The wheels, each spun by an independent electric motor, dragged at the dust. The Rover bucked like an aluminum bronco, bounding out of its thirty-year parking spot, throwing Henry against his straps.

Following Apollo tracks as fresh as if they had been laid down yesterday, they headed east, towards the rille.

It was an exciting ride.

The turns were sharp. Every time Geena steered, all four wheels swivelled. The ground here was all bumps and hollows, an artillery field of craters, and every time they hit an obstacle one or two wheels would come looming off of the ground.

Henry, strapped to his lawn chair on top of this thing, was thrown around, especially when Geena took a swerve to avoid a rock or a crater.

“Holy shit,” he said.

“Don’t be a baby,” Geena said. “It’s only eight miles an hour. We’d be beaten by a San Francisco cable car.”

“Yeah, but how many hummocks per hour are we hitting?”

Geena pushed up the speed. The Rover bounced high off the ground, and threw up huge rooster tails of black dust behind them.

“Let me explain something to you,” she said as she drove. “Our consumables are being used up all the time.”

“Sure.”

“So at no point are we going to drive further than our walkback limit.”

“Which is the distance we can walk back to the shelter, with the oxygen in our backpacks. In case the Rover breaks down. I know. That makes sense to me.”

“Yes. But because our consumables go down steadily, that walkback limit gets tighter and tighter with time. And we are going to stay within that limit, all the time.”

“Sure,” Henry said.

“If that means we have to leave the rille before you’re ready, we do it. If it means we have to miss out on interesting-looking detours, we do it.”

“Geena—”

“And I’m going to be conservative, because the navigation computer on this thing doesn’t work any more. As far as walkback is concerned I’m the boss.”

He shrugged, a clumsy gesture in his suit. “Sure. You’re the boss.”

If she wanted to feel in control, if that was her way of avoiding the funk she suffered on the way in, it was fine by him.

…There were, Henry realized afresh, craters everywhere.

Some of the craters were subdued depressions, almost rimless, as if dug out of loose sand. They were easy to traverse; the Rover just rolled down a gentle slope. But others — mostly smaller — were sharper, with well-defined rims, the classic cup shapes of story books. The younger craters were full of rubble, like builders” slag, concentrations of angular blocks, and they had littered rims. Geena had to drive around those babies.