There was a lot of bitter conflict among the nations sending people to the Moon — the violation of international agreements on quotas and priorities went on daily — and it looked to Henry as if humanity was just going to transport all its old prejudices and inner conflicts intact to the new world, and presumably beyond. Depressing, but entirely predictable.

The evacuation was gigantic, but it could never be complete.

It would be possible to save only a fraction of the billions of people with which Earth had once teemed. Hence the Bottleneck laws. If the population was reduced to the minimum, by savage birth control measures, then, simply, there would be less people to be abandoned, to die, when the end came.

Most people accepted that. About the only thing humans could control about this catastrophe was their own numbers: the human souls who would be spared a birth that would doom them only to the flame.

Most people, it seemed to Henry, were doing their best, in this changing world. Behaving honourably, remarkably so in the circumstances. Surveys showed most populations around the planet were restricting their child birth rates voluntarily, accepting the Bottleneck laws.

And, it was estimated, millions could be saved, before the final destruction.

Remarkable, he thought. I bootstrapped a world. In the end, perhaps I really did save mankind. A fraction of it, anyhow.

He’d saved Jack, at least: still just twenty-one years old, the boy was healthy as an ox and smart as a tack. Maybe that one achievement was enough, to justify Henry’s life.

Now Jack was going to the Moon. But not us, Henry thought. There is nowhere for us, but here.

Jane stirred again. He kissed the top of her head, the thinning hair there, and she settled deeper into sleep.

As it turned out the Karroo was their last trip together, before Jane entered what the doctors delicately called her terminal stage: when their various treatments served no further purpose, and Henry, geologist turned amateur palaeontologist, became a nurse.

Some of what they had to face was much as he anticipated. The painkillers and their side-effects. Her loss of appetite; he learned to cook Lebanese-style, masses of small, spiced dishes, to tempt her. After she was bed-ridden, there was the need to care for her skin: rubber rings, protective pads for her heels and elbows, and a bed cradle to keep the weight of the covers off her legs.

And there were some things he didn’t anticipate. The constipation that doubled her in pain. The soreness in her mouth, which he treated with lip salves, mouth rinses and flavoured crushed ice for her to suck.

He wanted to move her bed downstairs, in their home in Houston, but she wouldn’t accept that. It would be the mark of the end, she said.

She would die upstairs.

Strange thing. He’d been to the Moon, but he’d never seen anyone die close up.

It wasn’t sudden. She slept more, sometimes drifting into unconsciousness, from which he couldn’t rouse her. Her breathing became noisy, like a rattle, but the doctors said it was just moisture on her chest.

Sometimes, though, when she appeared unconscious she was aware, but unable to speak or see. But her hearing probably still worked — hearing was the last sense she lost — and so he spoke to her, reading her letters from Jack on the Moon, or news items, or, just, talking to her.

Until there came a day when she seemed to fall ever more deeply into sleep, and she simply stopped breathing, and that was all.

And Henry knew that he would be alone, for the rest of his life.

4

And ten years more…

Ten years on, ten years older, and here was Henry putting on his spacesuit, fifty-five years old and utterly alone, letting the e-letter buzz in his earpiece for the fourth time, devouring this communication from the nearest thing to a son he ever had.

Dear Dad…

…I took little Nadezhda out to see the ecopoiesis farms in your old stamping ground of Aristarchus. They tell me they modelled the ecosystems here on the dry valleys of Antarctica, back when there used to be ice caps. Mats of green algae and cyanobacteria, lapping up the sunlight, resistant to the shortage of water and low partial pressure of oxygen, pumping out the oxygen. In some of the more clement areas there are even lichens and mosses, growing out in the open…

The ground here was mud, baked utterly dry, cracked into hexagons the size of dinner plates. No water anywhere, of course. Mud, as far as Henry could see, ocean bottom mud, baked dry and hard as concrete; mud, and sand dunes, and salt flats, and gravel fans, covering this dried-up ocean bed.

…We went to see the Apollo Museum there, at Aristarchus. They put it under a dome and reconstructed a lot of the original landing site, right down to the footprints they repaired from the rain damage they suffered. The day we were there they had Tracy Malone, the daughter of one of the astronauts, unveiling a plaque to her father, along with Geena, your ex-wife, who’s been working on lunar heritage projects now she’s retired. Quite symbolic: a representative of the first wave of lunar travellers, and the second, Geena, surrounded by the likes of us, the third. We introduced ourselves to Geena and she said to say hello. They showed Tracy Malone the place her father wrote her name in the dust with his fingertip. It’s under glass now. She cried a river, and it was a nice moment of closure, but I don’t think anyone had the heart to tell her they had to reconstruct it from the photos…

The sky was just a dome of mud-orange haze. But it wasn’t hard to see his way here, about as bright as an early evening in LA used to be. In fact there was more sunlight than appeared, still enough to sustain agriculture, to feed what was left of the Earth’s population, under the big domes in the old deserts.

Not that there was much left of the Earth’s population, all things considered. And if the stories were true about Siberia — it was said that because of the Venus radiation, and a lot of ancillary shit when the Chernobyl-era reactors out there started to go pop, a new homo species had emerged, viable, unable to interbreed with outsiders — the estimates of surviving human populations might be even further off.

…Nadezhda is going to spend her next break from school working at the Tycho carbon-sequestration pit.

I’ve got mixed feelings about her working there.

With all those burners and flues, Tycho is heavily industrial — something like Pittsburgh used to be, or the Ruhr cities. And with the same darker social side. They burn the biomass to recover volatiles, before burying the carbon-rich residue. It’s all part of the global scheme to maximize the production of free oxygen, which not many of us understand… But Tycho is one of the few places where the work we’re doing is simple enough for a five-year-old kid to contribute to.

I’ve taken Nadezhda around the place I work, the oxygen fountain at Landsberg. It sounds exotic — the ten-thousand-megaton thermonukes, the controlled energy cascades from Moonseed beds, all of it cracking the lunar regolith for oxygen — but there isn’t much, really, to see.

It can be a little bleak here.

For the foreseeable future, humans are going to be consuming eighty per cent of the lunar biosphere’s net primary production. And that’s a hell of a lot, maybe three times as high as humans ever reached on old Earth.

That means all the arable land surface we make, even most of the plankton in the crater lakes, is going to have to be turned over to crops. Other than humans, only those creatures that can survive in fields and orchards can be permitted. Any that need virgin forest or any kind of undisturbed habitat are going to have to stay in the zygote banks for now.