by Isaac Asimov
Travel was fast, in spite of its awkwardness. ZH50 spoke occasionally to guide his companions away from the deeper chasms, though one or the other of them would sometimes issue a startled gasp or exclamation when carried by a “step” over a drop deep enough to jar an Earth-trained nervous system but dismissed by the robot as safe. Their startlingly sharp shadows, that of each helmet surrounded by a Brocken halo visible only to its owner, pointed the way. Dibrofiad was quickly out of sight; even had Miranda been smooth, five kilometers would have put the ship below the horizon.
Finally Chile stopped them with a gesture. “We turn left here. A straight path toward the point marked by Dumbo would have brought us to the foot of Barco. Be careful; there is less than a kilometer to go. Be sure to aim no step beyond a spot you can see.”
The speed of the group slowed accordingly, until he stopped them again. “Tripod fashion from now on; use your sticks. No free fall.”
An unusually smooth horizon now faced them. Neither Rob nor Sheila could estimate its distance; none of the numerous wrinkles and shadows on the ground ahead offered any clue to size, and there was no reason to suppose the general surface was horizontal even if they had been able, in the feeble gravity, to be sure of vertical. They knew from the Dumbo display that there was a possibly lethal drop beyond the edge, but this could have been fifty meters away or five hundred.
“Where’s the spur?” Sheila asked.
“There.” Chile pointed. “Its tip has enough downslope to be invisible from where we stand, though if you jump straight up for a few meters you could distinguish
“Thanks, I’m not sure I could go straight up. I’ll take your word. What’s the actual distance?”
“We are just under one hundred fifty meters from the main line of the edge and from the base of the spur. I advise you not to get any closer, but if you want to see me all the way to the end, you will have to. Please go very slowly indeed, and do not pass me under any circumstances.”
Nearly erect now, using the alpenstocks, and never having more than one foot or stick off the ice at a time, the trio edged forward.
“I wish you would stay back,” Chile repeated when the distance had shrunk to fifty meters. “We have no data on the strength of this ice. We could be providing the heaviest load it has experienced since it formed. It would be much safer if I went forward alone and brought back whatever may be there.”
“No collecting yet, Chile,” Sheila replied. She made no comment on the danger the robot had implied, but was conscious of it. The cliff might even have an overhang. “Nothing gets moved from its original site until we make final decision about what’s coming home with us. We don’t want to spoil more than we can help for later researchers.”
The robot, who knew this perfectly well, made no reply; but both Sheila and Rob knew that First Law tension must be building up in him. They kept safely behind him as he approached the edge, the woman doing nothing to oppose her companion’s obvious intention to keep ahead of her, and stopped when they were close enough to see the far end of the projection.
There was something there. Ling had a scope – a monocular whose eye relief allowed it to be used through his face plate – but this was little help. He could tell that the object was cubical like the other finds, but much larger, seven or eight centimeters on the edge. It seemed to have been set into the dirty ice of the cliff, with two thirds of its height above the surface and an equal fraction projecting outward. The cube faces they could see appeared to be covered with regular lines of dots which sparkled faintly on their mirror-like background.
“How close do you think you can get, Chile?” the man asked at length, after Sheila had also done her best with the scope.
“Close enough to pick it up, if you wish. I can concentrate better if you stay back.”
“Don’t touch it, but examine it as closely as you can. We’ll wait here on the solid ground; I have some First Law tensions myself, now that we’re near enough to the edge to look down,” Sheila responded.
“Good. I’ll crawl, to get my head as close to it as possible. Shall I keep reporting to you as I note anything new, or merely log it as usual?”
“Don’t bother to tell us. Concentrate on observing.”
That may have been an unfortunate command, especially since both human beings were concentrating on the robot.
Chile’s “crawl” was faster than either watcher would have dared; it took him off the ground for a second or two every now and then. The surface, however, even out on the spur, was cracked and jagged enough to provide grips, so he retained control of his motion.
As he neared the end, his head hid the cube from the watchers. Ling started to move to one side to clear the view, but thought better of it after a step or two; he would have to go too far to be worth the risk.
“I have recorded everything I can sense,” Chile reported after a minute or so.
“What is it? What have you found?” Bronwen’s voice reached them.
“You report, Chile. You can tell her more than we,” ordered Sheila before Ling could start talking.
“It is a cube, six times the linear dimension of those we have found already, to the same four significant figures by which they match each other” replied ZH50. “As far as is revealed by any radiation I can perceive, it is made of the same material. The three vertical faces I can see are covered with a pattern of –”
“Sheila! Back!”
Ling, facing sideways to keep both his companions in view, had seen the danger first, and tucked up at the sight; his cry startled the woman into a different reaction, unfortunately. She straightened slightly, and the motion carried her several centimeters upward.
The crack and bump pattern around their feet had not changed, but a new cliff had reached a height of several centimeters a couple of body lengths behind them. The woman couldn’t quite see it; she had no ground contact t? let her turn, and the face plates limited the field of view.
“Jump back! At least ten meters! The cliff face is letting go!”
