Alastair Reynolds - Poseidon's Wake

Even the smallest of these worlds had been detected and characterised centuries ago and in most cases subjected to direct imaging of surface features. Still, even the mighty Ocular had not been able to study every single planet around every star, even in the local stellar neighbourhood — there were simply too many candidates. Gliese 163 lay further away than many of the better-studied solar systems, beyond the reach of the holoships, and so there had been no incentive to obtain more accurate data. Beyond the star’s habitable zone was a barren, Earth-sized planet. Cold and nearly airless, it would not have merited his attention except for one thing. On the planet’s face, sweeping around into view as it rotated, was another Mandala.

It was same size as the alien structure on Crucible, different in its details but unquestionably the work of the same intelligence. In those first few waking hours, Kanu had stared at it in wonder and a kind of stupefied bewilderment, astonished that it should fall on him to be the first to witness and document this discovery. It turned out that it was visible, in ghostly form, in the Ocular data. But the resolution had not been quite sufficient to reveal it for the thing it was: an artificial blemish rather than the work of nature.

Now a question occurred to him. It was one thing to accept Mandala as a singular phenomenon, but if there were two of them, then there were probably others.

How many more?

He laughed. He had no idea, beyond the instinct that two were not sufficient. The Mandala Makers would do things in threes. Or fours. Or multitudes.

‘Out of your depth already, merman,’ he said to himself.

‘I might venture that we are all equally out of our respective depths,’ Swift said, standing several metres to Kanu’s right, stroking his chin in idle fascination as he studied the new images. ‘There is no precedent for this. Well, exactly one precedent — the other Mandala. But we know so little about that, we are scarcely on firmer ground than if we had never seen anything similar. Would you care to take a closer look at it?’

‘Definitely. But no matter what course we set now, we’ll have to swing around the star first. What about that heavy planet, further in? Looks as if our present course will take us quite close.’

It was the largest world that was not a gas giant, and it orbited Gliese 163 once every twenty-six days. That was a ludicrously short ‘year’ by any measure, but the star was a red dwarf — cooler and smaller than Earth’s sun — and such a tight orbit placed the big planet well within the bounds of habitability. It had been given a name: Poseidon. There were other Poseidons, Kanu knew, and he would be unwise to attach undue significance to such a thing. But given the history of his family and their long and tempestuous involvement with the people of the sea, it could not help but feel apt.

More than that, Poseidon was a waterworld. Its mass was higher than Earth’s, and it was also larger. Oceans blanketed it from pole to pole, with no dry land anywhere. Indeed, those oceans were far too deep for any features to have pushed their way through to dry air. Warm at the surface — uncomfortably so — the oceans plunged down through endless black kilometres, finally becoming cool. Animals could survive in those clement depths, but they would have a hard time thriving in the surface waters.

Which was not to say that there was no life at the ocean’s upper extremity. From space, the blue of the dayside ocean was broken by smears and swatches of green, ranging in size from tiny islands to expanses with the area of terrestrial continents. It only took a few scans to establish that these features were vast floating structures, rising and flexing with the ocean’s solar tides rather than having the waters lap over them. From this distance, they looked as thick and dense as forests. But in fact the living mats were tenuous, seldom more than a few centimetres thick and subject to a constant process of shearing and re-formation — no more substantial than rafts of floating seaweed or kelp. They were an explanation for the free oxygen in the atmosphere, but it was hard to see how anything built on them would not break through into the underlying water.

Nonetheless they were an example of a rich alien ecology, and Kanu would have looked forward to gathering more information were it not for the other things on Poseidon. Icebreaker was imaging them clearly, and they were an affront to everything Kanu thought he knew about planets.

There were arches in the ocean. Dozens of them, dotted all over the visible face, always in open water rather than cutting up through the green swatches, and they rose so far that their tops vaulted out of the atmosphere and into airless space, a hundred kilometres above the sea. He stared at them for long minutes, convinced — despite himself — that they had to be an excusable analytical error, a figment of the ship’s confused sensors.

But the harder Icebreaker looked, the more real the arches became. They were not phantoms.

They were solid entities, casting measurable shadows across a continent’s worth of ocean. Each arch had a shallow rim and a flat face like the tread of a wheel. They gave off a radar backscatter suggestive of metals — the only hint of metals anywhere on Poseidon.

‘What are they?’

She might have been standing behind him for as long as he had been staring at the arches — so absorbed was Kanu in their mystery that he had not noticed Nissa’s arrival on the command deck.

He angled around in the chair. ‘I don’t know. They’re not the thing I mentioned — the thing I wanted you to see. How are you feeling?’

‘If I wasn’t well, the casket wouldn’t have let me out of skipover.’ But perhaps that reply was harsher than she had intended. ‘I’m all right. Sore, stiff and very thirsty. I’ve never done this before. My head feels cold. I’ve never had it shaved.’

‘Nor me,’ Kanu said. ‘And I feel the same — or did, anyway. But a few hours up and about seems to help.’ He pushed aside the console so he could stand. It did not feel right to sit while Nissa had to stand.

‘No, stay where you are,’ she said softly. Not an order, but a clear expression of her feelings. She was here out of curiosity — a need to know what was in store — but nothing had been forgiven, and he should not presume she would put aside her grievances any time soon.

‘Artificial structures,’ Kanu said, just as softly. ‘No one’s seen anything like those before, here or anywhere else. They’re still a bit hazy at this range, but our approach will take us a lot closer to Poseidon.’

‘You said this wasn’t the thing.’

‘It isn’t — although right now I’m not sure which is the more amazing discovery. The eighth planet out — let me get an enlargement up. It has a name, too — Paladin — and a circular orbit, about half an AU, which swings it around Gliese 163 in just over two hundred days. It’s Earth-sized, but much too far from the star to be habitable.’

Nissa waited until Icebreaker had projected its best image of Paladin onto the screen. She looked at it in silence for a few moments.

‘I’ve seen something like that before.’

‘We all have. It’s like the structure on Crucible — another version of the same thing. Can you imagine how significant this is? It’s more than just another Mandala. It tells us — begins to tell us, anyway — that there has to be something more to Mandala. A deeper significance than anything we’ve worked out so far.’

‘How so?’

‘The M-builders wouldn’t have gone to the trouble of making two of them if it didn’t mean something. And now that it turns out there are two, I think there must be more. Dozens, hundreds — who knows? We’re just beginning to push into true interstellar space. There are hundreds of billions of other solar systems out there — maybe there are billions of Mandalas!’