Xeelee: Endurance

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Prologue

The spacecraft from Earth sailed through rings of ice.

In its first week in orbit around Saturn it passed within a third of a million kilometres of Titan, Saturn’s largest moon, sensors peering curiously down at unbroken haze. The craft had been too heavy to launch direct with the technology of the time, so its flight path, extending across seven years, had taken it on swingbys past Venus, Earth and Jupiter. Primitive it was, but it was prepared for Titan. An independent lander, a fat pie-dish three metres across, clung to the side of the main body.

Dormant for most of the interplanetary cruise, the probe was at last woken and released. And, two weeks later, it dropped into the thick atmosphere of Titan itself.

Much of the probe’s interplanetary velocity was shed in ferocious heat, and then the main parachute inflated. Portals opened and booms unfolded, and, more than a billion kilometres from the nearest human engineer, instruments peered out at Titan. Some fifty kilometres up the surface slowly became visible. This first tantalising glimpse was like a high-altitude view of Earth, though rendered in sombre reds and browns.

The landing in gritty water-ice sand was slow, at less than twenty kilometres per hour.

After a journey of so many years the surface mission lasted mere minutes before the probe’s internal batteries were exhausted, and the chatter of telemetry fell silent. It would take two more hours for news of the adventure to crawl at light-speed to Earth – by which time a thin organic rain was already settling on the probe’s upper casing, as the last of its internal heat leaked away.

And then, all unknown to the probe’s human controllers back on Earth, a manipulator not unlike a lobster’s claw closed around Huygens’ pie-dish hull and dragged the crushed probe down beneath the water-ice sand.

1

‘There’s always been something wrong with Titan.’

These were the first words I ever heard Harry Poole speak – though I didn’t know the man at the time – words that cut through my hangover like a drill.

‘It’s been obvious since the first primitive probes got there seventeen hundred years ago.’ He had the voice of an old man, eighty, maybe even ninety, a scratchy texture. ‘A moon with a blanket of air, a moon that cradles a whole menagerie of life under its thick atmosphere. But that atmosphere’s not sustainable.’

‘Well, the mechanism is clear enough. Greenhouse effects from the methane component keep the air from cooling and freezing out.’ This was another man’s voice, gravelly, sombre, the voice of a man who took himself too seriously. A voice that sounded familiar. ‘Sunlight drives methane reactions that dump complex hydrocarbons in the stratosphere—’

‘But, son, where does the methane come from?’ Harry Poole pressed. ‘It’s destroyed by the very reactions that manufacture all those stratospheric hydrocarbons. Should all be gone in a few million years, ten million tops. So what replenishes it?’

At that moment I could not have cared less about the problem of methane on Saturn’s largest moon, even though, I suppose, it was a central facet of my own career. The fog in my head, thicker than Titan’s tholin haze, was lifting slowly, and I became aware of my body, aching in unfamiliar ways, stretched out on some kind of couch.

‘Maybe some geological process.’ This was a woman’s voice, brisk. ‘That or an ecology, a Gaia process that keeps the methane levels up. Those are the obvious options.’

‘Surely, Miriam,’ Harry Poole said. ‘One or the other. That’s been obvious since the methane on Titan was first spotted from Earth. But nobody knows. Oh, there have been a handful of probes over the centuries, but nobody’s taken Titan seriously enough to nail it. Always too many other easy targets for exploration and colonisation – Mars, the ice moons. Nobody’s even walked on Titan!’

Another man, a third, said, ‘But the practical problems – the heat loss in that cold air – it was always too expensive to bother, Harry. And too risky . . .’

‘No. Nobody had the vision to see the potential of the place. That’s the real problem. And now we’re hamstrung by these damn sentience laws.’

‘But you think we need to go explore.’ That gravel voice.

‘We need Titan, son,’ Harry Poole said. ‘It’s the only hope I see of making our wormhole link at Saturn pay for itself. Titan is, ought to be, the key to opening up Saturn and the whole outer System. We need to prove the sentience laws don’t apply there, and move in and start opening it up. That’s what this is all about.’

The woman spoke again. ‘And you think this wretched creature is the key.’

‘Given he’s a sentience curator, and a crooked one at that, yes . . .’

When words like ‘wretched’ or ‘crooked’ are bandied about in my company it’s generally Jovik Emry, my good self, that’s being discussed. I took this as a cue to open my eyes. Some kind of glassy dome stretched over my head, and beyond that a slice of sky-blue. I recognised the Earth as seen from space. And there was something else, a sculpture of electric-blue thread that drifted over a rumpled cloud layer.

‘Oh, look,’ said the woman. ‘It’s alive.’

I stretched, swivelled and sat up. I was stiff and sore, and had a peculiar ache at the back of my neck, just beneath my skull. I looked around at my captors. There were four of them, three men and a woman, all watching me with expressions of amused contempt. Well, it wasn’t the first time I’d woken with a steaming hangover in an unknown place surrounded by strangers. I would recover quickly. I was as young and healthy as I could afford to be: I was over forty, but AS-preserved at my peak of twenty-three.

We sat on couches at the centre of a cluttered circular deck, domed over by a scuffed carapace. I was in a GUTship, then, a standard interplanetary transport, if an elderly one; I had travelled in such vessels many times, to Saturn and back. Through the clear dome I could see more of those electric-blue frames drifting before the face of the Earth. They were tetrahedral, and their faces were briefly visible, like soap films that glistened gold before disappearing. These were the mouths of wormholes, flaws in spacetime, and the golden shivers were glimpses of other worlds.

I knew where I was. ‘This is Earthport.’ My throat was dry as Moondust, but I tried to speak confidently.

‘Well, you’re right about that.’ This was the man who had led the conversation earlier. That ninety-year-old voice, comically, came out of the face of a boy of maybe twenty-five, with blond hair, blue eyes, a smooth AntiSenescence marvel. The other two men looked around sixty, but with AS so prevalent it was hard to tell. The woman was tall, her hair cut short, and she wore a functional jumpsuit; she might have been forty-five. The old-young man spoke again. ‘My name is Harry Poole. Welcome to the Hermit Crab, which is my son’s ship—’

‘Welcome? You’ve drugged me and brought me here—’

One of the sixty-year-olds laughed, the gruff one. ‘Oh, you didn’t need drugging; you did that to yourself.’

‘You evidently know me – and I think I know you.’ I studied him. He was heavy set, dark, not tall, with a face that wasn’t built for smiling. ‘You’re Michael Poole, aren’t you? Poole the wormhole engineer.’

Poole just looked back at me. Then he said to the blond man, ‘Harry, I have a feeling we’re making a huge mistake trying to work with this guy.’

Harry grinned. ‘Give it time, son. You’ve always been an idealist. You’re not used to working with people like this. I am. We’ll get what we want out of him.’

I turned to him. ‘Harry Poole. You’re Michael’s father, aren’t you?’ I laughed at them. ‘A father who AS-restores himself to an age younger than your son. How crass. And, Harry, you really ought to get something done about that voice.’

The third man spoke. ‘I agree with Michael, Harry. We can’t work with this clown.’ He was on the point of being overweight, and had a crumpled, careworn face. I labelled him as a corporate man who had grown old labouring to make somebody else rich – probably Michael Poole and his father.

I smiled easily, unfazed. ‘And you are?’

‘Bill Dzik. And I’ll be working with you if we go through with this planned jaunt to Titan. Can’t say it’s an idea I like.’

This was the first I had heard of a trip to Titan. Well, whatever they wanted of me, I’d had quite enough of the dismal hellhole of the Saturn system, and had no intention of going back now. I had been in worse predicaments before; it was just a question of playing for time and looking for openings. I rubbed my temples. ‘Bill – can I call you Bill? I don’t suppose you could fetch me a coffee?’

‘Don’t push your luck,’ he growled.

‘Tell me why you kidnapped me.’

‘That’s simple,’ Harry said. ‘We want you to take us down to Titan.’

Harry snapped his fingers, and a Virtual image coalesced before us, a bruised orange spinning in the dark: Titan. It hung before Saturn itself, which was a pale-yellow crescent with those tremendous rings spanning space, and more moons suspended like lanterns. And there, glimmering in orbit just above the plane of the rings, was a baby-blue tetrahedral frame, the mouth of Michael Poole’s latest wormhole, a hyper-dimensional road offering access to Saturn and all its wonders – a road, it seemed, rarely travelled.

‘That would be illegal,’ I pointed out.

‘I know. And that’s why we need you.’ And Harry grinned, a cold expression on that absurdly young face.

2

‘If it’s an expert on Titan you want,’ I said, ‘keep looking.’

‘You’re a curator,’ Miriam said, contempt thick in her voice. ‘You work for the intra-System oversight panel on sentience law compliance. Titan is in your charge!’

‘Not by choice,’ I murmured. ‘Look – as you evidently targeted me, you must know something of my background. I haven’t had an easy career . . .’ My life at school, supported by my family’s money, had been a saga of drunken jaunts, sexual escapades, petty thieving and vandalism. As a young man I never lasted long at any of the jobs my family found for me, largely because I was usually on the run from some wronged party or other.

Harry said, ‘Some career. In the end you got yourself sentenced to an editing, didn’t you?’

If the authorities had had their way I would have had the contents of my much-abused brain downloaded into an external store, my memories edited, my unhealthy impulses ‘reprogrammed’, and the lot loaded back again – my whole self rebooted. ‘It represented death to me,’ I said. ‘I wouldn’t have been the same man as I was before. My father took pity on me—’

‘And bought you out of your sentence,’ Bill Dzik said. ‘And got you a job in sentience compliance. A sinecure.’

I looked at Titan’s dismal colours. ‘It is a miserable posting. But it pays a bit, and nobody cares much what you get up to, within reason. I’ve only been out a few times to Saturn itself, and the orbit of Titan; the work’s mostly admin, run from Earth. I’ve held down the job. Well, I really don’t have much choice.’

Michael Poole studied me as if I were a vermin infesting one of his marvellous interplanetary installations. ‘This is the problem I’ve got with agencies like the sentience-oversight curacy. I might even agree with its goals. But it doesn’t do what it’s supposed to achieve, all it does is get in the way of enterprise, and it’s populated by time-wasters like you.’

I found myself taking a profound dislike to the man. Whatever my faults I’m no hypocrite, and I’ve never been able to stomach being preached at. ‘I did nobody any harm,’ I snapped back at him. ‘Not much, anyhow. Not like you with your grand schemes, Poole, reordering the whole System for your own profit.’

Michael would have responded, but Harry held up his hand. ‘Let’s not get into that again. And after all he’s right. Profit, or the lack of it, is the issue here. As for you, Jovik, even in this billion-kilometres-remote “sinecure” you’re still up to your old tricks, aren’t you?’

I said nothing, cautious until I worked out how much he knew.

Harry waved his hand at his Virtual projection. ‘Look – Titan is infested with life. That’s the basic conclusion of the gaggle of probes that, over the centuries, have orbited Titan or penetrated its thick air and crawled over its surface or dug into its icy sand. But life isn’t the point. The whole Solar System is full of life. Life is commonplace. The question is sentience. And sentience holds up progress.’

‘It’s happened to us before,’ Michael Poole said to me. ‘The development consortium I lead, that is. We were establishing a wormhole Interface at a Kuiper object called Baked Alaska, thirteen years back, out on the rim of the System. Our plan was to use the ice as reaction mass to fuel GUTdrive starships. Well, we discovered life there, life of a sort, and it wasn’t long before we identified sentience. The xenobiologists called it a Forest of Ancestors. The project ground to a halt; we had to evacuate the place—’

‘Given the circumstances in which you’ve brought me here,’ I said, ‘I’m not even going to feign interest in your war stories.’

‘All right,’ Harry said. ‘But you can see the issue with Titan. Look, we want to open it up for development. It’s a factory of hydrocarbons and organics. We can make breathable air: nitrogen from the atmosphere, and oxygen extracted from water ice. We can use all that methane and organic chemistry to make plastics or fuel or even food. Titan should be the launch pad for the opening-up of the outer System, indeed the stars. But we’re not going to be allowed to develop Titan if there’s sentience there. And our problem is that, on this world with plenty of biochemistry and primitive life, nobody has established that there isn’t intelligence too.’

I started to see it. ‘So you want to mount a quick and dirty expedition – incidentally violating the planetary-protection aspects of the sentience laws – prove there’s no significant mind down there, and get the clearance to move in the digging machines. Right?’ And I saw how Bill Dzik, Miriam and Michael Poole exchanged unhappy glances. There was dissension in the team over the morality of all this, a crack I might be able to exploit. ‘Why do you need this so badly?’ I asked.

So they told me. It was a saga of interplanetary ambition. But at the root of it, as is always the case, was money – or the lack of it.

3

Harry Poole said, ‘You know our business, Jovik. Our wormhole engineering is laying down rapid-transit routes through the System, which will open up a whole family of worlds to colonisation and development. But we have grander ambitions than that.’

I asked, ‘What ambitions? Starships? I read about that.’

‘That and more,’ Michael Poole said. ‘For the last few decades we’ve been working on an experimental ship being built in the orbit of Jupiter . . .’

And he told me about his precious Cauchy project. By dragging a wormhole portal around a circuit light years across, the GUTship Cauchy would establish a wormhole bridge – not across space – but across fifteen centuries, to the future. So, having already connected the worlds of humanity with his wormhole subway, Michael Poole now hoped to short-circuit past and future themselves. That, at least, seemed to be the idea. I looked at Poole with new respect, and some fear. The man was a genius, or mad.

‘But,’ I said, ‘to fund such dreams you need money.’

Harry said, ‘Jovik, you need to understand that a mega-engineering business like ours is a ferocious devourer of cash. It’s like the days of the pioneering railway builders back in the nineteenth century. We fund each new project with the profit of our previous ventures and with fresh investment – but that investment depends on the success of earlier schemes.’

‘Ah. And now you’re stumbling. Yes? And this is all to do with Saturn.’

Harry sighed. ‘The Saturn transit was a logical development. The trouble is, nobody needs to go there. Saturn pales beside Jupiter! Saturn has ice moons; well, there are plenty in orbit around Jupiter. Saturn’s atmosphere could be mined, but so can Jupiter’s, at half the distance from Earth.’

Miriam said, ‘Saturn also lacks Jupiter’s ferociously energetic external environment, which we’re tapping ourselves in the manufacture of the Cauchy.’

‘Fascinating,’ I lied. ‘You’re an engineer too, then?’

‘A physicist,’ she replied, awkward. She sat next to Michael Poole but apart from him. I wondered if there was anything deeper between them.

‘The point,’ said Harry, ‘is that there’s nothing at Saturn you’d want to go there for – no reason for our expensive wormhole link to be used. Nothing except—’

‘Titan,’ I said.

‘If we can’t go in legally, we need somebody to break us through the security protocols and get us down there.’

‘So you turned to me.’

‘The last resort,’ said Bill Dzik with disgust in his voice.

‘We tried your colleagues,’ Miriam said. ‘They all said no.’

‘Well, that’s typical of that bunch of prigs.’

Harry, always a diplomat, smiled at me. ‘So we’re having to bend a few pettifogging rules, but you have to see the vision, man, you have to see the greater good.’

‘Have I? Actually the question is, what’s in it for me? You know I’ve come close to the editing suites before. Why should I take the risk of helping you now?’

‘Because,’ Harry said, ‘if you don’t you’ll certainly face a reboot.’ So now we came to the dirty stuff, and Harry took over; he was clearly the key operator in this little cabal, with the engineer types uncomfortably out of their depth. ‘We know about your sideline.’

With a sinking feeling I asked, ‘What sideline?’

And he used his Virtual display to show me. There went one of my doctored probes arrowing into Titan’s thick air, a silver needle that stood out against the murky organic backdrop, supposedly on a routine monitoring mission – but in fact with a quite different objective.

There are pockets of liquid water to be found just under Titan’s surface – frozen-over crater lakes, kept warm for a few thousand years by the residual heat of the impacts that created them. My probe now shot straight through the icy carapace of one of those crater lakes, and into the liquid water beneath. Harry fast-forwarded and we watched the probe’s ascent module push its way out of the lake and up into the air, on its way to my colleagues’ base on Enceladus.

‘You’re sampling the subsurface life from the lakes,’ Harry said sternly. ‘And selling the results.’

