'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.'

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 sixteen 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.