'As you've told us at least a dozen times -, Poole's mind tuned out the discussion, so that it was a background of meaningless noise. He was a thousand years in the past, recalling the only excitement of Discovery's mission before the final disaster. Though he and Bowman were perfectly aware that 7794 was merely a lifeless, airless chunk of rock, that knowledge scarcely affected their feelings. It was the only solid matter they would meet this side of Jupiter, and they had stared at it with the emotions of sailors on a long sea voyage, skirting a coast on which they could not land.
It was turning slowly end over end, and there were mottled patches of light and shade distributed at random over its surface. Sometimes it sparkled like a distant window, as planes or outcroppings of crystalline material flashed in the Sun...
He remembered, also, the mounting tension as they waited to see if their aim had been accurate. It was not easy to hit such a small target, two thousand kilometres away, moving at a relative velocity of twenty kilometres a second.
Then, against the darkened portion of the asteroid, there had been a sudden, dazzling explosion of light. The tiny slug – pure Uranium 238 – had impacted at meteoric speed: in a fraction of a second, all its kinetic energy had been transformed into heat. A puff of incandescent gas had erupted briefly into space, and Discovery's cameras were recording the rapidly fading spectral lines, looking for the tell-tale signatures of glowing atoms. A few hours later, back on Earth, the astronomers learned for the first time the composition of an asteroid's crust. There were no major surprises, but several bottles of champagne changed hands.
Captain Chandler himself took little part in the very democratic discussions around his semi-circular table: he seemed content to let his crew relax and express their feelings in this informal atmosphere. There was only one unspoken rule: no serious business at mealtimes. If there were any technical or operational problems, they had to be dealt with elsewhere.
Poole had been surprised – and a little shocked – to discover that the crew's knowledge of Goliath's systems was very superficial. Often he had asked questions which should have been easily answered, only to be referred to the ship's own memory banks. After a while, however, he realized that the sort of in-depth training he had received in his days was no longer possible: far too many complex systems were involved for any man or woman's mind to master. The various specialists merely had to know what their equipment did, not how. Reliability depended on redundancy and automatic checking, and human intervention was much more likely to do harm than good.
Fortunately none was required on this voyage: it had been as uneventful as any skipper could have hoped, when the new sun of Lucifer dominated the sky ahead.
III – THE WORLDS OF GALILEO
(Extract, text only, Tourist's Guide to Outer Solar System, v 219.3)
Even today, the giant satellites of what was once Jupiter present us with major mysteries. Why are four worlds, orbiting the same primary and very similar in size, so different in most other respects?
Only in the case of Io, the innermost satellite, is there a convincing explanation. It is so close to Jupiter that the gravitational tides constantly kneading its interior generate colossal quantities of heat – so much, indeed, that Io's surface is semi-molten. It is the most volcanically active world in the Solar System; maps of Io have a half-life of only a few decades.
Though no permanent human bases have ever been established in such an unstable environment, there have been numerous landings and there is continuous robot monitoring. (For the tragic fate of the 2571 Expedition, see Beagle 5.)
Europa, second in distance from Jupiter, was originally entirely covered in ice, and showed few surface features except a complicated network of cracks. The tidal forces which dominate Io were much less powerful here, but produced enough heat to give Europa a global ocean of liquid water, in which many strange life-forms have evolved.
In 2010 the Chinese ship Tsien touched down on Europa on one of the few outcrops of solid rock protruding through the crust of ice. In doing so it disturbed a creature of the Europan abyss and was destroyed (see Spacecraft Tsien, Galaxy, Universe).
Since the conversion of Jupiter into the mini-sun Lucifer in 2061, virtually all of Europa's ice-cover has melted, and extensive vulcanism has created several small islands.
As is well-known, there have been no landings on Europa for almost a thousand years, but the satellite is under continuous surveillance.
Ganymede, largest moon in the Solar System (diameter 5260 kilometres), has also been affected by the creation of a new sun, and its equatorial regions are warm enough to sustain terrestrial life-forms, though it does not yet have a breathable atmosphere. Most of its population is actively engaged in terraforming and scientific research; the main settlement is Anubis (pop 41,000), near the South Pole.
