppose you’ve checked with the embassy.”

“Of course, and got a fifty-line print-out of his family tree. Most impressive—half the American aristocracy for the last hundred years. Lots of Cabots and Du Ponts and Kennedys and Kissingers. And before that, a couple of African kings.”

“It may impress you, Colin,” interjected Duncan, “but now that I’ve glanced at the program, it all seems a little childish. Grown men pretending to be historical figures. Are they really going to throw tea into Boston Harbor?”

Before Colin could answer, Grandfather Makenzie stepped in. A discussion among the three Makenzies—which was something seldom overheard by outsiders—was more in the nature of a monologue than an argument. Because their three personas differed only through the accidents of background and education, genuine disagreements among them were virtually unknown. When difficult decisions had to be made, Duncan and Colin would take opposing viewpoints and debate them before Malcolm—who would listen without saying a word, though his eyebrows could be very eloquent. He seldom had to give a judgment, because the two advocates usually reached a synthesis without much difficulty; but when he did, that was the end of the matter. It was quite a good way to run a family—or a world.

“I don’t know about the tea, which would certainly be a waste at fifty solars a kilo, but you’re being too hard on Mr. Washington and his friends. When we have five hundred years behind us, we’ll be justified in a little pomp and ceremony. And never forget—the Declaration of Independence was one of the most important historical events of the last three thousand years. We wouldn’t be here without it. After all, the Treaty of Phobos opens with the words: When in the course of human events, it becomes necessary for one people...”

“Quite inappropriate in that context. On the whole, Earth was heartily glad to get rid of us.”

“Perfectly true, but don’t ever let the Terrans hear it.”

“I’m still confused,” said Duncan rather plaintively. “Just what does the good general want from us? How can we raw colonials contribute to the proceedings?”

“He’s only a professor, not a general,” replied Colin. “They’re extinct, even on Earth. As I see it, a few nicely composed speeches, drawing whatever parallels you can find between our historical situations. A certain exotic charm—you know; a whiff of the frontier, where men still live dangerously. The usual barbarian virility, so irresistible to decadent Terrans of all sexes. And, not least, a low-keyed yet genuine gratitude for the unexpected gift of an open Earth-Titan return ticket with all expenses for a two-month stay. That solves several of our problems, and we should appreciate it.”

“Very true,” Duncan replied thoughtfully, “even though it wrecks our plans for the next five years.”

“It doesn’t wreck them,” said Colin. “It advances them. Time gained is time created. And success in politics—”

“—depends upon the masterful administration of the unforeseen, as you are so fond of saying. Well, this invitation is certainly unforeseen, and I’ll try to master it. Have we sent an official thank you?”

“Only a routine acknowledgment. I suggest that you follow it up, Duncan, with a personal note to President—er—Professor Washington.”

“They’re both right,” said Malcolm, rereading the formal invitation. “It says here: ‘Chairman of the Quincentennial Celebration Committee, and President of the Historical Association of Virginia.” So you can take your choice.”

“We’ve got to be very careful about this, or someone will bring it up in the Assembly. Was the invitation official, or personal?”

“It’s not government to government, I’m happy to say, since the Committee sponsored it. And the fax was addressed to the Honorable Malcolm Makenzie, not to the President.” The Honorable Malcolm Makenzie, also President of Titan, was clearly pleased at this subtle distinction.

“Do I detect in this the fine hand of your good friend Ambassador Farrell?” asked Colin.

“I’m sure the idea never occurred to him.”

“I thought as much. Well, even if we are on firm legal grounds, that won’t stop the objections. There will be the usual cries of privilege, and we’ll be accused once again of running Titan for our personal benefit.”

“I’d like to know who started the word ‘fiefdom’ circulating. I had to look it up.”

Colin ignored the older man’s interruption. As Chief Administrator, he had to face the day-to-day problems of running the world, and could not afford the slight irresponsibility that Malcolm was beginning to show in his old age. It was not senility—Grandfather was still only a hundred and twenty-four—but rather, the carefree, Olympian attitude of one who had seen and experienced everything, and had achieved all his ambitions.

“There are two points in our favor,” Colin continued. “No official funds are involved, so we can’t be criticized for using government money. And let’s have no false modesty—Earth will expect a Makenzie. It might even be regarded as an insult if one of us didn’t go. And as Duncan is the only possibility, that settles the matter.”

“You’re perfectly correct, of course. But not everyone will see it that way. All the families will want to send their younger sons and daughters.”

“There’s nothing to stop them,” Duncan interjected.

“How many could afford it? We couldn’t.”

“We could if we didn’t have some expensive extras in mind. So can the Tanaka-Smiths, the Mohadeens, the Schwartzes, the Deweys...”

“But not, I believe, the Helmers.”

Colin spoke lightly, but without humor, and there was a long silence while all three Makenzies shared a single thought. Then Malcolm said slowly: “Don’t underrate Karl. We have only power and brains. But he has genius, and that’s always unpredictable.”

“But he’s crazy,” protested Duncan. “The last time we met, he tried to convince me that there’s intelligent life on Saturn.”

“Did he succeed?”

“Almost.”

“If he’s crazy—which I doubt, despite that famous breakdown—then he’s even more dangerous. Especially to you, Duncan.”

Duncan made no attempt to answer. His wiser and older twins understood his feelings, even if they could never fully share them.

“There is one other point,” said Malcolm thoughtfully, “and it may be the most important of all. We may have only ten years in which to change the whole basis of our economy. If you can find an answer to this problem on your trip—even a hint of an answer!—you’ll be a hero when you come home. No one will criticize any of your other activities, public or private.”

“That’s a tall order. I’m not a magician.”

“Then perhaps you’d better start taking lessons. If the Asymptotic Drive isn’t pure magic, I don’t know what is.”

“Just a minute!” said Colin. “Isn’t the first A-Drive ship going to be here in just a few weeks?”

“The second. There was that freighter, Fomalhaut. I went aboard, but they wouldn’t let me see anything. Sirius is the first passenger liner—she enters parking orbit—oh—in about thirty days.”

“Could you be ready by then, Duncan?”

“I very much doubt it.”

“Of course you can.”

“I mean physiologically. Even on a crash program, it takes months to prepare for Earth gravity.”

“Um.. But this is far too good an opportunity to miss—everything is falling into place beautifully. After all, you were born on Earth.”

“So were you. And how long did you take to get ready when you went back?”

Colin sighed.

“It seemed like ages, but by now they must have improved the techniques. Don’t they have neuroprogramming while you sleep?”

“It’s supposed to give you horrible dreams, and I’ll need all the sleep I can get. Still, what’s good for Titan...”

He had no need to complete the quotation, which had been coined by some unknown cynic half a century ago. In thirty years, Duncan had never really doubted this old cliché—once intended to wound, now virtually adopted as a family motto.

What was good for the Makenzies was indeed good for Titan.

4. The Red Moon

Of the eighty-five known natural satellites, only Ganymede, lord of the Jovian system, exceeds Titan in size—and that by a narrow margin. But in another respect Titan has no rivals; no other moon of any planet has more than a trace of atmosphere. Titan’s is so dense that if it were made of oxygen, it would be easy for man to breathe.

When this fact was discovered, late in the twentieth century, it presented the astronomers with a first-class mystery. Why should a world not much larger than the Earth’s totally airless Moon be able to hold onto any atmosphere—particularly one rich in hydrogen, lightest of all gases? It should long ago have leaked away into space.

Nor was that the only enigma. Like the Moon, almost all other satellites are virtually colorless, covered with rock and dust shattered by ages of meteoric bombardment. But Titan is red—as red as Mars, whose baleful glare reminded men in ancient times of bloodshed and of war.

The first robot probes solved some of Titan’s mysteries, but, as is always the case, raised a host of new problems. The red color came from a layer of low, thick clouds, made from much the same bewildering mixture of organic compounds as the Great Red Spot of Jupiter. Beneath those clouds was a world more than a hundred degrees hotter than it had any right to be; indeed, there were regions of Titan where a man needed little more than an oxygen mask and a simple thermofoil suit to move around in the open. To everyone’s great surprise, Titan had turned out to be the most hospitable place in the Solar System, next to Earth itself.

Part of the unexpected warmth came from the greenhouse effect, as the hydrogenous atmosphere trapped the feeble rays of the distant sun. But a good deal more was due to internal sources; the equatorial region of Titan abounded in what, for want of a better phrase, might be called cold volcanoes. On rare occasions, indeed, some of them actually erupted liquid water.

This activity, triggered by radioactive heat generated deep in the core of Titan, spewed megatons of hydrogen compounds into the atmosphere, and so continually made up for the leakage into space. One day, of course, the buried reserves—like the lost oil fields of Earth—would all be gone, but the geologists had calculated that Titan could hold the vacuum of space at bay for at least two billion years. Man’s most vigorous atmospheric mining activities would have only a negligible influence on this figure.

Like the Earth, Titan has distinct seasons—though it is difficult to apply the word “summer” where the temperature at high noon seldom climbs to fifty below. And as Saturn takes almost thirty years to circle the sun, each of the Titanian seasons is more than seven Terran years in length.