I shrugged; there was no point denying it. ‘I guess you know the background. The creatures down there are related to Earth life, but very distantly. Different numbers of amino acids, or something – I don’t know. The tiniest samples are gold dust to the biochemists, a whole new toolkit for designer drugs and genetic manipulation . . .’ I had one get-out. ‘You’ll have trouble proving this. By now there won’t be a trace of our probes left on the surface.’ Which was true; one of the many ill-understood aspects of Titan was that probes sent down to its surface quickly failed and disappeared, perhaps as a result of some kind of geological resurfacing.

Harry treated that with the contempt it deserved. ‘We have full records. Samples of the material you stole from Titan. Even a sworn statement by one of your partners.’

I flared at that. ‘Who?’ But, of course, it didn’t matter.

Harry said sweetly, ‘The point is the sheer illegality – and committed by you, a curator, whose job is precisely to guard against such things. If this gets to your bosses, it’s back to the editing suite for you, my friend, and this time even Papa won’t be able to bail you out.’

‘So that’s it. Blackmail.’ I did my best to inject some moralistic contempt into my voice. And it worked; Michael, Miriam, Bill wouldn’t meet my eyes.

But it didn’t wash with Harry. ‘Not the word I’d use. But that’s pretty much it, yes. So what’s it to be? Are you with us? Will you lead us to Titan?’

I wasn’t about to give in yet. I got to my feet. ‘At least let me think about it. You haven’t even offered me that coffee.’

Michael glanced at Harry, who pointed at a dispenser on a stand near my couch. ‘Use that one.’

There were other dispensers in the cabin – why that particular one? I filed away the question and walked over to the dispenser. At a command it produced a mug of what smelled like coffee. I sipped it gratefully and took a step across the floor towards the transparent dome.

‘Hold it,’ Michael snapped.

‘I just want to take in the view.’

Miriam said, ‘OK, but don’t touch anything. Follow that yellow path.’

I grinned at her. ‘Don’t touch anything? What am I, contagious?’ I wasn’t sure what was going on, but probing away at these little mysteries had to help. ‘Please. Walk with me. Show me what you intend to do here.’

Miriam hesitated for a heartbeat. Then, with an expression of deep distaste, she got to her feet. She was taller than I was, and lithe, strong-looking.

We walked together across the lifedome, a half-sphere a hundred metres wide. Couches, control panels and data entry and retrieval ports were clustered around the geometric centre of the dome; the rest of the transparent floor area was divided up by shoulder-high partitions into lab areas, a galley, a gym, a sleeping area and shower. The layout looked obsessively plain and functional to me. This was the vessel of a man who lived for work, and only that; if this was Michael Poole’s ship, it was a bleak portrait of him.

We reached the curving hull. Glancing down I could see the ship’s spine, a complex column a couple of kilometres long leading to the lode of asteroid ice used for reaction mass by the GUTdrive module within. And all around us wormhole Interfaces drifted like snowflakes, while intra-System traffic passed endlessly through the great gateways.

‘All this is a manifestation of your lover’s vision,’ I said to Miriam, who stood by me.

‘Michael’s not my lover,’ she shot back, irritated. The electric-blue light of the exotic-matter frames shone on her cheekbones.

‘I don’t even know your full name,’ I said.

‘Berg,’ she said reluctantly. ‘Miriam Berg.’

‘Believe it or not, I’m not a criminal. I’m no hero, and I don’t pretend to be. I just want to get through my life, and have a little fun on the way. I shouldn’t be here, and nor should you.’ Deliberately I reached for her shoulder. A bit of physical contact might break through that reserve.

But my fingers passed through her flesh, breaking up into a mist of pixels until they were clear of her flesh, and then reformed. I felt a distant ache in my head.

I stared at Miriam Berg. ‘What have you done to me?’

‘I’m sorry,’ she said gravely.

I sat on my couch once more – my couch, a Virtual projection like me, the only one in the dome I wouldn’t have fallen through, and sipped a coffee from my Virtual dispenser, the only one that I could touch.

It was, predictably, Harry Poole’s scheme. ‘Just in case the arm-twisting over the sample-stealing from Titan wasn’t enough.’

‘I’m a Virtual copy,’ I said.

‘Strictly speaking, an identity backup . . .’

I had heard of identity backups, but could never afford one myself, nor indeed fancied it much. Before undertaking some hazardous jaunt you could download a copy of yourself into a secure memory store. If you were severely injured or killed, the backup could be loaded into a restored body, or a vat-grown cloned copy, or even allowed to live on in some Virtual environment. You would lose the memories you had acquired after the backup was made, but that was better than non-existence . . . That was the theory. In my opinion it was an indulgence of the rich; you saw backup Virtuals appearing like ghosts at the funerals of their originals, distastefully lapping up the sentiment.

And besides, the backup could never be you, the you who had died; only a copy could survive. That was the idea that started to terrify me now. I am no fool, and imaginative to a fault.

Harry watched me taking this in.

I could barely ask the question: ‘What about me? The original. Did I die?’

‘No,’ Harry said. ‘The real you is in the hold, suspended. We took the backup after you were already unconscious.’

So that explained the ache at the back of my neck: that was where they had jacked into my nervous system. I got up and paced around. ‘And if I refuse to help? You’re a pack of crooks and hypocrites, but I can’t believe you’re deliberate killers.’

Michael would have answered, but Harry held up his hand, unperturbed. ‘Look, it needn’t be that way. If you agree to work with us, you, the Virtual you, will be loaded back into the prime version. You’ll have full memories of the whole episode.’

‘But I won’t be me.’ I felt rage building. ‘I mean, the copy sitting here. I won’t exist any more – any more than I existed a couple of hours ago, when you activated me.’ That was another strange and terrifying thought. ‘I will have to die! And that’s even if I cooperate. Great deal you’re offering. Well, into Lethe with you. If you’re going to kill me anyway I’ll find a way to hurt you. I’ll get into your systems like a virus. You can’t control me.’

‘But I can.’ Harry clicked his fingers.

And in an instant everything changed. The four of them had gathered by Harry’s couch, the furthest from me. I had been standing; now I was sitting. And beyond the curved wall of the transparent dome, I saw that we had drifted into Earth’s night.

‘How long?’ I whispered.

‘Twenty minutes,’ Harry said carelessly. ‘You have an off switch. Of course I can control you. So which is it to be? Permanent extinction for all your copies, or survival as a trace memory in your host?’ His grin hardened, and his young-old face was cold.

So the Hermit Crab wheeled in space, seeking out the wormhole Interface that led to Saturn. And I, or rather he who had briefly believed he was me, submitted to a downloading back into his primary, myself. How ironic that this was a violation of the very sentience protection laws it was my duty to uphold.

He, the identity copy, died to save my life. I salute him.

4

Released from my cell of suspended animation, embittered, angry, I chose to be alone.

I walked to the very rim of the lifedome, where the transparent carapace met the solid floor. Looking down I could see the flaring of superheated, ionised steam pouring from the GUTdrive nozzles. The engine, as you would expect, was one of Poole’s own designs. ‘GUT’ stands for ‘Grand Unified Theory’, which describes the fundamental forces of nature as aspects of a single superforce. This is creation physics. Thus men like Michael Poole use the energies which once drove the expansion of the universe itself for the triviality of pushing forward their steam rockets.

Soon the Hermit Crab drove us into the mouth of the wormhole that led to the Saturn system.

We flew lifedome first at the wormhole Interface, so that it was as if the electric-blue tetrahedral frame came down on us from the zenith. Those electric-blue struts were beams of exotic matter, a manifestation of a kind of antigravity field that kept this throat in space and time from collapsing. Every so often you would see the glimmer of a triangular face, a sheen of golden light filtering through from Saturn’s dim halls. It was quite beautiful, a sculpture of light.

The frame bore down, widening in my view, and fell around us, obscuring the view of Earth and Earthport.

Now I was looking up into a kind of tunnel, picked out by flaring sheets of light. This was a flaw in spacetime itself; the flashing I saw was the resolution of that tremendous strain into exotic particles and radiations. As the ship thrust deeper into the wormhole, fragments of blue-white light swam from a vanishing point directly above my head and swarmed down the spacetime walls. There was a genuine sensation of speed, of limitless, uncontrollable velocity. The lifedome creaked like a tin shack, and I thought I could hear that elderly GUTdrive screaming with the strain. I gripped a rail and tried not to cower.

The passage was at least mercifully short. Amid a shower of exotic particles we ascended out of another electric-blue Interface – and I found myself back in the Saturn system, for the first time in years.

I could see immediately that we were close to the orbit of Titan about its primary, for the planet itself, suspended in the scuffed sky of the lifedome, was about the size I remembered it: a flattened globe a good bit larger than the Moon seen from Earth. Other moons hung around the sky, points of light. The sun was off to the right, with its close cluster of inner planets, so Saturn was half-full. Saturn’s only attractive feature, the rings, were invisible, for Titan’s orbit is in the same equatorial plane as the ring system and the rings are edge-on. But the shadow of the rings cast by the sun lay across the planet’s face, sharp and unexpected.

There was nothing romantic in the view, nothing beautiful about it, not to me. The light was flat and pale. Saturn is about ten times as far from the sun as Earth is, and the sun is reduced to an eerie pinpoint, its radiance only a hundredth that at Earth: Saturn is misty and murky, an autumnal place. And you never forgot you were far from home when a human hand, held out at arm’s length towards the sun, could have covered all of the orbit of Earth.

The Crab swung about and Titan itself was revealed, a globe choked by murky brown cloud from pole to pole, even more dismal and uninviting than its primary. Evidently Michael Poole had placed his wormhole Interface close to the moon in anticipation that Titan would someday serve his purposes.

Titan was looming larger, swelling visibly. Our destination was obvious.

Harry Poole took charge. He had us put on heavy, thick-layered exosuits of a kind I’d never seen before. We sat on our couches like fat pupae; my suit was so thick my legs wouldn’t bend properly.

‘Here’s the deal,’ Harry said, evidently for my benefit. ‘The Crab came out of the wormhole barrelling straight for Titan. That way we hope to get you down there before any of the automated surveillance systems up here can spot us, or do anything about it. In a while the Crab will brake into orbit around Titan. But before then you four in the gondola will be thrown straight into an atmospheric entry.’ He snapped his fingers, and a hatch opened up in the floor beneath us to reveal the interior of another craft, mated to the base of the lifedome. This was evidently the ‘gondola’, some kind of landing shuttle. It was like a cave, brightly lit and with its walls crusted with data displays.

I said, ‘“Thrown straight in,” Harry? And what about you?’

He smiled with that young-old face. ‘I will be waiting for you in orbit. Somebody has to stay behind to bail you out, in case.’

‘This “gondola” looks small for the four of us.’

Harry said, ‘Well, weight has been a consideration. You’ll mass no more than a tonne, all up.’ He handed me a data slate. ‘Now this is where you come in, Jovik. I want you to send a covering message to the sentience-law compliance control base on Enceladus.’

I stared at the slate. ‘Saying what, exactly?’

Harry said, ‘The entry profile is designed to mimic an unmanned mission. You’re going in hard, high deceleration. I want you to make yourselves look that way in the telemetry – as if this is just another unmanned probe going in for a bit of science, or a curacy inspection, or whatever it is you bureaucrat types do. Attach the appropriate permissions. I’m quite sure you’re capable of that.’

I was sure of it too. I opened the slate with a wave of my hand, quickly mocked up a suitable profile, let Harry’s systems check I hadn’t smuggled in any cries for help, and squirted it over to Enceladus. Then I handed the slate back. ‘There. Done. You’re masked from the curacy. I’ve done what you want.’ I waved at the looming face of Titan. ‘So you can spare me from that, can’t you?’

‘We discussed that,’ said Michael Poole, with just a hint of regret in his voice. ‘We decided to take you along as a fall-back, Jovik, in case of problems, any kind of challenge from Enceladus. Even if they’ve discovered the craft is manned, having you aboard will give us some cover.’

I snorted. ‘They’ll see through that.’

Miriam shrugged. ‘It’s worth it if it buys us a bit more time.’

Bill Dzik stared at me, hard. ‘Just don’t get any ideas, desk jockey. I’ll have my eye on you all the way down and all the way back.’

‘And listen,’ Harry said, leaning forward. ‘If this works out, Jovik, you’ll be rewarded. We’ll see to that. We’ll be able to afford it, after all.’ He grinned that youthful grin. ‘And just think. You will be one of the first humans to walk on Titan! So you see, you’ve every incentive to cooperate, haven’t you?’ He checked a clock on his data slate. ‘We’re close to the release checkpoint. Down you go, team.’

They all sneered at that word, ‘team’, and at the cheerful tone of the man who was staying behind. But we filed dutifully enough through the hatch and down into that cave of instrumentation, Miriam first, then me, and Bill Dzik at my back. Michael Poole was last in; I saw him embrace his father, stiffly, evidently not a gesture they were used to.

In the gondola, our four couches sat in a row, so close that my knees touched Miriam’s and Dzik’s when we were all crammed in there in our suits. The hull was all around us, close enough for me to have reached out and touched it in every direction, a tight-fitting shell. Poole pulled the hatch closed, and I heard a hum and whir as the independent systems of this craft came online. There was a rattle of latches, and then a kind of sideways shove that made my stomach churn. We were already cut loose from the Crab, and were falling free, and rotating.

Poole touched a panel above his head, and the hull turned transparent. Now it was as if we four in our couches were suspended in space, surrounded by glowing instrument panels, and blocky masses that must be the power supply, life support, supplies. Above me the Crab slid across the face of Saturn, GUTdrive flaring, and below me the orange face of Titan loomed large.

I whimpered. I have never pretended to be brave.

Miriam Berg handed me a transparent bubble-helmet. ‘Lethe, put this on before you puke.’

I pulled the helmet over my head; it snuggled into the suit neck and made its own lock.

Bill Dzik was evidently enjoying my discomfort. ‘You feel safer in the suit, right? Well, the entry is the most dangerous time. But you’d better hope we get through the atmosphere’s outer layers before the hull breaches, Emry. These outfits aren’t designed to work as pressure suits.’

‘Then what use are they?’

‘Heat control,’ Michael Poole said, a bit more sympathetic. ‘Titan’s air pressure is fifty per cent higher than Earth’s, at the surface. But that thick cold air just sucks away your heat. Listen up, Emry. The gondola’s small, but it has a pretty robust power supply – a GUTengine, in fact. You’re going to need that power to keep warm. For short periods your suit will protect you; there are power cells built into the fabric. But you won’t last more than a few hours away from the gondola. Got that?’

I was hardly reassured. ‘What about the entry itself? Your father said we’ll follow an unmanned profile. That sounds . . . vigorous.’

Bill Dzik barked a laugh. Nobody else replied.

Poole and the others began to work through pre-entry system checks. Harry murmured in my ear, telling me that fresh identity backups had just been taken of each of us and stored in the gondola’s systems. I was not reassured.

I lay helpless, trussed up and strapped in, as we plummeted into the sunlit face of Titan.

5

Fifteen minutes after cutting loose from the Crab, the gondola encountered the first wisps of Titan’s upper atmosphere, thin and cold, faintly blue all around us. Still a thousand kilometres above the ground, I could feel the first faltering in the gondola’s headlong speed. Titan’s air is massive and deep, and I was falling backside first straight into it.

The first three minutes of the entry were the worst, as we plunged into the air with an interplanetary velocity, and our speed was reduced violently. Three hundred kilometres above the surface the deceleration peaked at sixteen gravities. Cushioned by Poole’s inertial field I felt no more than the faintest shaking, but the gondola shuddered and banged. Meanwhile a shock wave preceded us, a cap of gas that glowed brilliantly: Titan air battered to plasma by the dissipating kinetic energy of the gondola.

This fiery entry phase was mercifully brief. But when it was over, still we fell helplessly. After another three minutes we were within a hundred and fifty kilometres of the surface, and immersed in an orange haze, the organic-chemistry products of the destruction of Titan’s methane by sunlight. Poole tapped a panel, and a mortar fired above us, hauling out a pilot parachute a couple of metres across. This stabilised us in the thickening air, our backs to the surface, our faces to the sky. Then the main parachute unfolded, spreading reassuringly.

