He was still dog tired after the trip. But he couldn’t sleep. Even when he lay flat in his bunk, he said, it felt as if his body was tilted head down. There was, he said, too much gravity here.

A lot of stuff had happened up there, she suspected, that he would never tell her.

He ruffled her hair. “You think you’ll ever get to go to the Moon?”

“What for? There’s nothing there but a bunch of old rocks.”

“I thought you liked rocks. Your collection—”

“I like real rocks.”

“Moon rocks are real.”

“But they won’t let you touch “em.”

“Maybe. Anyhow, you’re wrong. About the Moon. It’s not just rocks. If you lived there you could make metals, and oxygen to breathe, and there’s silica to make glass. And with the water from the Poles, you could farm up there.”

“Water? I thought there’s no air.”

“There isn’t. But there is ice at the Poles. Deep in the dark, where the sun never shines.”

“Really? A lot of ice?”

Her father hesitated. “Well, some people think so.”

“Anyhow,” she said, “I don’t want to be a farmer.”

Her father stared up at the Moon. “You know, you’re special. I wrote your name up there, in the dust, and it will be there for a million years.”

“You told me, Dad.”

“Yeah.”

A cloud passed over the Moon’s face. It got colder.

They went indoors to watch TV.

One day, human scientists would call it the Impactor.

It had about the mass of Mars, a tenth of Earth’s. Humans would later speculate that it was a young planet in its own right.

But they were wrong. It was not a planet.

The object barrelled through the dusty plane of the Solar System.

But there seemed to be something in the way.

…And on the Moon, the Rover had jolted across the bright dust, climbing gentle slopes under the black sky, bathed in the sun’s flat light.