The tiny sun, taking eight days to cross the sky, is seldom visible through the cloud cover, and there is very little temperature difference between day and night—or, for that matter, between Poles and Equator. Titan thus lacks climate; but it can, on occasion, produce its own quite spectacular brand of weather.

The most impressive meteorological phenomenon is the so-called Methane Monsoon, which often—though not invariably—occurs with the onset of spring in the northern hemisphere. During the long winter, some of the methane in the atmosphere condenses in local cold spots and forms shallow lakes, up to a thousand kilometers square but seldom more than a few meters deep, and often covered with fantastically shaped bergs and floes of ammonia ice. However, it requires the exceedingly low temperature of minus a hundred and sixty to keep methane liquefied, and no part of Titan is ever that cold for very long.

A “warm” wind, or a break in the clouds—and the methane lakes will flash suddenly into vapor. It is as if, on Earth, one of the oceans were to evaporate, abruptly increasing its volume hundreds of times and so completely changing the state of the atmosphere. The result would be catastrophic, and on Titan it is sometimes scarcely less so. Wind speeds of up to five hundred kilometers an hour have been recorded—or to be accurate, estimated from their aftereffects. They last only for a few minutes; but that is quite long enough. Several of the early expeditions were annihilated by the monsoon, before it became possible to predict its onset.

Before the first landings on Titan, at the beginning of the twenty-first century, some optimistic exobiologists had hoped to find life around the relatively warm oases that were known to exist. This hope was slow to fade, and for a while it was revived by the discovery of the strange wax formations of the famous Crystal Caves. But by the end of the century, it was quite certain that no indigenous life forms had ever existed on Titan.

There had never been any expectation of finding life on the other moons, where conditions were far more hostile. Only Iapetus and Rhea, less than half the size of Titan, had even a trace of atmosphere. The remaining satellites were barren aggregates of rock, overgrown snowballs, or mixtures of both. By the mid-2200’s, more than forty had been discovered, the majority of them less than a hundred kilometers in diameter. The outer ones—twenty million kilometers from Saturn—all moved in retrograde orbits and were clearly temporary visitors from the asteroid belt; there was much argument as to whether they should be counted as genuine satellites at all. Though some had been explored by geologists, many had never been examined, except by robot space probes, but there was no reason to suppose that they held any great surprises.

Perhaps one day, when Titan was prosperous and getting a little dull, future generations would take up the challenge of these tiny worlds. Some optimists had talked of turning the carbon-rich snowballs into orbital zoos, basking beneath the warmth of their own fusion suns and teeming with strange life forms. Others had dreamed of private pleasure domes and low-gravity resorts, and islands in space for experiments in super-technology life styles. But these were fantasies of a Utopian future; Titan needed all its energies now to solve its coming crisis, in this demimillennial year of 2276.

5. The Politics of Time And Space

When only two Makenzies were talking together, their conversation was even more terse and telegraphic than when all three were present. Intuition, parallel thought processes, and shared experience filled in gaps that would have made much of their discourse wholly unintelligible to outsiders.

“Handle?” asked Malcolm.

“We?!” retorted Colin.

“Thirty-one? Boy!”

Which might be translated into plain English as:

“Do you think he can handle the job?”

“Have you any doubts that we could?”

“At thirty-one? I’m not so sure. He’s only a boy.”

“Anyway, we’ve no choice. This is a God-sent—or Washington-sent—opportunity that we can’t afford to miss. He’ll have to get a crash briefing on Terran affairs, learn all that’s necessary about the United States...”

“That reminds me—what is the United States these days? I’ve lost count.”

“Now there are forty-five states—Texas, New Mexico, Alaska, and Hawaii have rejoined the Union, at least for the Centennial year.”

“Just what does that mean, legally?”

“Not very much. They pretend to be autonomous, but pay their regional and global taxes like everyone else. It’s a typical Terran compromise.”

Malcolm, remembering his origins, sometimes found it necessary to defend his native world against such cynical remarks.

“I often wish we had a little more Terran compromise here. It would be nice to inject some in Cousin Armand.”

Armand Helmer, Controller of Resources, was not in fact a cousin of Malcolm’s, but a nephew of his ex-wife, Ellen. However, in the closed little world of Titan everyone except recent immigrants was related to everybody else, and the designations “uncle,” “aunt,” “nephew,” “cousin” were tossed around with cheerful inaccuracy.

“Cousin Armand,” said Colin with some satisfaction, “is going to be very upset when he learns that Duncan is on his way to Earth.”

“And what will he do about it?” Malcolm asked softly.

It was a good question, and for a moment both Makenzies brooded over the deepening rivalry between their family and the Helmers. In some ways, it was commonplace enough; both Armand and his son, Karl, were Terran-born, and had brought with them across a billion kilometers that maddening aura of superiority that was so often the hallmark of the mother world. Some immigrants eventually managed to eradicate it, thought the process was difficult. Malcolm Makenzie had succeeded only after three planets and a hundred years, but the Helmers had never even tried. And although Karl had been only five years old when he left Earth, he seemed to have spent the subsequent thirty trying to become more Terran than the Terrans. Nor could it have been a coincidence that all his wives had been from Earth.

Yet this had been a matter of amusement, rather than annoyance, until only a dozen years ago. As boys, Duncan and Karl had been inseparable, and there had been no cause for conflict between the families until Armand’s swift rise through the technological hierarchy of Titan had brought him into a position of power. Now the Controller did not bother to conceal his belief that three generations of Makenzies were enough. Whether or not he had actually coined the “What’s good for the Makenzies...” phrase, he certainly quoted it with relish.

To do Armand justice, his ambitions seemed more concentrated on his only son than on himself. That alone would have been sufficient to put some strains on the friendship between Karl and Duncan, but it would probably have survived paternal pressures from either direction. What had caused the final rift was still something of a mystery, and was associated with a psychological breakdown that Karl had experienced fifteen years ago.

He had emerged from it with all his abilities intact, but with a marked change of personality. After graduating with honors at the University of Titan, he had become involved in a whole range of research activities, from measurements of galactic radio waves to studies of the magnetic fields around Saturn. All this work had some practical relevance, and Karl had also played a valuable role in the establishment and maintenance of the communications network upon which Titanian life depended. It would be true to say, however, that his interests were theoretical rather than practical, and he sometimes tried to exploit this whenever the old “Two Cultures” debate raised its hoary head.

Despite a couple of centuries of invective from both sides, no one really believed that Scientists, with a capital S, were more cultured (whatever that meant) than Engineers. The purity of theoretical knowledge was a philosophical aberration which would have been laughed out of court by those Greek thinkers who had had it foisted on them more than a thousand years earlier. The fact that the greatest sculptor on Earth had begun his career as a bridge designer, and the best violinist on Mars was still doing original work in the theory of numbers, proved exactly nothing one way or the other. But the Helmers liked to argue that it was time for a change; the engineers had run Titan for long enough, and they had the perfect replacement, who would bring intellectual distinction to his world.

At thirty-six, Karl still possessed the charm that had captivated all his peers, but it seemed to many—and certainly to Duncan—that this was now underlined by something hard, calculating, and faintly repellent. He could still be loved, but he had lost the ability to love; and it was strange that none of his spectacular marriages had produced any offspring.

If Armand hoped to challenge the Makenzie regime, Karl’s lack of an heir was not his only problem. Whatever the Seven Worlds might say about their independence, the center of power was still on Earth. As, two thousand years ago, men had once gone to Rome in search of justice, or prestige, or knowledge, so in this age the Imperial planet called to its scattered children. No man could be taken seriously in the arena of Solar politics unless he was personally acquainted with the key figures of Terran affairs, and had traced his way at least once through the labyrinth of the terrestrial bureaucracy.

And to do this, one had to go to Earth; as in the days of the Caesars, there was no alternative. Those who believed otherwise—or pretended to—risked being tagged with the dreaded word “colonial.”

It might have been different if the velocity of light were infinite; but it was a mere billion kilometers an hour—and therefore, realtime conversation would be forever impossible between Earth and anyone beyond the orbit of the Moon. The global electronic village which had existed for centuries on the mother world could never be extended into space; the political and psychological effects of this were enormous, and still not fully understood.

For generations, earth-dwellers had been accustomed to being in each other’s presence at the touch of a button. The communications satellites had made possible, and then inevitable, the creation of the World State in all but name. And despite many earlier fears, it was a state still controlled by men, not by machines.

There were perhaps a thousand key individuals, and ten thousand important ones—and they talked to each other incessantly from Pole to Pole. The decisions needed to run a world sometimes had to be made in minutes, and for this the instantaneous feedback of face-to-face conversation was essential. Across a fraction of a light-second, that was easy to arrange, and for three hundred years men had taken it for granted that distance could no longer bar them from each other.

But with the establishment of the first Mars Base, this intimacy had ended. Earth could talk to Mars—but its words would always take at least three minutes to get there, and the reply would take just as long. Conversation was thus impossible, and all business had to be done by Telex or its equivalent.

