He stood still. He leaned forward and checked the gauge on his chest. There was no change, and he didn’t feel any difference. Just that one pop.

Maybe he had bumped against the oxygen inflow port, or the outflow. If he obstructed the flow, that would cause a momentary transient; it might even have been a slight increase in pressure.

His monitors stayed stable. A glitch, then.

The incident was enough to brush him with fear.

Sobered, he went to work.

Side by side, carrying tools and equipment, they walked away from the Shoemaker, towards the Rover.

The Apollo Lunar Rover was a home-workshop beach buggy: about the size of a low-slung jeep, but with no body, or windshield, or engine.

“Oh, shit,” Henry said. “Have we really got to ride this thing?”

“Better than walking. You know what the Apollo guys called it?”

“Hit me.”

“Chitty Chitty Boeing Boeing.”

They bounced around the Rover, inspecting it.

The Rover was an aluminum frame, ten feet long, maybe six wide. It had four fat wheels — actually not quite wheels, but wire mesh tyres, with metal chevrons for tread. There were fenders, of orange fibreglass. There were two bucket seats with plastic webbing, and a minimal controller — just a gearshift-like hand controller between the seats, and a display console the size of a small TV. No steering wheel. At the back of the buggy there were bags for storage of equipment and samples.

The front of the thing was cluttered up with cameras and comms equipment. The TV camera still pointed at the sky, where it had followed the final departure of the astronauts in their LM ascent stage. The camera was coated in insulation foil, which had split and cracked. The umbrella-shaped high-gain antenna still pointed at Earth, where the Apollo astronauts had left it, for the Earth had not moved in all the years since.

This Rover was a working vehicle. He could see how the straps on the backs of the frame chairs were stretched and displaced from use. There were still dusty footprints on the foot rests fitted to the ribbed frame, and the mark of a hand, imprinted in lunar dust, on the TV camera’s insulation. And one fender at the rear had cracked, and had been crudely patched with silver wire and what looked like a checklist cover, though the text and graphic had long since faded. The Rover looked as if it had been used just yesterday, as if its original drivers would come back in a couple hours for a fourth or fifth EVA.

Tracks, crisply ribbed, snaked off back over the ground, diminishing into the distance.

The Rovers had been built from scratch by Boeing in just two years. There had only ever been four of these babies, and all of them had been flown to the Moon, and all of them had been left up here, in the clean airless sunlight. Two million bucks apiece.