Sheila lashed downward with her feet, but to no effect; it would be two or three seconds at least before she could touch ground again, and longer before she could really aim a leap even using her stick. Ling, thinking quickly, whipped his own alpenstock upward and away from her. He wasted no time watching it spin out of sight. The reaction, as he had intended, sent him drifting downward and back toward his companion.
“Pull your legs up! Be ready to kick hard when I say! I’ll aim you!”
She might have felt like objecting – she had not full confidence in his judgment, and certainly didn’t want him making any sacrifices for her – but was far too sensible to argue at such a time. Drawing up her feet, she let him drift under her.
Ling seized her ankles, and let her inertia slow his upper half, swinging his own feet back under him as their two-body system started to spin. As he had hoped – he always claimed it was a plan – his boots touched the ground closer to the edge than the common center of mass of their bodies.
“Push off!” he snapped. Sheila insisted afterward that he couldn’t really have been planning, since he knew perfectly well that her mass was much less than his. As she finished her kick he pushed upward on the ankles he still held, and simultaneously thrust with his own feet; but he jumped much too hard. As he was firmly reminded later, human legs are stronger than human arms, and there was no way his arms could transfer all the momentum his legs supplied. Some of it stayed with him as he released her. Sheila spun away from the falling surface as he had hoped, upward and back toward safety. However, instead of being still against the ice to leap again, Rob Ling was also drifting upward, out of touch with the falling block and with nowhere near the speed he had passed on to his companion.
For several seconds, however, he gave no thought to his own predicament; too much else was happening. He was spinning much more slowly than Sheila, but fast enough to get a fairly continuous view of his surroundings. At one moment he could see Chile at the
tip of the spur, a second or so later the woman, now several meters above and in the opposite direction. This was all right; but on the second spin, with the new cliff face now over ten centimeters high, a thought crossed his mind.
“Chile! That cube may be smashed when it hits the bottom! Salvage it and protect it!”
The robot had obeyed literally the earlier order to concentrate on the cube, and was unaware of Ling’s danger. He took hold of the object with both hands, using his elbows as fulcrums, and tried to pull it up. It didn’t come, and the leverage started to raise his own body. However, the block gave him a good hold, when squeezed from both sides between his hands, so he was able to double up and bring his feet under him without risk of going over the edge. He placed them on each side of the specimen and began to push himself and pull it upward, increasing his force very gradually to avoid the obvious result of its suddenly breaking free. Ling watched whenever he could, with increasing tension; but before anything came of the robot’s labors, his companion’s voice distracted him.
“Rob, you moron, what were you trying to do? How are you going to get up here? Here – catch my stick!” She tried to hurl her alpenstock toward him, but her own spin betrayed her. He watched it whirl by a meter out of reach, strike the ice, and bury its sharp end in the surface.
“Relax, lady. I’ll get back down in a little while, and can jump again. Look – it’s not falling free; it must be sliding along the break. I’ll catch up.”
“When?”
“Hmmm... maybe ten or fifteen seconds.”
“How far down will the ice be by then? Will you still be able to jump that far?”
“Sure. We’ve all made bigger jumps here. The lovebirds did a forty-three-second one holding hands a couple of weeks ago, when they were celebrating their name anniversary:”
“What’s going on over there?” Bronwen’s voice came in. The Eiras didn’t really resent the geochemist’s frequent way of referring to them, since it was certainly not inaccurate, but her voice was a little sharp.
“Cliff edge broke under us. Still plenty of time to get back up,” Ling replied tersely.
“Chile! How did you –” Sheila’s voice cut in, and broke off as suddenly. Rob was facing the robot as she spoke, and saw nothing to motivate the question; there had been no visible motion by ZH50 since starting to lift. Then his body spin carried the man around to face toward cliff and woman, and the words made sense. Drifting through the vacuum only a few meters from her was a form which, in the dim light, seemed exactly like Chile.
The resemblance was mostly its black color, Rob realized almost at once; this was by far the best look he had had at the ghost. As far as general outline and size were concerned, it could have been any other member of the group. Each environment suit, however, bore a brilliant color pattern matching the team name, pale green for the Jengibres and orange for the Eiras, with black helmets for the men and white for the women. The pattern was for ease of seeing and instant recognition rather than any artistic consideration. For a moment, Ling’s bright hopes collapsed; it would have been quite possible for someone to send a group with only robots from Earth. In fact, that had been considered at some length. No ETI...
Then he was facing Chile again, just in time to see the robot’s feet and legs suddenly crush through the surface.
A robot’s reaction time is electronic as far as perception goes, but mechanical response is another matter, especially for one built to work in Uranus system temperatures. Chile’s legs sank for their full length, and what in a human being would have been his seat struck the ice sharply. About two cubic meters of the spur’s tip broke away under the blow, carrying robot and cube along. Ling watched helplessly as they began to sink slowly beyond the edge of the larger block, which unlike them was not yet falling completely free. Then his attention shifted again at a cry – a real shriek this time – from Sheila.
“What are you doing?”
