The backpack’s pumps and fans whirred, and she could feel the soft rush of oxygen over her face. The pack was a reassuring mass on her back, replete with energy, supplies for heat and cooling, water, air; she was a little bubble of Earth life, she thought, bouncing around on the surface of the Moon.

Maybe fifty yards from the Shoemaker, she turned to face the sun. The light glared through her gold-tinted faceplate. There stood the Shoemaker, Henry on it watching her, a little gold-coloured platform with a white snowman perched on the top. The lander looked strangely light, as if it might blow away. Its gaudy gold and black and silver looked ludicrous: overdesigned, for this gentle, subtle landscape.

Behind the Shoemaker she looked across the width of a big crater, a bowl bigger than a football stadium, shadows stretching across the ground towards her from rocks and craters. She could see the old Apollo lander, nestled close to the crater’s shadowed far wall, a squat, boxy structure, unmistakeable.

And there, only a hundred yards from the Apollo, stood the second Shoemaker, laden with the supplies that would keep them alive.

“How about that,” she said. “Can’t be more than six hundred feet away.” She felt elated — the first lunar landing for more than thirty years, and it was pinpoint accurate. “Outstanding.”

“You got the job,” Henry said drily. “Now, will you help me down from here?”

So here was Henry, unbelievably, standing on the Moon, a geologist on the ultimate field trip. He turned, slowly, trying to understand where he was. The sun dominated seeing on the Moon, he realized immediately.

The sun was like a giant, intensely bright searchlight, pure white, overwhelming everything, and the mental picture he built up of the landscape here depended completely on the angle to the sun.

At zero phase angle — if he looked down-sun, with his own shadow stretching across the untrodden surface — it was difficult for him to make out shadows. Most objects were visible, but the contrasts were washed out. But he could see shadows if he looked cross-sun, so the trick was to look from left to right, to pick up the shadows, and shapes and sizes and glints, and he could orient himself that way. And if he walked up-sun, with the shadows stretching towards him, the sun was very bright, glaring in his visor.

When he looked at his own shadow the sunlight around it came bouncing straight back at him. The shadow of his body was surrounded by a glow, a halo around his helmet.

He inspected the mineral ground. Cinereous, he thought. The colour of ash…

But there were colours here, he realized suddenly.

He stopped and looked around more carefully.