Callisto is again wholly different. Its entire surface is covered by impact craters of all sizes, so numerous that they overlap. The bombardment must have continued for millions of years, for the newer craters have completely obliterated the earlier ones. There is no permanent base on Callisto, but several automatic stations have been established there.
17 – Ganymede
It was unusual for Frank Poole to oversleep, but he had been kept awake by strange dreams. Past and present were inextricably mixed; sometimes he was on Discovery, sometimes in the Africa Tower – and sometimes he was a boy again, among friends he had thought long-forgotten.
Where am I? he asked himself as he struggled up to consciousness, like a swimmer trying to get back to the surface. There was a small window just above his bed, covered by a curtain not thick enough to completely block the light from outside. There had been a time, around the mid-twentieth century, when aircraft had been slow enough to feature First Class sleeping accommodation: Poole had never sampled this nostalgic luxury, which some tourist organizations had still advertised in his own day, but he could easily imagine that he was doing so now.
He drew the curtain and looked out. No, he had not awakened in the skies of Earth, though the landscape unrolling below was not unlike the Antarctic. But the South Pole had never boasted two suns, both rising at once as Goliath swept towards them.
The ship was orbiting less than a hundred kilometres above what appeared to be an immense ploughed field, lightly dusted with snow. But the ploughman must have been drunk – or the guidance system must have gone crazy – for the furrows meandered in every direction, sometimes cutting across each other or turning back on themselves. Here and there the terrain was dotted with faint circles -ghost craters from meteor impacts aeons ago.
So this is Ganymede, Poole wondered drowsily. Mankind's furthest outpost from home! Why should any sensible person want to live here? Well, I've often thought that when I've flown over Greenland or Iceland in winter-time...
There was a knock on the door, a 'Mind if I come in?', and Captain Chandler did so without waiting for a reply.
'Thought we'd let you sleep until we landed – that end-of-trip party did last longer than I'd intended, but I couldn't risk a mutiny by cutting it short.'
Poole laughed.
'Has there ever been a mutiny in space?'
'Oh, quite a few but not in my time. Now we've mentioned the subject, you might say that Hal started the tradition... sorry – perhaps I shouldn't – look – there's Ganymede City!'
Coming up over the horizon was what appeared to be a criss-cross pattern of streets and avenues, intersecting almost at right-angles but with the slight irregularity typical of any settlement that had grown by accretion, without central planning. It was bisected by a broad river – Poole recalled that the equatorial regions of Ganymede were now warm enough for liquid water to exist – and it reminded him of an old wood-cut he had seen of medieval London.
Then he noticed that Chandler was looking at him with an expression of amusement... and the illusion vanished as he realized the scale of the 'city'.
'The Ganymedeans,' he said dryly, 'must have been rather lar
ge, to have made roads five or ten kilometres wide.'
'Twenty in some places. Impressive, isn't it? And all the result of ice stretching and contracting. Mother Nature is ingenious... I could show you some patterns that look even more artificial, though they're not as large as this one.'
'When I was a boy, there was a big fuss about a face on Mars. Of course, it turned out to be a hill that had been carved by sand-storms... lots of similar ones in Earth's deserts.'
'Didn't someone say that history always repeats itself? Same sort of nonsense happened with Ganymede City – some nuts claimed it had been built by aliens. But I'm afraid it won't be around much longer.'
'Why?' asked Poole in surprise.
'It's already started to collapse, as Lucifer melts the permafrost. You won't recognize Ganymede in another hundred years... there's the edge of Lake Gilgamesh – if you look carefully – over on the right-'
'I see what you mean. What's happening – surely the water's not boiling, even at this low pressure?'
'Electrolysis plant. Don't know how many skillions of kilograms of oxygen a day. Of course, the hydrogen goes up and gets lost – we hope.'
