A Fall of Moondust

Lawson had just begun to dismantle the infrared scanner when he stopped to consider his action. Since he had practically completed the blasted thing, he might as well test it, out of sheer scientific curiosity. He prided himself, rightly, as a practical experimenter; this was something unusual in an age when most so-called astronomers were really mathematicians who never went near an observatory.

He was now so tired that only sheer cussedness kept him going. If the scanner had not worked the first time, he would have postponed testing it until he had had some sleep. But by the good luck that is occasionally the reward of skill, it did work; only a few minor adjustments were needed before the image of the Sea of Thirst began to build up upon the viewing screen.

It appeared line by line, like an old-fashioned TV picture, as the infrared detector scanned back and forth across the face of the Moon. The light patches indicated relatively warm areas, the dark ones, regions of cold. Almost all the Sea of Thirst was dark, except for a brilliant band where the rising sun had already touched it with fire. But in that darkness, as Tom looked closely, he could see some very faint tracks, glimmering as feebly as the paths of snails through some moonlit garden back on Earth.

Beyond doubt, there was the heat trail of Selene; and there also, much fainter, were the zigzags of the dust-skis that even now were searching for her. All the trails converged toward the Mountains of Inaccessibility and there vanished beyond his field of view.

He was much too tired to examine them closely, and in any event it no longer mattered, for this merely confirmed what was already known. His only satisfaction, which was of some importance to him, lay in the proof that another piece of Lawson-built equipment had obeyed his will. For the record, he photographed the screen, then staggered to bed to catch up with his arrears of sleep.

Three hours later he awoke from a restless slumber. Despite his extra hour in bed, he was still tired, but something was worrying him and would not let him sleep. As the faint whisper of moving dust had disturbed Pat Harris in the sunken Selene, so also, fifty thousand kilometers away, Tom Lawson was recalled from sleep by a trifling variation from the normal. The mind has many watchdogs; sometimes they bark unnecessarily, but a wise man never ignores their warning.

Still bleary-eyed, Tom left the cluttered little cell that was his private cabin aboard Lagrange, hooked himself on to the nearest moving belt, and drifted along the gravityless corridors until he had reached the Observatory. He exchanged a surly good morning (though it was now late in the satellite's arbitrary afternoon) with those of his colleagues who did not see him in time to take avoiding action. Then, thankful to be alone, he settled down among the instruments that were the only things he loved.

He ripped the photograph out of the one-shot camera where it had been lying all night, and looked at it for the first time. It was then that he saw the stubby trail emerging from the Mountains of Inaccessibility, and ending a very short distance away in the Sea of Thirst .

He must have seen it last night when he looked at the screen—but he had not noticed it. For a scientist, that was a serious, almost an unforgivable, lapse, and Tom felt very angry with himself. He had let his preconceived ideas affect his powers of observation.

What did it mean? He examined the area closely with a magnifier. The trail ended in a small, diffuse dot, which he judged to be about two hundred meters across. It was very odd—almost as if Selene had emerged from the mountains, and then taken off like a spaceship.

Tom's first theory was that she had blown to pieces, and that this smudge of heat was the aftermath of the explosion. But in that case, there would have been plenty of wreckage, most of it light enough to float on the dust. The skis could hardly have missed it when they passed through this area—as the thin, distinctive track of one showed it had indeed done.

There had to be some other explanation, yet the alternative seemed absurd. It was almost impossible to imagine that anything as large as Selene could sink without trace in the Sea of Thirst , merely because there had been a quake in that neighborhood. He certainly could not call the Moon on the evidence of a single photograph and say, “You're looking in the wrong place.” Though he pretended that the opinion of others meant nothing to him, Tom was terrified of making a fool of himself. Before he could advance this fantastic theory, he would have to get more evidence.

Through the telescope, the Sea was now a flat and featureless glare of light. Visual observation merely confirmed what he had proved before sunrise: there was nothing more than a few centimeters high projecting above the dust surface. The infrared scanner was no greater help; the heat trails had vanished completely, wiped out hours ago by the sun.