In theory, this should have been good enough, and usually it was. But there were disastrous exceptions—costly and sometimes fatal interplanetary misunderstandings resulting from the fact that the two men at the opposite ends of the circuit did not really know each other, or comprehend each other’s ways of thought, because they had never been in personal contact.

And personal contact was essential at the highest levels of statesmanship and administration. Diplomats had known this for several thousand years, with their apparatus of missions and envoys and official visits. Only after that contact, with its inevitable character evaluation, had been made, and the subtle links of mutual understanding and common interest established, could one do business by long-distance communications with any degree of confidence.

Malcolm Makenzie could never have achieved his own rise on Titan without the friendships made when he had returned to Earth. Once he had thought it strange that a personal tragedy should have led him to power and responsibility beyond all the dreams of his youth; but unlike Ellen, he had buried his dead past and it had ceased to haunt him long ago.

When Colin had repeated the pattern, forty years later, and had returned to Titan with the infant Duncan, the position of the clan had been immensely strengthened. To most of the human race, Saturn’s largest moon was now virtually identified with the Makenzies. No one could hope to challenge them if he could not match the network of personal contacts they had established not only on Earth, but everywhere else that mattered. It was through this network, rather than official channels, that the Makenzies, as even their opponents grudgingly admitted, Got Things Done.

And now a fourth generation was being prepared to consolidate the dynasty. Everyone knew that this would happen eventually, but no one expected it so soon.

Not even the Makenzies. And especially not the Helmers.

6. By The Bonny, Bonny Banks of Loch Hellbrew

In the past, Duncan had always cycled to Grandmother Ellen’s home, or taken an electric cart whenever he had to deliver some household necessity. This time, however, he walked the two-kilometer tunnel from the city, carrying fifty kilos of carefully distributed mass—which, however, only gave him ten kilos of extra weight. Had he known that such characters had once existed, he might have felt a strong affinity with old-time smugglers, wearing a stylish waistcoat of gold bars.

Colin had presented him with the complex harness of webbing and pouches, with a heartfelt “Thank God I’ll never have to use it again! I knew I had it around somewhere, but it took a couple of days to find. It’s only too true that the Makenzies never throw anything away.”

Duncan found that it needed both hands to lift the harness off the table; when he unzipped one of the many small pouches, he found that it contained a pencil-sized rod of dull metal, astonishingly massive.

“What is it?” he asked. “It feels heavier than gold.”

“It is. Tungsten superalloy, if I remember. The total mass is seventy kilos, but don’t start wearing it all at once. I began at forty, and added a couple of kilos a day. The important thing is to keep the distribution uniform, and to avoid chafing.

Duncan was doing some mental arithmetic, and finding the results very depressing. Earth gravity was five time Titan’s—yet this diabolical device would merely double his local weight.

“It’s impossible,” he said gloomily. “I’ll never be able to walk on Earth.”

“Well, I did—thought it wasn’t easy at first. Do everything that the doctors tell you, even if it sounds silly. Spend all the time you can in baths, or lying down. Don’t be ashamed to use wheelchairs or prosthetic devices, at least for the first couple of weeks. And never try to run.”

“Run!”

“Sooner or later you’ll forget you’re on Earth, and then you’ll break a leg. Like to bet on it?”

Betting was one of the useful Makenzie vices. The money stayed in the family, and the loser always learned some valuable lesson. Though Duncan found it impossible to imagine five gravities, it could not be denied that Colin had spent a year on Earth and had survived to tell the tale. So this was not a bet that promised favorable odds.

Now he was beginning to believe Colin’s prediction, and he scarcely noticed the extra mass—at least when he was moving in a straight line. It was only when he tried to change direction that he felt himself in the grip of some irresistible force. Not counting visitors from Earth, he was probably now the strongest man on Titan. It was not that his body was developing new strength; rather, it was recovering latent powers which had been slumbering, waiting for the moment when they would be called forth. In a few more years, what he was now attempting would be too late.

The four-meter-wide tunnel had been lasered, years ago, through the rim of the small crater which surrounded Oasis. Originally, it had been a pipeline for the ammoniated petrochemicals of the aptly named Loch Hellbrew, one of the region’s chief natural resources. Most of the lake had gone to feed the industries of Titan; later, the tapping of the moon’s internal heat, as part of the local planetary engineering project, had caused the remainder to evaporate.

There had been a certain amount of quiet grumbling when Ellen Makenzie had made her intentions clear, but the Department of Resources had pumped the remaining hydrogen-methane fog out of the tunnel, and now it carried oxygen, to the annual annoyance of the auditors, on inventory as part of the city’s air reserve. There were two manually operated bulkheads, as well as the city’s own backup seals. Anyone went beyond the second bulkhead at his own risk, but that was negligible. The tunnel was through solid rock, and since the pressure inside was higher than ambient, there was no danger of Titanian poisons leaking inward.

Half a dozen side tunnels, all of them now blocked, led out of the main passageway. When he had first come here as a small boy, Duncan had filled those sealed-off shafts with wonder and magic. Now he knew that they merely led to long-abandoned surge chambers. Yet though all the mystery was gone, it still seemed to him that these corridors were haunted by two ghosts. One was a little girl who had been known and loved by only a handful of pioneers; the other was a giant who had been mourned by millions.

There had been endless jokes about Robert Kleinman’s name, for he was almost two meters tall, and proportioned accordingly. And his talents had matched his physique; he had been a master pilot at the age of thirty, despite the difficulty of fitting him into standard space equipment. Duncan had never considered him particularly good-looking, but in this matter he was outvoted by a small army of women—including Ellen Makenzie.

Grandma had met Captain Kleinman only a year after the final parting with Malcolm; she may have been on an emotional rebound, but he certainly was not. Yet thereafter the Captain had never looked at another woman, and it had become one of those love affairs famous on many worlds. It had lasted throughout the planning and preparations for the first expedition to Saturn and the fitting-out of the Challenger in orbit off Titan. And as far as Ellen Makenzie was concerned it had never died; it was frozen forever at the moment when the ship met its mysterious and still inexplicable doom, deep in the jet streams of the South Temperate Zone.

Moving rather more slowly than when he had started his walk, Duncan came to the final bulkhead. On Grandma’s hundredth birthday, the younger members of the family had painted it in brilliant fluorescent colors, which had faded not at all in the last dozen years. Since Ellen had never referred to it, and never heard questions which she did not wish to answer, there was no way of discovering if she appreciated the gift.

“I’m here, Grandma,” Duncan called into the antique intercom which had been presented to her by some anonymous admirer long ago. (It was still clearly marked “Made in Hong Kong,” and had been dated circa 1995. Shameful to relate, there had been one attempt to steal it, though since theft was virtually unknown on Titan, this was probably only a childish prank or an anti-Makenzie gesture.

There was, as usual, no reply, but the door unlatched at once and Duncan walked through into the tiny foyer. Grandma’s electrocycle occupied the place from which it had not moved for years. Duncan checked the battery and kicked the tires, as he always did with great conscientiousness. No need for any pumping or charging this time; if the old lady suddenly felt the impulse to descend upon the city, there was nothing to prevent her.

The kitchen, which was a unit lifted intact from a small orbital passenger shuttle, was a little tidier than usual. Presumably one of the voluntary helpers had just made her weekly visit. Nevertheless, the usual sickly sour smell of slow culinary disintegration and inadequate recycling was heavy in the air, and Duncan held his breath as he hurried through into the living room. He never accepted more than a cup of coffee from Grandma, and feared accidental poisoning if he ever sampled the products of her robot reconstituter. But Ellen seemed to thrive on it; over the years she must have established some kind of symbiosis with her kitchen. It still lived up to the manufacturer’s “fail-safe” guarantee, even though it did produce the most peculiar odors. Doubtless Grandma never noticed them. Duncan wondered what she would do when the final disaster occurred.

The main living room was as crowded as ever. Against one wall were the shelves of carefully labeled rocks—a complete mineralogy of Titan and the other examined moons of Saturn, as well as samples from each of the rings. As long as Duncan could remember, there had been just one section empty, as if, even now, Grandma was still waiting for Kleinman to return.

The opposite wall was more sparsely occupied with communications and information equipment, and racks of micromodules which if completely saturated, could have held more knowledge than all the libraries of Earth up to the twenty-first century. The rest of the room was a compact little workshop, most of the floor space being occupied by the machines that had fascinated Duncan throughout his childhood, and that he would associate with Grandma Ellen as long as he lived.

There were petrological microscopes, polishing and cutting tools, ultrasonic cleaners, laser knives, and all the shining paraphernalia of gemologist and jeweler. Duncan had learned to use most of them, over the years, though he had never acquired more than a fraction of his grandmother’s skill and almost wholly lacked her artistic talents. What he did share, to a much greater extent, were her mathematical interests, exemplified by the small computer and associated holographic display.