For fifteen minutes we drifted, sinking slowly into a deep ocean of cold, sluggish air. Poole and his colleagues worked at their slates, gathering data from sensors that measured the physical and chemical properties of the atmosphere. I lay silent, curious too, but frightened for my life.

As we fell deeper into the hydrocarbon smog the temperature fell steadily. Sixty kilometres above the surface we fell through a layer of cloud into clearer air beneath, and then, at forty kilometres, through a thin layer of methane clouds. The temperature was close to its minimum here, at only seventy degrees or so above absolute zero. Soon it would rise again. As Poole and his team had discussed, greenhouse effects from the mysterious methane that shouldn’t have been there warm Titan’s air all the way to the ground.

Fifteen minutes after its unpacking, the main parachute was cut away, and a smaller stabiliser canopy opened. Much smaller. We began to fall faster, into the deep ocean of air. ‘Lethe,’ I said. ‘Why did we dump the big chute? We’re still forty kilometres high!’

Bill Dzik laughed at me. ‘Don’t you know anything about the world you’re supposed to be guarding, curator? The air’s thick here, and the gravity’s low, only a seventh of Earth normal. Under that big parachute we’d be hanging in the air all day . . .’

The gondola lurched sideways, shoved by the winds. At least that shut Dzik up. But the winds eased as we fell further, until the air was as still and turgid as deep water. We were immersed now in orange petrochemical haze, though the sun was plainly visible as a brilliant point source of light, surrounded by a yellow-brown halo. The crew gathered data on the spectra of the solar halo, seeking information on aerosols, solid or liquid particles suspended in the air.

And, gradually, beneath our backs, Titan’s ground became visible. I twisted around to see. Cumulus clouds of ethane vapour lay draped over continents of water ice. Of the ground itself I saw a mottling of dark and white patches, areas huge in extent, pocked by what looked like impact craters, and incised by threading valleys cut by flowing liquid, ethane or methane. The crew continued to collect their science data. An acoustic sounder sent out complex pulses of sound. Miriam Berg showed me how some echoes came back double, with reflections from the surfaces and bottoms of crater lakes, like the one my sampling probe had entered.

The gondola rocked beneath its parachute. Poole had suspended the inertial shielding, and, swinging in Titan’s one-seventh gravity, I was comfortable in my thick, softly layered exosuit. The crew’s murmuring as they worked was professional and quiet. I think I actually slept, briefly.

Then there was a jolt. I woke with a snap. The parachute had been cut loose, and was drifting away with its strings dangling like some jellyfish. Our fall was slow in that thick air and gentle gravity, but fall we did!

And then, as Bill Dzik laughed at me again, a new canopy unfurled into the form of a globe, spreading out above us. It was a balloon, perhaps forty, fifty metres across; we were suspended from it by a series of fine ropes. As I watched a kind of hose snaked up from beneath the gondola’s hull and pushed up into the mouth of the balloon, and it began to inflate.

‘So that’s the plan,’ I said. ‘To float around Titan in a balloon! Not very energetic for a man who builds interplanetary wormholes, Poole.’

‘But that’s the point,’ Poole said testily, as if I had challenged his manhood. ‘We’re here under the noses of your curators’ sensors, Emry. The less of a splash we make the better.’

Miriam Berg said, ‘I designed this part of the mission profile. We’re going to float around at this altitude, about eight kilometres up – well above any problems with the topography, but under most of the cloud decks. We ought to be able to gather the science data we need from here. A couple of weeks should be sufficient.’

‘A couple of weeks in this coffin!’

Poole thumped the walls of the gondola. ‘This thing expands. You’ll be able to get out of your suit. It’s not going to be luxury, Emry, but you’ll be comfortable enough.’

Miriam said, ‘When the time comes we’ll climb back up to space from this altitude. The Crab doesn’t carry an orbit-to-surface flitter, but Harry will send down a booster unit to rendezvous with us and lift the gondola to orbit.’

I stared at her. ‘You’re saying we don’t carry the means of getting off this moon?’

Miriam said evenly, ‘Mass issues. We need to stay under the curacy sensors’ awareness threshold. Plus we’re supposed to look like an unmanned probe, remember. Look, it’s not a problem.’

‘Umm.’ Call me a coward, many have. But I didn’t like the idea that my only way off this wretched moon was thousands of kilometres away, and my access to it depended on a complicated series of rendezvous and coupling manoeuvres. ‘So what’s keeping us aloft? Hydrogen, helium?’

Poole pointed at that inlet pipe. ‘Neither. This is a hot-air balloon, Emry, a Montgolfier.’ And he gave me a lecture on how hot-air technology is optimal if you must go ballooning on Titan. You have the buoyancy of the thick air, and the gravity is weak, and at such low temperatures you get a large expansion of your heated gas in response to a comparatively small amount of energy. Add all these factors into the kind of trade-off equation men like Poole enjoy so much, and out pops hot-air ballooning as the low-energy transport of choice on Titan.

Miriam said, ‘We’re a balloon, not a dirigible; we can’t steer. But for a mission like this it’s enough for us to go pretty much where the wind takes us; all we’re doing is sampling a global ecosphere. And we can choose our course to some extent. The prevailing winds on Titan are easterly, but below about two kilometres there’s a strong westerly component. That’s actually a tide, raised by Saturn in the thick air down there. So we can select which way we get blown, just by ascending and descending.’

‘More stealth, I suppose. No need for engines.’

‘That’s the idea. We’ve arrived in the local morning. Titan’s day is fifteen Earth days long, and we can achieve a lot before nightfall – in fact I’m intending that we should chase the daylight. Right now we’re heading for the south pole, where it’s summer.’ And at the summer pole, as even I knew, methane and ethane pooled in open lakes – the only stable bodies of surface liquid in the System, aside from those on Earth and Triton.

Poole grinned. ‘Summer on Titan. And we’re riding the oldest flying machine of all!’ Evidently he was starting to enjoy himself.

Miriam smiled back, and their gloved hands locked together.

The envelope snapped and billowed above us as the warm air filled it up.

6

So we drifted over Titan’s frozen landscape, heading for the south pole. For now Michael Poole kept us stuck in that unexpanded hull, and indeed inside our suits, though we removed our helmets, while the crew put the gondola through a fresh series of post-entry checks. I had nothing to do but stare out through the transparent walls at the very Earthlike clouds that littered the murky sky, or over my shoulder at the landscape that unfolded beneath me.

Now that we were low enough to make out detail, I saw that those darker areas were extensive stretches of dunes, lined up in parallel rows by the prevailing wind. The ground looked raked, like a tremendous zen garden. And the lighter areas were outcroppings of a paler rock, plateaus scarred by ravines and valleys. At this latitude there were no open bodies of liquid, but you could clearly see its presence in the recent past, in braided valleys and the shores of dried-out lakes. This landscape of dunes and ravines was punctuated by circular scars that were probably the relics of meteorite impacts, and by odder, dome-like features with irregular calderas – volcanoes that spewed a ‘lava’ of liquid water. All these features had names, I learned, assigned to them by Earth astronomers centuries dead, who had pored over the first robot-returned images of this landscape. But as nobody had ever come here those names, borrowed from vanished paradises and dead gods, had never come alive.

I listened absently as Poole and the others talked through their science programme. The atmosphere was mostly nitrogen, just as on Earth, but it contained five per cent methane, and that methane was the key to Titan’s wonders, and mysteries. Even aside from its puzzling central role in the greenhouse effects which stabilised the atmosphere, methane was also central to the complicated organic chemistry that went on there. In the lower atmosphere methane reacted with nitrogen to create complex compounds called tholins, a kind of plastic, which fell to the ground in a sludgy rain. When those tholins landed in liquid water, such as in impact-warmed crater lakes, amino acids were produced – the building blocks of our kind of life . . .

As I listened to them debate these issues it struck me that none of them had begun his or her career as a biologist or climatologist: Poole and Berg had both been physicists, Dzik an engineer and more lately a project manager. However, both Berg and Dzik had had specialist training to a decent academic standard to prepare for this mission. Ambitious types like these expected to live a long time; periodically they would re-educate themselves and adopt entirely different professions. I have never had any such ambition. I had a good education that had bequeathed me a good vocabulary and got me selected for my sinecure as a curator, along with my father’s influence – but that was about as much use as it had been to me. Why waste time going through it all again? Besides, somehow, despite AS technology, I do not imagine myself reaching any great age.

Their talk had an edge, however, even in those first hours. They were all ethically troubled by what they were doing, and those doubts surfaced now that they were away from Harry Poole’s goading.

‘At some point,’ Miriam Berg said, ‘we’ll have to face the question of how we’ll react if we do find sentience here.’

Bill Dzik shook his head. ‘Sometimes I can’t believe we’re even here, that we’re having this conversation at all. I remember exactly what you said on Baked Alaska, Michael. If we couldn’t protect the ecology, “we’ll implode the damn wormhole. We’ll get funds for the Cauchy some other way.” That’s what you said.’

Poole said harshly, clearly needled, ‘That was thirteen years ago, damn it, Bill. Situations change. People change. And the choices we have to make change too . . .’

As they argued, I was the only one looking ahead, the way we were drifting under our balloon. Through the murk I thought I could see the first sign of the ethane lakes of the polar regions, sheets of coal-black liquid surrounded by fractal landscapes, like a false-colour mock-up of Earth’s own Arctic. And I thought I could see movement, something rising up off those lakes. Mist, perhaps? But there was too much solidity about those rising forms for that.

And then those forms emerged from the mist, solid and looming.

I pulled my helmet on my head and gripped my couch. I said, ‘Unless one of you does something fast, we may soon have no choices left at all.’

They looked at me, the three of them in a row, distracted, absorbed by their science. Then they looked ahead, to see what I saw.

They were like birds, black-winged, with white lenticular bodies. Those wings actually flapped in the thick air as they flew up from the polar seas, a convincing simulacrum of the way birds fly in the air of Earth. Oddly they seemed to have no heads.

And they were coming straight towards us.

Michael Poole snapped, ‘Lethe. Vent the buoyancy!’ He stabbed at a panel, and the others went to work, pulling on their helmets as they did so.

I felt the balloon settle as the hot air was released from the envelope above us. We were sinking but we seemed to move in dreamy slow motion, while those birds loomed larger in our view with every heartbeat.

Then they were on us. They swept over the gondola, filling the sky above, black wings flapping in an oily way that, now they were so close, seemed entirely unnatural, not like terrestrial birds at all. They were huge, each with a wingspan of ten, fifteen metres. I thought I could hear them, a rustling, snapping sound carried to me through Titan’s thick air.

And they tore into the envelope. The fabric was designed to withstand Titan’s methane rain, not an attack like this; it exploded into shreds, and the severed threads waved in the air. Some of the birds suffered; they tangled with our threads or collided with each other and fell away, rustling. One crashed into the gondola itself, crumpled like tissue paper, and fell, wadded up, far below us.

And we fell too, following our victim-assassin to the ground. Our descent from the best part of eight kilometres high took long minutes; we soon reached terminal velocity in Titan’s thick air and weak gravity. We had time to strap ourselves in, and Poole and his team worked frantically to secure the gondola’s systems. In the last moment Poole flooded the gondola with a foam that filled the internal space and held us rigid in our seats, like dolls in packaging, sightless and unable to move.

Even so I felt the slam as we hit the ground.

7

The foam drained away, leaving the four of us sitting in a row. We had landed on Titan the way we had entered its atmosphere, backside first, and now we lay on our backs with the gondola tilted over, so that I was falling against Miriam Berg, and the mass of Bill Dzik was weighing on me. The gondola’s hull had reverted to opacity so that we lay in a close-packed pearly shell, but there was internal light and the various data slates were working, though they were filled with alarming banks of red.

The three of them went quickly into a routine of checks. I ignored them. I was alive. I was breathing, the air wasn’t foul, and I was in no worse discomfort than having Dzik’s unpleasant bulk pressed against my side. Nothing broken, then. But I felt a pang of fear as sharp as that experienced by the Virtual copy of me when he had learned he was doomed. I wondered if his ghost stirred in me now, still terrified.

And my bowels loosened into the suit’s systems. Never a pleasant experience, no matter how good the suit technology. But I wasn’t sorry to be reminded that I was nothing but a fragile animal, lost in the cosmos. That may be the root of my cowardice, but give me humility and realism over the hubristic arrogance of a Michael Poole any day.

Their technical chatter died away.

‘The lights are on,’ I said. ‘So I deduce we’ve got power.’

Michael Poole said, gruffly reassuring, ‘It would take more than a jolt like that to knock out one of my GUTengines.’

Dzik said spitefully, ‘If we’d lost power you’d be an icicle already, Emry.’

‘Shut up, Bill,’ Miriam murmured. ‘Yes, Emry, we’re not in bad shape. The pressure hull’s intact, we have power, heating, air, water, food. We’re not going to die any time soon.’

But I thought of the flapping birds of Titan and wondered how she could be so sure.

Poole started unbuckling. ‘We need to make an external inspection. Figure out our options.’

Miriam followed suit, and laughed. She said to me, ‘Romantic, isn’t he? The first human footfalls on Titan, and he calls it an external inspection.’ Suddenly she was friendly. The crash had evidently made her feel we had bonded in some way.

But Bill Dzik dug an elbow in my ribs hard enough to hurt through the layers of my suit. ‘Move, Emry.’

‘Leave me alone.’

‘We’re packed in here like spoons. It’s one out, all out.’

Well, he was right; I had no choice.

Poole made us go through checks of our exosuits, their power cells, the integrity of their seals. Then he drained the air and popped open the hatch in the roof before our faces. I saw a sky sombre and brown, dark by comparison with the brightness of our internal lights. Flecks of black snow drifted down. The hatch was a door from this womb of metal and ceramics out into the unknown.

We climbed up through the hatch in reverse order from how we had come in: Poole, Dzik, myself, then Miriam. The gravity, a seventh of Earth’s, was close enough to the Moon’s to make that part of the experience familiar at least, and I moved my weight easily enough. Once outside the hull, lamps on my suit lit up in response to the dark.

I dropped down a metre, and thus drifted to my first footfall on Titan.

The sandy surface crunched under my feet. I knew the sand was water ice, grains hard as glass in the intense chill. The sand was ridged into ripples, as if by a receding tide, and pebbles lay scattered, worn and eroded. A wind buffeted me, slow and massive, and I heard a low bass moan. A black rain smeared my faceplate.

The four of us stood together, chubby in our suits, the only humans on a world larger than Mercury. Beyond the puddle of light cast by our suit lamps an entirely unknown landscape stretched off into the infinite dark.

Miriam Berg was watching me. ‘What are you thinking, Jovik?’ As far as I know these were the first words spoken by any human standing on Titan.

‘Why ask me?’

‘You’re the only one of us who’s looking at Titan and not at the gondola.’

I grunted. ‘I’m thinking how like Earth this is. Like a beach somewhere, or a high desert, the sand, the pebbles. Like Mars, too, outside Kahra.’

‘Convergent processes,’ Dzik said dismissively. ‘But you are an entirely alien presence. Here, your blood is as hot as molten lava. Look, you’re leaking heat.’

And, looking down, I saw wisps of vapour rising up from my booted feet.

We checked over the gondola. Its inner pressure cage had been sturdy enough to protect us, but the external hull was crumpled and damaged, various attachments had been ripped off, and it had dug itself into the ice.

Poole called us together for a council of war. ‘Here’s the deal. There’s no sign of the envelope; it was shredded, we lost it. The gondola’s essential systems are sound, most importantly the power. The hull’s taken a beating, though.’ He banged the metal wall with a gloved fist; in the dense air I heard a muffled thump. ‘We’ve lost the extensibility. I’m afraid we’re stuck in these suits.’

‘Until what?’ I said. ‘Until we get the spare balloon envelope inflated, right?’

‘We don’t carry a spare,’ Bill Dzik said, and he had the grace to sound embarrassed. ‘It was a cost-benefit analysis—’

‘Well, you got that wrong,’ I snapped back. ‘How are we supposed to get off this damn moon now? You said we had to make some crackpot rendezvous with a booster pack.’

Poole tapped his chest, and a Virtual image of Harry’s head popped into existence in mid-air. ‘Good question. I’m working on options. I’m fabricating another envelope, and I’ll get it down to you. Once we have that gondola aloft again, I’ll have no trouble picking you up. In the meantime,’ he said more sternly, ‘you have work to do down there. Time is short.’

