On Mars, or on the Moon, you could sometimes -with a slight effort of imagination, and if you ignored the alien sky - pretend that you were on Earth. This was impossible here, because the towering - often overhanging - snow sculptures showed only the slightest concession to gravity. You had to look very carefully at your surroundings to decide which way was up.
The Valley of Black Snow was unusual, because it was a fairly solid structure - a rocky reef embedded in volatile drifts of water and hydrocarbon ice. The geologists were still arguing about its origin, some maintaining that it was really part of an asteroid that had encountered the comet ages ago. Corings had revealed complex mixtures of organic compounds, rather like frozen coal-tar - though it was certain that life had never played any part in their formation.
The "snow" carpeting of the floor of the little valley was not completely black; when Floyd raked it with the beam of his flashlight it glittered and sparkled as if embedded with a million microscopic diamonds. He wondered if there were indeed diamonds on Halley: there was certainly enough carbon here. But it was almost equally certain that the temperatures and pressures necessary to create them had never existed here.
On a sudden impulse, Floyd reached down and gathered two handfuls of the snow: he had to push with his feet against the safety line to do so, and had a comic vision of himself as a trapeze artist walking a tightrope - but upside down. The fragile crust offered virtually no resistance as he buried head and shoulders into it; then he pulled gently on his tether and emerged with his handful of Halley.
He wished that he could feel it through the insulation of his gloves, as he compacted the mass of crystalline fluff into a ball that just fitted the palm of his hand. There it lay, ebony black yet giving fugitive flashes of light as he turned it from side to side.
And suddenly, in his imagination, it became the purest white - and he was a boy again, in the winter playground of his youth, surrounded with the ghosts of his childhood. He could even hear the cries of his companions, taunting and threatening him with their own projectiles of immaculate snow...
The memory was brief, but shattering, for it brought an overwhelming sensation of sadness. Across a century of time, he could no longer remember a single one of those phantom friends who stood around him; yet some, he knew, he had once loved...
His eyes filled with tears, and his fingers clenched around the ball of alien snow. Then the vision faded; he was himself again. This was not a moment of sadness, but of triumph.
"My God!" cried Heywood Floyd, his words echoing in the tiny, reverberant universe of his spacesuit, "I'm standing on Halley's Comet - what more do I want! If a meteor hits me now, I won't have a single complaint!"
He brought up his arms and launched the snowball towards the stars. It was so small, and so dark, that it vanished almost at once, but he kept on staring into the sky.
And then, abruptly - unexpectedly - it appeared in a sudden explosion of light, as it rose into the rays of the hidden Sun. Black as soot though it was, it reflected enough of that blinding brilliance to be easily visible against the faintly luminous sky.
Floyd watched it until it finally disappeared - perhaps by evaporation, perhaps by dwindling into the distance. It would not last long in the fierce torrent of radiation overhead; but how many men could claim to have created a comet of their own?
18: Old Faithful
The cautious exploration of the comet had already begun while Universe still remained in the polar shadow. First, one-man EMUs (few people now knew that stood for External Manoeuvring Unit) gently jetted over both day- and nightside, recording everything of interest. Once the preliminary surveys had been completed, groups of up to five scientists flew out in the onboard shuttle, deploying equipment and instruments at strategic spots.
The Lady Jasmine was a far cry from the primitive space pods of the Discovery era, capable of operating only in a gravity-free environment. She was virtually a small spaceship, designed to ferry personnel and light cargo between the orbiting Universe and the surfaces of Mars, Moon, or the Jovian satellites. Her chief pilot, who treated her like the grande dame she was, complained with mock bitterness that flying round a miserable little comet was far beneath her dignity.
When he was quite sure that Halley - on the surface at least - held no surprises, Captain Smith lifted away from the pole. Moving less than a dozen kilometers took Universe to a different world, from a glimmering twilight that would last for months to a realm that knew the cycle of night and day. And with the dawn, the comet came slowly to life.
As the Sun crept above the jagged, absurdly close horizon, its rays would slant down into the countless small craters that pockmarked the crust. Most of them would remain inactive, their narrow throats sealed by incrustations of mineral salts. Nowhere else on Halley were such vivid displays of colour; they had misled biologists into thinking that here life was beginning, as it had on Earth, in the form of algal growths. Many had not yet abandoned that hope, though they would be reluctant to admit it.
From other craters, wisps of vapour floated up into the sky, moving in unnaturally straight trajectories because there were no winds to divert them. Usually nothing else happened for an hour or two; then, as the Sun's warmth penetrated to the frozen interior, Halley would begin to spurt - as Victor Willis had put it "like a pod of whales".
Though picturesque, it was not one of his more accurate metaphors. The jets from the dayside of Halley were not intermittent, but played steadily for hours at a time. And they did not curl over and fall back to the surface, but went rising on up into the sky, until they were lost in the glowing fog which they helped create.