The computer, like the kitchen, was long overdue of retirement. But it was completely autonomous, so Grandma did not have to rely in any way upon the immensely larger storage facilities in the city. Although her computer had a memory scarcely larger than that of a human brain, it was sufficient for her rather modest purposes. Her interest in minerals had led her, inevitably, to crystallography, then to group theory, and then to the harmless obsession that had dominated so much of her lonely existence. Twenty years ago, in this same room, she had infected Duncan with it. In his case, the disease was no longer virulent, having run its course in a few months; but he knew, with amused tolerance, that he would suffer occasional relapses throughout his life. How incredible that five perfectly identical squares could create a universe that neither man nor computer would ever be able to explore fully...

Nothing in the familiar room had changed since his last visit, three weeks ago. He could even imagine that Grandma had not moved; she was still sitting at her worktable, sorting rocks and crystals, while behind her the read-out screen intermittently flashed solutions of some problem the computer was analyzing. She was, as usual, wearing a long gown that made her look like a Roman matron, though Duncan was quite sure that no Roman matron’s dress ever appeared quite so disheveled or, to be perfectly frank, so overdue for the laundry. While Duncan had known her, Ellen’s care of her equipment had never extended to her personal appearance.

She did not rise, but tilted her head slightly so that he could deliver his usual affectionate kiss. As he did so, he noticed that the external world, at least, had been touched by change.

The view from Grandma’s picture window was famous—but by reputation only, since few indeed had been privileged to see it with their own eyes. Her home was partly countersunk into a ledge overlooking the dried-up bed of Loch Hellbrew and the canyon that led into it, so it presented her with a 180-degree panorama of Titan’s most picturesque landscape. Sometimes, when storms raged through the mountains, the view disappeared for hours behind clouds of ammonia crystals. But today the weather was clear and Duncan could see for at least twenty kilometers.

“What’s happening over there?” he asked.

At first, he had thought it was one of the fire fountains that sometimes erupted in unstable areas; but in that case the city would have been in danger, and he would have heard of it long ago. Then he realized that the brilliant yet smoky column of light burning steadily on the hill crest three or four kilometers away could only be man-made.

“There’s a fusor running over at Huygens. I don’t know what they’re doing, but that’s the oxygen burn-off.”

“Oh, one of Armand’s projects. Doesn’t it annoy you?”

“No—I think it’s beautiful. Besides, we need the water. Look at those rain clouds... real rain. And I think there’s something growing over there. I’ve noticed a change in color on the rocks since that flame started burning.”

“That’s quite possible—the bioengineering people will know all about it. One day you may have a forest to look at, instead of all this bare rock.”

He was joking, of course, and she knew it. Except in very restricted areas, no vegetation could grow here in the open. But experiments like this were a beginning, and one day...

Over there in the mountain, a hydrogen fusion plant was at work, melting down the crust of Titan to release all the elements needed for the industries of the little world. And as half that crust consisted of oxygen, now needed only in very small quantities in the closed-cycle economies of the cities, it was simply allowed to burn off.

“Do you realize, Duncan,” said Grandma suddenly, “how neatly that flame symbolizes the difference between Titan and Earth?”

“Well, they don’t have to melt rocks there to get everything they need.”

“I was thinking of something much more fundamental. If a Terran wants a fire, he ignites a jet of hydrocarbons and lets it burn. We do exactly the opposite. We set fire to a jet of oxygen, and let it burn in our hydromethane atmosphere.

This was such an elementary fact of life—indeed an ecological platitude—that Duncan felt disappointed; he had hoped for some more startling revelation. His face must have reflected his thoughts, for Grandma gave him no chance to comment.

“What I’m trying to tell you,” she said, “is that it may not be as easy for you to adjust to Earth as you imagine. You may know—or think you know—what conditions are like there, but that knowledge isn’t based on experience. When you need it in a hurry, it won’t be there. Your Titan instincts may give the wrong answers. So act slowly, and always think twice before you move.”

“I’ve no choice about acting slowly—my Titan muscles will see to that.”

“How long will you be gone?”

“About a year. My official invitation is for two months, but now the trip’s being paid for, I’ll have funds for a much longer stay. And it seems a pity to waste the opportunity, since it’s my only one.”

He tried to keep his voice as cheerfully optimistic as he could, though he knew perfectly well the thoughts that must be passing through Grandma’s mind. They were both aware that this might be their last meeting. One hundred fourteen was not an excessive age for a woman—but, truly, what did Grandma have to live for? The hope of seeing him again, when he returned from Earth? He liked to think so...

And there was another matter, never to be referred to, yet hovering in the background. Grandma knew perfectly well the main purpose of his visit to Earth, and the knowledge must, even after all these years, be like a dagger in her heart. She had never forgive Malcolm; she had never accepted Colin; would she continue to accept him when he returned with little Malcolm?

Now she was hunting around, with a clumsiness quite unlike her normal precise movements, in one of the cubbyholes of her work desk.

“Here’s a souvenir to take with you.”

“What—oh, it’s beautiful!” He was not being excessively polite; sheer surprise had forced the reaction from him. The flat, crystal-lidded box he was now holding in his hands was, indeed, one of the most exquisite works of geometrical art he had ever seen. And Grandma could not have chosen any single object more evocative of his youth and of the world that, though he was now about to leave it, must always be his home.

As he stared at the mosaic of colored stones that exactly filled the little box, greeting each of the familiar shapes like an old friend, his eyes misted and the years seemed to roll away. Grandma had not changed; but he was only ten...

7. A Cross of Titanite

“You’re old enough now, Duncan, to understand this game... though it’s very much more than a game.”

Whatever it is, thought Duncan, it doesn’t look very exciting. What can you do with five identical squares of white plastic, a couple of centimeters on a side?”

“Now the first problem,” continued Grandma, “is to see how many different patterns you can make, by putting all these squares together.”

“While they lie flat on the table?”

“Yes, with the edges matching exactly—overlapping isn’t allowed.”

Duncan started to shuffle the squares.

“Well,” he began, “I can put them all in a straight line like this... then I can switch the end one to make an L... and the one at the other end to make a U...”

He quickly produced half a dozen different assemblies of the five squares, then found that he was repeating himself.

“I think that’s all—oh, stupid of me.”

He had missed the most obvious figure of all—the cross, or X, formed by putting one square in the middle and the other four surrounding it.

“Most people,” said Grandma, “find that one first. I don’t know what this proves about your mental processes. Do you think you’ve found them all?”

Duncan continued to slide the squares around, and eventually discovered three more figures. Then he gave up.

“That’s the lot,” he announced confidently.

“The what about this one? Said Grandma, moving the squares swiftly to make a figure that looked like a humpbacked F.

“Oh!”

“And this...”

Duncan began to feel very foolish, and was much relieved when Grandma continued: “You did fairly well—you only missed these two. Altogether, there are exactly twelve of these patterns—no more and no less. Here they are. You could hunt forever—you won’t find another one.”

She brushed aside the five little squares, and laid on the table a dozen brightly colored pieces of plastic. Each was different in shape, and together they formed the complete set of twelve figures that, Duncan was now quite prepared to admit, were all that could be made from five equal squares.

But surely there must be more to it than this. The game couldn’t have finished already. No, Grandma still had something up her sleeve.

“Now listen carefully, Duncan. Each of these figures—they’re called pentominoes, by the way—is obviously the same size, since they’re all made from five identical squares. And there are twelve of them, so the total area is sixty squares. Right?”

“Um... yes.”

“Now sixty is a nice round number, which you can split up in lots of ways. Let’s start with ten multiplied by six, the easiest one. That’s the area of this little box—ten units by six units. So the twelve pieces should fit exactly into it, like a simple jigsaw puzzle.”

Duncan looked for traps—Grandma had a fondness for verbal and mathematical paradoxes, not all of them comprehensible to a ten-year-old victim—but he could find none. If the box was indeed the size Grandma said, then the twelve pieces should just fit into it. After all, both were sixty units in area.

Wait a minute... the area might be the same, but the shape could be wrong. There might be no way of making the twelve pieces fit this rectangular box, even though it was the right size.

“I’ll leave it to you,” said Grandma, after he had shuffled pieces around for a few minutes. “But I promise you this—it can be done.”

Ten minutes later, Duncan was beginning to doubt it. It was easy enough to fit ten of the pieces into the frame—and once he had managed eleven. Unfortunately, the hole then left in the jigsaw was not the same shape as the piece that remained in his hand—even though, of course, it was of exactly the same area. The hole was an X, the piece was a Z...

Thirty minutes later, he was fairly bursting with frustration. Grandma had left him completely alone, while she conducted an earnest dialogue with her computer; but from time to time she gave him an amused glance, as if to say “See—it isn’t as easy as you thought...”

Duncan was stubborn for his age. Most boys of ten would have given up long ago. (It never occurred to him, until years later, that Grandma was also doing a neat job of psychological testing.) He did not appeal for help for almost forty minutes...

Grandma’s fingers flickered over the mosaic. The U and the X and L slid around inside their restraining frame—and suddenly the little box was exactly full. The twelve pieces had been perfectly fitted into the jigsaw.