‘When we get back to the Crab,’ Bill Dzik said to Poole, ‘you hold him down and I’ll kill him.’

‘He’s my father,’ said Michael Poole. ‘I’ll kill him.’

Harry dissolved into a spray of pixels.

Poole said, ‘Look, here’s the deal. We’ll need to travel if we’re to achieve our science goals; we can’t do it all from this south pole site. We do have some mobility. The gondola has wheels; it will work as a truck down here. But we’re going to have to dig the wreck out of the sand first, and modify it. And meanwhile Harry’s right about the limited time. I suggest that Bill and I get on with the engineering. Miriam, you take Emry and go see what science you can do at the lake. It’s only a couple of kilometres’ – he checked a wrist map patch and pointed – ‘that way.’

‘OK.’ With low-gravity grace Miriam jumped back up to the hatch, and retrieved a pack from the gondola’s interior.

I felt deeply reluctant to move away from the shelter of the wrecked gondola. ‘What about those birds?’

Miriam jumped back down and approached me. ‘We’ve seen no sign of the birds since we landed. Come on, curator. It will take your mind off how scared you are.’ And she tramped away into the dark, away from the pool of light by the gondola.

Poole and Dzik turned away from me. I had no choice but to follow her.

8

Walking any distance was surprisingly difficult.

The layered heat-retaining suit was bulky and awkward, but it was flexible, and in that Titan was unlike the Moon with its vacuum, where the internal pressure forces even the best skinsuits to rigidity. But on Titan you are always aware of the resistance of the heavy air. At the surface the pressure is half as much again as on Earth, and the density of the air four times that at Earth’s surface. It is almost like moving underwater. And yet the gravity is so low that when you dig your feet into the sand for traction you have a tendency to go floating off the ground. Miriam showed me how to extend deep, sharp treads from the soles of my boots to dig into the loose sand.

It is the thickness of the air that is the survival challenge on Titan; you are bathed in an intensely cold fluid, less than a hundred degrees above absolute zero, that conducts away your heat enthusiastically, and I was always aware of the silent company of my suit’s heating system, and the power cells that would sustain it for no more than a few hours.

‘Turn your suit lights off,’ Miriam said to me after a few hundred metres. ‘Save your power.’

‘I prefer not to walk into what I can’t see.’

‘Your eyes will adapt. And your faceplate has image enhancers set to the spectrum of ambient light here . . . Come on, Jovik. If you don’t I’ll do it for you; your glare is stopping me from seeing too.’

‘All right, damn it.’

With the lights off, I was suspended in brown murk. But my eyes did adapt, and the faceplate subtly enhanced my vision. Titan opened up around me, a plain of sand and wind-eroded rock under an orange-brown sky – again not unlike Mars. Clouds of ethane or methane floated above me, and beyond them the haze towered up, layers of organic muck tens of kilometres deep. Yet I could see the sun in that haze, a spark low on the horizon, and facing it a half-full Saturn, much bigger than the Moon in Earth’s sky. Of the other moons or the stars, indeed of the Crab, I could see nothing. All the colours were drawn from a palette of crimson, orange and brown. Soon my eyes longed for a bit of green.

When I looked back I could see no sign of the gondola, its lights already lost in the haze. I saw we had left a clear line of footsteps behind us. It made me quail to think that this was the only footstep trail on all this little world.

We began to descend a shallow slope. I saw lines in the sand, like tide marks. ‘I think we’re coming to the lake.’

‘Yes,’ Miriam said. ‘It’s summer here, at the south pole. The lakes evaporate, and the ethane rains out at the north pole. In time it will be winter here and summer there, and the cycle will reverse. Small worlds have simple climate systems, Jovik. As I’m sure a curator ought to know . . .’

We came to the edge of the ethane lake. In that dim light it looked black like tar, and sluggish ripples crossed its surface. Patches of something more solid lay on the liquid, circular sheets almost like lilies, repellently oily. The lake stretched off black and flat to the horizon, which curved visibly, though it was blurred in the murky air.

It was an extraordinary experience to stand there in an exosuit and to face an ocean on such an alien world, the sea black, the sky and the shore brown. And yet there was again convergence with the Earth. This was, after all, a kind of beach. Looking around I saw we were in a sort of bay, and to my right, a few kilometres away, a river of black liquid had cut a broad valley, braided like a delta, as it ran into the sea.

And, looking that way, I saw something lying on the shore, crumpled black around a grain of paleness.

Miriam wanted samples from the lake, especially of the plates of gunk that floated on the surface. She opened up her pack and extracted a sampling arm, a remote manipulator with a claw-like grabber. She hoisted this onto her shoulder and extended the arm, and I heard a whir of exoskeletal multipliers. As the arm plucked at the lily-like features, some of them broke up into strands, almost like jet-black seaweed, but the arm lifted large contiguous sheets of a kind of film that reminded me of the eerie wings of the Titan birds that had attacked us.

Miriam quickly grew excited at what she was finding.

‘Life,’ I guessed.

‘You got it. Well, we knew it was here. We even have samples taken by automated probes. Though we never spotted those birds before.’ She hefted the lake stuff, films of it draped over her gloved hand, and looked at me. ‘I wonder if you understand how exotic this is. I’m pretty sure this is silane life. That is, based on a silicon chemistry, rather than carbon . . .’

The things on the lake did indeed look like black lilies. But they were not lilies, or anything remotely related to life like my own. Life of our chemical sort is based on long molecules, with a solvent to bring components of those molecules together. Our specific sort of terrestrial life, which Miriam called ‘CHON life’, after its essential elements carbon, hydrogen, oxygen and nitrogen, uses water as its solvent, and carbon-based molecules as its building blocks: carbon can form chains and rings, and long stable molecules like DNA.

‘But carbon’s not the only choice, and nor is water,’ Miriam said. ‘At terrestrial temperatures silicon bonds with oxygen to form very stable molecules.’

‘Silicates. Rock.’

‘Exactly. But at very low temperatures, silicon can form silanols, which are capable of dissolving in very cold solvents – say, in this ethane lake here. When they dissolve they fill up the lake with long molecules analogous to our organic molecules. These can then link up into polymers using silicon-silicon bonds, silanes. They have weaker bonds than carbon molecules at terrestrial temperatures, but it’s just what you need in a low-energy, low-temperature environment like this. With silanes as the basis you can dream up all sorts of complex molecules analogous to nucleic acids and proteins—’

‘Which is what we have here.’

‘Exactly. Nice complicated biomolecules for evolution to play with. They are more commonly found on the cooler, outer worlds – Neptune’s moon Triton for example. But this lake is cold enough. The energy flow will be so low that it must take a lo-ong time for anything much to grow or evolve. But on Titan there is plenty of time.’ She let the filmy stuff glide off her manipulator scoop and back into the lake. ‘There’s so much we don’t know. There has to be an ecology in there, a food chain. Maybe the films are the primary producers – an equivalent of the plankton in our oceans, for instance. But where do they get their energy from? And how do they survive the annual drying-out of their lakes?’

‘Good questions,’ I said. ‘I wish I cared.’

She stowed her sample bottles in her pack. ‘I think you care more than you’re prepared to admit. Nobody as intelligent as you is without curiosity. It goes with the territory. Anyhow we should get back to the gondola.’

I hesitated. I hated to prove her right, that there was indeed a grain of curiosity lodged in my soul. But I pointed at the enigmatic black form lying further along the beach. ‘Maybe we should take a look at that first.’

She glanced at it, and at me, and headed that way without another word.

It turned out, as I had suspected, that the crumpled form was a bird. I recalled one hitting our gondola during their assault and falling away; perhaps this was that very casualty.

It was essentially a block of ice, about the size of my head, wrapped up in a torn sheet of black film. With great care Miriam used her manipulator arm to pick apart the film, as if she was unwrapping a Christmas present. The ice mass wasn’t a simple lump but a mesh of spindly struts and bars surrounding a hollow core. It had been badly damaged by the fall. Miriam took samples of this and of the film.

‘That ice lump looks light for its size,’ I said. ‘Like the bones of a bird.’

‘Which makes sense if it’s a flying creature.’ Miriam was growing excited. ‘Jovik, look at this. The filmy stuff of the wings looks identical to the samples I took from the surface of the lake. It has to be silane. But the ice structure is different.’ She broke a bit of it open, and turned on a suit lamp so we could see a mass of very thin icicles, like fibres. It was almost sponge-like. Inside the fine ice straws were threads of what looked like discoloured water. ‘Rich in organics,’ Miriam said, glancing at a data panel on her manipulator arm. ‘I mean, our sort of organics, CHON life, carbon-water – amino acids, a kind of DNA. There are puzzles here. Not least the fact that we find it here, by this lake. CHON life has been sampled on Titan before. But it’s thought carbon-water life can only subsist here in impact-melt crater lakes, and we’re a long way from anything like that . . .’

Her passion grew, a trait I have always found attractive.

‘I think this is a bird, one of those we saw flying at us. But it seems to be a composite creature, a symbiosis of these silicon-based wings and the ice lump – silane life cooperating with CHON life! Just remarkable. You wonder how it came about in the first place . . . but I guess there are examples of survival strategies just as intricate in our own biosphere. Give evolution enough time and anything is possible. I wonder what it is they both want, though, what the two sides in this symbiosis get out of the relationship . . .

‘It’s a genuine discovery, Jovik. Nobody’s seen this before – life from two entirely different domains working together. And I wouldn’t have noticed it if not for you.’ She held out the ice lump to me. ‘They’ll probably name it after you.’

Her enthusiasm was fetching, but not that much. ‘Sure. But my concern right now is how much power we have left in these suit heaters. Let’s get back to the gondola.’

So she stowed away the remaining fragments of the Titan bird, Jovik Emry’s contribution to Solar System science, and we retraced our path back to the gondola.

9

The days are very long on Titan, and by the time we got back to the gondola nothing seemed to have changed about the landscape or the sky – not a diffuse shadow had shifted. We found Poole and Dzik, surrounded by alien mystery, happily fixing big balloon wheels to axles slung beneath the crumpled hull. Boys will be boys.

When they were done, we all climbed back aboard. Poole had reset some of the interior lamps so they glowed green, yellow and blue; it was a relief to be immersed once more in bright Earth light.

We set off in our gondola-truck for the next part of our expedition. We were making, I was told, for an impact crater believed to hold liquid water, which itself was not far from a cryovolcano, another feature of interest for the expedition. This site was perhaps a hundred kilometres from where we had come down.

Miriam transferred her lake samples to cold stores, and ran some of them through a small onboard science package. She jabbered about what she had discovered. Poole encouraged her more than Dzik did, but even that wasn’t much. Dzik and Poole were more interested at that moment in playing with the gondola. They sat at an improvised driver’s console and fussed over gear ratios and the performance of the big tyres. Poole even insisted on driving the bus himself, though Titan was so flat and dull for the most part he could easily have left the chore to the onboard systems. That proved to me the fallacy of not bringing along specialist biologists on a jaunt like this. It was only Miriam who seemed to have a genuine passion for the life systems we were supposed to be here to study; Dzik and Poole were too easily distracted by the technology, which was, after all, only a means to an end.

They had, however, rearranged the interior to make it feel a little less cramped. The couches had been separated and set up around the cabin, so you could sit upright with a bit of elbow room. The cabin was pressurised so we could remove our helmets, and though the expandable walls didn’t work any more there was room for one at a time to shuck off his or her exosuit. Poole ordered us to do so; we had already been inside the suits for a few hours, and the suits, and ourselves, needed some down time. Poole had set up a curtained-off area where we could let our discarded suits perform their self-maintenance functions while we had showers – of water recycled from our urine and sweat, which was deemed a lot safer than melt from the ice moon. Poole himself used the shower first, and then Miriam. She was hasty, eager to get back to her work, and kept talking even while she cleaned up.

After Miriam was out of the shower I took my turn. It was a miserable drizzle and lukewarm at that, but it was a relief to let my skin drink in the water. I was quick, though; with the unknown dangers of Titan only centimetres away beyond the gondola’s fragile metal walls, I didn’t want to spend long outside the security of the suit.

It was scarcely a comfortable ride, even discounting the calculating face of Harry Poole glaring from wall-mounted slates. I was relieved when, after a couple of hours, we reached our destination.

At that point Bill Dzik was in the shower. Safely suited up, with Dzik’s offensive presence absent, I was able to sit forward in my couch and peer over Miriam’s and Poole’s shoulders at the landscape outside. That cryovolcano was a mound that pushed out of the landscape some kilometres to the west of us. It had the look of a shield volcano, like Hawaii or Mons Olympus, a flat-profiled dome with a caldera on the top. It wasn’t erupting while we sat there, but I could see how successive sheets of ‘lava’ had plated its sides. That lava was water ice, heavily laced with ammonia, which had come gushing up from this world’s strange mantle, a sea of liquid water locked under the ice, kilometres below our tyres.

As for the crater lake, I saw nothing but a plain, flatter and even more featureless than the average, covered with a thin scattering of ice sand. But the lake was there, hidden. Poole extracted radar images which showed the unmistakable profile of an impact crater, directly ahead of us, kilometres wide. Such is the vast energy pulse delivered by an infalling asteroid or comet – or, in Saturn’s system, perhaps a ring fragment or a bit of a tide-shattered moon – that the water locally can retain enough heat to remain liquid for a long time, perhaps thousands of years. Such a lake had formed here, and then frozen over with a thin crust, on top of which that skim of sand had been wind-blown. But the briny lake remained under the ice, hoarding its heat.

And, studded around the lake’s circular rim, we saw more sponge-like masses like the one we had discovered wrapped up in silane film at the shore of the polar lake. These masses were positioned quite regularly around the lake, and many were placed close by crevasses that seemed to offer a route down into the deep structure of the ice rock beneath us. Miriam started gathering data eagerly.

Meanwhile, Poole was puzzling over images returned from the very bottom of the crater lake. He had found motion, obscure forms labouring. They looked to me like machines quarrying a rock deposit. But I could not read the images well enough, and as Poole did not ask for my opinions I kept my mouth shut.

Miriam Berg was soon getting very agitated by what she was finding. Even as she gathered the data and squirted it up to Harry Poole in the Crab, she eagerly hypothesised. ‘Look – I think it’s obvious there are at least two kinds of life here, the silanes of the ethane lakes and the CHON sponges. I’ve done some hasty analysis on the CHON tissues. They’re like us, but not identical. They use a subtly different subset of amino acids to build their proteins; they have a variant of our DNA in there – a different set of bases, a different coding system. The silanes, meanwhile, are like the life systems we’ve discovered in the nitrogen pools on Triton, but again not identical, based on a different subset of silicon-oxygen molecular strings.

‘It’s possible both forms of life were brought here through panspermia – the natural wafting of life between the worlds in the form of something like spores, blasted off their parent world by impacts and driven here by sunlight and gravity. If the System’s CHON life arose first on Earth or Mars, it might easily have drifted here and seeded in a crater lake, and followed a different evolutionary strategy. Similarly the silanes at the poles floated here from Triton or somewhere else, found a congenial place to live, and followed their own path, independently of their cousins . . .’ She shook her head. ‘It seems remarkable that here we have a place, this moon, a junction where families of life from different ends of the Solar System can coexist.’

‘But there’s a problem,’ Bill Dzik called from his shower. ‘Both your silanes and your sponges live in short-term environments. The ethane lakes pretty much dry up every Titan year. And each crater lake will freeze solid after a few thousand years.’

‘Yes,’ Miriam said. ‘So both forms need to migrate. And that’s how, I think, they came to cooperate . . .’

She sketched a hasty narrative of the CHON sponges leaving the crater lakes as they cooled, and finding their way to the summer pole. Maybe they got there by following deep crevasses, smashed into Titan’s ice crust by the impacts that dug out crater lakes like this one in the first place. Down there they would find liquid water, kilometres deep and close to the ammonia ocean. It would be cold, briny, not to terrestrial tastes, but it would be liquid, and survivable. And at the pole they would find the silane lilies floating on their ethane seas. The lilies in turn needed to migrate to the winter pole, where their precious life-stuff ethane was raining out.