At first, the science team treated the geysers as cautiously as if they were vulcanologists approaching Etna or Vesuvius in one of their less predictable moods. But they soon discovered that Halley's eruptions, though often fearsome in appearance, were singularly gentle and well-behaved; the water emerged about as fast as from an ordinary firehose, and was barely warm. Within seconds of escaping from its underground reservoir, it would flash into a mixture of vapour and ice crystals; Halley was enveloped in a perpetual snowstorm, falling upward. Even at this modest speed of ejection, none of the water would ever return to its source. Each time it rounded the Sun, more of the comet's life-blood would haemorrhage into the insatiable vacuum of space.
After considerable persuasion, Captain Smith agreed to move Universe to within a hundred metres of Old Faithful, the largest geyser on the dayside. It was an awesome sight - a whitish-grey column of mist, growing like some giant tree from a surprisingly small orifice in a three-hundred-metre-wide crater which appeared to be one of the oldest formations on the comet. Before long, the scientists were scrambling all over the crater, collecting specimens of its (completely sterile, alas) multi-coloured minerals, and casually thrusting their thermometers and sampling tubes into the soaring water-ice-mist column itself. "If it tosses any of you out into space," warned the Captain, "don't expect to be rescued in a hurry. In fact, we may just wait until you come back."
"What does he mean by that?" a puzzled Dimitri Mihailovich had asked. As usual, Victor Willis was quick with the answer.
"Things don't always happen the way you'd expect in celestial mechanics. Anything thrown off Halley at a reasonable speed will still be moving in essentially the same orbit - it takes a huge velocity change to make a big differenc. So one revolution later, the two orbits will intersect again - and you'll be right back where you started. Seventy-six years older, of course."
Not far from Old Faithful was another phenomenon which no one could reasonably have anticipated. When they first observed it, the scientists could scarcely believe their eyes. Spread out across several hectares of Halley, exposed to the vacuum of space, was what appeared to be a perfectly ordinary lake, remarkable only for its extreme blackness.
Obviously, it could not be water; the only liquids which could be stable in this environment were heavy organic oils or tars. In fact, Lake Tuonela turned out to be mo
re like pitch, quite solid except for a sticky surface layer less than a millimetre thick. In this negligible gravity, it must have taken years - perhaps several trips round the warming fires of the Sun - for it to have assumed its present mirror-flatness.
Until the Captain put a stop to it, the lake became one of the principal tourist attractions on Halley's Comet. Someone (nobody claimed the dubious honour) discovered that it was possible to walk perfectly normally across it, almost as if on Earth; the surface film had just enough adhesion to hold the foot in place. Before long, most of the crew had got themselves videoed apparently walking on water...
Then Captain Smith inspected the airlock, discovered the walls liberally stained with tar, and gave the nearest thing to a display of anger that anyone had ever witnessed from him.
"It's bad enough," he said through clenched teeth, "having the outside of the ship coated with - soot. Halley's Comet is about the filthiest place I've ever seen..."
After that, there were no more strolls on Lake Tuonela.
19: At the End of the Tunnel
In a small, self-contained universe where everyone knows everyone else, there can be no greater shock than encountering a total stranger.
Heywood Floyd was floating gently along the corridor to the main lounge when he had this disturbing experience. He stared in amazement at the interloper, wondering how a stowaway had managed to avoid detection for so long. The other man looked back at him with a combination of embarrassment and bravado, obviously waiting for Floyd to speak first.
"Well, Victor!" he said at last. "Sorry I didn't recognize you. So you've made the supreme sacrifice, for the cause of science - or should I say your public?"
"Yes," Willis answered grumpily. "I did manage to squeeze into one helmet - but the damn bristles made so many scratching noises no one could hear a word I said."
"When are you going out?"
"Just as soon as Cliff comes back - he's gone caving with Bill Chant."
* * *
The first flybys of the comet, in 1986, had suggested that it was considerably less dense than water -which could only mean that it was either made of very porous material, or was riddled with cavities. Both explanations turned out to be correct.
At first, the ever-cautious Captain Smith flatly forbade any cave-exploring. He finally relented when Dr Pendrill reminded him that his chief assistant Dr Chant was an experienced speleologist - indeed, that was one of the very reasons he had been chosen for the mission.
"Cave-ins are impossible, in this low gravity," Pendrill had told the reluctant Captain. "So there's no danger of being trapped."
"What about being lost?"
"Chant would regard that suggestion as a professional insult. He's been twenty kilometers inside Mammoth Cave. Anyway, he'll play out a guideline."
"Communications?"
"The line's got fibre optics in it. And his suit radio will probably work most of the way."
"Umm. Where does he want to go in?"
"The best place is that extinct geyser at the base of Etna Junior. It's been dead for at least a thousand years."
"So I suppose it should keep quiet for another couple of days. Very well - does anyone else want to go?"
"Cliff Greenburg has volunteered - he's done a good deal of underwater cave-exploring, in the Bahamas."
"I tried it once - that was enough. Tell Cliff he's much too valuable. He can go in as far as he can still see the entrance - and no further. And if he loses contact with Chant, he's not to go after him, without my authority."
Which, the Captain added to himself, I would be very reluctant to give...
Dr Chant knew all the old jokes about speleologists wanting to return to the womb, and was quite sure he could refute them.
