Alastair Reynolds - Poseidon's Wake

The moons’ orbits ranged in diameter. The smallest nearly skimmed Poseidon’s atmosphere, almost down to the tops of the arches, while the widest spanned a distance of ten light-seconds. Between these extremes lay another fifteen shells. There were forty-five of these tiny moon-like objects in total, but no natural moons.

Kanu’s instinct was to avoid them. But they threshed around Poseidon in perfectly repeatable patterns, tracing staunchly Newtonian paths like marbles in grooves. Clearly their individual masses did not perturb each other, or the effects had been allowed for in some way. He could already calculate their positions to many centuries hence and be confident of his predictions. Threading Icebreaker through the weave of moons was a trivial matter: there were countless viable trajectories. The hard part would be choosing which he preferred; how close he was prepared to get to the world and to any one of its moons.

There was time to think it over — and of course it would not be a decision he took alone.

Nissa remained distant, offering no hint of imminent forgiveness. But her anger had softened to the point where they were able to have mostly cordial exchanges, even if there remained an underlying and unresolved tension. They kept themselves to themselves, occupying different bedrooms. Icebreaker was not a large starship, but there was space enough for privacy.

They did manage to put aside their differences long enough to eat together. They sat opposite each other, in high, stiff elephant-carved dining chairs, in a room set off from the control deck. Sometimes they ate in silence or with some musical accompaniment, often very old recordings. Occasionally the walls displayed moving images of African landscapes at dusk, skies like flame, trees like dark paper cut-outs against that brightness.

‘With your permission,’ Kanu said one evening, ‘we’ll take a closer look at Poseidon.’

‘Permission?’

‘Wrong word. Mutual consent. If you agree it’s the right thing to do.’

Nissa was silent. Kanu knew better than to press her. He studied her face, her eyes averted from his gaze — as if the act of eating demanded her total concentration. He still loved her. The more she pulled away from him, the more he wanted her. He thought of gravity, of inverse squares and the swarm of moons girdling Poseidon.

‘You’d have to be a corpse not to be interested in those arches,’ she said eventually. ‘That doesn’t mean I’m enthusiastic, or that I like this situation.’ She ate on. ‘I just want to know as much as possible, given that my survival may depend on the choices we make.’

‘I feel similarly.’

She shot him a sceptical look. ‘Do you?’

‘On one level, I’m terrified of that planet. It’s too huge — and those arches? They’re a slap in the face, a boot crushing down on human ambition. But I want to know what they’re for. I want to see them up close.’

Nissa poured herself a glass of wine, steadfastly omitting to charge Kanu’s glass at the same time.

‘There’s a Mandala on that other planet.’

‘Paladin.’

‘And arches on Poseidon. They don’t look alike, but I suppose they both require a technology beyond anything we have. Do you think they were put there by the same culture?’

‘No clue, but I’d like to find out. My guess? There’s a connection. To those moons, too.’

‘And what about the chunk of rock orbiting Paladin that Icebreaker can’t explain?’

‘I don’t know. It doesn’t appear to fit. The other things are recognisably alien — Mandala, the arches, maybe the land masses on Poseidon, the forty-five moons in those weird orbits. This is just a lump of rock that’s slightly too warm. I scanned it with radar, too — some metallic backscatter, but it’s different in composition from the arches’ signature. It could just be mineral deposits baked onto the surface — you’d have to ask a geologist.’

‘But you don’t think so.’

‘I think it’s something else that doesn’t belong, but which is different in nature from the other things. This system is strange enough that we’d have sent an expedition here sooner or later, so why would it not have interested other civilisations? Maybe we’re not the first explorers.’

‘There’s something missing, though. Something that ought to be here but isn’t.’

‘I had the same thought.’

‘Where are the Watchkeepers?’ Nissa asked.

Icebreaker ’s planned course took them into the thresh of moons, slipping through their paths halfway between Poseidon and the highest orbit of its satellites. The trajectory would provide an opportunity to look at the moons in closer detail, but Kanu’s chief interest lay in the arches, rising from the ocean like the glimpsed coils of sea serpents.

Slowly their view of the arches improved. Only the tops were free of atmosphere, but much of their height was in extremely tenuous air, offering little obstruction to Icebreaker ’s sensors. The arches were semicircular, rising one hundred kilometres from the ocean’s surface — identical in every dimension to the limit of Icebreaker ’s measurements. Beneath the water there was a hint of continuation, a suggestion that the arches were in fact only the visible portions of half-submerged wheels, but that was as much detail as they could discern from space.

If they were wheels, then their treads were a kilometre wide, very narrow in comparison to their heights. Their rims were also about a kilometre thick, and there were no spokes or hubs. The arches — wheels, perhaps — were made primarily of some pale grey non-metallic substance, presumably possessing immense structural strength. From deep space, Icebreaker had detected the radar backscatter of metals, but this turned out to be a kind of ornamentation or embellishment added to the surface of the wheels. Cut into the rim and the treads, inlaid or recessed, perhaps even as a bas-relief — it was impossible to tell from space — was a suggestion of dense metallic patterning. To obtain a clearer, more detailed view, they would need to get much closer than five light-seconds. Icebreaker was not meant for atmospheric flight, but it could land on top of one of the wheels, which in turn would give them indirect access to the surface. Other than Fall of Night , there was nothing aboard Icebreaker that could serve as a shuttle, lander or re-entry vehicle — at least nothing with the capability of returning. If their other options were exhausted, there were single-use escape capsules which ought to be able to make it down to Poseidon’s seas.

But not now. This was a first pass, a scouting expedition. When they gained a better look around the system, identified the origin of the signal and found water ice to convert to hydrogen, which would in turn feed the initialising tanks for the PCP drive and guarantee them a trip home — then they could think about taking a closer look at the wheels.

‘We need another word for them,’ Kanu mused. ‘“Wheel” isn’t big enough. Worldwheels, perhaps. Do you like that? The Worldwheels of Poseidon . Has a certain ring to it.’

‘Whatever you think.’

‘I think this is wonderful and terrifying, and I wouldn’t miss it for a heartbeat.’

‘You came here to aid the robots, not to sightsee. Don’t forget the real reason for this trip.’

He smiled, still in the happy rush of discovery. ‘How could I?’

‘And what does Swift make of all this?’

‘Swift is all intellect — brilliant and fast. Swift by name, Swift by nature — but Swift doesn’t actually know very much. There wasn’t room in my head for him to carry a universe’s worth of wisdom — I carry my memories, my life experience. Swift can draw on my knowledge to some extent, sample my memories, but mainly he’s here to serve as witness, to guide my interpretations and actions.’