Miriam mimed, her fist touching her flattened palm. ‘So they come together, the sponges and the lilies—’

‘To make the Titan birds,’ I said.

‘That’s the idea. The timing must be complicated, but both need to migrate. The birds come flapping up out of the lake, just as we saw, heading for the winter pole: sponges as bodies or brains, silanes as wings, one seeking cold, one warmth, but both needing to be on the move. Maybe the sponges get dropped off at fresh crater lakes along the way, across the surface of the planet. It’s a true symbiosis, with two entirely different spheres of life intersecting – and cooperating, for without the migration neither form could survive alone.’ She looked at us, suddenly doubtful. ‘We’re all amateurs here. I guess any competent biologist could pick holes in that theory the size of Saturn’s rings.’

Dzik said, ‘No competent biologist would even be hypothesising this way, not with so few facts.’

‘No,’ Harry said tinnily from his slate. ‘But at least you’ve come up with a plausible model, Miriam. And all without the need to evoke even a scrap of sentience. Good job.’

‘There are still questions,’ Miriam said. ‘Maybe the sponges provide the birds’ intelligence, or at least some kind of directionality. But what about power? The lilies especially are a pretty low-energy kind of life form . . .’

Michael Poole said, ‘Maybe I can answer that; I’ve been doing some analysis of my own. I can tell you a bit more about the silane lilies’ energy source. Believe it or not – even on a world as murky as this – I think they’re photosynthesising.’ And he ran through the chemistry he thought he had identified, using entirely different compounds and molecular processing pathways from the chlorophyll-based green-plant photosynthesis of Earth life.

‘Of course,’ Miriam said. ‘I should have seen it. I never even asked myself what the lilies were doing while they were lying around on the lake’s surface . . . Trapping sunlight!’

Harry was growing excited too. ‘Hey, if you’re right, son, you may already have paid for the trip. Silane-based low-temp photosynthesisers would be hugely commercially valuable. Think of it, you could grow them on those nitrogen lakes on Triton, and go scudding around the outer System on living solar sails.’ His grin was wide, even in the reduced Virtual image.

Poole and Miriam were smiling too, staring at each other with a glow of connection. Theirs was a strange kind of symbiosis, like silane lily and CHON sponge; they seemed to need the excitement of external discovery and achievement to bring them together.

Well, there was a happy mood in that grounded gondola, the happiest since we had crashed. Even Bill Dzik as he showered was making grunting, hog-like noises of contentment.

And then there was a crunching sound, like great jaws closing on bone, and the whole bus tipped to one side.

I had my helmet over my head in a heartbeat. Poole and Miriam staggered and started shouting instructions to each other.

Then there was another crunch, a ripping sound – and a scream, a gurgling, quickly strangled, and an inward rush of cold air that I felt even through my exosuit. I turned and saw that, near the shower partition, a hole had been ripped in the side of the gondola’s flimsy hull, revealing Titan’s crimson murk. Something like a claw, or a huge version of Miriam’s manipulator arm, was working at the hull, widening the breach.

And Bill Dzik, naked, not metres from the exosuit that could have saved him, was already frozen to death.

That was enough for me. I flung open the hatch in the gondola roof and lunged out, not waiting for Miriam or Poole. I hit the Titan sand and ran as best I could. I could hear crunching and chewing behind me. I did not look back.

When I had gone a hundred metres I stopped, winded, and turned. Poole and Miriam were following me. I was relieved that at least I was not stranded on Titan alone.

And I saw what was becoming of our gondola. The machines that had assailed it – and they were machines, I had no doubt of it – were like spiders of ice, with lenticular bodies perhaps ten metres long, each equipped with three grabber claws attached to delicate low-gravity limbs. Four, five of these things were labouring at the wreck of our gondola. I saw that they had gone for the wheels first, which was why we had tipped over, and now were making a fast job of ripping the structure apart. Not only that, beyond them I saw a line of similar-looking beasts carrying off silvery fragments – they could only be pieces of the gondola – and hauling them up the rising ground towards the summit of the cryovolcano. Some of the larger components of the wreck they left intact, such as the GUTengine module, but they carried them away just as determinedly.

In minutes, I saw, there would be little left of our gondola on the ice surface – not much aside from Bill Dzik, who, naked, sprawled and staring with frozen eyeballs, made an ugly corpse, but had not deserved the fate that had befallen him.

Harry Poole’s head popped into Virtual existence before us. ‘Well,’ he said, ‘that complicates things.’

Michael swatted at him, dispersing pixels like flies.

10

‘Dzik is dead,’ I said. ‘And so are we.’ I turned on Michael Poole, fists bunched in the thick gloves. ‘You and your absurd ambition – it was always going to kill you one day, and now it’s killed us all.’

Michael Poole snorted his contempt. ‘And I wish I’d just thrown you into a jail back on Earth and left you to rot.’

‘Oh, Lethe,’ Miriam said with disgust. She was sifting through the scattered debris the spiders had left behind. ‘Do you two have any idea how ridiculous you look in those suits? Like two soft toys squaring up for a fight. Anyhow, you aren’t dead yet, Jovik.’ She picked up bits of rubbish, rope, a few instruments, some of her precious sample flasks, enigmatic egg-shaped devices small enough to fit in her fist – and food packs.

Michael Poole’s curiosity snagged him. ‘They didn’t take everything.’

‘Evidently not. In fact, as you’d have noticed if you weren’t too busy trading insults with your passenger, they didn’t take us. Or Bill.’

‘What, then?’

‘Metal. I think. Anything that has a significant metal component is being hauled away.’

‘Ah.’ Poole watched the spiders toiling up their volcano, bits of our ship clutched in their huge claws. ‘That makes a sort of sense. One thing this moon is short of is metal. Has been since its formation. Even the core is mostly light silicate rock, more like Earth’s mantle than its iron core. Which maybe explains why every surface probe to Titan across seventeen hundred years has disappeared without a trace – even the traces of your illegal sample collectors, Emry. They were taken for the metal.’

I felt embarrassed to contribute to this dry discussion, but I referred to the blocky shapes I had seen toiling on the lake floor, in the radar images of the deeps. ‘As if they were quarrying? Maybe they were relatives of these spiders, after the metallic content of the meteorite that dug out the crater in the first place.’

Poole pursed his lips, clearly trying not to look impressed. ‘Sounds a good guess. The metal in a fair-sized space rock could take centuries to extract.’

‘Well, in any event, they left useful stuff behind,’ said Miriam, picking through the debris. ‘Anything ceramic, glass fibre, plastic. And the food packs. I’ll show you how to interface them to your suit’s systems, Emry, you can get at the food without opening up your helmet . . . We won’t starve, at least.’

Poole, you see, had homed in on theory, while Miriam focused on the essentials that might keep us alive. That tells you everything about the man’s lofty nature, and its flaws.

‘But they took the GUTengine, didn’t they?’ I put in sharply. ‘Our power source. Without which we’ll soon freeze to death, no matter how well fed we are.’

‘And, incidentally,’ Miriam said, ‘the identity-backup deck. We cached the backups in the GUTengine’s own control and processing unit, the most reliable store on the gondola. If we lose that, we lose the last trace of poor Bill too.’

I couldn’t help but glance at Dzik’s corpse, fast-frozen on the ice of Titan.

Not Poole, though. He was watching those receding spiders. ‘They’re heading down into the volcano. Which is a vent that leads down into the mantle, the ammonia sea, right? Why? What the hell are those things?’

Miriam said, ‘One way to find out.’ She hefted one of those ceramic eggs in her right hand, pressed a stud that made it glow red, and hurled it towards the nearest spider. It followed a low-gravity arc, slowing quickly in the thick air, and it seemed to take an age to fall. But her aim was good, and it landed not a metre from the spider.

And exploded. Evidently it had been a grenade. The spider shattered satisfactorily, those ugly claws going wheeling through the air.

Miriam had already started to run towards the spider. ‘Come on.’ You couldn’t fault her directness.

Poole followed, and I too, unwilling to be left alone with Bill’s frozen remains. Poole called, ‘What did you do that for?’

‘We want to know what we’re dealing with, don’t we?’

‘And why are we running?’

‘So we can get there before the other spiders get rid of the corpse.’

And sure enough the other spiders, still laden with bits of the gondola, had already turned, and were closing on their shattered fellow. They didn’t seem perturbed by the sudden destruction of one of their kind, or of our approaching presence.

We got there first, and we squatted around the downed spider in a splash of suit light. The spider hadn’t broken open; it was not enclosed by a hull or external carapace. Instead it had shattered into pieces, like a smashed sculpture. We pawed at the debris chunks, Miriam and Poole talking fast, analysing, speculating. The chunks appeared to be mostly water ice, though Poole speculated it was a particular high-pressure form. The internal structure was not simple; it reminded me of a honeycomb, sharp-edged chambers whose walls enclosed smaller clusters of chambers and voids, on down through the length scales like a fractal. Poole pointed out threads of silver and a coppery colour – the shades were uncertain in Titan’s light. They were clearly metallic.

The other spiders closed in on the corpse. Wary of getting chomped by accident we backed off, dimming our suit lights.

Miriam asked, ‘So, biological or artificial? What do you think?’

Poole shrugged. ‘They seem dedicated to a single purpose, and have metallic components. That suggests artificial. But that body interior looks organic. Grown.’

I felt like putting Poole in his place. ‘Maybe these creatures transcend your simple-minded categories. Perhaps they are the result of a million years of machine evolution. Or the result of a long symbiosis between animal and technology.’

Poole shook his head. ‘My money’s on biology. Given enough time, necessity and selection can achieve remarkable things.’

Miriam said, ‘But why would their systems incorporate metal if it’s so rare here?’

‘Maybe they’re not native to Titan,’ I said. ‘Maybe they didn’t evolve here.’ But they weren’t listening to me. And besides, they didn’t want to hear any kind of theory that implied sentience. ‘The real question is,’ I said more urgently, ‘what do we do now?’

The head of Harry Poole, projected somehow by our suit’s comms systems, once more popped into existence, the size of an orange, floating in the air. The small scale made his skin look even more unnaturally smooth. ‘And that,’ he said, ‘is the first intelligent question you’ve asked since we press-ganged you, Jovik. You ready to talk to me now?’

Michael Poole glared at his father, then turned and sucked water from the spigot inside his helmet. ‘Tell us how bad it is, Harry.’

‘I can’t retrieve you for seven days,’ Harry said.

I felt colder than Titan. ‘But the suits—’

‘Without recharge our suits will expire in three days,’ Poole said. ‘Four at the most.’

I could think of nothing to say.

Harry looked around at us, his disembodied head spinning eerily. ‘There are options.’

‘Go on,’ Poole said.

‘You could immerse yourselves in the crater lake. The suits could withstand that. It’s cold in there, the briny stuff is well below freezing, but it’s not as cold as the open air. Kept warm by the residual heat of impact, remember. Even so you would only stretch out your time by a day or two.’

‘Not enough,’ Miriam said. ‘And we wouldn’t get any work done, floating around in the dark in a lake.’

I laughed at her. ‘Work? Who cares about work now?’

Poole said, ‘What else, Harry?’

‘I considered options where two people might survive, rather than three. Or one. By sharing suits.’

The tension between us rose immediately.

Harry said, ‘Of course those spiders also left you Bill’s suit. The trouble is the power store is built into the fabric of each suit. To benefit you’d have to swap suits. I can’t think of any way you could do that without the shelter of the gondola; you’d freeze to death in a second.’

‘So it’s not an option,’ Poole said.

Miriam looked at us both steadily. ‘It never was.’

I wasn’t sure if I was relieved or not, for I had been determined, in those few moments when it seemed a possibility, that the last survivor in the last suit would be myself.

‘So,’ Poole said to Harry, ‘what else?’

‘You need the gondola’s GUTengine to recharge your suits,’ Harry said. ‘There’s just no alternative.’

I pointed at the toiling spiders on the cryovolcano. ‘Those beasts have already thrown it into that caldera.’

‘Then you’ll have to go after it,’ Harry said, and, comfortably tucked up in the Crab, he grinned at me. ‘Won’t you?’

‘How?’ I was genuinely bewildered. ‘Are we going to build a submarine?’

‘You won’t need one,’ Harry said. ‘You have your suits. Just jump in . . .’

‘Are you insane? You want us to jump into the caldera of a volcano, after a bunch of metal-chewing monster spiders?’

But Miriam and Poole, as was their way, had pounced on the new idea. Miriam said, ‘Jovik, you keep forgetting you’re not on Earth. That “volcano” is just spewing water, lava that’s colder than your own bloodstream.’ She glanced at Harry. ‘The water’s very ammonia-rich, however. I take it our suits can stand it?’

‘They’re designed for contact with the mantle material,’ Harry said. ‘We always knew that was likely. The pressure shouldn’t be a problem either.’

Poole said, ‘As for the spiders, they will surely leave us alone if we keep away from them. We know that. We might even use them in the descent. Follow the spiders, find the engine. Right?’

Harry said, ‘And there’s science to be done.’ He displayed data in gleaming Virtual displays – cold summaries only metres away from Bill Dzik’s corpse. Harry said that his preliminary analysis of our results showed that the primary source of the atmosphere’s crucial methane was not in the surface features, but a venting from the cryovolcanoes. ‘And therefore the ultimate source is somewhere in the ammonia sea,’ Harry said. ‘Biological, geological, whatever – it’s down there.’

‘OK,’ Poole said. ‘So we’re not going to complete the picture unless we go take a look.’

‘You won’t be out of touch. I’ll be able to track you, and talk to you all the way in. Our comms link have a neutrino-transmission basis; a few kilometres of ice or water isn’t going to make any difference to that.’

A few kilometres? I didn’t like the sound of that.

‘So that’s that,’ Miriam said. ‘We have a plan.’

‘We have a shared delusion,’ I said.

They ignored me. Poole said, ‘I suggest we take an hour out. We can afford that. We should try to rest; we’ve been through a lot. And we need to sort through these supplies, figure out what we can use.’

‘Yeah,’ said Miriam. ‘For instance, how about nets of ice as ballast?’

So he and Miriam got down to work, sorting through the junk discarded by the spiders, knotting together cables to make nets. They were never happier than when busy on some task together.

And there was Bill Dzik, lying on his back, stark naked, frozen eyes staring into the murky sky. I think it tells you a lot about Michael Poole and even Miriam that they were so focused on their latest goal that they had no time to consider the remains of this man with whom they had worked, apparently, for decades. Well, I had despised the man, and he had despised me, but something in me cringed at the thought of leaving him like that.

I looked around for something I could use as a shovel. I found a strut and a ceramic panel from some internal partition in the gondola, and used cable to join them together. Then I dug into the soil of Titan. The blade went in easily; the icy sand grains didn’t cling together. As a native of Earth’s higher gravity I was over-powered for Titan, and lifted great shovelfuls easily. But a half-metre or so down I found the sand was tighter packed and harder to penetrate, no doubt some artefact of Titan’s complicated geology. I couldn’t dig a grave deep enough for a man the size of Bill Dzik. So I contented myself with laying him in my shallow ditch, and building a mound over him. Before I covered his face I tried to close his eyes, but of course the lids were frozen in place.

All the time I was working I clung to my anger at Michael Poole, for it was better than the fear.

11

So we climbed the flank of the cryovolcano, paralleling the trail followed by the ice spiders, who continued to toil up the slope hauling the last useful fragments of our gondola. We were laden too with our improvised gear – rope cradles, bags of ice-rock chunks for ballast, food packs. Miriam even wore a pack containing the pick of her precious science samples.

It wasn’t a difficult hike. When we had risen above the sand drifts we walked on bare rock-ice, a rough surface that gave good footing under the ridges of our boots. I had imagined we’d slip walking up a slope of ice, but at such temperatures the ice under your feet won’t melt through the pressure of your weight, as on Earth, and it’s that slick of meltwater that eliminates the friction. It was as if we climbed a surface of rough rock.

But despite the easy climb, as we neared the caldera my legs felt heavy. I had no choice but to go on, to walk into ever greater danger, as I’d had no real choice since being press-ganged in the first place.

At last we stood at the lip of the caldera. We looked down over a crudely carved bowl perhaps half a kilometre across, water-ice rock laced with some brownish organic muck. Most of the bowl’s floor was solid – evidently the cryovolcano was all but dormant – but there was a wide crevasse down which the spiders slid into darkness, one after another.

