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 that 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 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 gbout 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 men 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 asit 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 hover sled 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. Part 11

I - -1 L Transit

I I

SIRIUS

After three hundred years of spaceships that were mostly fuel tanks,

Sirius was not quite believable. She seemed to have far too many windows, and there were entrance hatches in most improbable places, some of them still gaping open as cargo was loaded. At least she was taking on some hydrogen, thought Duncan sourly; it would be adding insult to economic injury if she made the round trip on a single fueling. She was capable of doing this, it was rumored, though at the cost of doubling her transit time.

It was also hard to believe that this stubby cylinder, with the smooth mirror-bright ring of the radiation baffle surrounding the drive unit like a huge sunshade, was one of the fastest objects ever built by man. Only the interstellar probes, now far out into the abyss on their centuries-long journeys, could exceed her theoretical maximum-almost one percent of the velocity of light. She would never achieve even half this speed, because she had to carry enough propel lent to slow down and rendezvous with her destination. Nevertheless, she could make the voyage from Saturn to Earth in twenty days, despite a minor detour to avoid the hazards-largely psychological-of the asteroid belt.

The forty-minute flight from surface to parking orbit was not Duncan’s first experience of space; he had made several brief trips to neighboring moons, aboard this same shuttle. The Titanian passenger fleet consisted of exactly five vessels, and as none possessed the expensive luxury of centrifugal gravity, all safety belts were secured throughout the voyage.

Any passenger who wished to sample the joys and hazards of weightlessness would have just under two hours to experience it aboard

Sirius, before the drive started to operate. Although Duncan had always felt completely at ease in free fall, he let the stewards float him, an inert and unresisting package, through the airlock and into the ship.

It had been rather too much to expect the Centennial Committee to provide a single cabin-there were only four on the ship-and Duncan knew that he would have to share a double. L.3 was a minute cell with two folding bunks, a couple of lockers, two seats-also folding-and a mirror-vision screen.

There was no window looking out into space; this, the Welcome Aboard! brochure carefully explained, would create unacceptable structural hazards.

Duncan did not believe this for a moment, and wondered if the designers feared an attempt by claustrophobic passengers to claw a way out.

And there were no toilet facilities-these were all in an adjacent cubicle, which serviced the four cabins around it. Well, it was only going to be for a few weeks…. Duncan’s spirits rose somewhat after he had gained enough confidence to start exploring his little world. He quickly learned to visualize his location by following the advice printed on the shipboard maps; it was convenient to think of Sirius as a cylindrical tower with ten floors. The fifty cabins were divided between the sixth and seventh floors. Immediately below, on the fifth level, was the lounge, recreation and dining area.