Chandler's voice trailed off into silence. Then he resumed, in an unusually diffident tone: 'All that beautiful water down there – Ganymede doesn't need half of it! Don't tell anyone, but I've been working out ways of getting some to Venus.'
'Easier than nudging comets?'
'As far as energy is concerned, yes – Ganymede's escape velocity is only three klicks per second. And much, much quicker – years instead of decades. But there are a few practical difficulties..
'I can appreciate that. Would you shoot it off by a mass-launcher?'
'Oh no – I'd use towers reaching up through the atmosphere, like the ones on Earth, but much smaller. We'd pump the water up to the top, freeze it down to near absolute zero, and let Ganymede sling it off in the right direction as it rotated. There would be some evaporation loss in transit, but most of it would arrive – what's so funny?'
'Sorry – I'm not laughing at the idea – it makes good sense. But you've brought back such a vivid memory. We used to have a garden sprinkler – driven round and round by its water jets. What you're planning is the same thing – on a slightly bigger scale... using a whole world...'
Suddenly, another image from his past obliterated all else. Poole remembered how, in those hot Arizona days, he and Rikki had loved to chase each other through the clouds of moving mist, from the slowly revolving spray of the garden sprinkler.
Captain Chandler was a much more sensitive man than he pretended to be: he knew when it was time to leave.
'Gotta get back to the bridge,' he said gruffly. 'See you when we land at Anubis.'
18 – Grand Hotel
The Grand Ganymede Hotel – inevitably known throughout the Solar System as 'Hotel Grannymede' was certainly not grand, and would be lucky to get a rating of one-and-a-half stars on Earth. As the nearest competition was several hundred million kilometres away, the management felt little need to exert itself unduly.
Yet Poole had no complaints, though he often wished that Danil was still around, to help him with the mechanics of life and to communicate more efficiently with the semi-intelligent devices with which he was surrounded. He had known a brief moment of panic when the door had closed behind the (human) bellboy, who had apparently been too awed by his guest to explain how any of the room's services functioned. After five minutes of fruitless talking to the unresponsive walls, Poole had finally made contact with a system that understood his accent and his commands. What an 'All Worlds' news item it would have made – 'Historic astronaut starves to death, trapped in Ganymede hotel room'!
And there would have been a double irony. Perhaps the naming of the Grannymede's only luxury suite was inevitable, but it had been a real shock to meet an ancient life-size holo of his old shipmate, in full-dress uniform, as he was led into – the Bowman Suite. Poole even recognized the image: his own official portrait had been made at the same time, a few days before the mission began.
He soon discovered that most of his Goliath crewmates had domestic arrangements in Anubis, and were anxious for him to meet their Significant Others during the ship's planned twenty-day stop. Almost immediately he was caught up in the social and professional life of this frontier settlement, and it was Africa Tower that now seemed a distant dream.
Like many Americans, in their secret hearts, Poole had a nostalgic affection for small communities where everyone knew everyone else – in the real world, and not the virtual one of cyberspace. Anubis, with a resident population less than that of his remembered Flagstaff, was not a bad approximation to this ideal.
The three main pressure domes, each two kilometres in diameter, stood on a plateau overlooking an ice-field which stretched unbroken to the horizon. Ganymede's second sun
– once known as Jupiter – would never give sufficient heat to melt the polar caps. This was the principal reason for establishing Anubis in such an inhospitable spot: the city's foundations were not likely to collapse for at least several centuries.
And inside the domes, it was easy to be completely indifferent to the outside world. Poole, when he had mastered the mechanisms of the Bowman Suite, discovered that he had a limited but impressive choice of environments. He could sit beneath palm trees on a Pacific beach, listening to the gentle murmur of the waves – or, if he preferred, the roar of a tropical hurricane. He could fly slowly along the peaks of the Himalayas, or down the immense canyons of Mariner Valley. He could walk through the gardens of Versailles or down the streets of half a dozen great cities, at several widely spaced times in their history. Even if the Hotel Grannymede was not one of the Solar System's most highly acclaimed resorts, it boasted facilities which would have astounded all its more famous predecessors on Earth.