If you listened carefully you could hear a crunching sound, from deep within the crevasse. This crack in the world was what we were going to descend into.

‘Don’t even think about it,’ Miriam murmured to me. ‘Just do it.’

But first we needed a tame spider.

We climbed a few paces down the flank, and stood alongside the toiling line of spiders. Miriam actually tried to lasso one of the creatures as it crawled past us. This was a bit overambitious, as the thick air and low gravity gave her length of cable a life of its own. So she and Poole worked out another way. With a bit of dexterity they managed to snag cable loops around a few of a spider’s limbs, and Poole threw cable back and forth under the beast’s belly and over its back and tied it off, to make a kind of loose net around the spider’s body. The spider didn’t even notice these activities, it seemed, but continued its steady plod.

‘That will do,’ Poole said. ‘All aboard!’ Grasping his own burden of pack and ballast nets he made a slow-motion leap, grabbed the improvised netting, and set himself on the back of the spider. Miriam and I hurried to follow him.

So there we were, the three of us sitting on the back of the beast! ‘On any other day,’ I ventured, ‘this would seem strange.’ That won me a laugh from Miriam.

The first few minutes of the ride weren’t so bad, though the spider’s motion was jolting and ungainly, we had to cling to our cables, and we always had the unpleasant awareness that there was no conscious mind directing this beast to which we were strapped.

Then the lip of the caldera came on us, remarkably quickly. I wrapped my hands and arms tighter in the netting.

‘Here we go!’ Michael Poole cried, and he actually whooped as the spider tipped head first over the lip of the crevasse – and began to climb down a vertical wall. I could not see how it was clinging to the sheer surface – perhaps with suckers, or perhaps its delicate limbs found footholds. But my concern was for myself, for as the spider tipped forward we three fell head over heels, clinging to the net, a slow low-gravity fall that ended with us all hanging upside down.

‘Climb up!’ Poole called. ‘It will be easier if we can settle near the back end.’

It was good advice but easier said than done, for to climb I had to loosen my grip on the cable to which I was clinging. I was the last to reach the arse end of the descending spider, and find a bit of respite in a surface I could lie on.

And all the while the dark of the chasm closed around us, and that dreadful crunching, chewing noise from below grew louder. I looked up to see the opening of this chimney as a ragged gash of crimson-brown, the only natural light; it barely cast a glow on the toiling body of the spider. Impulsively I ordered my suit to turn on its lights, and we were flooded with glare.

Poole asked, ‘Everybody OK?’

‘Winded,’ Miriam said. ‘And I’m glad I took my claustrophobia pills before getting into the gondola. Look below. What’s that?’

We all peered down. It was a slab of ice that appeared to span the crevasse. For an instant I wondered if this was as deep as we would have to go to find our GUTengine. But there was no sign of toiling spiders here, or of the pieces of our gondola, and I feared I knew what was coming next. That sound of crunching grew louder and louder, with a rhythm of its own.

‘Brace yourselves,’ Poole said. Pointless advice.

Our spider hit the ice floor. It turned out to be a thin crust, easily broken – that was the crunching we had heard, as spider after spider smashed through this interface. Beyond the broken crust I caught one glimpse of black, frothy water, before I was dragged down into it, head first. For the ice was the frozen surface of a subterranean ocean.

Immersed, I was no colder, but I could feel a sticky thickness all around me, as if I had been dropped into a vat of syrup. My suit lamps picked out enigmatic flecks and threads that filled the fluid surrounding me. When I looked back, I saw the roof of this vent already freezing over, before it was broken by the plunging form of another spider, following ours.

Michael Poole was laughing. ‘Dunked in molten lava, Titan style. What a ride!’

I moaned, ‘How much longer? How deep will we go?’

‘As deep as we need to. Have patience. But you should cut your lights, Emry. Save your power for heating.’

‘No, wait.’ Miriam was pointing at the ice wall that swept past us. ‘Look there. And there!’

And I made out tubular forms, maybe half a metre long or less, that clung to the walls, or, it seemed, made their purposeful way across it. It was difficult to see any detail, for these visions quickly shot up and out of our field of view.

‘Life?’ Poole asked, boyishly excited once more.

Miriam said, ‘It looks like it, doesn’t it?’ Without warning, she loosened one hand from the net, grabbed at one of the tubes and dragged it away from its hold on the wall. It wriggled in her hand, pale and sightless, a fat worm; its front end, open like a mouth, was torn.

‘Ugh,’ I said. ‘Throw it back!’

But Miriam was cradling the thing. ‘Oh, I’m sorry. I hurt you, didn’t I?’

Poole bent over it. ‘Alive, then.’

‘Oh, yes. And if it’s surviving in this ammonia lava, I wouldn’t mind betting it’s a cousin of whatever’s down below in the sea. More life, Michael!’

‘Look, I think it’s been browsing on the ice. They are clustered pretty thickly over the walls.’

And when I looked, I saw he was right; there the tube-fish were, nibbling away, working their way slowly up the vent.

Poole speculated, ‘Maybe they actively keep the vent open?’ He took a small science box from Miriam’s pack, and there, together – even as we rode that alien’s back down into the throat of the volcano – they briskly analysed the beast’s metabolism, and the contents of the water we were immersed in, and sent the results back to the Hermit Crab. Even Harry’s Virtual head popped up before us, grinning inanely, in that extreme situation.

I had seen enough. With a snap, I made my suit turn its lights off. I had no desire to sit shivering in the dark as invisible ice walls plummeted past me. But I was gambling that curiosity would get the better of Poole and Miriam, and I was right; soon it was Poole whose suit glowed, spending his own precious power to light me up, as they laboured over their pointless science.

At length they came to some conclusion. ‘So I was right,’ Miriam breathed at last. ‘This vent, and the mantle ocean, host a whole other domain – a third on Titan, in addition to the silanes and the CHON sponges. Ammono life . . .’

The moon’s liquid mantle is thought to be a relic of its formation, in a part of the solar nebula where ammonia was common.

Titan was born with a rocky core and a deep ocean, of water laced with ammonia. The ocean might have stayed open for a billion years, warmed by greenhouse effects under a thick primordial atmosphere. A billion years is plenty of time for life to evolve. Eventually the ocean surface froze over to form an icy crust, and at the ocean’s base complex high-pressure forms of ice formed a deep solid layer enclosing the silicate core. Ice above and below, but still the liquid ocean persisted between, ammonia-rich water, very alkaline, very viscous. And in that deep ocean had emerged a unique kind of life, adapted to its strange environment, based on chemical bonds between carbon and nitrogen-hydrogen chemical groups rather than carbon-oxygen, using ammonia as its solvent rather than water: ‘ammono life’, the specialists call it.

‘Yes, a third kind of life,’ Miriam said. ‘One unknown elsewhere in the Solar System so far as I know. So here on Titan you have a junction of three entirely different domains of life: native ammono life in the mantle ocean, CHON life in the crater lakes blown in from the inner System, and the silane lilies wafting in from Triton and the outer cold. Incredible.’

‘More than that,’ Harry said tinnily. ‘Michael, that tube-fish of yours is not a methanogen – it doesn’t create methane – but it’s full of it. Methane is integral to its metabolism, as far as I can see from the results you sent me. It even has methane in its flotation bladders.’

Miriam looked at the tube-fish blindly chewing at the ice walls. ‘Right. They collect it somehow, from some source deep in the ocean. They use it to float up here. They even nibble the cryovolcano vent walls, to keep them open. They have to be integral to delivering the methane from the deep ocean sources, up through the crevices in the ice cap and to the atmosphere. So you have the three domains not just sharing this moon but cooperating in sustaining its ecology.’

Harry said, ‘Quite a vision. And as long as they’re all stupid enough, we might make some money out of this damn system yet.’

Miriam let go of her tube-fish, like freeing a bird; it wriggled off into the dark water. ‘You always were a realist, Harry.’

I thought I saw blackness below us, in the outer glimmer of Poole’s suit lamps. I called, ‘How deep is this ice crust, before we get to the mantle ocean?’

‘Around thirty-five kilometres,’ Harry replied.

‘And how deep are we now?’

‘Oh, around thirty-five kilometres.’

Michael Poole gasped. ‘Lethe. Grab hold, everybody.’

It was on us at once: we had almost passed through this vent we had followed all the way down from the cryovolcano mouth at the surface, this passage right through the ice crust of Titan. I gripped the net and shut my eyes.

The spider let go of the wall and dropped into the void. As we passed out of the vent, through the roof of ice and into the mantle beneath, I felt the walls recede from me, a wash of pressure, a vast opening-out. And we fell into the dark and the cold.

12

Now that the walls were gone from under its limbs I could feel that the spider was swimming, or perhaps somehow jetting, ever deeper into that gloopy sea, while the three of us held on for our lives.

Looking up I saw the base of Titan’s solid crust, an ice roof that covered the whole world, glowing in the light of Poole’s lamps but already receding. And I thought I saw the vent from which we had emerged, a much eroded funnel around which tube-fish swam languidly. Away from the walls I could more easily see the mechanics of how the fish swam; lacking fins or tails they seemed to twist through the water, a motion maybe suited to the viscosity of the medium. They looked more like bloated bacteria than fish.

Soon we were so far beneath the ice roof that it was invisible, and we three and the spider that dragged us down were a single point of light falling into the dark.

And then Poole turned off his suit lamps!

I whimpered, ‘Lethe, Poole, spare us.’

‘Oh, have a heart,’ Miriam said, and her own suit lit up. ‘Just for a time. Let him get used to it.’

I said, ‘Get used to what? Falling into this endless dark?’

‘Not endless,’ Poole said. ‘The ocean is no more than – how much, Harry?’

‘Two hundred and fifty kilometres deep,’ Harry said, mercifully not presenting a Virtual to us. ‘Give or take.’

‘Two hundred and fifty . . . How deep are you intending to take us, Poole?’

‘I told you,’ Michael Poole said grimly. ‘As deep as we need to go. We have to retrieve that GUTengine, Emry. We don’t have a choice – simple as that.’

‘And I have a feeling,’ Miriam said bleakly, ‘now we’re out of that vent, that we may be heading all the way down to the bottom. It’s kind of the next logical choice.’

‘We’ll be crushed,’ I said dismally.

‘No,’ Harry Poole piped up. ‘Look, Jovik, just remember Titan isn’t a large world. The pressure down there is only about four times what you’d find in Earth’s deepest oceans. Five, tops. Your suit is over-engineered. Whatever it is that kills you, it won’t be crushing.’

‘How long to the bottom, then?’

Harry said, ‘You’re falling faster than you’d think, given the viscosity of the medium. That spider is a strong swimmer. A day, say.’

‘A day!’

Miriam said, ‘There may be sights to see on the way down.’

‘What sights?’

‘Well, the tube-fish can’t exist in isolation. There has to be a whole ammono ecology in the greater deeps.’

My imagination worked overtime. ‘Ammono sharks. Ammono whales.’

Miriam laughed. ‘Sluggish as hell, in this cold soup. And besides, they couldn’t eat you, Jovik.’

‘They might spit me out but I’d rather they didn’t try at all. And even if we survive – even if we do find our damn GUTengine down there on the ice – how are we supposed to get back out of here?’

Poole said easily, ‘All we need to do is dump our ballast, our bags of ice, and we’ll float up. We don’t need to bring up the GUTengine, remember, just use it to recharge the suits.’

Miriam said, ‘A better option might be to hitch a ride back with another spider.’

‘Right. Which would solve another problem,’ Poole said. ‘Which is to find a cryovolcano vent to the surface. The spiders know the way, evidently.’

Harry said, ‘And even without the spiders I could guide you. I can see you, the vent mouths, even the GUTengine. This neutrino-radar technology was worth the money it cost. There’s no problem, in principle.’

At times I felt less afraid of the situation than of my companions, precisely because of their lack of fear.

Miriam fetched something from a pack at her waist, I couldn’t see what, and glanced at Poole. ‘Jovik’s not going to survive a descent lasting a day. Not in the dark.’

Poole looked at me, and at her. ‘Do it.’

‘Do what?’

But I had no time even to flinch as she reached across, and with expert skill pressed a vial into a valve in the chest of my exosuit. I felt a sharp coldness as the drug pumped into my bloodstream, and after that only a dreamless sleep, cradled in the warmth of my cushioned suit.

So I missed the events of the next hours, the quiet times when Poole and Miriam tried to catch some sleep themselves, the flurries of excitement when strange denizens of Titan’s ammono deep approached them out of the dark.

And I missed the next great shock suffered by our dysfunctional little crew when the base of Titan’s underground ocean, an ice floor three hundred kilometres beneath the surface, at last hove into view. The strange landscape of this abyssal deep, made of folded high-pressure ices littered by bits of meteorite rock, was punctured by vents and chasms, like an inverted mirror image of the crust far above us. And the spider we rode did not slow down. It hurled itself into one of those vents, and once more its limbs began to clatter down a wall of smooth rock-ice.

Harry warned Miriam and Poole that this latest vent looked as if it penetrated the whole of this inner layer of core-cladding ice – Ice VI, laced by ammonia dihydrate – a layer another five hundred kilometres deep. At the base of this vent there was only Titan’s core of silicate rocks, and there, surely, the spiders’ final destination must lie.

There was nothing to be done but to endure this extension of the ride. It would take perhaps a further day. So Poole and Miriam allowed the spider to drag us down. More tube-fish, of an exotic high-pressure variety, grazed endlessly at the icy walls. Miriam popped me another vial to keep me asleep, and fed me intravenous fluids. Harry fretted about the exhaustion of our power, and the gradual increase of pressure; beneath a column of water and ice hundreds of kilometres deep, we were approaching our suits’ manufactured tolerance. But they had no choice but to continue, and I, unconscious, had no say in the matter.

When the ride was over, when the spider had at last come to rest, Miriam woke me up.

I was lying on my back on a lumpy floor. The gravity felt even weaker than it had on the surface. Miriam’s face hovered over me, illuminated by suit lamps. Smiling, she said, ‘Jovik. Look what we found.’

I sat up. I felt weak, dizzy, hungry. Beside me, in their suits, Miriam and Poole sat watching my reaction. Then I remembered where I was and the fear cut in.

I looked around quickly. Even by the glow of the suit lamps I could not see far. The murkiness and floating particles told me I must be still immersed in the water of Titan’s deep ocean. I saw a roof of ice above me – not far above, a hundred metres or so. Below me was a surface of what looked like rock, dark and purple-streaked. I was in a sort of ice cavern, then, whose walls were off in the dark beyond our bubble of light. I learned later that I was in a cavern dug out beneath the lower icy mantle of Titan, between it and the rocky core, eight hundred kilometres below the icy plains where I had crash-landed days before. Around us I saw ice spiders, toiling away at their own enigmatic tasks, and bits of equipment from the gondola, chopped up, carried here and deposited. There was the GUTengine! My heart leapt; perhaps I would yet live through this.

But even the engine wasn’t what Miriam was smiling about. She repeated, ‘Look what we found.’

I looked.

Set in the floor, in this rocky core of a world, was a hatch.

13

They allowed me to eat and drink, and void my bladder. Moving around was difficult, the cold water dense and syrupy; every movement I made was accompanied by the whir of servomotors as the suit laboured to assist me. I was reassured to know that the GUTengine was still functioning, and that my suit cells had been recharged. In principle I could stay alive long enough to get back to the Hermit Crab. All I had to do was find my way out of the core of this world, up through eight hundred kilometres of ice and ocean . . . I clung to the relief of the moment, and put off my fears over what was to come next.

Now that I was awake, Michael Poole, Miriam Berg, and Virtual Harry rehearsed what they had figured out about methane processing on Titan. Under that roof of ice, immersed in that chill high-pressure ocean, they talked about comets and chemistry, and all the while the huge mystery of the hatch in the ground lay between us, unaddressed.

Harry said, ‘On Earth, ninety-five per cent of the methane in the air is of biological origin. The farts of animals, the rot of vegetation. So could the source be biological here? You guys have surveyed enough of the environment to rule that out. There could in principle be methanogen bugs living in those ethane lakes, for instance, feeding off reactions between acetylene and hydrogen, but you found nothing significant. What about a delivery of the methane by infalling comets? It’s possible, but then you’d have detected other trace cometary gases, which are absent from the air. Only one plausible possibility remains . . .’

