True enough, thought Floyd; in fact it will get clearer. And there was no disgrace in missing something that terrestrial – or lunar – astronomers had observed. Jupiter was very big, they had been very busy, and the telescopes on the Moon and in Earth orbit were a hundred times more powerful than the instrument he was using now.
But it was getting more and more peculiar. For the first time, Floyd began to feel a distinct sense of unease. Until that moment, it had never occurred to him that the spot could be anything but a natural formation – some trick of Jupiter’s incredibly complex meteorology. Now he began to wonder.
It was so black, like night itself. And so symmetrical; as it came into clearer view it was obviously a perfect circle. Yet it was not sharply defined; the edge had an odd fuzziness, as if it was a little out of focus.
Was it imagination, or had it grown, even while he was watching? He made a quick estimate, and decided that the thing was now two thousand kilometres across. It was only a little smaller than the still-visible shadow of Europa, but was so much darker that there was no risk of confusion.
‘Let’s have a look,’ said Vasili, in a rather condescending tone. ‘What do you think you’ve found? Oh…’ His voice trailed away into silence.
This is it, thought Floyd, with a sudden icy conviction. Whatever it may be.
47
Final Flyby
Yet on further reflection, after the initial amazement had worn off, it was hard to see how a spreading black stain on the face of Jupiter could represent any kind of danger. It was extraordinary – inexplicable – but not as important as the critical events now only seven hours in the future. A successful burn at perijove was all that mattered; they would have plenty of time to study mysterious black spots on the way home.
And to sleep; Floyd had given up all attempts at that.
Though the feeling of danger – at least, of known danger – was much less than on their first approach to Jupiter, a mixture of excitement and apprehension kept him wide awake. The excitement was natural and understandable; the apprehension had more complex causes. Floyd made it a rule never to worry about events over which he could have absolutely no control; any external threat would reveal itself in due time and be dealt with then. But he could not help wondering if they had done everything possible to safeguard the ships.
Apart from onboard mechanical failures, there were two main sources of concern. Although the tapes that secured Leonov and Discovery together had shown no tendency to slip, their severest test was still to come. Almost equally critical would be the moment of separation when the smallest of the explosive charges once intended to jolt Big Brother would be used at uncomfortably close quarters. And, of course, there was Hal.
He had carried out the deorbiting manoeuvre with exquisite precision. He had run the simulations of the Jupiter flyby, right down to Discovery’s last drop of fuel, without any comments or objections. And although Chandra, as agreed, had carefully explained what they were trying to do, did Hal really understand what was happening?
Floyd had one overriding concern, which in the preceding few days had become almost an obsession. He could picture everything going perfectly, the ships halfway through the final manoeuvre, the enormous disk of Jupiter filling the sky only a few hundred kilometres below them – and then Hal electronically clearing his throat and saying:
‘Dr Chandra, do you mind if I ask you a question?’ It did not happen exactly that way.
The Great Black Spot, as it had been inevitably christened, was now being carried out of sight by Jupiter’s swift rotation. In a few hours the still-accelerating ships would catch up with it over the nightside of the planet, but this was the last chance for a close daylight observation.
It was still growing at an extraordinary speed; in the last two hours, it had more than doubled its area. Except for the fact that it retained its blackness as it expanded, it resembled an ink-stain spreading in water. Its boundary – now moving at near-sonic speed in the Jovian atmosphere – still looked curiously fuzzy and out of focus; at the very highest power of the ship’s telescope, the reason for this was at last apparent.
Unlike the Great Red Spot, the Great Black Spot was not a continuous structure; it was built up from myriads of tiny dots, like a half-tone print viewed through a magnifying glass. Over most of its area, the dots were so closely spaced that they were almost touching, but at the rim they became more and more widely spaced, so that the Spot ended in a grey penumbra rather than at a sharp frontier.
There must have been almost a million of the mysterious dots, and they were distinctly elongated – ellipses rather than circles. Katerina, the least imaginative person aboard, surprised everybody by saying that it looked as if someone had taken a sackful of rice, dyed it black, and poured it on the face of Jupiter.
And now the Sun was dropping down behind the huge, swiftly narrowing arch of the dayside, as for the second time Leonov raced into the Jovian night for an appointment with destiny. In less than thirty minutes the final burn would commence, and things would start to happen very quickly indeed.
Floyd wondered if he should have joined Chandra and Curnow, standing watch on Discovery. But there was nothing he could do; in an emergency, he would only be in the way. The cut-off switch was in Curnow’s pocket, and Floyd knew that the younger man’s reactions were a good deal swifter than his own. If Hal showed the slightest sign of misbehaviour, he could be disconnected in less than a second, but Floyd felt certain that such extreme measures would not be necessary. Since he had been allowed to do things his own way, Chandra had cooperated completely in setting up the procedures for a manual takeover, should that unfortunate necessity arise. Floyd was confident that he could be trusted to carry out his duty – however much he might regret the need.
Curnow was not quite so sure. He would be happier, he had told Floyd, if he had multiple redundancy in the form of a second cut-off switch – for Chandra. Meanwhile there was nothing that anyone could do but wait and watch the approaching cloudscape of the nightside, dimly visible by the reflected light of passing satellites, the glow of photo-chemical reactions, and frequent titanic lightning flashes from thunderstorms larger than Earth.
The sun winked out behind them, eclipsed in seconds by the immense globe they were so swiftly approaching. When they saw it again, they should be on their way home.
‘Twenty minutes to ignition. All systems nominal.’
‘Thank you, Hal.’
I wonder if Chandra was being quite truthful, thought Curnow, when he said that Hal would be confused if anyone else spoke to him. I’ve talked to him often enough, when nobody was around, and he always understood me perfectly. Still, there’s not much time left for friendly conversation now, though it would help to reduce the strain.
What’s Hal really thinking – if he thinks – about the mission? All his life, Curnow had shied away from abstract, philosophical questions: I’m a nuts-and-bolts man, he had often claimed, though there were not too many of either in a spaceship. Once, he would have laughed at the idea, but now he began to wonder: Did Hal sense that he would soon be abandoned, and if so, would he resent it? Curnow almost reached for the cut-off switch in his pocket, but checked himself. He had already done this so often that Chandra might be getting suspicious.
For the hundredth time, he rehearsed the sequence of events that were due to take place during the next hour. The moment that Discovery’s fuel was exhausted, they would close down all but essential systems, and dash back to Leonov through the connecting tube. That would be decoupled, the explosive charges would be fired, the ships would drift apart – and Leonov’s own engines would start to fire. The separation should take place, if everything went according to plan, just when they were making their closest approach to Jupiter; that would take maximum advantage of the planet’s gravitational largesse.
‘Fifteen minutes to ignition. All systems nominal.’
‘Thank you, Hal.’
‘By the way,’ said Vasili, from the other ship, ‘we’re catching up with the Great Black Spot again. Wonder if we can see anything new.’
I rather hope not, thought Curnow; we’ve got quite enough on our hands at the moment. Nevertheless, he gave a quick glance at the image Vasili was transmitting on the telescope monitor.
At first he could see nothing except the faintly glimmering nightside of the planet; then he saw, on the horizon, a foreshortened circle of deeper darkness. They were rushing toward it with incredible speed.