“Well, you knew the answer!” said Duncan, rather lamely.

“The answer?” retorted Grandma. “Would you care to guess how many different ways these pieces can be fitted into their box?”

There was a catch here—Duncan was sure of it. He hadn’t found a single solution in almost an hour of effort—and he must have tried at least a hundred arrangements. But it was possible that there might be—oh—a dozen different answers.

“I’d guess there might be twenty ways of putting those pieces into the box,” he replied, determined to be on the safe side.

“Try again.”

That was the danger signal. Obviously, there was much more to this business than met the eye, and it would be safer not to commit himself.

Duncan shook his head.

“I can’t imagine.”

“Sensible boy. Intuition is a dangerous guide—though sometimes it’s the only one we have. Nobody could ever guess the right answer. There are more than two thousand distinct ways of putting these twelve pieces back into their box. To be precise, 2,339. What do you think of that?”

It was not likely that Grandma was lying to him, yet Duncan felt so humiliated by his total failure to find even one solution that he blurted out: “I don’t believe it!”

Grandma seldom showed annoyance, though she could become cold and withdrawn when he had offended her. This time, however, she merely laughed and punched out some instructions to the computer.

“Look at that,” she said.

A pattern of bright lines had appeared on the screen, showing the set of all twelve pentominoes fitted into the six-by-ten frame. It held for a few seconds, then was replaced by another obviously different, though Duncan could not possibly remember the arrangement briefly presented to him. Then came another... and another, until Grandma canceled the program.

“Even at this fast rate,” she said, “it takes five hours to run through them all. And take my word for it—though no human being has ever checked each one, or ever could—they’re all different.”

For al long time, Duncan stared at the collection of twelve deceptively simple figures. As he slowly assimilated what Grandma had told him, he had the first genuine mathematical revelation of his life. What had at first seemed merely a childish game had opened endless vistas and horizons—though even the brightest of ten-year-olds could not begin to guess the full extent of the universe now opening up before him.

This moment of dawning wonder and awe was purely passive; a far more intense explosion of intellectual delight occurred when he found his first very own solution to the problem. For weeks he carried around with him the set of twelve pentominoes in their plastic box, playing with them at every odd moment. He got to know each of the dozen shapes as personal friends, calling them with a good deal of imaginative distortion: the odd group, F, I, L, P, N and the ultimate alphabetical sequence T, U, V, W, X, Y, Z.

And once in a sort of geometrical trance or ecstasy which he was never able to repeat, he discovered five solutions in less than an hour. Newton and Einstein and Chen-tsu could have felt no greater kinship with the gods of mathematics in their own moments of truth...

It did not take him long to realize, without any prompting from Grandma, that it might also be possible to arrange the pieces in other shapes besides the six-by-ten rectangle. In theory, at least, the twelve pentominoes could exactly cover rectangles with sides of five-by-twelve units, four-by-fifteen units, and even the narrow strip only three units wide and twenty long.

Without too much effort, he found several examples of the five-by-twelve and four-by-fifteen rectangles. Then he spent a frustrating week, trying to align the dozen pieces into a perfect three-by-twenty strip. Again and again he produced shorter rectangles, but always there were a few pieces left over, and at last he decided that this shape was impossible.

Defeated, he went back to Grandma—and received another surprise.

“I’m glad you made the effort,” she said. “Generalizing—exploring every possibility—is what mathematics is all about. But you’re wrong. It can be done. There are just two solutions; and if you find one, you’ll also have the other.”

Encouraged, Duncan continued the hunt with renewed vigor. After another week, he began to realize the magnitude of the problem. The number of distinct ways in which a mere twelve objects could be laid out essentially in a straight line, when one also allowed for the fact that most of them could assume at least four different orientations, was staggering.

Once again, he appealed to Grandma, pointing out the unfairness of the odds. If there were only two solutions, how long would it take to find them?

“I’ll tell you,” she said. “If you were a brainless computer, and put down the pieces at the rate of one a second in every possible way, you could run through the whole set in”—she paused for effect—“rather more than six million years.”

Earth years or Titan years? thought the appalled Duncan. Not that it really mattered...

“But you aren’t a brainless computer,” continued Grandma. “You can see at a glance whole categories that won’t fit into the pattern, so you don’t have to bother about them. Try again...”

Duncan obeyed, though without much enthusiasm or success. And then he had a brilliant idea.

Karl was interested, and accepted the challenge at once. He took the set of pentominoes, and that was the last Duncan heard of him for several hours.

The he called back, looking a little flustered.

“Are you sure it can be done?” he demanded.

“Absolutely. In fact, there are two solutions. Haven’t you found even one? I thought you were good at mathematics.”

“So I am. That’s why I know how tough the job is. There are over a quadrillion possible arrangements to be checked.”

“How do you work that out?” asked Duncan, delighted to discover something that had baffled his friend.

Karl looked at a piece of paper covered with sketches and numbers.

“Well, excluding forbidden positions, and allowing for symmetry and rotation, it comes to factorial twelve times two to the twenty-first—you wouldn’t understand why! That’s quite a number; here it is.”

He held up a sheet on which he had written, in large figures, the imposing array of digits:

Duncan looked at the number with satisfaction; he did not doubt Karl’s arithmetic.

“So you’ve given up.”

“NO! I’m just telling you how hard it is.” And Karl, looking grimly determined, switched off.

The next day, Duncan had one of the biggest surprises of his young life. A bleary-eyed Karl, who had obviously not slept since their last conversation, appeared on his screen.

“Here it is,” he said, exhaustion and triumph competing in his voice.

Duncan could hardly believe his eyes; he had been convinced that the odds against success were impossibly great. But there was the narrow rectangular strip, only three squares wide and twenty long, formed from the complete set of twelve pieces...

With fingers that trembled slightly from fatigue, Karl took the two end sections and switched them around, leaving the center portion of the puzzle unchanged.

“And here’s the second solution,” he said. “Now I’m going to bed. Good night—or good morning, if that’s what it is.”

For a long time, a very chastened Duncan sat staring at the blank screen. He did not as yet understand what had happened. He only knew that Karl had won against all reasonable expectations.

It was not that Duncan really minded; he loved Karl too much to resent his little victory, and indeed was capable of rejoicing in his friend’s triumphs even when they were at his own expense. But there was something strange here, something almost magical.

It was Duncan’s first glimmer of the power of intuition, and the mind’s mysterious ability to go beyond the available facts and to short-circuit the process of logic. In a few hours, Karl had completed a search that should have required trillions of operations, and would have tied up the fastest computer in existence for an appreciable number of seconds.

One day, Duncan would realize that all men had such powers, but might use them only once in a lifetime. In Karl, the gift was exceptionally well developed; form that moment onward, Duncan had learned to take seriously even his most outrageous speculations.

That was twenty years ago; whatever had happened to that little set of plastic figures? He could not remember when he had last seen it.

But here it was again, reincarnated in colored minerals—the peculiar rose-tinted granite from the Galileo Hills, the obsidian of the Huygens Plateau, the pseudomarble of the Herschel Escarpment. And there—it was unbelievable, but doubt was impossible in such a matter—was the rarest and most mysterious of all the gemstones found on this world. The X of the puzzle was made of Titanite itself; no one could ever mistake that blue-black sheen with its fugitive flecks of gold. It was the largest piece that Duncan had ever seen, and he could not even guess at its value.

“I don’t know what to say,” he stammered. “It’s beautiful—I’ve never seen anything like it.”

He put his arms around Grandma’s thin shoulders—and found, to his distress, that they were quivering uncontrollably. He held her gently until the shaking stopped, knowing there were no words for such moments, and realizing as never before that he was the last love of her empty life, and he was leaving her to her memories.

8. Children of The Corridors

There was a sense of sadness and finality about almost everything that he did in these last days. Sometimes it puzzled Duncan; he should be excited, anticipating the great adventure that only a handful of men on his world could ever share. And though he had never before been out of touch with his friends and family for more than a few hours, he was certain that a year’s absence would pass swiftly enough among the wonders and distractions of Earth.

So why this melancholy? If he was saying farewell to the things of his youth, it was only for a little while, and he would appreciate them all the more when he returned...

When he returned. That, of course, was the heart of the problem. In a real sense, the Duncan Makenzie who was now leaving Titan would never return; indeed, that was the purpose of the exercise. Like Colin thirty years ago, and Malcolm forty years before that, he was heading sunward in search of knowledge, of power, of maturity—and, above all, of the successor which his own world could never give him. for, of course, being Malcolm’s duplicate, he too carried in his loins the fatal Makenzie gene.

Sooner than he had expected, he had to prepare his family for the new addition. After the usual number of experiments, he had settled down with Marissa four years ago, and he loved her children as much, he was certain, as if they had been his own flesh and blood. Clyde was now six years old, Carline three. They in their turn appeared to be as fond of Duncan as of their real fathers, who were now regarded as honorary members of Clan Makenzie. Much the same thing had happened in Colin’s generation—he had acquired or adopted three families—and in Malcolm’s. Grandfather had never gone to the trouble of marrying again after Ellen had left him, but he had never lacked company for long. Only a computer could keep track of the comings and goings on the periphery of the clam; it often seemed that most of Titan was related to it in some way or other. One of Duncan’s major problems now was deciding who would be mortally offended if he failed to say good-bye.