When Titan was young, still warm from its birth and before it froze, its ammonia-water ocean had extended all the way to the rocky core. There, chemical processes could have produced plentiful methane: the alkaline water reacting with the rock would liberate hydrogen, which in turn would react with sources of carbon, monoxide or dioxide or carbon grains, to manufacture methane. But that process would have been stopped as soon as the ice layers plated over the rock core, insulating it from liquid water. What was needed, then, was some way for chambers to be kept open at the base of the ice, where liquid water and rock could still react at their interface. And as for a way for the methane produced in the depths to be brought up through the ice to the ocean, and then released in the atmosphere . . .

‘The tube-fish,’ I said.

‘And their relatives, yes.’

Looking up at the ice ceiling above me, I saw how it had been shaped and scraped, as if by lobster claws. ‘So the spiders keep these chambers open, to allow the methane-creating reactions to continue. And the tube-fish carry the methane to the ocean, through vents they in turn help keep open.’

‘That’s it,’ Michael Poole said, wonder in his voice. ‘They do it to keep a supply of methane pumping up into the atmosphere. And they’ve been doing it for billions of years. Have to have been, for the ecologies up there to have evolved as they have – the tube-fish, the CHON sponges, the silanes. This whole world is an engine, a very old engine. It’s an engine for creating methane, for turning what would otherwise be just another nondescript ice moon into a haven, whose purpose is to foster the life forms that inhabit it.’

‘Ha!’ I barked laughter. ‘So all this is technology. Therefore the spiders are clearly sentient – or their makers are, or were. You don’t even need this hatch in the ground to make that case. You have found precisely what you were afraid of, haven’t you, Michael Poole? Sentience at the heart of Titan. You will never be allowed to open it up for exploitation now. So much for your commercial ambitions!’

‘Which you were going to share in,’ Harry reminded me, scowling.

I sneered. ‘Oh, I’d only have wasted the money on drugs and sex. To see you world-builders crestfallen is worth that loss. So,’ I said. ‘To the final mystery. What’s under the hatch?’

They glanced at each other. ‘The final answers, we hope,’ Michael Poole said.

Miriam said, ‘We’ve no idea what’s under there. We’ve put off looking until we brought you round, Jovik.’

Poole said, ‘We need everybody awake, ready to react. We might even need your help.’ He looked at me with faint disgust. ‘And,’ he said more practically, ‘it’s probably going to take three of us to open it. Come see.’

We all floated through the gloopy murk.

The hatch was a disc of some silvery metal, perhaps three metres across, set flush in the rocky ground. Spaced around its circumference were three identical grooves, each maybe ten centimetres deep. In the middle of each groove was a mechanism like a pair of levers, hinged at the top.

Michael said, ‘We think you operate it like this.’ He knelt and put his gloved hands to either side of the levers, and mimed pressing them together. ‘We don’t know how heavy the mechanism will be. Hopefully each of us can handle one set of levers, with the help of our suits.’

‘Three mechanisms,’ I said. ‘This is a door meant to be operated by a spider, isn’t it? One handle for each of those three big claws.’

‘We think so,’ Miriam said. ‘The handles look about the right size for that. We think they must need to be worked simultaneously – by one spider, or three humans.’

‘I can’t believe that after a billion years all they have is a clunky mechanical door.’

Poole said, ‘It’s hard to imagine a technology, however advanced, that won’t have manual backups. We’ve seen that the spiders themselves aren’t perfect; they’re not immune to breakdown and damage.’

‘As inflicted by us.’ I gazed reluctantly at the hatch. ‘Must we do this? You’ve found what you wanted – or didn’t want. Why expose us to more risk? Can’t we just go home?’

Miriam and Michael just stared at me, bewildered. Miriam said, ‘You could walk away, without knowing?’

Poole said, ‘Well, we’re not leaving here until we’ve done this, Emry, so you may as well get it over.’ He crouched down by his handle, and Miriam did the same.

I had no choice but to join them.

Poole counted us down: ‘Three, two, one.’

I closed my gloved hands over the levers and pushed them together. It was awkward to reach down, and the mechanism felt heavy; my muscles worked, and I felt the reaction push me up from the floor. But the levers closed together.

The whole hatch began to vibrate.

I let go and moved back quickly. The others did the same. We stood in a circle, wafted by the currents of the ammonia sea, and watched that hatch slide up out of the ground.

It was like a piston, rising up one metre, two. Its sides were perfectly smooth, perfectly reflective, without a scuff or scratch. It looked brand new; I wondered how old it must be. Michael Poole, fool that he was, reached up a gloved monkey-curious hand to touch it, but Miriam restrained him. ‘I’d like to measure the manufacturing tolerances on that thing,’ he murmured.

Then the great slab, around three metres wide and two tall, slid sideways. Poole had to scurry out of the way. Its scrape across the rough rock ground was audible, faintly. The shifted hatch revealed a hole in the ground, a circle – and at first I thought it was perfectly black. But then I saw elusive golden glimmers, sheets of light like soap bubbles; if I turned my head a little I lost it again.

‘Woah,’ Harry Poole said. ‘There’s some exotic radiation coming out of that hole. You should all back off. The suits have heavy shielding, but a few metres of water won’t hurt.’

I didn’t need telling twice. We moved away towards the GUTengine, taking the light with us. The hole in the ground, still just visible in the glow of our suit lamps, looked a little like one of the ethane lakes on the surface, with that metallic monolith beside it. But every so often I could make out that elusive golden-brown glimmer. I said, ‘It looks like a facet of one of your wormhole interfaces, Poole.’

‘Not a bad observation,’ Poole said. ‘And I have a feeling that’s exactly what we’re looking at. Harry?’

‘Yeah.’ Harry was hesitating. ‘I wish you had a better sensor suite down there. I’m relying on instruments woven into your suits, internal diagnostic tools in the GUTengine, some stray neutrino leakage up here . . . Yes, I think we’re seeing products of stressed spacetime. There are some interesting optical effects too – light lensed by a distorted gravity field.’

‘So it’s a wormhole interface?’ Miriam asked.

‘If it is,’ Poole said, ‘it’s far beyond the clumsy monstrosities we construct. And whatever is on the other side of that barrier, my guess is it’s not on Titan . . .’

‘Watch out,’ Miriam said.

A spider came scuttling past us towards the hole. It paused at the lip, as if puzzled that the hole was open. Then it tipped forward, just as the spider we rode into the volcano had dipped into the caldera, and slid head first through that sheet of darkness. It was as if it had fallen into a pool of oil, which closed over the spider without a ripple.

‘I wouldn’t recommend following,’ Harry said. ‘The radiations in there are deadly, suit or no suit; you couldn’t survive the passage.’

‘Lethe,’ Michael Poole said. He was disappointed!

‘So are we done here, at last?’ I asked.

Poole snapped, ‘I’ll tell you something, Emry, I’m glad you’re here. Every time we come to an obstacle and you just want to give up, it goads me into trying to find a way forward.’

‘There is no way forward,’ I said. ‘It’s lethal. Harry said so.’

‘We can’t go in ourselves,’ Miriam agreed. ‘But how about a probe? Something radiation-hardened, a controlling AI – with luck we could just drop it in there and let it report back.’

‘That would work,’ Poole said. Without hesitation the two of them walked over to the GUTengine, and began prying at its mechanisms.

For redundancy the engine had two control units. Miriam and Poole detached one of these. Containing a sensor suite, processing capabilities and a memory store, it was a white-walled box the size of a suitcase. Within this unit and its twin were stored the identity backups that had been taken of us before our ride into Titan’s atmosphere. The little box was even capable of projecting Virtuals; Harry’s sharp image was being projected right now by the GUTengine hardware, rather than through a pooling of our suits’ systems as before.

This box was small enough to be dropped through the interface; hardened against radiation it should survive a passage through a wormhole – though none of us could say if it would survive what lay on the other side. And it had transmitting and receiving capabilities. Harry believed its signals would make it back through the interface, though probably scrambled by gravitational distortion and other effects; he was confident he could construct filtering algorithms from a few test signals.

The unit was perfectly equipped to serve as a probe through the hatch, save for one thing. What the control box didn’t have was intelligence.

Michael Poole stroked its surface with a gloved hand. ‘We’re sending this beast into an entirely unknown situation. It’s going to have to work autonomously, figure out its environment, perform some kind of sensor sweep, before it can even start to work out how to talk to us. Running a GUTengine is a pretty simple and predictable job; the AI in there isn’t capable of handling an exploration like this.’

‘But,’ I said, ‘it carries in its store backups of four human intellects – mine, dead Bill, and you two geniuses. What a shame we can’t all ride along with it!’

My sarcasm failed to evoke the expected reaction. Poole and Miriam looked at each other, electrified. Miriam shook her head. ‘Jovik, you’re like some idiot savant. You keep on coming up with such good ideas. I think you’re actually far smarter than you admit yourself to be.’

I said honestly, ‘I have no idea what you’re talking about.’

‘The idea you’ve suggested to them,’ Harry said gently, ‘is to revive one of the dormant identity-backup copies in the unit’s store, and use that as the controlling intelligence.’

‘Me and my big mouth.’

As always when they hit on some new idea, Poole and Miriam were like two eager kids. Poole said rapidly, ‘It’s going to be a shock for the copy to wake up, to move straight from atmospheric entry where it was downloaded, to this point. It would be least disconcerting if we projected a full human animus. A complete body.’

‘You’re telling me,’ said the head of Harry Poole.

‘And some enclosing environment,’ Miriam said. ‘Just a suit? No, to be adrift in space brings problems with vertigo. I’d have trouble with that.’

‘The lifedome of the Crab,’ Poole said. ‘That would be straightforward enough to simulate to an adequate degree. And a good platform for observation. The power would be sufficient to sustain that for a few hours at least . . .’

‘Yes.’ Miriam grinned. ‘It would feel like a voyage in the Crab. Our observer will feel safe, in control. I’ll get to work on it . . .’

I said, ‘OK. So you’re planning to project a Virtual copy of one of us through the wormhole. And how will you get him or her back?’

They looked at me, as if I’d asked yet another foolish question.

‘That won’t be possible,’ Poole said. ‘The unit will be lost. It’s possible we could transmit back a copy of the memories the Virtual accrues on the other side – integrate them somehow with the backup in the GUTengine’s other store—’

‘No,’ Harry said regretfully. ‘The data rate through that interface would never allow even that. For the copy in there it’s a one-way trip.’

‘Well, that’s entirely against the sentience laws,’ I put in. They ignored me. But to point this out was, after all, my paid job.

Poole said, ‘That’s settled, then. The question is, who? Which of the four of us are we going to wake up from cyber-sleep and send into the unknown?’

I noticed that Harry’s disembodied floating head looked away, as if he were avoiding the question.

Poole and Miriam looked at each other.

‘We should give it to Bill,’ Miriam said firmly.

‘Yeah. There’s no other choice. Bill’s gone, and we can’t bring his stored backup home with us . . . We should let his backup have the privilege of doing this. It will make the sacrifice worthwhile.’

I stared at them. ‘This is the way you treat your friends? By killing them, reviving backups and sending them to another certain death?’

Poole glared at me. ‘Bill won’t see it that way, believe me. You and a man like Bill Dzik have nothing in common, Emry. Don’t judge him by your standards.’

‘Fine. Just don’t send me.’

‘Oh, I won’t. You don’t deserve it.’

It took them only a few more minutes to prepare for the experiment. The control pack didn’t need any physical modifications, and it didn’t take Miriam long to programme instructions into its limited onboard intelligence. She provided it with a short orientation message, in the hope that Virtual Bill wouldn’t be left entirely bewildered at the sudden transition he would experience.

Poole picked up the pack with his gloved hands, and walked towards the interface, or as close as Harry advised him to get. Then Poole lifted the pack over his head. ‘Good luck, Bill.’ He threw the pack towards the interface – or rather pushed it; its weight was low but its inertia was just as it would have been on Earth, and besides Poole had to fight against the resistance of the syrupy sea. For a while it looked as if the pack might fall short. ‘I should have practised a couple of times,’ Poole said ruefully. ‘Never was any use at physical sports . . .’

But he got it about right. The pack clipped the rim of the hole, then tumbled forward and fell slowly, dreamlike, through that black surface. As it disappeared, autumn gold glimmered around it.

Then we had to wait, the three of us plus Harry. I began to wish that we had agreed some time limit; obsessives like Poole and Miriam were capable of standing there for hours before admitting failure.

In the event it was only minutes before a scratchy voice sounded in our suit helmets. ‘Harry? Can you hear me?’

‘Yes!’ Harry called, grinning. ‘Yes, I hear you. The reception ought to get better, the clean-up algorithms are still working. Are you all right?’

‘Well, I’m sitting in the Crab lifedome. It’s kind of a shock to find myself here, after bracing my butt to enter Titan. Your little orientation show helped, Miriam.’

Poole asked, ‘What do you see?’

‘The sky is . . . strange.’

Miriam was looking puzzled. She turned and looked at Harry. ‘That’s not all that’s strange. That’s not Bill!’

‘Indeed not,’ came the voice from the other side of the hole. ‘I am Michael Poole.’

14

So, while a suddenly revived Michael Poole floated around in other-space, the original Poole and his not-lover Miriam Berg engaged in a furious row with Harry. Despite the circumstances, I found all this amusing.

Poole stormed over to the GUTengine’s remaining control pack, and checked the memory’s contents. It had never contained backup copies of the four of us after all; it contained only one ultra-high-fidelity copy, of Michael Poole himself. I could not decide which scared me more: the idea that no copies of myself existed in that glistening white box, or the belief I had entertained previously that there had. I am prone to existential doubt, and am uncomfortable with such notions.

But such subtleties were beyond a raging Michael Poole. ‘Miriam, I swear I knew nothing about this.’

‘Oh, I believe you.’

They both turned on the older Poole. ‘Harry?’ Michael snapped. ‘What in Lethe did you do?’

Disembodied-head Harry looked shifty, but he was going to brazen it out. ‘As far as I’m concerned there’s nothing to apologise for. The storage available on the Crab was always limited, and it was worse in the gondola. Michael’s my son. Of course I’m going to protect him above others. What would you do? I’m sorry, Miriam, but—’

‘You aren’t sorry at all,’ Miriam snapped. ‘And you’re a cold-hearted bastard. You knowingly sent a backup of your son, who you say you’re trying to protect, through that wormhole to die!’

Harry looked uncomfortable. ‘It’s just a copy. There are other backups, earlier copies—’

‘Lethe, Dad,’ Michael Poole said, and he walked away, bunching his fists. I wondered how many similar collisions with his father the man had had to suffer in the course of his life.

‘What’s done is done,’ came a whisper. And they all quit their bickering, because it was Michael Poole who had spoken – the backup Poole, the one recently revived, the one beyond the spacetime barrier. ‘I know I don’t have much time. I’ll try to project some imagery back . . .’

Harry, probably gratefully, popped out of existence, thus vacating the available processing capacity, though I was sure his original would be monitoring us from the Crab.

Poole murmured to Miriam, ‘You speak to him. Might be easier for him than having to deal with me.’

She clearly found this idea distressing. But she said, ‘All right.’

Gradually images built up in the air before us, limited views grainy with pixels and flickering.

And we saw Virtual Poole’s strange universe.

The Virtual Crab floated over a small object – like an ice moon, like one of Titan’s Saturnian siblings, pale and peppered with worn impact craters. I saw how its surface was punctured with holes, perfectly round and black. These looked like our hatch; the probe we had dispatched must have emerged from one of them. Things that looked like our spiders toiled to and fro between the holes, travelling between mounds of some kind of supplies. They were too distant to see clearly. All this was bathed in a pale-yellow light, diffuse and without shadows.

The original Poole said, ‘You think those other interfaces connect up to the rest of Titan?’

‘I think so,’ Miriam said. ‘This can’t be the only deep-sea methane-generation chamber. Passing through the wormholes and back again would be a way for the spiders to unify their operations across the moon.’

‘So the interface we found, set in the outer curved surface of Titan’s core, is one of a set that matches another set on the outer curved surface of that ice moon. The curvature would seem to flip over when you passed through.’

