Instead the land fell away into the hollow, its edge ragged, the floor littered with boulders. As he climbed down Yuri found himself walking on life: a green undergrowth of what looked like lichen, something like mosses, a kind of crisp furry grass-analogue that was like lots of skinny stems crowded in clumps, and a few young trees, none more than a few metres high. The green was the green of the different photosynthesis of Per Ardua, duller than Earth’s palette.

At the lowest point of the hollow they found a mud pool, bubbling, smeared with purple and green – bacteria perhaps. Around the inner slopes Yuri made out more stromatolites, a bunch like huge toadstools over there, another crowd like slim pillars, all with greasy-looking carapaces but in a variety of colours, green, golden-brown, even crimson. To Yuri it was as if they had walked into a lost world, where everything familiar was distorted.

‘Sulphur,’ Martha said, wrinkling her nose. ‘Smell that? That’s why this clearing is here, the trees can’t grow. Maybe this is some kind of volcanic caldera.’

Yuri said, ‘Or it might be another of those collapsed features, like the Cowpat.’

Onizuka snorted. ‘What does it matter? Who cares about geology?’

‘We should care, bonehead,’ Lemmy said sharply. ‘We know there’s some kind of geological uplift going on here. The ColU’s been measuring it. Like a volcano waiting to blow. If this becomes a live caldera not five kilometres from the camp—’

‘ “Bonehead”?’ Onizuka raised the crossbow and again pointed it at Lemmy’s face. ‘You don’t get to speak to me like that, you little prick.’

‘Hey, hey.’ Martha moved in, standing between them, glaring at Onizuka. ‘Take it easy, hero.’

But Onizuka glared at Lemmy, who returned his stare more or less bravely, and Yuri thought he could see the shadow of Pearl Hanks standing between them. Yuri turned away. If he got involved it would only increase the tension.

Onizuka backed off. ‘Christ, I could do with a drink.’ He shucked off his pack. ‘Let’s take a break.’

They sat, opened their packs. As they ate, Yuri saw movement on the far side of the bowl. He got up, food in hand, and walked forward to see better.

More tripods were moving over there, more structures of stem-like rods centred on densely woven basket-like core bodies. But these were huge, heavy, graceful creatures, very tall, maybe three, four metres, and they towered over the stromatolite garden through which they glided. They were much slower-moving than the kite flyer, or the scavengers that had consumed it, and Yuri had a chance to see how their bodies worked. They were like construction kits made up of those stems, of all lengths it seemed, from twigs shorter than his own fingers to big stout pillars like elephant bones, combined at joints that allowed them to move in a variety of complex ways. And the joints were being made and unmade in a fluid fashion as the beast progressed, as if the creatures were being rebuilt on the move.

Yuri watched one particularly large beast approach a stromatolite, impossibly balancing on its three fat legs.

Lemmy came to stand beside him. ‘Quite a sight. The stromatolites standing around like that, like a rocket park, like one I saw at Hellas once, on Mars, the big Chinese base there. And these critters – wow. Look at that.’

That big beast had now produced a kind of appendage, curling over the top of its upright body, like a scorpion sting – and it plunged the sting into the carapace of a stromatolite; Yuri could hear the crack. Evidently the big tripod started to feed, sucking out mushy material from the stromatolite.

Now Yuri saw another creature of a different kind, a bundle of stems that moved with a stealthy roll rather than the usual spinning-stool movement: smaller, more graceful, faster, quietly approaching the big feeder – quietly watchful, it seemed to Yuri, though he could see nothing like eyes.

‘Food chain,’ Lemmy said. ‘The stromatolites grow in the light of the sun, like vegetation on Earth. Those big slow things with the stings are herbivores, browsing the stromatolites. And then—’

‘Here come the carnivores.’

‘Yeah. A whole hierarchy of them, probably.’

A shadow passed over them, filmy, complex, and they both looked up. A flyer was crossing the sky, triple vanes turning languidly with soft rustles, a huge structure even compared to the kite Onizuka had shot down in the forest. As its shadow passed over the pit, creatures of various sizes fled from the stromatolite garden, or hid out of sight.

Yuri grunted. ‘What a sight. Like a pterosaur.’

‘What’s a pterosaur?’

Yuri felt oddly sorry for Lemmy. He suspected Lemmy was a hell of a lot brighter than he was, the way he kept figuring stuff out. But, after a shit life, he knew a lot less. ‘Earth stuff, Mars boy. Come on, we ought to take some samples for the ColU.’

Together they walked into the hollow, tucking samples into sacks at their waists.

CHAPTER 17

They got back to the camp late, after around twelve hours away.

The explorers delivered their samples to the ColU. The colonisation unit immediately began to pick apart the bags of green muck and greasy marrow with murmurs of satisfaction that even to Yuri’s ears were intensely irritating. It said it intended to put together a family tree of life on this planet of Proxima, the better to exploit it – not exterminate it, it was no threat, it couldn’t eat you or infect you, but to push it aside and use its remains as feedstock for human farming. So samples like this were food and drink to the ColU. When it began to speculate about predator-prey interactions – on Earth the predators hunted mostly at dawn or dusk, but maybe they would strike at any time here on timeless Per Ardua, a difference that would have effects that would ripple down through the whole biosphere, and blah blah – Yuri just walked away.

After another few hours, following a meal of ship’s rations and desultory talk around the fire, most of them began to drift to bed. Lemmy, Onizuka and Harry Thorne stayed up. They had started a poker school, or rather had continued it from their days on the ship. When Mardina forbade them to bet ration packs they had started to use tokens made of stems, taken from around the lake and broken up to different lengths to give multiples of ten, a hundred.

Yuri, trying to settle in his own small one-man fold-out tent, heard Lemmy laugh. ‘I’m a stem millionaire tonight! The richest guy on Per Ardua.’

‘You’re still a little prick, you little prick.’

The game soon broke up, and the couples went off, Martha with John Synge, Abbey with Matt Speith, Pearl with Lemmy, leaving the rest high and dry, as Onizuka put it. Yuri could hear it all, tell who was going where and with whom.

Tonight Matt stayed up, however, for it was his turn on sentry watch. In his tent, Yuri listened to Matt whistling through his teeth.

He kind of liked Matt Speith. Matt was an artist; as a child he had been a refugee, with his similarly arty family, from a terminally flooding Manhattan. He was vague, ineffectual, not particularly strong or attractive: ‘Neither use nor ornament,’ he said of himself. He seemed to have stumbled into poverty, and into the UN sweep that had taken him first to Mars and now to Proxima, without really noticing it, like he was sleepwalking into disaster. But he was quiet, unassuming, resilient in a calm kind of way, and always prepared to talk about anything – anything that wasn’t to do with Mars, the Ad Astra, or Prox c, anyhow.

He was the best artist on Per Ardua, probably. Every world needed an artist. Matt was a lousy sentry, however. That night he didn’t even call the alert until Pearl’s scream had already woken everybody up.

Even before he was fully awake Yuri pushed out of his tent, barefoot, wearing only his trousers. As usual when his sleep was disturbed he blinked in the full daylight, surprised to find Prox high in the sky when his body told him it was three or four in the morning.