Quite apart from the time factor, he had other reasons for making as few farewells as possible. Every one of his friends and relatives—as well as almost complete strangers—seemed to have some request for him, some mission they wanted him to carry out as soon as he reached Earth. Or, worse still, there was some essential item (“It won’t be any trouble”) they wanted him to bring back. Duncan calculated that he would have to charter a special freighter if he acquiesced to all these demands.

Every job now had to be divided into one of two categories. There were the things that must be done before he left Titan, and those that could be postponed until he was aboard ship. The latter included his studies of current terrestrial affairs, which kept slipping despite Colin’s increasingly frantic attempts to update him.

Extricating himself from his official duties was also no easy task, and Duncan realized that in a few more years it would be well-nigh impossible. He was getting involved in too many things, though that was a matter of deliberate family policy. More than once he had complained that his title of Special Assistant to the Chief Administrator gave him responsibility without power. To this, Chief Administrator Colin had retorted: “Do you know what power means in our society? Giving orders to people who carry them out—only if and when they feel like it.”

This was, of course, a gross libel on the Titanian bureaucracy, which functioned surprisingly well and with a minimum of red tape. Because all the key individuals knew each other, an immense amount of business got done through direct personal contact. Everyone who had come to Titan had been carefully selected for intelligence and ability, and knew that survival depended upon co-operation. Those who felt like abandoning their social responsibilities first had to practice breathing methane at a hundred below.

One possible embarrassment he had at least been spared. He could hardly leave Titan without saying good-bye to his once closest friend—but, very fortunately, Karl was off-world. Several months ago he had left on one of the shuttles to join a Terran survey ship working its way through the outer moons. Ironically enough, Duncan had envied Karl his chance of seeing some unknown worlds; now it was Karl who would be envious when he heard that Duncan was on his way to Earth. The thought gave him more sadness than pleasure; the Makenzies, whatever their faults, were not vindictive. Yet Duncan could not help wondering how often Karl’s reveries would now turn sunward, and to the moment long ago when their emotions had been irrevocably linked with the mother world.

Duncan was just sixteen, and Karl twenty-one, when the cruise liner Mentor had made her first, and it was widely hoped only, rendezvous with Titan. She was a converted fusion-drive freighter—slow but economical, provided adequate supplies of hydrogen could be picked up at strategic points.

Mentor had stopped at Titan for her final refueling, on the last leg of a grand tour that had taken her to Mars, Ganymede, Europa, Pallas, and Iapetus, and had included fly-bys of Mercury and Eros. As soon as she had loaded some fifteen thousand tons of hydrogen, her exhausted crew planned to head back to Earth on the fastest orbit they could compute, if possible after marooning all the passengers.

The cruise must have seemed a good idea when a consortium of Terran universities had planned it several years earlier. And so indeed it had turned out, in the long run, for Mentor graduates had since proved their worth throughout the Solar System. But when the ship staggered into her parking orbit, under the command of a prematurely gray captain, the whole enterprise looked like a first-magnitude disaster.

The problems of keeping five hundred young adults entertained and out of mischief on a six-months’ cruise aboard even the largest spaceliner had not been given sufficient thought; the law professor who had signed on as master-at-arms was later heard to complain bitterly about the complete absence from the ship’s inventory of hypodermic guns and knockout gas. On the other hand, there had been no deaths or serious injuries, only one pregnancy, and everyone had learned a great deal, though not necessarily in the areas that the organizers had intended. The first few weeks, for example, were mostly occupied by experiments in zero-gravity sex, despite warnings that this was an expensive addiction for those compelled to spend most of their lives on planetary surfaces.

Other shipboard activities, it was widely believed, were not quite so harmless. There were reports of tobacco-smoking—not actually illegal, of course, but hardly sensible behavior when there were so many safe alternatives. Even more alarming were persistent rumors that someone had smuggled an Emotion Amplifier on board Mentor. The so-called joy machines were banned on all planets, except under strict medical control; but there would always be people to whom reality was not good enough, and who would want to try something better.

Notwithstanding the horror stories radioed ahead from other ports of call, Titan had looked forward to welcoming its young visitors. It was felt that they would add color to the social scene, and help establish some enjoyable contacts with Mother Earth. And anyway, it would be for only a week...

Luckily, no one dreamed that it would be for two months. This was not Mentor’s fault; Titan had only itself to blame.

When Mentor fell into its parking orbit, Earth and Titan were involved in one of their periodical wrangles over the price of hydrogen, F.O.B. Zero Gravitational Potential (Solar Reference). The proposed 15 percent rise, screamed the Terrans, would cause the collapse of interplanetary commerce. Anything under 10 percent, swore the Titanians, would result in their instant bankruptcy and would make it impossible for them to import any of the expensive items Earth was always trying to sell. To any historian of economics, the whole debate was boringly familiar.

Unable to get a firm quotation, Mentor was stranded in orbit with empty fuel tanks. At first, her captain was not too unhappy; he and the crew could do with the rest, now that the passengers had shuttled down to Titan and had fanned out all over the face of the hapless satellite. But one week stretched into two, then three, then a month. By that time, Titan was ready to settle on almost any terms; unfortunately, Mentor had now missed her optimum trajectories, and it would be another four weeks before the next launch window opened. Meanwhile, the five hundred guests were enjoying themselves, usually much more than their hosts.

But to the younger Titanians, it was an exciting time which they would remember all their lives. On a small world where everyone knew everybody else, half a thousand fascinating strangers had arrived, full of tales, many of them quite true, about the wonders of Earth. Here were men and women, barely into their twenties, who had seen forests and prairies and oceans of liquid water, who had strolled unprotected under an open sky beneath a sun whose heat could actually be felt...

This very contrast in backgrounds, however, was a possible source of danger. The Terrans could not be allowed to go wandering around by themselves, even inside the habitats. They had to have escorts, preferable responsible people not too far from their own age group, to see that they did not inadvertently kill either themselves or their hosts.

Naturally, there were times when they resented this well-intentioned supervision, and even tried to escape from it. One group succeeded; it was very lucky, and suffered no more than a few searing whiffs of ammonia. Damage was so slight that the foolish adventurers required only routine lung transplants, but after this exploit there was no more serious trouble.

There were plenty of other problems. The sheer mechanics of absorbing five hundred visitors was a challenge to a society where living standards were still somewhat Spartan, and accommodation limited. At first, all the unexpected guests were housed in the complex of corridors left by an abandoned mining operation, hastily converted into dormitories. Then, as quickly as arrangements could be made, they were farmed out—like refugees from some bombed city in an ancient war—to any households that were able to cope with them. At this stage, there were still many willing volunteers, among them Colin and Sheela Makenzie.

The apartment was lonely, now that Duncan’s pseudosibling Glynn had left home to work on the other side of Titan; Sheela’s other child, Yuri, had been gone for a decade. Though Number 402, Second Level, Meridian Park was hardly spacious by Terran standards, Assistant Administrator Colin Makenzie, as he was then, had selected one of the homeless waifs for temporary adoption.

And so Calindy had come into Duncan’s life—and into Karl’s.

9. The Fatal Gift

Catherine Linden Ellerman had celebrated her twenty-first birthday just before Mentor reached Saturn. By all accounts, it had been a memorable party, giving the final silvery gloss to the captain’s remaining hairs. Calindy would have sailed through untouched; next to her beauty, that was her most outstanding characteristic. In the midst of chaos—even chaos that she herself had generated—she was the calm center of the storm. With a self-possession far beyond her years, she seemed to young Duncan the very embodiment of Terran culture and sophistication. He could smile wryly, one and a half decades later, at his boyish naïveté; but it was not wholly unfounded. By any standards, Calindy was a remarkable phenomenon.

Duncan knew, of course, that all Terrans were rich. (How could it be otherwise, when each was the heir to a hundred thousand generations?) But he was overawed by Calindy’s display of jewels and silks, never realizing that she had a limited wardrobe which she varied with consummate skill. Most impressive of all was a stunningly beautiful coat of golden fur—the only one ever seen on Titan—made from the skins of an animal called a mink. That was typical of Calindy; no one else would have dreamed of taking a fur coat aboard a spaceship. And she had not done so—as malicious rumor pretended—because she had heard it was cold out around Saturn. She was much too intelligent for that kind of stupidity, and I knew exactly what she was doing; she had brought her mink simply because it was beautiful.

Perhaps because he could see her only through a mist of adoration, Duncan could never visualize her, in later years, as an actual person. When he thought of Calindy, and tried to conjure up her image, he did not see the real girl, but always his only replica of her, in one of the bubble stereos that had become so popular in the ’50’s.

