Stephen Baxter - Xeelee: Endurance

It was the fourth millennium.

Earth was restored. Great engineering projects had stabilised and preserved the planets fragile ecosystem: Earth was the first planet to be terraformed.

Meanwhile, the Solar System was opened up. Based in the orbit of Jupiter, an engineer called Michael Poole industriously took microscopic wormholes natural flaws in spacetime and expanded them to make transit links big enough to pass spaceships, enabling the inner System to be traversed in a matter of hours rather than months.

Poole Interfaces were towed out of Jupiters orbit and set up all over the System. The Jovian moons became hubs for interplanetary commerce.

And Poole and his colleagues pushed further out.

AD 3685

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, Saturns 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 probes 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 probes 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 probes upper casing, as the last of its internal heat leaked away.

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

Theres always been something wrong with Titan.

These were the first words I ever heard Harry Poole speak though I didnt know the man at the time words that cut through my hangover like a drill.

Its 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 atmospheres 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 mans 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. Its 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 Saturns largest moon, even though, I suppose, it was a central facet of my own career. The fog in my head, thicker than Titans 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 womans 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. Thats 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 nobodys taken Titan seriously enough to nail it. Always too many other easy targets for exploration and colonisation Mars, the ice moons. Nobodys 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. Thats the real problem. And now were hamstrung by these damn sentience laws.

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

We need Titan, son, Harry Poole said. Its 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 dont apply there, and move in and start opening it up. Thats what this is all about.

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

Given hes a sentience curator, and a crooked one at that, yes . . .

When words like wretched or crooked are bandied about in my company its generally Jovik Emry, my good self, thats 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. Its 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 wasnt the first time Id 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, youre 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 sons ship

Welcome? Youve drugged me and brought me here

One of the sixty-year-olds laughed, the gruff one. Oh, you didnt need drugging; you did that to yourself.