“I know. But I’d rather be home.”

“Umm.” He thought that over. “Where is home now, for you? Houston? Or—”

“Russia,” she said firmly. “With Arkady’s family. They always made me welcome.”

“Shows where we went wrong, huh.”

“Frankly, yes.”

“I’m sorry. About Arkady.”

She nodded. “I know. But it was unavoidable.”

“Yes,” he said. “Yes, I think it was. But I can see you loved him.”

After a time, she said, “What about you? Scotland?”

He shrugged. “Hell, no. Scotland is Olympus Mons now. Nobody will be going back there… I need to find Jane, and her kid, and we’ll find some place that will last a little longer than Britain.”

“I wish you well,” she said seriously. “I wish you happiness.”

“Thanks.”

“I mean it.”

“I know you do,” he said. “What about Rocky?”

“My mother still has him.” She added, “Much you care.” But he could tell it was a reflex jab.

He looked around. “Maybe one day this will be home, for somebody. That’s the idea, anyhow.”

“You think they’ll let us come back?”

“No,” he said sadly.

“Why not?”

“Because we’ll be too old to breed,” he said bluntly. “Our time is gone, Geena. Gone with Earth. It’s up to the children now… Hats.”

“What?”

“Hats. When the sun breaks through, we’ll fry. No ozone layer up there, remember. And I don’t suppose you packed any sun-cream. Maybe we can take the S-band antenna off the Rover, use it as a parasol.”

“You have a strange sense of priority, Henry.”

“I have a strange mind.”

“What else?”

“It wouldn’t hurt to find a source of water.” He dug a bare toe into the ground; the little pit he excavated slumped back immediately, like wet sand. “The rain is just going to soak away into this stuff. We ought to find the basin of a young crater. Maybe Aristarchus. The regolith is only a few inches thick there, and we should find liquid water pooling. Then we have to keep moving.”

“Moving? Where?”

“East, of course. We ought to go east.”

“Why?”

“Because night will come.” He looked at the sky, seeking the sun. “It isn’t lunar noon yet; we have some time. But the terminator, the line between night and day, moves across the landscape at around ten miles an hour. We can’t outrun it. We have to give ourselves as much time as we can, hope they get the resupply to us before night falls—”

“And what happens then?”

He looked at her, his eyes narrow over his mask. “Figure it out. No sunlight for fourteen days.”

“Oh. The mud is going to freeze—”

“Geena, depending on the atmospheric dynamics, the air is probably going to freeze. For two weeks the Moon will be like it used to be, and we’re going to have to find some way to live through it.” He shrugged. “Or maybe we should just hole up inside our lava tube. We’ll have to think about it. As long as it doesn’t collapse, or flood. I sure don’t want to be caught out in the open when the sun goes down. There will be a wind from hell, all that air sweeping around from the hot side to the cold—”

“But the air will boil off after dawn.”

“Most of it. Some of it is going to collect back where it came from, the cold traps at the Poles. And it will stay there. Nothing has changed the basic geometry of the Moon, Geena. Eventually all this lovely air will finish up back where it started, back at the Poles… Somebody is going to have to figure out a way to stop that, some day.

“But that won’t be for a while. For now, the comet debris is still boiling off, powered by the Moonseed… I figure things won’t start to stabilize until all the ice has boiled off. Which will take a year, at least.” He squinted at the Earth. “Maybe they will send the first biogens. There’s no reason to delay. Photosynthetic plants, algae maybe, to start the job of turning all this sunlight and carbon dioxide to oxygen and food.”

“Henry, how long is all this—” she waved a hand “—going to last?”

“Well, even if we keep it from freezing at the Poles, long-term the atmosphere is going to leak away into space. But it’s a slow process. It’s like putting a bucket of water in the desert. Sure, the water evaporates, but it takes a long time because it can only get out through the comparatively small surface area of the top. In the same way the upper rim of the atmosphere will only allow the air to leak out slowly…”

She pulled at her mask, adjusting it. “Always the scientist. You tell me everything except what I want to know. How long is long term, Henry?”

He shrugged. “Maybe ten thousand years.”

She said gently, “Time enough to think of something else, then.”

“I guess so. Come on. Let’s go pack.”

Side by side, arguing, planning, they walked back towards the lava tube.

2

A year later…

She was in hospital when Henry returned from the Moon.

She hadn’t wanted it this way, but the tests had become overwhelming: the best American technology, X-rays and scans and ultrasound and blood tests, and a whole set of -scopies which left her bewildered, sore and humiliated: sigmoidoscopy, colonoscopy, gastroscopy, bronchoscopy, cystoscopy.

“I didn’t know I had so many orifices,” she told Henry.

“Oh, Christ, Jane,” he said, and he sat on the edge of her bed.

After a year on the Moon his gait and movements were clumsy, as if he expected everything around him to happen in slo-mo. She could see where the rigours of reentry to Earth’s atmosphere had left him bruised, around the neck and eyes.

And every pore, every fold in his skin, was etched with deep-ingrained Moon dust.

Still, it was Henry, more dear to her than she had anticipated — and more distressed than she had, somehow, imagined, when she had played through this scene in her head.

“It isn’t so bad,” she said. “Leukaemia. I’m only here for tests; I’ll be out of here soon. I might live for years.”

“But not forever,” he said.

“No. Not forever.”

“It ain’t fair.”

He was trying to handle this, she realized, and she needed to give him time. She’d had more than a year to get used to the idea.

He said, “You never even told me.”

“The NASA psychologists wouldn’t let me. They were worried about your morale, up there on the Moon.”

“Pointy-headed assholes,” he murmured. He took her hand. “But it ain’t fair, whether you told me or not. I did it for you.”

“Did what?”

He shrugged. “Blew up the Moon. Saved mankind. Whatever it was I did it for you, for us. To give us a future.”

“Maybe the NASA shrinks were right, then.”

They fell silent, and started to avoid each other’s eyes.

After all, what were you supposed to say? How’s your cancer? How was life on the Moon?

She dug out a letter from the stack on her bedside table. “I got this from someone called Garry Beus.”

“Beus?”

“Son of Monica Beus? The physicist lady you knew?”

He nodded stiffly.

She said, “She learned about me, through my connection to you, before she died, and told Garry.” She glanced over the letter. “So he wrote to me. Kind thought. He’s in the Air Force here. He’s applying for the astronaut corps, the new Earth-Moon ferry pilot positions they are opening up… He says Monica left a memory box for him. Actually for his children, her grandchildren. Do you think I should do that for Jack?”

But he didn’t reply. When she looked up at him again he was crying, the tears spilling down his cheeks, pooling Moon dust in the lines under his eyes.