He took his instrument bag off his shoulder, and placed it carefully at the back of the ledge. Then he got to his knees, and crept forward to the lip of the ledge. The suit fought him the whole way, but he crawled determinedly.

He stuck his head over the edge.

His torchlight splashed down over the steepening rille wall. More basalt layers. He inspected them briefly, noting their thickness, their difference in composition.

The whole history of mare volcanism was laid out here, clear as a road-map. He longed for a couple of grad students, a truck-load of sample bags. Maybe just by visual inspection, a couple of samples, he could achieve some good science here…

But he knew he mustn’t. His objective lay further on, and he must hurry to achieve it before his life support limits cut him short.

He lifted his head, and let his torch beam play further down the slope.

It looked as if the base of the rille, here, was no more than thirty or forty feet below him. The surface was smooth, silvery and flat.

It looked as if a river of some fluid had been dammed here.

Moonseed dust.

He raised his head further. His ellipse of light lengthened, until the glow became too attenuated to make out. As far as he could see, across the width of the rille, and to left and right along its length, the Moonseed dust lay, shimmering in his torchlight. It looked as if a river of mercury had come lapping through the rille’s dusty walls.

He found a loose rock, a fist-sized pebble an arm’s-length away. On impulse, he picked it up. He looked at the big astronaut’s Rolex on his wrist, set its timer, and dropped the rock.

He watched the rock fall, at first with dreamy slowness, and then with greater, more Earth-like velocity as the slow gravity had time to work. If he got the timing right he would be able to calculate pretty accurately how far below him that surface was…

In the light of his torch, the rock hit the surface, and disappeared. The Moonseed dust closed over it without a ripple, as if it had never existed.

He checked his watch. Four seconds. The Moonseed was forty-two, forty-three feet below him.

He knew he had to wait for the results of his seismic analysis. But already he knew what he would find out.

The whole damn Moon was rotten with Moonseed, just as he’d suspected.

And yet the Moon was still here, unlike Venus.