And upon Earth, there must be many eyes turned toward the waxing Moon more than ever before, now that the Moon meant so much to mankind. It was possible, but unlikely, that even now some of those eyes were peering through powerful telescopes at the faint spark of Selene's floodlights as it crept through the lunar night. But it would mean nothing to them when that spark flickered and died.
For a million years the bubble had been growing, like a vast abscess, below the root of the mountains. Throughout the entire history of Man, gas from the Moon's not yet wholly dead interior had been forcing itself along lines of weakness, accumulating in cavities hundreds of meters below the surface. On nearby Earth, the ice ages had marched past, one by one, while the buried caverns grew and merged and at last coalesced. Now the abscess was about to burst.
Captain Harris had left the controls on autopilot and was talking to the front row of passengers when the first tremor shook the boat. For a fraction of a second he wondered if a fan blade had hit some submerged obstacle; then, quite literally, the bottom fell out of his world.
It fell slowly, as all things must upon the Moon. Ahead of Selene, in a circle many acres in extent, the smooth plain puckered like a navel. The Sea was alive and moving, stirred by the forces that had waked it from its age-long sleep. The center of the disturbance deepened into a funnel, as if a giant whirlpool were forming in the dust. Every stage of that nightmare transformation was pitilessly illuminated by the earthlight, until the crater was so deep that its far wall was completely lost in shadow, and it seemed as if Selene were racing into a curving crescent of utter blackness an arc of annihilation.
The truth was almost as bad. By the time that Pat had reached the controls, the boat was sliding and skittering far down that impossible slope. Its own momentum and the accelerating flow of the dust beneath it were carrying it headlong into the depths. There was nothing he could do but attempt to keep on an even keel, and to hope that their speed would carry them up the far side of the crater before it collapsed upon them.
If the passengers screamed or cried out, Pat never heard them. He was conscious only of that dreadful, sickening slide, and of his own attempts to keep the cruiser from capsizing. Yet even as he fought with the controls, feeding power first to one fan, then to the other, in an effort to straighten Selene's course, a strange, nagging memory was teasing his mind. Somewhere, somehow, he had seen this happen before.
That was ridiculous, of course, but the memory would not leave him. Not until he reached the bottom of the funnel and saw the endless slope of dust rolling down from the crater's star-fringed lip did the veil of time lift for a moment.
He was a boy again, playing in the hot sand of a forgotten summer. He had found a tiny pit, perfectly smooth and symmetrical, and there was something lurking in its depths something completely buried except for its waiting jaws. The boy had watched, wondering, already conscious of the fact that this was the stage for some microscopic drama. He had seen an ant, mindlessly intent upon its mission, stumble at the edge of the crater and topple down the slope.
It would have escaped easily enough but when the first grain of sand had rolled to the bottom of the pit, the waiting ogre had reared out of its lair. With its forelegs, it had hurled a fusillade of sand at the struggling insect, until the avalanche had overwhelmed it and brought it sliding down into the throat of the crater.
As Selene was sliding now. No ant lion had dug this pit on the surface of the Moon, but Pat felt as helpless now as that doomed insect he had watched so many years ago. Like it, he was struggling to reach the safety of the rim, while the moving ground swept him back into the depths where death was waiting. A swift death for the ant, a protracted one for him and his companions.
The straining motors were making some headway, but not enough. The falling dust was gaining speed and, what was worse, it was rising outside the walls of the cruiser. Now it had reached the lower edge of the windows; now it was creeping up the panes; and at last it had covered them completely. Pat cut the motors before they tore themselves to pieces, and as he did so, the rising tide blotted out the last glimpse of the crescent Earth. In darkness and in silence, they were sinking into the Moon.
CHAPTER 3
In the banked communications racks of Traffic Control, Earthside North, an electronic memory stirred uneasily. The time was one second past twenty hundred hours GMT: a pattern of pulses that should arrive automatically on every hour had failed to make its appearance.
With a swiftness beyond human thought, the handful of cells and microscopic relays looked for instructions. WAIT FIVE SECONDS, said the coded orders. IF NOTHING HAPPENS, CLOSE CIRCUIT 10011001.
The minute portion of the traffic computer as yet concerned with the problem waited patiently for this enormous period of time long enough to make a hundred million twenty figure additions, or to print most of the contents of the Library of Congress. Then it closed circuit 10011001.
High above the surface of the Moon, from an antenna which, curiously enough, was aimed directly at the face of the Earth, a radio pulse launched itself into space. In a sixth of a second it had flashed the fifty thousand kilometers to the relay satellite known as Lagrange II, directly in the line between Moon and Earth. Another sixth of a second and the pulse had returned, much amplified, flooding Earthside North from pole to equator.
In terms of human speech, it carried a simple message. HELLO, SELENE, the pulse said. I AM NOT RECEIVING YOUR BEACON. PLEASE REPLY AT ONCE.
The computer waited for another five seconds. Then it sent out the pulse again, and yet again. Geological ages had passed in the world of electronics, but the machine was infinitely patient.
Once more, it consulted its instructions. Now they said: CLOSE CIRCUIT 10101010. The computer obeyed. In Traffic Control, a green light flared suddenly to red, a buzzer started to saw the air with its alarm. For the first time, men as well as machines became aware that there was trouble, somewhere on the Moon.
The news spread slowly at first, for the Chief Administrator took a very poor view of unnecessary panic. So, still more strongly, did the Tourist Commissioner; nothing was worse for business than alerts and emergencies even when, as happened in nine cases out of ten, they proved to be due to blown fuses, tripped cutouts, or oversensitive alarms. But on a world like the Moon, it was necessary to be on one's toes. Better be seared by imaginary crises than fail to react to real ones.
It was several minutes before Commissioner Davis reluctantly admitted that this looked like a real one. Selene's automatic beacon had failed to respond on one earlier occasion, but Pat Harris had answered as soon as he had been called on the cruiser's assigned frequency. This time, there was silence. Selene had not even replied to a signal sent out on the carefully guarded MOONCRASH band, reserved solely for emergencies. It was this news that brought the Commissioner hurrying from the Tourist Tower along the buried glideway into Clavius City.
At the entrance to the Traffic Control center, he met the Chief Engineer, Earthside. That was a bad sign; it meant that someone thought that rescue operations would be necessary. The two men looked at each other gravely, each obsessed by the same thought.
I hope you don't need me, said Chief Engineer Lawrence. Where's the trouble? All I know is that a Mooncrash signal's gone out. What ship is it?
It's not a ship. It's Selene; she's not answering, from the Sea of Thirst.