"That must be a damn noisy place, with all its thumpings and bumpings and gurglings," he argued. "I love caves because they're so peaceful and timeless. You know that nothing has changed for a hundred thousand years, except that the stalactites have grown a bit thicker."
But now, as he drifted deeper into Halley, playing out the thin, but virtually unbreakable thread that linked him to Clifford Greenburg, he realized that this was no longer true. As yet, he had no scientific proof, but his geologist's instincts told him that this subterranean world had been born only yesterday, on the time-scale of the universe. It was younger than some of the cities of man.
The tunnel through which he was gliding in long, shallow leaps was about four metres in diameter, and his virtual weightlessness brought back vivid memories of cave-diving on Earth. The low gravity contributed to the illusion; it was exactly as if he was carrying slightly too much weight, and so kept drifting gently downwards. Only the absence of all resistance reminded him that he was moving through vacuum, not water.
"You're just getting out of sight," said Greenburg, fifty metres in from the entrance. "Radio link still fine. What's the scenery like?"
"Very hard to say - I can't identify any formations, so I don't have the vocabulary to describe them. It's not any kind of rock - it crumbles when I touch it - I feel as if I'm exploring a giant Gruyère cheese."
"You mean it's organic?"
"Yes - nothing to do with life, of course - but perfect raw material for it. All sorts of hydrocarbons - the chemists will have fun with these samples. Can you still see me?"
"Only the glow of your light, and that's fading fast."
"Ah - here's some genuine rock - doesn't look as if it belongs here - probably an intrusion - ah - I've struck gold!"
"You're joking!"
"It fooled a lot of people in the old West - iron pyrites. Common on the outer satellites, of course, but don't ask me what it's doing here..."
"Visual contact lost. You're two hundred metres in."
"I'm passing through a distinct layer - looks like meteoric debris - something exciting must have happened back then - I hope we can date it - wow!"
"Don't do that sort of thing to me!"
"Sorry - quite took my breath away - there's a big chamber ahead - last thing I expected - let me swing the beam around...
"Almost spherical - thirty, forty metres across. And - I don't believe it - Halley is full of surprises - stalactites, stalagmites."
"What's so surprising about that?"
"No free water, no limestone here, of course - and such low gravity. Looks like some kind of wax. Just a minute while I get good video coverage... fantastic shapes... sort of thing a dripping candle makes... that's odd..."
"Now what?"
Dr Chant's voice had shown a sudden alteration in tone, which Greenburg had instantly detected.
"Some of the columns have been broken. They're lying on the floor. It's almost as if..."
"Go on!"
"... as if something has - blundered - into them."
"That's crazy. Could an earthquake have snapped them?"
"No earthquakes here - only microseisms from the geysers. Perhaps there was a big blow-out at some time. Anyway, it was centuries ago. There's a film of this wax stuff over the fallen columns - several millimetres thick."
Dr Chant was slowly recovering his composure. He was not a highly imaginative man - spelunking eliminates such men rather quickly - but the very feel of the place had triggered some disturbing memory. And those fallen columns looked altogether too much like the bars of a cage, broken by some monster in an attempt to escape.
Of course, that was perfectly absurd - but Dr Chant had learned never to ignore any premonition, any danger signal, until he had traced it to its origin. That caution had saved his life more than once; he would not go beyond this chamber until he had identified the source of his fear. And he was honest enough to admit that 'fear' was the correct word.
"Bill - are you all right? What's happening?"
"Still filming. Some of these shapes remind me of Indian temple sculpture. Almost erotic."
He was deliberately turning his mind away from the direct confrontation of his fears, hoping thereby to sneak up on them unawares, by a
kind of averted mental vision. Meanwhile the purely mechanical acts of recording and collecting samples occupied most of his attention.
There was nothing wrong, he reminded himself, with healthy fear; only when it escalated into panic did it become a killer. He had known panic twice in his life (once on a mountainside, once underwater) and still shuddered at the memory of its clammy touch. Yet - thankfully - he was far from it now, and for a reason which, though he did not understand it, he found curiously reassuring. There was an element of comedy in the situation.
And presently he started to laugh - not with hysteria, but with relief.
"Did you ever see those old Star Wars movies?" he asked Greenburg.
"Of course - half a dozen times."
"Well, I know what's been bothering me. There was a sequence when Luke's spaceship dives into an asteroid - and runs into a gigantic snake-creature that lurks inside its caverns."
"Not Luke's ship - Hans Solo's Millennium Falcon. And I always wondered how that poor beast managed to eke out a living. It must have grown very hungry, waiting for the occasional titbit from space. And Princess Leia wouldn't have been more than an hors-d'oeuvre, anyway."
"Which I certainly don't intend to provide," said Dr Chant, now completely at ease. "Even if there is life here - which would be marvellous - the food chain would be very short. So I'd be surprised to find anything bigger than a mouse. Or, more likely, a mushroom... Now let's see - where do we go from here... There are two exits on the other side of the chamber... the one on the right is bigger... I'll take that..."
"How much more line have you got?"
"Oh, a good half-kilometer. Here we go... I'm in the middle of the chamber... damn, bounced off the wall... now I've got a hand-hold... going in head-first... smooth walls, real rock for a change... that's a pity..