How many thousands of times he had taken that apparently solid, yet almost weightless sphere in his hands, shaken it gently, and thus activated the five-second loop! Through the subtle magic of organized gas molecules, each releasing its programmed quantum of light, Calindy’s face would appear out of the swirling mists—tiny, yet perfect in form and color. At first she would be in profile; then she would turn and suddenly—Duncan could never be sure of the moment when it arrived—there would be the faint smile that only Leonardo could have captured in an earlier age. She did not seem to be smiling at him, but at someone over his shoulder. The impression was so strong that more than once Duncan had looked back, startled, to see who was standing behind him.

Then the image would fade, the bubble would become opaque, and he would have to wait five minutes before the system recharged itself. It did not matter; he had only to close his eyes and he could still see the perfect oval face, the delicate ivory skin, the lustrous black hair gathered up into a toque and held in place by a silver comb that had belonged to a Spanish princess, when Columbus was a child. Calindy liked playing roles, though she took none of them too seriously, and Carmen was one of her favorites.

When she entered the Makenzie household, however, she was the exiled aristocrat, graciously accepting the hospitality of kindly provincials, with what few family heirlooms she had been able to save from the Revolution. As this impressed no one except Duncan, she quickly became the studious anthropologist, taking notes for her thesis on the quaint habits of primitive societies. This role was at least partly genuine, for Calindy was really interested in differing life styles; and by some definitions, Titan could indeed by classed as primitive—or, at least, undeveloped.

Thus the supposedly unshockable Terrans were genuinely horrified at encountering families with three—and even four!—children on Titan. The twentieth century’s millions of skeleton babies still haunted the conscience of the world, and such tragic but understandable excesses as the “Breeder Lynching” campaign, not to mention the burning of the Vatican, had left permanent scars on the human psyche. Duncan could still remember Calindy’s expression when she encountered her first family of six: outrage contended with curiosity, until both were moderated by Terran good manners. He had patiently explained the facts of life to her, pointing out that there was nothing eternally sacred about the dogma of Zero Growth, and that Titan really needed to double its population every fifty years. Eventually she appreciated this logically, but she had never been able to accept it emotionally. And it was emotion that provided the driving force of Calindy’s life; her will and beauty and intelligence were merely its servants.

For a young Terran, she was not promiscuous. She once told Duncan—and he believed her—that she never had more than two lovers at a time. On Titan, to Duncan’s considerable distress, she had only one.

Even if the Helmers and Makenzies had not been related through Grandma Ellen, it was inevitable that she would have met Karl, at one of the countless concerts and parties and dances arranged for Mentor’s castaways. So Duncan could not really blame himself for introducing them; it would have made not difference in the end. Yet even so, he would always wonder...

Karl was then almost twenty-two—a year older than Calindy, though far less experienced. He still possessed the slightly overmuscled build of the native-born Terran, but had adapted so well to the lower gravity that he moved more gracefully than most men who had spent their entire lives on Titan. He seemed to possess the secret of power without clumsiness.

And in a quite literal sense, he was the Golden Boy of his generation. Though he pretended to hate the phrase, Duncan knew that he was secretly proud of the title someone had given him in his teens: “The boy with hair like the sun.” The description could only have been coined by a visitor from Earth. No Titanian would have thought of it—but everyone agreed that it was completely appropriate. For Karl Helmer was one of those men upon whom, for their own amusement, the Gods had bestowed the fatal gift of beauty.

Only years later, and partly thanks to Colin, did Duncan begin to understand all the nuances of the affair. Soon after his twenty-third birthday, the Makenzies received the last Star Day card that Calindy ever sent them.

“I still don’t know if I made a mistake,” Colin said ruefully as he fingered the bright rectangle of paper that had carried its conventional greetings halfway across the Solar System. “But it seemed a good idea at the time.”

“Well, I don’t think it did any harm, in the long run.”

Colin looked at him strangely.

“I wonder. Anyway, it certainly didn’t turn out as I expected.”

“And what did you expect?”

It was sometimes a great advantage, and sometimes downright embarrassing, to have a father who was also your thirty-year-older identical twin. He knew all the mistakes you were going to make, because he had made them already. It was impossible to conceal any secrets from him, because his thought processes were virtually the same. In such a situation, the only policy that made any sense was complete honesty, as far as that could be achieved by human beings.

“I’m not quite sure. But the moment I saw Calindy, shining like a nova amid all that gloom and chaos down in the old mine workings, I wanted to learn more about her... wanted to make her part of my life. You know what I mean.”

Duncan could only nod his head in silent agreement.

“Sheela didn’t mind—after all, I’m not a baby-snatcher! And we both hoped that Calindy would give you someone to think about besides Karl.”

“I was already getting over that, anyway. It was much too frustrating.”

Colin chuckled, not unsympathetically.

“So I can imagine. Karl was spreading himself pretty thin. Half of Titan was in love with him in those days—still is, for that matter. Which is why we must keep him out of politics. Remind me to tell you about Alcibiades someday.

“Who?”

“Ancient Greek general—too clever and charming for his own good. Or for anyone else’s.”

“I appreciate your concern,” said Duncan, with only a slight trace of sarcasm. “But that increased my problems a hundred percent. As she made quite clear, I was much too young for Calindy, and of course Karl was now interested only in her. And to make matters worse, they didn’t even mind me sharing their bed—as long as I didn’t get in the way. In fact—”

“Yes?”

Duncan’s face darkened. How strange that he had never thought of this before, yet how obvious it was!”

“Didn’t mind, hell! They enjoyed having me there, just to tease me! At least Karl did.”

It should have been a shattering revelation, yet somehow it did not hurt as much as he would have expected. He must have realized for a long time, without admitting it to himself, that there was a very definite streak of cruelty in Karl. Certainly his lovemaking often lacked tenderness and consideration; there were even times when he had scared Duncan into something approaching impotence. And to do that to a virile sixteen-year-old was no mean feat.

“I’m glad you’ve realized that,” said Colin somberly. “You had to find it out for yourself—you wouldn’t have believed us. But whatever Karl did, he certainly paid for it. That breakdown was serious. And, frankly, I don’t believe his recovery is as complete as the doctors claim.”

This was also a new thought to Duncan, and he turned it over in his mind. Karl’s breakdown was still a considerable mystery, which the Helmer family had never discussed with outsiders. The romantics had a simple explanation: he was heartbroken over the loss of Calindy. Duncan had always found this too hard to accept. Karl was too tough to pine away like some character in an old-time melodrama—especially when there were at least a thousand volunteers waiting to console him. Yet it was undeniable that the breakdown had occurred only a few weeks after Mentor had, to everyone’s relief, blasted Earthward.

After that, there had been a complete change in his personality; whenever Duncan met him in these last few years, he had seemed almost a stranger.

Physically, he was as beautiful as ever—perhaps even more so, thanks to his greater maturity. And he could still be friendly, though there were sudden silences when he seemed to retreat into himself for no apparent reason. But real communication was missing; maybe it had never been there...

No, that was unfair and untrue. They had known many shared moments before Calindy entered their lives. And one, though only one, after she had left.

That was still the deepest pain that Duncan had ever known. He had been inarticulate with grief when they had made their farewells in the shuttle terminus at Meridian, surrounded by scores of other parting guests. To its great surprise, Titan had suddenly discovered that it was going to miss its young visitors; nearly every one of them was surrounded by a tearful group of local residents.

Duncan’s grief was also, to no small extent, complicated with jealousy. He never discovered how Karl—or Calindy—had managed it, but they flew up in the shuttle together, and made their final farewells on the ship. So when Duncan glimpsed Calindy for the last time, when she waved back at him from the quarantine barrier, Karl was still with her. In that desolating moment, he did not suppose that he would ever see her again.

When Karl returned on the last shuttle flight, five hours later, he was drawn and pale, and had lost all his usual vivacity. Without a word, he had handed Duncan a small package, wrapped in brightly colored paper, and bearing the inscription of LOVE FROM CALINDY.

Duncan had opened it with trembling fingers; a bubble stereo was inside. It was a long time before he was able to see, through the mist of tears, the image it contained.

Much later that same day, as they clung together in mutual misery, an obvious question had suddenly occurred to Duncan.

“What did she give you, Karl?” he had asked.

There was a sudden pause in the other’s breathing, and he felt Karl’s body tense slightly and draw away from him. It was an almost imperceptible gesture; probably Karl was not even aware of it.

When he answered, his voice was strained and curiously defensive.

“It’s—it’s a secret. Nothing important; perhaps one day I’ll tell you.”

Even then, Duncan knew that he never would; and somehow he already realized that this was the last night they would ever spend together.

10. World’s End

Ground Effect Vehicles were very attractive in a low-gravity, dense-atmosphere environment, but they did tend to rearrange the landscape, especially when it consisted of fluffy snow. That was only a problem, however, to anyone following in the rear. When it reached its normal cruising speed of two hundred kilometers an hour, the hoversled left its private blizzard behind it, and the view ahead was excellent.

