The wind was dying. He was still buffeted by gusts — he imagined the air scouring in great currents over this huge lava plain, the new lands it had conquered, seeking equilibrium — but it wasn’t as violent as before.

And he was still breathing. He could hear, above the diminishing battering of the breeze, the steady hiss of his oxygen supply. Good NASA engineering, conservative to the last.

He tried to stand up.

Jane put down the toy telescope.

The naked-eye Moon was bright: brighter than Jane had ever known it, as bright as if the sun had exploded. It cast a sharp shadow behind her, and the sky, masking the stars, was a deep, lustrous blue she’d never seen before: the new Moonlight, scattered by Earth’s ash-laden air. And the great lantern hanging in the sky shed enough light for her to pick out the details of the landscape, the coast, the sparkling waves. There were colours, she realized: colours by Moonlight.

Actually, it was unearthly.

The very light seemed unnatural: neither full daylight, nor night, nor Moonlight. And the Moon continued to evolve in the sky, a crawling, sparking thing. The Moon wasn’t supposed to change…

But it was wonderful.

Jack’s face, upturned, was shining in the new light. He was crying, the tears streaming down his cheeks, the moisture sparkling.

She could hear sounds: dogs barking, birds, the rustle of insects.

The animals think it’s daylight, she realized. It was the opposite of an eclipse. She wondered how long it would take them to adapt to the new world in the sky, to throw off all that evolution.

She shivered.

She could hear people cheering. Clapping, from gardens and patios all over the neighbourhood.

Now there were flashes around the cloud-covered pole of the Moon: sparks, urgent flappings of yellow light, sparking, dying, reforming like trick candles. They were auroras. Lightning strikes. The first storms.

Weather, on the Moon.

She imagined faces all over the darkened hemisphere of the planet, in shattered homes and refugee camps, turned up to the new Moon, which hung in the sky bright as a sun: a symbol of hope, inchoate yet, but nevertheless real. It was the most beautiful thing she had ever seen. For the first time in many days, her soul was lifted above her own concerns, her fears for Jack.

She lifted the telescope again, but now her own vision was blurred with tears.

His suit bent at the waist, comparatively easily. The suit was still pressurized, above ambient — but now there was air out there, not just vacuum; he wasn’t a starfish any more.

It was hard to see out of his gold sun-visor, though. It had been scoured and starred comprehensively by that first wave of fragments. But when he raised it, his helmet remained clear.

There was a soft sound, a gentle tap, on his helmet. Another on his shoulder. And his chest.

The pattering came more steadily now. And when he looked around he could see new craters being dug into the battered regolith, little pits a couple of inches wide, all around him.

He tipped back and raised his face to the hidden sky.

Raindrops, falling towards his face.

It wasn’t like rain on Earth. This was Moon rain.

The biggest drops were blobs of liquid a half-inch across. They came down surrounded by a mist of much smaller drops. The drops fell slowly, perhaps five or six feet in a second. The drops were big flattened Frisbees of liquid, flattened out by air resistance. They caught the murky light, shimmering.

When the drops hit his visor, they impacted with a fat, liquid noise; their splash was slow and languid. The drops spread out rapidly, or else collapsed into many smaller, more compact droplets over the plexiglass.

He stood up. He stood in Moon rain, the first for five billion years, wishing it could go on forever.

He leaned forward, compensating for the mass of his pack, and looked down. As it hit the ground, each raindrop broke up into many smaller drops, which trickled rapidly into the regolith, turning it to mud.

PART V

BOTTLENECK

1

A day later…

Well, after a day, the Moon hadn’t exploded, but outside the lava tube, the wind and rain kept on. The roof of the inflatable shelter sagged, because it couldn’t sustain its own weight over the pressure of the new air outside. It made getting around harder; Henry had to shove billows of fabric out of his face the whole time. It was irritating.

They were both hot and miserable, and they bickered.

But then the rain stopped, or at least tailed off a little. They could hear it, even inside the shelter.

So Henry was going to get to go outside, to explore the new Moon. He felt like a kid, waking up on the morning after a snow fall.

He put on his blue coveralls, regolith-stained gloves and Moon boots. He checked over his POS, his portable oxygen system. There were straps for him to fix the pack to his chest, and more to tie on his scuba-diver mask. There was the smell of rubber, of stale sweat, inside the mask; and immediately he put it on it started to mist up.

Geena watched him. Behind her, their lunar surface suits lay abandoned in a corner, greyed fabric sagging, like two fat men slumping side by side; Henry’s fishbowl helmet stared at him accusingly from where he had dumped it.

She said, “You sure this is going to be enough?”

“I’m sure. Believe me. Haven’t I been right so far?”

“About the Moon, maybe.”

He eyed her. They were going to be stranded together here for a while yet.

“I think we need to get out of here before we kill each other,” he said.

“Amen to that.”

Geena ran one last check of the shelter’s systems, and then followed Henry out of the cramped airlock. They carried their comms unit between them.

Henry looked up from the base of the rille. Before the nuke, he recalled, he’d been able to see stars up there.

Now, things were different. Now, the narrow rille was roofed over by a slab of grey sky, fat with cumulus clouds that looked low enough to touch. The murky light diffused down over the walls of the rille, and his blue coverall.

It was still raining, in fact, a slow drizzle of fat drops that hammered on his POS faceplate and rapidly soaked into his coverall.

But he wasn’t cold. In fact the air was hot.

…But it was thin, just a layer of carbon dioxide, nitrogen, water vapour and trace gases amounting to maybe a sixth of Earth’s atmospheric pressure. Like a mountaintop.

You wouldn’t want it much thicker, in fact. The gravity was one-sixth G, so to get the same air pressure as Earth you’d need a column height six times that of Earth’s. And then you’d suffer from a lot of haze and a greenhouse effect, all that cee-oh-two trapping excessive heat.

So, thin and dry was best, just the way it should be. It was as if they had been transported to the summit of a mountain two hundred and forty thousand miles tall, wrapped in comet air.

When he took a step, he squelched in red-brown mud. It was soaked regolith. He could swear the rille was a little deeper than it had been before — well, perhaps it was; perhaps the deeper regolith layers had collapsed. After a couple of steps it was hard to lift his boots, low gravity or not, so caked were they in clinging lunar mud.

He reached the walls of the rille. They were shallow, but now they were slick with mud, and their profile seemed to have changed. Further down the rille he could see evidence of landslips, great swathes of mud which had come shearing off the rille walls.

And, down the centre of a valley cut a billion years before by a flow of lava, a rivulet of water was gathering. It was the start of a river which would gather, Henry knew, until it pooled with dozens of others in the great sea that must be forming in the Oceanus Procellarum.