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…”

He felt his heart thump. The rille layers were a record of the Moon’s volcanism, the strata left by ancient basalt floods, driven by an internal heat that had all but died almost as soon as the Moon formed.

The only other volcanic remnants Apollo crews had found had been dug out by impacts, shattered and melted and reformed, scattered over the surface, heavily processed. In the rille walls, though, he was facing true lunar bedrock. What he had come for.

Samples of basalt from the maria — the lunar seas, like Apollo 11’s Tranquillity — would take you back as far as the age of mare volcanism, when founts of lava had flooded the great impact basins. But if you wanted to look further you had to go find bedrock: dusty windows on even greater antiquity, all the way back to the birth of the Moon.

Bedrock was the core of the mission, as far as Jays was concerned. And a big fat sample of bedrock, maybe from deep inside that old rille, would be his trophy fish.

He felt his soul expanding.

Nobody had ever seen this sight before, nobody. And, no matter who came after him, for whatever purpose, no matter how much smarter they were than him, they could never take that away. Schröter’s Valley would forever be a part of him.

He went over a crest, and was now descending into the rille itself. But there was no sharp drop-off; like every other surface here the rille wall was eroded to smoothness, and the footing was secure, the regolith layer thin.

For a moment he thought he glimpsed a stretch of the very bottom of the rille. Something shining there. But that was impossible, of course. It had to be a trick of the light. A scuff on his faceplate.

…And then he saw it, sheltering beneath a hummock in the regolith. It was a dark basalt, a lava lump about the size and shape of a football. When he brushed away the regolith he could see it was protruding from a rock layer, like the ones he could see so clearly on the far side of the rille.

Jays wanted to get this one right.

He took careful photographs of the rock in its resting place. Then he tried to set up the gnomon beside it, the smart little tripod that would give him scale, local vertical and orientation compared to the angle of the sun.

This was called documenting the sample. The idea was that back on Earth, if they knew exactly how the sample had been taken, the scientists would be able to reconstruct the geology of the area at leisure.

But the documenting turned out to be a scramble. The slope was too steep for the gnomon, and he wasn’t sure the photographs would pick out the rock from its background. He did his best; but the guys in the geology back rooms didn’t always understand how tough their procedures were to follow once you were here… Still, surely the rock would be worth it.

Of course the rock would be given a number of its own. A five-digit code: “eight” for Apollo 18, “six” because this was their sixth survey stop, and a number for the sample in the order they’d taken samples here, which had to be up in the forties or fifties already, he figured.

He bent sideways, stiff in his inflated suit. He was able just to pick up the rock; it fit his hand as if it had been meant for him.

He put his prize in a numbered Teflon bag. Then he photographed the place the rock had come from.

Movement. The dust was stirring, where he’d lifted the rock. When he looked again, the movement wasn’t there.

Never had been there. Been out here too long, Jays.

Tom was calling. They had to complete a rake sample, a random representative selection of the rocks here, and then move on.

He had just arrived, having come all this way, and it was already time to leave.

Jays took a last glance down inside the rille. He tried to peer down as deep as he could, straining to see to the bottom. The slope looked easy; he wished he could go a little further, deeper into the rille. But he knew he mustn’t. He was a long way from Tom’s helping hands, if he ran into trouble. And anyhow, he was behind the timeline.

He knew he wouldn’t mention what he’d seen to Tom.

On impulse, he leaned over, scooped up another fragment of the bedrock sample, stuffed it inside a sample bag and crammed it into a pocket on his leg.

Then, his bedrock under his arm, he snapped shut his sun visor and clambered back up the slope, towards Tom and the waiting Rover.

After a four-billion-year wait, the visit with its burst of activity had lasted only three days, the final flurry of dust settling after only seconds.

At Aristarchus Base, Rover tracks and footprints converged on the truncated base of the abandoned Lunar Module. The blast of the departed ascent stage’s engine had left a new ray system, streaks of dust which overlaid the footprints.

Now the Moon was inert once more, the sculpted hills of the Aristarchus ejecta blanket rising above this puddle of pitted, frozen basalt, their slopes bathed in sunlight, shining like fresh snow.

Waiting.

In places, the disturbed dust stirred. Glowed softly silver.

Geena Bourne woke up before dawn. She was, of course, alone in the apartment.

She got up in the dark and walked around putting on lights.

Henry had gone.

Fled. But he’d taken nothing. No furniture, no carpets or curtains, no CDs or books, not even his own clothes. Nothing but his geology hammer, as far as she could see.

Oh, and Rocky, their labrador, the Rock Hound.

Shit.

It was worse than if he’d taken everything, or trashed the place.

Still, she knew where he’d be. She pulled a coat over her pyjamas, got in the car and drove out, through the night, to the USGS.

It was cold. Always cold, here in the mountains.

The Cascades Observatory of the United States Geological Survey was a squat, unimposing two-storey building, a slab of cinder-block. In the harsh, incomplete glow of its security lights it looked sinister, like some prison block transported from Soviet Russia.

She had a little trouble with the guards. Lady, it’s 3 a.m. Do you know what time it is? 3 a.m… But her NASA pass and a little sweet-talking got her inside.