But it was ridiculous to indulge in terrestrial nostalgia, when he had come half-way across the Solar System to visit a strange new world. After some experimenting, Poole arranged a compromise, for enjoyment – and inspiration -during his steadily fewer moments of leisure.
To his great regret, he had never been to Egypt, so it was delightful to relax beneath the gaze of the Sphinx – as it was before its controversial 'restoration' – and to watch tourists scrambling up the massive blocks of the Great Pyramid. The illusion was perfect, apart from the no-man's-land where the desert clashed with the (slightly worn) carpet of the Bowman Suite.
The sky, however, was one that no human eyes had seen until five thousand years after the last stone was laid at Giza. But it was not an illusion; it was the complex and ever-changing reality of Ganymede.
Because this world – like its companions – had been robbed of its spin aeons ago by the tidal drag of Jupiter, the new sun born from the giant planet hung motionless in its sky. One side of Ganymede was in perpetual Lucifer-light – and although the other hemisphere was often referred to as the 'Night Land', that designation was as misleading as the much earlier phrase 'The dark side of the Moon'. Like the lunar Farside, Ganymede's 'Night Land' had the brilliant light of old Sol for half of its long day.
By a coincidence more confusing than useful, Ganymede took almost exactly one week – seven days, three hours -to orbit its primary. Attempts to create a 'One Mede day = one Earth week' calendar had generated so much chaos that they had been abandoned centuries ago. Like all the other residents of the Solar System, the locals employed Universal Time, identifying their twenty-four-hour standard days by numbers rather than names.
Since Ganymede's newborn atmosphere was still extremely thin and almost cloudless, the parade of heavenly bodies provided a never-ending spectacle. At their closest, Io and Callisto each appeared about half the size of the Moon as seen from Earth – but that was the only thing they had in common. Io was so close to Lucifer that it took less than two days to race around its orbit, and showed visible movement even in a matter of minutes. Callisto, at over four times Io's distance, required two Mede days – or six
teen Earth ones – to complete its leisurely circuit.
The physical contrast between the two worlds was even more remarkable. Deep-frozen Callisto had been almost unchanged by Jupiter's conversion into a mini-sun: it was still a wasteland of shallow ice craters, so closely packed that there was not a single spot on the entire satellite that had escaped from multiple impacts, in the days when Jupiter's enormous gravity field was competing with Saturn's to gather up the debris of the outer Solar System. Since then, apart from a few stray shots, nothing had happened for several billion years.
On Io, something was happening every week. As a local wit had remarked, before the creation of Lucifer it had been Hell – now it was Hell warmed up.
Often, Poole would zoom into that burning landscape and look into the sulphurous throats of volcanoes that were continually reshaping an area larger than Africa. Sometimes incandescent fountains would soar briefly hundreds of kilometres into space, like gigantic trees of fire growing on a lifeless world.
As the floods of molten sulphur spread out from volcanoes and vents, the versatile element changed through a narrow spectrum of reds and oranges and yellows when, chameleon-like, it was transformed into its vari-coloured allotropes. Before the dawn of the Space Age, no one had ever imagined that such a world existed. Fascinating though it was to observe it from his comfortable vantage point, Poole found it hard to believe that men had ever risked landing there, where even robots feared to tread... His main interest, however, was Europa, which at its closest appeared almost exactly the same size as Earth's solitary Moon, but raced through its phases in only four days. Though Poole had been quite unconscious of the symbolism when he chose his private landscape, it now seemed wholly appropriate that Europa should hang in the sky above another great enigma – the Sphinx.
Even with no magnification, when he requested the naked-eye view, Poole could see how greatly Europa had changed in the thousand years since Discovery had set out for Jupiter. The spider's web of narrow bands and lines that had once completely enveloped the smallest of the four Galilean satellites had vanished, except around the poles. Here the global crust of kilometre-thick ice remained unmelted by the warmth of Europa's new sun: elsewhere, virgin oceans seethed and boiled in the thin atmosphere, at what would have been comfortable room temperature on Earth.
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