But it was not cruising at two hundred klicks; it was flat out at three, and Duncan was beginning to wish he had stayed home. It would be very stupid if he broke his neck, on a mission where his presence was quite unnecessary, only two days before he was due to leave for Earth.

Yet there was not real danger. They were moving over smooth, flat ammonia snow, on a terrain known to be free from crevasses. Top speed was safe, and it was fully justified. This was too good an opportunity to miss, and he had waited for it for years. No one had ever observed a waxworm in the active phase, and this one was only eighty kilometers from Oasis. The seismographs had spotted its characteristic signature, and the environment computer had given the alert. The hoversled had been through the airlock within ten minutes.

Now it was approaching the lower slopes of Mount Shackelton, the well-behaved little volcano which, after much careful thought, the original settlers had decided to accept as a neighbor. Waxworms were almost always associated with volcanoes, and some were festooned with them—“like an explosion in a spaghetti factory,” as one early explorer had put it. No wonder that their discovery had caused much excitement; from the air they looked very much like the protective tunnels build by termites and other social insects on Earth.

To the bitter disappointment of the exobiologists, they had turned out to be a purely natural phenomenon—the equivalent, at a much lower temperature, of terrestrial lava tubes. The head of a waxworm moved, judging from the seismic records, at up to fifty kilometers an hour, preferring slopes of not more than ten degrees. They had even been known to go uphill for short distances, when the driving pressure was sufficiently high. Once the core of hot petrochemicals had passed along, what remained was a hollow tube as much as five meters in diameter. Waxworms were among Titan’s more benign manifestations; not only were they a valuable source of raw materials, but they could be readily adapted for storage space and even temporary surface housing—if one could get used to the rich orchestration of aliphatic smells.

The hoversled had another reason for speed; it was the season of eclipses. Twice ever Saturnian year, around the equinoxes, the sun would vanish behind the invisible bulk of the planet for up to six hours at a time. There would be no slow waning of light, as on Earth; with shocking abruptness, the monstrous shadow of Saturn would sweep across Titan, bringing sudden and unexpected night to any traveler who had been foolish enough not to check his calendar.

Today’s eclipse was due in just over an hour, which, unless they ran into obstacles, would give ample time to reach the waxworm. The sled was now driving down a narrow valley flanked by beautiful ammonia cliffs, tinted every possible shade of blue from the palest sapphire to deep indigo. Titan had been called the most colorful world in the Solar System—not excluding Earth; if the sunlight had been more powerful, it would have been positively garish. Although reds and oranges predominated, every part of the spectrum was available somewhere, though seldom for long in the same place. The methane storms and ammonia rains were continually sculpting the landscape.

“Hello, Sled Three,” said Oasis Control suddenly. “You’ll be out in the open again in five kilometers—less than two minutes at your present speed. Then there’s a ten-kilometer slope up to the Amundsen Glacier. From there, you should be able to see the worm. But I think you’re too late—it’s almost reached World’s End.”

“Damn,” said the geologist who had been handling the sled with such effortless skill. “I was afraid of that. Something tells me I’m never going to catch a worm on the run.”

He cut the speed abruptly as a flurry of snow reduced visibility almost to zero, and for a few minutes they were navigating on radar alone through a shining white mist. A film of sticky hydrocarbon slush started to build up on the forward windows, and would soon have covered them completely if the driver had not taken remedial action. A high-pitched whine filled the cabin as the sheets of tough plastic started to oscillate at near ultrasonic frequencies, and a fascinating pattern of standing waves appeared before the obscuring layer was flicked away.

Then they were through the little storm, and the jet-black wall of the Amundsen Glacier was visible on the horizon. In a few centuries that creeping mountain would reach Oasis, and it would be necessary to do something about it. During the years of summer, the viscosity of the carbon-impregnated oils and waxes became low enough for the glacier to advance at the breath-taking speed of several centimeters an hour, but during the long winter it was as motionless as rock.

Ages ago, local heating had melted part of the glacier and formed Lake Tuonela, almost as Stygian black as its parent but decorated by great whorls and loops where lighter material had been caught in patterns of turbulence, now frozen for eternity. Everyone who saw the phenomenon from the air for the first time though he was being original when he exclaimed: “Why, it looks exactly like a cup of coffee, just after you’ve stirred in the cream!”

As the sled raced over the lake, the pattern flickered past in a few minutes, too close for its swirls to be properly observed. Then there was another long slope, dotted with large boulders which could be avoided only by the full thrust of the underjets. This cut speed to less than a hundred klicks, and the sled labored up toward the crest in zigs and zags, the driver cursing and looking every few seconds at his watch.

“There it is!” Duncan shouted.

Only a few kilometers away, coming out of the mist that always enveloped the flanks of Mount Shackelton, was a thin white line, like a piece of rope laid across the landscape. It stretched away downhill until it disappeared over the horizon, and the driver swung the sled around to follow its track. But Duncan already knew that they were too late to achieve their main objective; they were much too close to World’s End. Minutes later, they were there, and the sled came to a stop at a respectful distance.

“That’s as close as I’m getting,” said the driver. “I wouldn’t like a gust to catch us when we’re skirting the edge. Who wants to go out? We still have thirty minutes of light.”

“What’s the temperature?” someone asked.

“Warm. Only fifty below. Single-layer suits will do.”

It was the first time Duncan had been out in the open for months, but there were some skills that nobody who lived on Titan ever allowed himself to forget. He checked the reserve oxygen pressure, the reserve tank, the radio, the fit of the neck seal—all those little details upon which his hopes of a peaceful old age depended. The fact that he would be within a hundred meters of safety, and surrounded by other men who could come to his aid in a moment, did not affect his thoroughness in the least.

Real spacers sometimes underestimated Titan, with disastrous results. It seemed altogether too easy to move around on a world where a pressure suit was unnecessary and the whole body could be exposed to the surrounding atmosphere. Nor was there any need to worry about freezing, even in the Titanian night. As long as the thermosuit retained its integrity, the body’s own hundred and fifty watts of heat could maintain a comfortable temperature indefinitely.

These facts could induce a sense of false security. A torn suit—which would be immediately noticed and repaired in a vacuum environment—might be ignored here as a minor discomfort until it was too late, and toes and fingers were quietly dropping off through frostbite. And although it seemed incredible that anyone could ignore an oxygen warning, or be careless enough to go beyond his point of no return, it had happened. Ammonia poisoning is not the nicest way to die.

Duncan did not let these facts oppress him, but they were always there at the back of his mind. As he walked toward the worm, his feet crunching through a thin crust like congealed candle grease, he kept automatically checking the positions of his nearest companions, in case they needed him—or he needed them.

The cylindrical wall of the worm now loomed above him, ghostly white, textured with little scales or platelets which were slowly peeling off and falling to the ground. Duncan removed a mitten and laid his bare hand on the tube. It was slightly warm and there was a gentle vibration; the core of hot liquid was still pulsing within, like blood through a giant artery. But the worm itself, controlled by the interacting forces of surface tension and gravity, had committed suicide.

While the others busied themselves with their measurements, photographs, and samples, Duncan walked to World’s End. It was not his first visit to that famous and spectacular view, but the impact had not diminished.

Almost at his feet, the ground fell away vertically for more than a thousand meters. Down the face of the cliff, the decapitated worm was slowly dripping stalactites of wax. From time to time an oily globule would break off and fall slowly toward the cloud layer far below. Duncan knew that the ground itself was another kilometer beneath that, but the sea of clouds that stretched out to the horizon had never broken since man had first observed it.

Yet overhead, the weather was remarkably clear. Apart from a little ethylene cirrus, nothing obscured the sky, and the sun was as sharp and bright as Duncan had ever seen it. He could even make out, thirty kilometers to the north, the unmistakable cone of Mount Shackelton, with its perpetual streamer of smoke.

“Hurry up and take your pictures,” said a voice in his radio. “You have less than five minutes.”

A million kilometers away, the invisible bulk of Saturn was edging toward the brilliant star that flooded this strange landscape with a light ten thousand times brighter than Earth’s full Moon. Duncan stepped back a few paces from the brink, but not so far that he could no longer watch the clouds below; he hoped he would be able to observe the shadow of the eclipse as it came racing toward him.

The light was going—going—gone. He never saw the onrushing shadow; it seemed that night fell instantly upon all the world.

He looked up toward the vanished sun, hoping to catch a glimpse of the fabled corona. But there was only a shrinking glow, revealing for a few seconds the curved edge of Saturn as the giant world swept inexorably across the sky. Beyond that was a faint and distant star, which in another moment would also be engulfed.

“Eclipse will last twelve minutes,” said the hoversled driver. “If any of you want to stay outside, keep away from the edge. You can easily get disoriented in the darkness.”

Duncan scarcely heard him. Something had caught at his throat, almost as if a whiff of the surrounding ammonia had invaded his suit.

He could not take his gaze off that faint little star, during the seconds before Saturn wiped it from the sky. He continued to stare long after it was gone, with all its promise of warmth and wonder, and the storied centuries of its civilization.

For the first time in his life, Duncan Makenzie had seen the planet Earth with his own unaided eyes.