the heart of Jupiter V. It was at least a quarter of a mile in length, and perhaps a hundred yards wide.
Time and geology could play some odd tricks with a world; but this was not one of them.
It was an unusually quiet and subdued group that gathered in the artificial gravity of the carousel for the luxury of coffee that could actually be drunk from cups, not squirted from plastic bulbs.
The wonder and the excitement of the discovery had already passed, to be replaced by more somber feelings. What until now had been only a possibility-and, to tell the truth, rather a remote one-had suddenly become an awesome reality. That pyramid on the Moon had been astonishing, but it was only a tiny thing. This was something altogether different-a whole world with a slice carved off, just as one may behead an egg with a knife.
'We're up against a technology,' said Bowman soberly, 'that makes us look like children building sandcastles on the beach.'
'Well,' answered Kaminski, 'we suspected that from the beginning. Now the big question is-are they still here?'
Jupiter V looked utterly lifeless, but an entire civilization could exist, miles below the surface, at the bottom of that rectangular chasm. The creatures who put TMA-1 on the Moon, three million years ago, could still be going about their mysterious business.
Perhaps they had already observed Discovery, and knew all about this mission. They might be totally uninterested in the primitive spacecraft orbiting at their threshold; or they might be biding their time.
FINAL ORBIT
This was the situation classified in the mission profile as 'Evidence of intelligent life-no sign of activity,' and the response had been outlined in detail. They would do nothing for ten days except transmit the prime numbers 1 . . . 2 . . . 3 . . . 5 . . . 7 . . . 11 . . . 13 . . . 17, at intervals of two minutes, over a broad band of the radio spectrum. Luckily, the loss of the main antenna complex did not affect this operation; the low-powered equipment on the Control Deck was quite adequate for such short-range work.
They called, and they listened on all possible frequencies; but there was no reply. Though this could indicate many things, it began to seem more and more likely that the tiny moonlet was abandoned. It was hard to believe that it could ever have been anything except a temporary encampment for an expedition-from Jupiter itself, or from the stars?
While they were waiting and watching, and continuing to survey the other four moons whenever the opportunity arose, Bowman prepared for the next step. If it was physically possible, Discovery would make a rendezvous with Jupiter V.
Kaminski spent hours considering approach orbits; Athena spent seconds computing them. The maneuver was a very difficult one, for though Jupiter V's own gravity was negligible, the satellite was trapped deep in Jupiter's enormous gravitational field. Discovery would have to make a speed change of over twenty thousand miles an hour to match orbits and achieve a rendezvous.
It could just be done-and, ironically, only the earlier disasters made it possible. The ship was more than a ton lighter than expected at this stage of the mission, for it had lost two crew members, a spacepod, and the antenna complex. That was enough to make the difference between a maneuver that was barely feasible, and one which had a good safety margin.
Once Discovery had entered the parking orbit around Jupiter V, she could never leave it; her propellant reserves would be completely exhausted. And though the recovery ship would hardly expect to find her here, it would soon spot her radio beacon and her flashing strobe lights. Nuclear batteries would power them for twenty years; their detectable range was only about a million miles, but that was ample.
As soon as he was sure of the calculations, Bowman wasted no more time. The ten days were up: Jupiter V was still silent. The mission profile said: 'Proceed with caution-in the event of hostility, withdraw.'
That was excellent advice-except that retreat would be impossible. Once they had used their final reserves, they would be wholly committed.
After more than fifty orbits of Jupiter V, they had mapped and inspected its entire surface, most of which was covered with an icy rime of frozen ammonia. There was no sign of life, no hint of any activity. A search for radio emissions or electrical interference was fruitless; the little moon appeared to be completely dead. The theory that it was some kind of abandoned base, perhaps even a deserted city-world that ages ago had come here from some other solar system, slowly gained ground. Hunter was its chief advocate; when asked where he thought the hypothetical star– people had gone, he answered: 'I think they were our ancestors.' He was more than half serious about this, and refused to budge in the face of all the anthropological and geological evidence that could be thrown at him.
On the fourth day they dropped two of the ship's soft-landing probes-one on Kimball's Plain, the other at its antipodes. The radioed reports were inconclusive: the seismographs could detect no tremors-the sensitive geophones, not a whisper of internal sound. As far as the instruments could tell, Jupiter V was a dead lump of rock.
After two more days of waiting to see if anything had emerged to investigate the probes, Bowman made his decision. The others had been expecting it; from time to time, each had quietly hinted to Bowman that he should be the one to make the first reconnaissance.
In the carousel lounge, which had once seemed so small but was now, alas, larger than they required, he outlined the plan.
'We have only two pods,' Bowman began, 'and I'm going to commit them both: I think it will be safer that way. If one gets in trouble, the other will be there to help.
'Two pods will go down to the surface; one will stay on the brink of the chasm and the other will go in for a distance of not more than a thousand meters-less, if there's the slightest sign of danger. I'll take the forward one; Jack will be my Number Two.'
At this, there were groans from Kaminski and Hunter; Bowman smiled and shook his head firmly.
'You have to stay behind and run the ship. If we don't come back, there's absolutely nothing you can do to help us. Your job is to watch, record what happens, and see that Earth gets the story-even if it's five years from now.'
He listened patiently while Hunter and Kaminski pressed their superior claims, but he had already made up his mind. They were all equally qualified, but Kimball had discovered this place, and it now bore his name. It was only fair that he should be first to set foot on it.
Within an hour, the airlocks opened and the two little pods jetted themselves slowly out into space. After a few seconds of careful braking, they had checked their orbital speed, and Discovery was pulling away from them at her regular two hundred miles an hour. They were falling free, in the weak gravity field of Jupiter V. Their tenthousand-foot drop here was equivalent to a fall of less than a hundred feet on earth; they could wait until they were quite close to the surface before attempting to brake.
After a one-minute hover at a thousand feet, Bowman gave the signal for the final descent. There were no landing problems on this utterly flat plain, and he had decided to come down within a hundred yards of the pit. A last burst of power canceled the space pod's five or six pounds of weight, and he hovered for a second to give Kimball the privilege of landing first. Then he touched down on Jupiter V with scarcely a bump.
He glanced out of the port, saw that Kimball was O.K., and called the ship.
'Bowman to Discovery. Landed on Jupiter V. Can you read me?'
The answer, as he had expected, was already fading. In the few minutes of their descent, the ship's orbit had taken it down to the horizon, and was dropping below the edge of the satellite.
'Discovery to Bowman. Message received but signal strength fading. Good luck. Will listen out and call you in ninety minutes.'
'Roger.'
Discovery was gone-not yet twenty miles away, but out of reach. It was true that she would be back again, by the inexorable laws of celestial mechanics, in just one and a half hours as she came up over the opposite horizon of this tiny world. That knowledge was some help, but not as much as they would have liked, to a pair of lonely men faced with a three-million-year-old enigma