By the time the man had turned far enough to see, it had been done. The ghost had almost collided with her and seized her arm; for a moment the two had formed another spinning two-body system. Then, using its legs, it had thrust itself off violently in a dive toward the edge, the reaction removing any doubt that Sheila would reach safe ground. Ling wondered for a moment whether it would strike him too; maybe it was a real robot acting under First Law. Then he saw it was aiming at Chile.
He himself was catching up with the main sliding mass, which must still be affected by friction. In a few more seconds he could jump, if he wanted to. A dozen meters up by then, and as far toward his own shadow – no problem. Plenty of time. As he touched the surface about three meters from Sheila’s stick, he even considered for a moment whether he should ride the mass down and get a closer look at the newcomer.
Then he realized that this might not be a good idea. The block was starting to tilt outward as friction continued to delay its inner part. He had no way of deciding how much spin it would acquire, but the Idea of being underneath when it reached bottom was as unattractive as the technique of climbing around it to stay on top was impractical. A blot of quick-frozen crimson glass under a mass of ice might make the day for some future archaeologist, but Ling was not feeling that altruistic. Chile could take care of things below; the new arrival had to be a robot. Surely no human being would make a deliberate dive into a hundred-and-fifty-meter gulf – though come to think of it such a drop wouldn’t have to be lethal – and maybe it was nonhuman in quite a different way – just tougher – why had it made the leap, apparently using Sheila merely as a convenient reaction mass for orbit correction?
“Rob! What are you doing? Don’t stay with that thing – get back up here, idiot!” The man returned to reality with a start which almost separated him from the surface again. He tapped the ground gently with a boot toe to swing himself onto the proper line, and kicked off hard. Again much harder than necessary; he was still rising as he passed over the new cliff edge, and another half minute elapsed before he landed not quite flat on his back. By this time, the detached fragment he had left was nearly halfway down the cliff, and Chile presumably even lower.
“Chile! Report!” Ling didn’t wait even to get to his feet to snap out the order.
“I no longer have the cube,” was the prompt response. “What is clearly another robot passed me in fall, and snatched it away. I saw it approach, but did not foresee its intentions. It has a somewhat greater downward component than I, and will land first, about eight seconds from now. I question the likelihood of my catching it, unless it turns out to be very much less agile than I. This is poor country for maneuvering. Do you wish me to try?”
“Keep it in sight,” Ling ordered without hesitation. “We want to figure out its origin if we can, and what it wants to do with the cube. Observe, and report at your own judgment.”
“Yes, Rob.”
“Can you talk to it?” asked Sheila.
“It has not responded to any standard signal impulses. If it was made by U.S. Robots, it is of a series unknown to me.”
“Does it emit anything?” Mike Eira’s voice came across the kilometers.
“Yes, it – pardon, Mike. Rob, it has just reached the ground, and immediately leaped back toward the cliff top. It should be near you and Sheila in fifty-five seconds. Mike, it has emitted many infrared bursts similar to those of the small cubes.”
“You’re recording them for Dumbo.”
“Of course. I have now reached the ground, and also leaped.”
“Maybe you should stay below, in case –”
“Too late, Bronwen. Rob said to keep it in sight, and I am now out of touch with the ground.”
“All right. It wasn’t much of an idea anyway.”
Silence supervened, while the robots orbited back toward the cliff top. The stranger just cleared the edge with a near zero vertical component; Chile had made more allowance for error and was three or four seconds longer getting his feet on the ground. By this time the ghost had settled to its kne
es – it was even more humanoid than had been obvious at first – and bent almost over the edge to put the cube down. A hemisphere which might have been dust, smoke, or ice fog expanded around the point of contact, spreading and thinning radially except where the ghost’s body blocked it, without the puffing and billowing which an atmosphere would have caused. After a few more seconds this ceased to form, and its remnants quickly dispersed to invisibility.
“The cube appears to have been replaced in essentially its original orientation,” Chile stated. Sheila and Ling were still too far back to see clearly, and were not approaching at all rapidly; there would be no loose mass to jump back from if they went over the edge on their own.
“Then we’ll stop worrying about it for now, and concentrate on the other robot,” Rob replied. “Chile, I’m afraid to ask this, but what can you tell us about the origin – the manufacture – of this thing?”
“As I said, it is not a make familiar to me. Like me, it appears designed to operate at the local temperature. It has no obviously nonstandard engineering.”
“You mean it could have been made by an appropriately skilled designer to simulate the motions and actions of a human or similar being.”
“Yes.”
None of the listeners bothered to ask whether there was any evidence of nonhuman origin; Chile didn’t have that kind of imagination, and certainly lacked appropriate experience. Ling and probably Mike Eira would have been afraid to ask anyway, though they could certainly think of sufficiently specific questions. For some seconds, ZH50 and his companions looked the ghost over silently, while it finished its work and slowly stood up. The human beings could now see some differences between it and their own robot; it was a few centimeters shorter, about Sheila’s height, its legs were shorter and its arms much longer for its size, and there was no neck. The head seemed fixed directly and immovably on top of the trunk.