This struck me as remarkable, a paradox difficult to grasp, but Poole was a wormhole engineer, and used to the subtleties of spacetime manipulated and twisted through higher dimensions; slapping two convex surfaces together was evidently child’s play to him, conceptually.

Miriam asked Virtual Poole, ‘But where are you? That’s an ice moon, a common object. Could be anywhere in the universe. Could even be in some corner of our own System.’

Poole’s Virtual copy said, his voice a whispery, channel-distorted rasp, ‘Don’t jump to conclusions, Miriam. Look up.’

The viewpoint swivelled, and we saw Virtual Poole’s sky.

A huge, distorted sun hung above us. Planetoids hung sprinkled before its face, showing phases from crescents to half-moons; some were entirely black, fly-speck eclipses against the face of the monster. Beyond the limb of the sun more stars hung, but they were also swollen, pale beasts, their misshapen discs visible. And the space between the stars did not look entirely black to me, but a faint, deep crimson overlaid with a pattern, a network of threads and knots.

‘What a sky,’ Poole murmured.

‘Michael, you’re far from home,’ Miriam called.

Virtual Poole replied, ‘Yes. Those stars don’t fit our main sequence. And their spectra are simple – few heavy elements. They’re more like the protostars of our own early universe, I think: the first generation, formed of not much more than the hydrogen and helium that came out of the Big Bang.’

‘No heavy elements,’ observed Miriam Berg. ‘No metals.’

‘I’ll send through the data I’m collecting—’

‘Getting it, son,’ came Harry Poole’s voice.

The others stayed quiet to let Virtual Poole speak. His words, the careful observations delivered by a man so far from home, or at least by a construct that felt as if it were a man, were impressive in their courage.

‘This is not our universe,’ he whispered. ‘I think that’s clear. This one is young, and small – according to the curvature of spacetime, only a few million light years across. Probably not big enough to accommodate our Local Group of galaxies.’

‘A pocket universe, maybe,’ Miriam said. ‘An appendix from our own.’

‘I can’t believe the things you have been calling “spiders” originated here,’ the Virtual said. ‘Their fabric is heavily reliant on metals. You said it, Miriam. No metals here, not in this entire cosmos. I guess that’s why they were scavenging metals from probes, meteorites.’

‘They come from somewhere else, then,’ Poole said. ‘There was nothing strange in the elemental abundance we recorded in the spider samples we studied. They come from elsewhere in our own universe. The pocket universe is just a transit interchange. Like Earthport.’

The Virtual said, ‘Yes. And maybe behind these other moons in my sky lie gateways to other Titans – other sustained ecologies, maybe with different biological bases. Other experiments, elsewhere in the universe.’

Miriam said, ‘So if metals are so essential for the spiders, why not have supplies brought to them through the interchange?’

‘Maybe they did, once,’ the Virtual said. ‘Maybe things broke down. There’s a sense of age here, Miriam. This is a young cosmos maybe, but I think this is an old place . . .’

The real Poole murmured, ‘It makes sense. The time axis in the baby universe needn’t be isomorphic with ours. A million years over here, a billion years there.’

The Virtual whispered, ‘Those spiders have been toiling at their task on Titan a long, long time. Whoever manufactured them, or bred them, left them behind a long time ago, and they’ve been alone ever since. Just doing their best to keep going. Looking at them, I get the impression they aren’t too bright. Just functional.’

‘But they did a good job,’ Miriam said.

‘That they did.’

‘But why?’ I blurted out. ‘What’s the purpose of all this, the nurturing of an ecology on Titan for billions of years – and perhaps similar on a thousand other worlds?’

‘I think I have an idea,’ Virtual Poole said. ‘I never even landed on Titan, remember. Perhaps, coming at all this so suddenly, while the rest of you have worked through the stages of your discovery, I see it differently . . .

‘Just as this pocket universe is a junction, so maybe Titan is a junction – a haven where different domains of life can coexist. And it’s been designed that way.

‘You’ve found the native ammono fish, the CHON sponges that may originate in the inner System, and the silanes from Triton or beyond. Maybe there are other families to find, if you had time to look. All these kinds of life, arising from different environments – but all with one thing in common. All born of planets, and of skies and seas, in worlds warmed by stars.

‘But the stars won’t last for ever. In the future the universe will change, until it resembles our own time even less than our universe resembles this young dwarf cosmos. What then? Look, if you were concerned about preserving life, all forms of life, into the very furthest future, then perhaps you would promote—’

‘Cooperation,’ said Miriam Berg.

‘You got it. Symbiosis. Maybe Titan is a kind of prototype, a forced cooperative ecology where life forms of such different origins are compelled to mix, to find ways of using each other to survive—’

‘And ultimately merge, somehow,’ Miriam said. ‘Well, it’s happened before. Each of us is a community, with once-disparate and very different life forms toiling away in each of our cells. It’s a lovely vision, Michael.’

‘More important than that, it’s plausible,’ Poole’s original self said gruffly. ‘Anyhow it’s a hypothesis that will do until something better comes along.’

I sneered at that. This dream of cosmic cooperation struck me as the romantic fantasy of a man alone and doomed to die, and soon. We all project our petty lives upon the universe. But I had no better suggestions to make. And, who knows? Perhaps Virtual Poole was right. None of us will live to find out.

‘Anyhow,’ I said, ‘charming as this is – are we done now?’

Miriam snapped, ‘We can’t abandon Michael.’

‘Go,’ whispered Virtual Poole. ‘There’s nothing you can do for me. I’ll keep observing, reporting, as long as I can.’

I gagged on his nobility.

Now Harry intruded, grabbing a little of the available Virtual projection capacity. ‘But we’ve still got business to conclude before you leave here.’

15

Poole frowned. ‘What business?’

‘We came here to prove that Titan is without sentience,’ Harry said. ‘Well, we got that wrong. Now what?’

Miriam Berg was apparently puzzled we were even having the conversation. ‘We report what we’ve found to the sentience oversight councils and elsewhere. It’s a major discovery. We’ll be rapped for making an unauthorised landing on Titan, but—’

‘Is that the sum of your ambition?’ I snapped. ‘To hope the authorities will be lenient if you reveal the discovery that is going to ruin you?’

She glared at me. ‘What’s the choice?’

‘Isn’t it obvious?’ I looked at her, and Poole, who I think was guessing what I was going to say, and Harry, who turned away as he usually did at moments of crisis. Suddenly, after days of existential terror and pointless wonders, I was in my own element, which is the murky world of human relationships, and I could see a way forward where they could not. ‘Destroy this,’ I said. I waved a hand. ‘All of it. You have your grenades, Miriam. You could bring this cavern down.’

‘Or,’ Harry said, ‘there is the GUTengine. If that were detonated, if unified-field energies were loosed in here, the wormhole interface too would surely be disrupted. I’d imagine that the connection between Titan and the pocket universe would be broken altogether.’

I nodded. ‘I hadn’t thought of that, but I like your style, Harry. Do it. Let this place be covered up by hundreds of kilometres of ice and water. Destroy your records. It will make no difference to the surface, what’s going on in the atmosphere, not immediately. Nobody will ever know all this was here.’

Harry Poole said, ‘That’s true. Even if methane generation stops immediately, the residual would persist in the atmosphere for maybe ten million years. I venture to suggest that if the various multi-domain critters haven’t learned to cooperate in that time, they never will. Ten megayears is surely enough.’

Miriam looked at the bizarrely drifting head, horrified by his words. ‘You’re suggesting a monstrous crime,’ she breathed. ‘To think of destroying such a wonder as this, a billion-year project – to destroy it for personal gain! Michael, Lethe, leave aside the morality, surely you’re too much of a scientist to countenance this.’

But Poole sounded anguished. ‘I’m not a scientist any more, Miriam. I’m an engineer. I build things. I think I sympathise with the goals of the spider makers. What I’m building is a better future for the whole of mankind – that’s what I believe. And if I have to make compromises to achieve that future . . . well. Maybe the spider makers had to make the same kind of choices. Who knows what they found here on Titan before the makers went to work on it – who knows what potential they destroyed?’

And in that little speech, I believe, you have encapsulated both the magnificence and the grandiose folly of Michael Poole. I wondered then how much damage this man might do to us all in the future, with his wormholes and his time-hopping starships – what horrors he, blinded by his ambition, might unleash.

Harry said unexpectedly, ‘Let’s vote on it. If you’re in favour of destroying the chamber, say yes.’

‘No!’ snapped Miriam.

‘Yes,’ said Harry and Poole together.

‘Yes,’ said I, but they all turned on me and told me I didn’t have a vote.

It made no difference. The vote was carried. They stood looking at each other, as if horrified by what they had done.

‘Welcome to my world,’ I said cynically.

Poole went off to prepare the GUTengine for its last task. Miriam, furious and upset, gathered together our equipment, such as it was, her pack with her science samples, our tangles of rope.

And Harry popped into the air in front of me. ‘Thanks,’ he said.

‘You wanted me to make that suggestion, didn’t you?’

‘Well, I hoped you would. If I’d made it they’d have refused, and Michael would never have forgiven me for suggesting it.’ He grinned. ‘I knew there was a reason I wanted to have you along, Jovik Emry. Well done. You’ve served your purpose.’

Virtual Poole, still in his baby universe, spoke again. ‘Miriam.’

She straightened up. ‘I’m here, Michael.’

‘I’m not sure how long I have left. What will happen when the power goes?’

‘I programmed the simulation to seem authentic, internally consistent. It will be as if the power in the Crab lifedome is failing.’ She took a breath, and said, ‘Of course you have other options to end it before then.’

‘I know. Thank you. Who were they, do you think? Whoever made the spiders? Did they build this pocket universe too? Or was it built for them? Like a haven?’

‘I don’t suppose we’ll ever know. Michael, I’m sorry. I—’

‘Don’t be. You know I would have chosen this. But I’m sorry to leave you behind. Miriam – look after him, the other Michael. I, we, need you.’

She looked at the original Poole, who was working at the GUTengine. ‘We’ll see,’ she said.

‘And tell Harry – well. You know.’

She held a hand up to the empty air. ‘Michael, please—’

‘It’s enough.’ The Virtuals he had been projecting broke up into blocks of pixels, and a faint hiss, the carrier of his voice, disappeared from my hearing. Alone in his universe, he had cut himself off.

The original Poole approached her, uncertain of her reaction. ‘It’s done. The GUTengine has been programmed. We’re ready to go, Miriam. As soon as we’re out of here, it will blow.’

She turned away from him, her face showing something close to hatred.

16

So, harnessed to a spider oblivious of the impending fate of its vast and ancient project, we rose into the dark. It had taken us days to descend to this place, and would take us days to return to the surface, where, Harry promised, he would have a fresh balloon waiting to pick us up.

This time, though I was offered escape into unconsciousness, I stayed awake. I had a feeling that the last act of this little drama had yet to play itself out. I wanted to be around to see it.

We were beyond the lower ice layers and rising through two hundred and fifty kilometres of sea when Miriam’s timer informed us that the GUTengine had detonated, far beneath us. Insulated by the ice layer, we felt nothing. But I imagined that the spider that carried us up towards the light hesitated, just fractionally.

‘It’s done,’ Poole said firmly. ‘No going back.’

Miriam had barely spoken to him since the cavern. She had said more words to me. Now she said, ‘I’ve been thinking. I won’t accept it, Michael. I don’t care about you and Harry and your damn vote. As soon as we get home I’m going to report what we found.’

‘You’ve no evidence—’

‘I’ll be taken seriously enough. And someday somebody will mount another expedition, and confirm the truth.’

‘All right.’ That was all he said. But I knew the matter was not over. He would not meet my mocking eyes.

I wasn’t surprised when, twelve hours later, as Miriam slept cradled in the net draped from the spider’s back, Poole took vials from her pack and pressed them into her flesh, one by a valve on her leg, another at the base of her spine.

I watched him. I’d seen this done before, more than once. ‘You’re going to edit her memories, aren’t you? Download her identity, edit it, load it back . . . All to keep her quiet. Planned this with Dad, did you?’

‘Shut up,’ he snarled, edgy, angry.

‘What will you make her believe – that she stayed up on the Crab with Harry the whole time, while you went exploring and found nothing? That would work, I guess.’

‘I’ve got nothing to say to you.’

But I had plenty to say to him. I am no saint myself, and Poole disgusted me as only a man without morality himself can be disgusted. ‘I think you love her. I even think she loves you. Yet you are prepared to mess with her head and her heart, even her personality, to serve your grandiose ambitions. Let me tell you something. The Poole she left behind in that pocket universe – the one she said goodbye to – he was a better man than you will ever be again. Because he was not tainted by the great crime you committed when you destroyed the cavern. And because he was not tainted by this.

‘And let me make some predictions. No matter what you achieve in the future, Michael Poole, this crime will always be at the root of you, gnawing away. And Miriam will never love you again. Even though you wipe out her memory of these events, there will always be something between you; she will sense the lie. She will leave you, and then you will leave her. One thing I know better than you is people, and what goes on in their hearts. You remember I said this.

‘And, Poole, maybe those whose work you have wrecked will some day force you to a reckoning.’

He was open, defenceless, and I was flaying him. He had no answer. He cradled the unconscious Miriam, even as his machines drained her memory.

We did not speak again until we emerged into the murky daylight of Titan.

Epilogue

It didn’t take the Virtual Poole long to check out the status of his fragile craft.

The power in the lifedome’s internal cells might last – what, a few hours? As far as he could tell there was no functional link between the dome and the rest of the Hermit Crab; none of his controls worked. Maybe that was beyond the scope of Miriam’s simulation. So he had no motive power.

He didn’t grouse about this, nor did he fear his future. Such as it was.

The universe beyond the lifedome was strange, alien. The toiling spiders down on the ice moon seemed like machines, not alive, not sentient. He tired of observing them. He turned on lights, green, blue. The lifedome was a little bubble of Earth, isolated.

Michael was alone, in this whole universe. He could feel it.

He got a meal together. The mundane chore, performed in a bright island of light around the lifedome’s small galley, was oddly cheering. Miriam’s simulation was good, here in his familiar personal space; he didn’t find any limits or glitches. Lovingly constructed, he thought.

He carried the food to his couch, lay back with the plate balancing on one hand, and dimmed the dome lights. He finished his food and set the plate carefully on the floor. He drank a glass of clean water.

Then he went to the freefall shower and washed in a spray of hot water. He tried to open up his senses, to relish every particle of sensation. There was a last time for everything, for even the most mundane experiences. He considered finding some music to play, a book to read. Somehow that might have seemed fitting.

The lights failed. Even the instrument slates winked out.

Well, so much for music. He made his way back to his couch. Though the sky was bright, illuminated by the nearest protosun, the air grew colder; he imagined the heat of the lifedome leaking out. What would get him first, the cold, or the failing air?

He wasn’t afraid. And he felt no regret that he had lost so much potential life, all those AS-extended years. Oddly, he felt renewed: young, for the first time in decades, the pressure of time no longer seeming to weigh on him.

He was sorry he would never know how his relationship with Miriam might have worked out. That could have been something. But he found, in the end, he was glad that he had lived long enough to see all he had.

He was beginning to shiver, the air sharp in his nostrils. He lay back in his couch and crossed his hands on his chest. He closed his eyes.

A shadow crossed his face.

He opened his eyes, looked up. There was a ship hanging over the lifedome.

Michael, dying, stared in wonder.

It was something like a sycamore seed wrought in jet black. Night-dark wings which must have spanned hundreds of kilometres loomed over the Crab, softly rippling.

The cold sank claws into his chest; the muscles of his throat abruptly spasmed, and dark clouds ringed his vision. Not now, he found himself pleading silently, his failing vision locked onto the ship, all his elegiac acceptance gone in a flash. Just a little longer. I have to know what this means. Please . . .

Poole’s consciousness was like a guttering candle flame. Now it was as if that flame was plucked from its wick. And the flame, with its tiny fear, its wonder, its helpless longing to survive, was spun out into a web of quantum functions, acausal and nonlocal.

The last heat fled from the craft; the air in the translucent dome began to frost over the comms panels, the couches, the galley, the abandoned body. And the ship and all it contained, no longer needed, broke up into a cloud of pixels.