When they were done they decompressed the shelter and climbed out, one by one, like fat grey-white grubs pushing out of a discarded shell.

He felt as if he was in some immense darkened room, where the light didn’t quite reach the walls, so that he was suspended in a patch of light in the middle of a darkened floor.

A morning that lasts a week. They’d first landed at something like 6:30 a.m., local time. The twelve hours they’d spent inside the shelter were equivalent to something like a half-hour in the lunar “day’: enough to shrink the shadows a little, but not by much.

Even so, all the pooled shadows were different, changing the feel of the landscape. Even the colours had changed, Henry saw, because the colours depended on the angle to the sunlight; the greys and browns, changing as he looked around, seemed to him a little more vivid.

He kept thinking he saw features, rocks and craters, he hadn’t noticed yesterday; but he soon realized they were the same rocks under different lighting, like a movie set that had been reassembled. The slopes of the crater walls and ejecta hills looked much less severe, almost gentle: not nearly the challenge they’d appeared yesterday. Maybe that was true. Maybe he was being fooled in the other direction.

The Moon was full of optical illusions, he thought. Given there was nothing here but bare rocks and flat sunlight, that was kind of surprising. It was a stage set put together by a master illusionist, a minimalist.

Maybe, he thought moodily, the Moon really is a magic world, a world of dream or nightmare, a world where distances and times can shift and swim, like a relativity student’s fever dream.

The Moon was, undoubtedly, a stranger and more interesting place than he expected.

He started to collect the equipment they would need for the day: tools and a couple of batteries for the Rover, his geological gear.

Reaching to lift a bag, he leaned too far, and fell.

When the fall began, his balance was lost quickly, especially when he tried to back up. The ground was uneven everywhere, and he kept treading on rocks and crater holes that made him stumble further. Besides, the heavy pack at his back gave him a centre of gravity aft of his midline, so he was always being pulled backwards.

But he fell with a dreamy slowness, like falling underwater. He had time to twist around, the stiff suit making him move as a unit, like a statue, and he could catch his footing before he fell. He just spun around, bent his knees and recovered, scuffing his feet to get them under him again.

Then he felt his ears pop.

He had to be losing pressure. He felt his heart pounding. Maybe he should call Geena.