It took only minutes to reach the stromatolites. Everywhere the builders were punching holes in the upper crust of the big structures, and were piling inside, squirming into the layers of bacteria and dirt within. Yuri saw that every one of these makeshift entrances was on the far side of the stromatolite from the angry star.

By the time Yuri and Mardina had got there, there wasn’t a builder to be seen. They stood beneath a big stromatolite, the hole in its shell easily big enough to allow an adult human to pass.

They looked at each other. Yuri asked, ‘What do you think?’

‘They’ve lived on this planet a lot longer than we have. Let’s trust them.’ She pushed herself head first through the break in the stromatolite’s shell, and shovelled out handfuls of gungy drab green matter to make room for herself. Soon she was inside the stromatolite entirely, and burrowing further in.

Yuri followed. It was not a comfortable feeling to be wriggling into this dark, slimy murk; he felt like some parasitic worm eating its way into a brain.

And then, beyond the gap in the shell, light flared, brilliant, as if somebody had thrown a switch in the sky.

CHAPTER 29

In his brief orientation, Major Lex McGregor had told the colonists that Proxima flared almost constantly, like all red dwarf stars, making explosive releases of magnetic energy that were visible across light years. Per Ardua’s atmosphere mostly shielded its cargo of life from the weather from space, but there were occasions, like, apparently, this time, when the sleet of ultraviolet and X-ray photons was too energetic, and broke through to the ground.

Life here had strategies to cope. The tough carapaces of the stems. The fact that a builder could simply replace a damaged stem, like a spare part. The builders sheltering their young in thick dome-like shelters. The trees folding away their leaves. Maybe creatures dwelling in the lakes and oceans retreated to the protection of the deeper water.

And maybe this was another strategy: to dive inside the thick shell, into the slimy interior, of a stromatolite. Would it work for humans? Yuri supposed they just had to hope so.

They were in a kind of cramped little cave in the slime, pressed together, slippery and sticky. The stromatolite’s inner matter continually threatened to slop down over the opening, and Yuri and Mardina were kept busy kicking this clear, so that a spray of mush gathered on the stony ground outside, brilliantly lit by the flare.

‘Those builders have dug in deeper,’ Mardina said.

‘Maybe they don’t need air.’

‘Well, we sure as hell do. Keep kicking.’

‘Yes, ma’am. How long do you think we should stay in here?’

‘We’ll see the light outside go back to normal. Or we could wait until the ColU comes to tell us it’s safe.’

‘Or maybe the builders will push us out,’ Yuri said.

‘Maybe.’

They looked at each other. Mardina’s face was just white eyes, white teeth, in a drab green mask. They burst out laughing. Then they seemed to relax a little more, pressed up against each other.

‘We’re not a bad team, I guess,’ Mardina said.

‘With the ColU in charge.’

‘Well, it thinks it is—’

‘I don’t want to die here,’ Yuri blurted.

She looked at him.

He wasn’t sure where that had come from. He scrambled to justify himself. ‘I don’t mean in this shell full of mush. I mean here, us, on Ardua. Everything we built just crumbling into the dirt.’

‘I thought you didn’t care about what we’re building.’

‘That was before we started building it. I never built anything before.’

‘I guess you didn’t . . . You know there’s only one option. One way we can change things.’

‘I know.’ He looked away. ‘To have a kid.’

‘We’ve talked about this,’ she said.

‘Actually we haven’t. Apart from when the ColU lectures us about anthropology.’

‘No. All right. So why do you want to talk about it now?’

‘I don’t.’

‘Well, you brought it up, ice boy. Look, you know what the issues are. Think about the lives our children would live. They’d be farm labourers at best, and incestuous baby machines at worst. You recoil from that, I do, and there’s good reason.’

‘I know. And there’s something else. What right do we have, to produce a kid in such circumstances?’

‘Rights? Umm. But these kids don’t exist yet. You know, in the ISF we had courses on ethics – not on this kind of extreme situation specifically. Yuri, none of us has a choice where we’re born, or in what circumstances. You’re just kind of dropped into the world at random. And traditionally parents have always seen their kids as resources. Kids work for you, you marry them off . . . So the conclusion is that the idea of rights of an unborn not to exist, if the situation it would be born into is uncomfortable – it’s all kind of nebulous.’

He thought that over. ‘No. It’s that argument that’s nebulous.’

She laughed. ‘So what do you suggest?’

Hesitantly, he said, ‘Suppose we did have a kid. Once it’s born it would have rights, yes? We could give it the right to choose whether to have more children with its siblings.’

‘Or its parents,’ she said firmly. ‘That’s part of the deal, and we have to face that.’

‘Only if we stick to this monster ISF plan. But there are other options.’

‘Like what?’

‘It, he or she, could go off alone. Or we could walk away when we’re too old to work, instead of being a burden. We haven’t got to choose now.’

‘No. In fact we give the kid the choice.’

‘Right.’

Mardina said, ‘I’ll tell you another possibility, Yuri. I know we argue about this. I’m still not convinced we really are stranded here, the way they told us . . .’

Not this again, he thought.

‘I know there must have been a lot of briefings that were kept from me. But I keep thinking there must be some kind of monitoring of this situation. There has to be. And if it is all some kind of survival test—’

‘It’s a test we might pass once we have a kid?’

‘Something like that. It’s possible. It would show we are committed to this world, wouldn’t it? To this life. Maybe that’s all we need to demonstrate.’

‘Yeah.’ He tried to think that through. ‘But in that case, by having the kid, we’d be doing the opposite, wouldn’t we? That’s kind of paranoid thinking, Mardina.’

She looked at him, in the green gloom. ‘But if we go ahead, for whatever reason, with whatever caveats in our heads – in the meantime, at least we’d have a kid.’

He tried to imagine that. Tried to imagine a life without children, without other people, with only his and Mardina’s face, for ever. ‘We’re never going to get another chance, are we? Except for this way. Neither of us.’

She sat back in silence.

They were coming to a decision, he realised. Maybe if the ColU left them alone a bit more they’d have made this choice sooner.

‘One problem,’ she said now. ‘We’re not sleeping together.’

‘Yeah,’ Yuri said. ‘But I’m not sexually . . . inactive.’

‘I know. I hear you.’

‘What?’

‘Ah – ah – ah. Jerkin’ the gherkin. Come on, Yuri, it’s a quiet planet. Look, I do it too. But I don’t think about you when I’m doing it.’

‘Fine. Then we can sleep together. And you can carry on not thinking about me.’

‘You can bet on it.’ She looked at him, and they laughed again. She said, ‘Do you think we’ve both finally gone insane?’

‘Possibly. Probably . . .’

There was a rustle from deeper back within the stromatolite’s bulk. The builders stirring, perhaps. Outside, the flare glow began to flicker, waning.

CHAPTER 30

2165

When it began, it began suddenly.

There was no choice to be made by Angelia as a whole, or by the near-million partials of which she was composed. The designers on Earth had built overrides into the probe’s governing software to ensure that. Selected by numbers produced by some automated sequencer, in their thousands and tens of thousands, sisters who had been together a decade were ripped out of the community and hurled off into the dark. Once out there they had no choice but to spread and turn and rebuild themselves as lenses and focus their light on the remaining core, rebuilt in its turn as an optical light mirror.