Her senses of direction and location, like those of human beings, were simply integrated memories of turns made and distances traveled; she knew that accumulating uncertainties in both would eventually put her badly off the truth. With only her own lights here in the caverns, there was little chance of long-range sighting, so direction errors in particular could accumulate quickly. Much too quickly for comfort.
The discomfort was vastly amplified when, at about the time Carol expected to get to the stream, they reached what looked like a channel that had no liquid flowing in it. It was not completely dry; there were puddles, which she quickly identified as ammonia, along the depression, but in no sense was it a stream or brook.
She reported at once to the others.
“Check carefully against your memory,” advised Joe. “The first thought to strike me is that it is your brook, run dry for some reason.”
“The storm?” suggested Molly.
“Conceivably but not obviously. It is precipitating heavily here, and I would assume that the liquid must be ammonia. It would be easier to imagine ways in which your stream could have been overfilled from the surface.”
“Streams and lakes are temporary things,” Molly pointed out. “They cut new channels and dam old ones with sediment. I’d say we simply have another set of observations to make, if this does turn out to be the same stream.”
“It is,” Carol said firmly. “I remember a lot of what we see now. We are just about where I expected to be, a little more than two hundred meters upstream from where Molly and I both left it awhile ago. In another four hundred or slightly more we should reach the point where it first came in from the side. Just a moment while I reset the robots. Yours first, Molly; let me at the panel.”
“Are the sounds you thought might be the storm any louder yet?” asked Charley.
“No,” both women answered at once. “Dead silence outside the armor,” added the Human.
“Was the change sudden?” asked Joe.
“I don’t really remember. Probably not. Do you recall, Carol?”
“If anything, I am less sure than you, but inclined to agree. If I’d noticed at all, I’d certainly remember; it just didn’t catch my attention. I’d hear better with no helmet, but I don’t think…”
“You shouldn’t risk taking that off!” exclaimed Charley in a horrified tone. Molly, feeling her usual pity for the Kan-trick when he was taking things too literally, quickly changed the subject; fortunately, opportunity had arisen.
“Carol! Isn’t that your rope?”
“It is. I was beginning to wonder—just a little—whether my own memory had been overpowered by suggestion, but that settles any possible argument about where we are. I knew we should reach it before we got to the place where the stream came in but didn’t want to set you looking for it. We’ll be back in the big cave almost at once; we’re going faster than you were before, remember. Hold on a moment—it will be better if you walk, I think. I’m going to have to run from one of these machines to the other to keep resetting the guidance—no, I can use the wind again, can’t I? Just set them to move away from ram pressure…”
“Not mine,” Molly pointed out. “We didn’t clear off all the ice.”
“That’s right. We should have washed it at one of the puddles we passed. Here’s one now; let me stop the thing—there. I still have some empty specimen cans, and sloshing ammonia against it should do the trick. I haven’t worked much with ice, but if polarity means anything it ought to be soluble.”
The cleaning process took only a minute or two, and the robots resumed their journey in somewhat wavering fashion; “downwind” was a less definite direction than the inertial one Carol had been using. The passage narrowed, as even Molly remembered, and presently the women emerged into the vast open space where Carol had first lost her friend’s trail. The fishline led off to the right.
“We’d better stay with it. I wouldn’t want to guess how many openings there might be in the upper part of this hole, or where they might go, and I couldn’t see enough for real guidance on the way down.” Molly, who had never considered doing otherwise, fully agreed, and the robot controls were again reset. This time Carol did have to move back and forth for frequent readjustments; the wind was no longer a guide, and she had only a rough idea of the curvature of the rock wall.
As Molly knew from the earlier conversations, there was about a kilometer to go before the rope trail would turn out across the cavern floor, and both students paid far more attention to the floor itself. There were the sparkling crystals that might be alive, the slippery patches and other areas that almost had to be, or that at least could represent chemistry on its way to becoming alive—a more believable state of affairs. Carol had paid little attention to this kilometer of distance, though she had traversed it three times already—once searching for the passage Molly had taken, and again and back to get the rope after finding the way. The first time, her attention had been on the wall, and the other two she had been in a hurry.
Even so, she was aware of a difference as her light beam probed across the cavern floor. Then it had been irregular rock, sometimes bare, sometimes hidden by the mysterious growths and coverings they had both encountered. Now, however ...
“Molly!” said the Shervah in a puzzled tone. “You never saw any liquid on the cave floor at all, did you—not even the little puddles I did?”
“Nothing. There might have been some under the crystals, but all I found was that sticky stuff. We have some of it, and if I don’t encounter any more of it I’ll be just as happy.”
“But look out there now! That’s not just a puddle!”
The Human swept her own light in the indicated direction and saw that her friend was right. It wasn’t just a puddle. It was a lake, extending as far as the light could carry her eyesight. This was not too far—perhaps a couple of hundred meters, since she could not use really bright light with Carol beside her—but they had not yet come that far from “her” tunnel. She must have crossed this part of the floor only a few hours ago, and it was certainly no lake then.
“The glittery stuff was all over this place earlier,” she pointed out. “We’d better see if it’s still there, underwater—I mean under the ammonia. I can’t really dive in this armor, but I should be able to see; how about you?”
“We’ll both look. Come on.”
The two explorers approached the edge of the lake cautiously, reporting the situation in detail to Charley and the others as they went.
“Both of you watch your temperatures” was the warning. Not even Charley tried to discourage the research.
Molly, fortunately, was ahead of her companion. “Watch out! Sticky!” she called suddenly, and with some difficulty retreated from the spot where her armored feet had tried to stay. She had not even reached the edge of the liquid, still half a dozen meters away. “This stuff was under the crystals before. I wonder what became of them?”
“The part you met was under the crystals. We don’t know it was nowhere else,” the Shervah pointed out cautiously.