Mikhail’s interest in this place was not lunar ice, however, but solar fire.

He turned away from the shadows and began to toil up the steepening slope of the rim mountain toward the light. The path was just a trail, beaten flat by human footprints. It was marked by streetlights, as everybody called them, small globe lamps hung from poles, so he could see what he was doing.

The slope was steep, each step an effort even in the Moon’s gentle one-sixth gravity. His suit helped, with a subtle hum from exoskeletal servos and a high-pitched whir of the fans and pumps that labored to keep his faceplate clear of condensed sweat. He was soon breathing hard, and his muscles ached pleasantly: this walk was his daily constitutional.

At last he reached the summit of the mountain and emerged into flat sunlight. A small collection of robot sensors huddled here, peering with unending electronic patience at the sun. But the light was too brilliant for Mikhail’s eyes, and his visor quickly opaqued.

The view around him was still more dramatic, and complex. He was standing on the rim of Shackleton, itself a comparatively minor crater, but here at its western rim Shackleton intersected the circles of two other craters. The landscape was jumbled on a superhuman scale: even the craters’ far rims were hidden by the Moon’s horizon. But with long practice Mikhail had trained himself to make out the chains of mountains, slowly curving, that marked the perimeters of these overlapping scars. And all this was thrown into stark relief by the low light of the sun as it rolled endlessly around the horizon, the long shadows it cast turning like clock hands.

The South Pole, shaped when the Moon was young by an immense impact that had bequeathed it the deepest crater in all the solar system, was the most contorted landscape on the Moon. A greater contrast to the flat basalt plain of Tranquillity where Armstrong and Aldrin had first landed, far to the north close to the Moon’s equator, would be hard to imagine.