Jays took a swig of water from the bag inside his suit. He felt his chin strap rasp against a week-old beard. He’d promised his daughter, Tracy, that he wouldn’t shave until he got home. After all, in the picture books, the explorers always came home with beards.

The Rover’s television camera was watching him, cold and judgemental. Time is ticking on, it seemed to say, billion-dollar seconds wasting while you stand there and goof off.

He turned and continued.

He reached a flat crest, and came suddenly on the rille.

He stopped. He raised the five-hundred-mil camera from its bracket on his chest, and took a horizontal pan, turning slowly, and then a vertical pan, all the time geologizing, describing what he saw.

The rille was up to eight miles wide, a half-mile deep, and all of a hundred miles long. Schröter’s Valley, the biggest rille known on the Moon. It was a river valley, but cut into the bottom of this dead lunar sea — not by water — by a lava flow, some time in the deep past.

He stepped forward again.

As he approached, the surface of the mare sloped gently towards the rille rim, and the regolith was getting visibly thinner. The rille walls sloped at maybe twenty-five or thirty degrees.

The sun was behind him. The far walls were in full sunlight, and now Jays was sure he could see layers: distinct strata in the rock, poking through the light dust coating.

Excited, he described what he saw. “Okay, Joe, I think I can see from top to bottom, one distinct layer about ten per cent, which has multiple layers within it. And another at about forty per cent down, which looks like a solid unit of a somewhat harder, tan-coloured rock, but it’s covered with fines and talus. We haven’t seen to the bottom; I think I’ll get the chance to go further down…”