Even as he fell through the roaring heart of the Great Red Spot, with the lightning of its continent-wide thunderstorms detonating around him, he knew why it had persisted for centuries though it was made of gases far less substantial than those that formed the hurricanes of Earth. The thin scream of hydrogen wind faded as he sank into the calmer depths, and a sleet of waxen snowflakes – some already coalescing into barely palpable mountains of hydrocarbon foam – descended from the heights above. It was already warm enough for liquid water to exist, but there were no oceans there; that purely gaseous environment was too tenuous to support them.
He descended through layer after layer of cloud, until he entered a region of such clarity that even human vision could have scanned an area more than a thousand kilometres across. It was only a minor eddy in the vaster gyre of the Great Red Spot; and it held a secret that men had long guessed, but never proved.
Skirting the foothills of the drifting foam mountains were myriads of small, sharply-defined clouds, all about the same size and patterned with similar red and brown mottlings. They were small only as compared with the inhuman scale of their surroundings; the very least would have covered a fair-sized city.
They were clearly alive, for they were moving with slow deliberation along the flanks of the aerial mountains, browsing off their slopes like colossal sheep. And they were calling to each other in the metre band, their radio voices faint but clear against the cracklings and concussions of Jupiter itself.
Nothing less than living gasbags, they floated in the narrow zone between freezing heights and scorching depths. Narrow, yes – but a domain far larger than all the biosphere of Earth.
They were not alone. Moving swiftly among them were other creatures so small that they could easily have been overlooked. Some of them bore an almost uncanny resemblance to terrestrial aircraft and were of about the same size. But they too were alive – perhaps predators, perhaps parasites, perhaps even herdsmen.
A whole new chapter of evolution, as alien as that which he had glimpsed on Europa, was opening before him. There were jet-propelled torpedoes like the squids of the terrestrial oceans, hunting and devouring the huge gasbags. But the balloons were not defenceless; some of them fought backs with electric thunderbolts and with clawed tentacles like kilometre-long chainsaws.
There were even stranger shapes, exploiting almost every possibility of geometry – bizarre, translucent kites, tetrahedra, spheres, polyhedra, tangles of twisted ribbons.
The gigantic plankton of the Jovian atmosphere, they were designed to float like gossamer in the uprising currents, until they had lived long enough to reproduce; then they would be swept down into the depths to be carbonized and recycled in a new generation.
He was searching a world more than a hundred times the area of Earth, and though he saw many wonders, nothing there hinted of intelligence. The radio voices of the great balloons carried only simple messages of warning or of fear. Even the hunters, who might have been expected to develop higher degrees of organization, were like the sharks in Earth’s oceans – mindless automata.
And for all its breathtaking size and novelty, the biosphere of Jupiter was a fragile world, a place of mists and foam, of delicate silken threads and paper-thin tissues spun from the continual snowfall of petrochemicals formed by lightning in the upper atmosphere. Few of its constructs were more substantial than soap bubbles; its most terrifying predators could be torn to shreds by even the feeblest of terrestrial carnivores.
Like Europa on a vastly grander scale, Jupiter was an evolutionary cul-de-sac. Consciousness would never emerge here; even if it did, it would be doomed to a stunted existence. A purely aerial culture might develop, but in an environment where fire was impossible, and solids scarcely existed, it could never even reach the Stone Age.
And now, as he hovered above the centre of a Jovian cyclone merely as large as Africa, he became aware once again of the presence controlling him. Moods and emotions were leaking into his own consciousness, though he could not identify any specific concepts or ideas. It was as if he were listening, outside a closed door, to a debate in progress, and in a language he could not understand. But the muffled sounds clearly conveyed disappointment, then uncertainty, then a sudden determination – though for what purpose he could not tell. Once again, he felt like a pet dog, able to share his master’s changing moods but not to comprehend them.
And then the invisible leash was taking him down toward the heart of Jupiter. He was sinking through the clouds, below the level where any form of life was possible.
Soon he was beyond the reach of the last rays from the faint and distant Sun. The pressure and temperature were swiftly mounting; already it was above the boiling point of water, and he passed briefly through a layer of superheated steam. Jupiter was like an onion; he was peeling it away skin by skin, though as yet he had travelled only a fraction of the distance to its core.
Beneath the steam was a witches’ brew of petrochemicals – enough to power for a million years all the internal-combustion engines that mankind had dyer built. It became thicker and denser; then, quite abruptly, it ended at a discontinuity only a few kilometres thick.
Heavier than any rocks on Earth, yet still a liquid, the next shell consisted of silicon and carbon compounds of a complexity that could have provided lifetimes of work for terrestrial chemists. Layer followed layer for thousands of kilometres, but as the temperature rose into the hundreds and then the thousands of degrees, the composition of the various strata became simpler and simpler. Halfway down to the core, it was too hot for chemistry; all compounds were torn apart, and only the basic elements could exist.
Next there came a deep sea of hydrogen – but not hydrogen as it had ever existed for more than a fraction of a second in any laboratory on Earth. This hydrogen was under such enormous pressure that it had become a metal.
He had almost reached the centre of the planet, but Jupiter had one more surprise in store. The thick shell of metallic yet still fluid hydrogen ended abruptly. At last, there was a solid surface, sixty thousand kilometres down.
For ages, the carbon baked out of the chemical reactions far above had been drifting down toward the centre of the planet. There it had gathered, crystallizing at a pressure of millions of atmospheres. And there, by one of Nature’s supreme jests, was something very precious to mankind.
The core of Jupiter, forever beyond human reach, was a diamond as big as the Earth.
39
In the Pod Bay
‘Walter – I’m worried about Heywood.’
‘I know, Tanya – but what can we do?’
Curnow had never seen Commander Orlova in so indecisive a mood; it made her seem much more appealing, despite his prejudice against small women.
‘I’m very fond of him, but that’s not the reason. His – I suppose gloom is the best word for it – is making everyone miserable. Leonov has been a happy ship. I want to keep it that way.’
‘Why don’t you talk to him? He respects you, and I’m sure he’ll do his best to snap out of it.’
‘I intend to do just that. And if it doesn’t work -‘ ‘Well?’
‘There’s one simple solution. What more can he do on this trip? When we start back for home, he’ll be in hibernation anyway. We could always – what do you say, jump the gun on him.’
‘Phew – the same dirty trick that Katerina played on me. He’d be mad when he woke up.’
‘But also safely back on Earth, and very busy. I’m sure he’d forgive us.’
‘I don’t think you’re serious. Even if I backed you up, Washington would raise hell. Besides, suppose something happened, and we really need him badly? Isn’t there a two-week buffer period, before you can revive anyone safely?’
‘At Heywood’s age, more like a month. Yes, we’d be committed. But what do you think could happen now? He’s done the job he was sent for – apart from keeping an eye on us. And I’m sure you’ve been well briefed about that in some obscure suburb of Virginia or Maryland.’
‘I neither confirm nor deny. And frankly, I’m a lousy undercover agent. I talk too much, and I hate Security. I’ve fought all my life to keep my rating below Restricted. Every time there was danger of being reclassified Confidential or, worse still, Secret, I’d go and create a scandal. Though that’s getting very difficult nowadays.’
‘Walter, you’re incorrupt -‘
‘Incorrigible?’
‘Yes, that’s the word I meant. But back to Heywood, please. Would you like to talk to him first?’