Still River

by Hal Clement

  She couldn’t have looked anywhere but at the robot. For the first time in hours, it stirred without their pushing or lifting. Soundlessly, and very slowly, it straightened to a true vertical, so that only one side of its base touched the rock. It began to lift, and Carol tensed, ready to snap the access port open and shut it down if it seemed about to do more than rise to—

  “Gravdh!!” the Shervah tore the little doorway open and reached in. Molly felt faint for a moment.

  “Carrie! What’s wrong?”

  “We had it set for the long fall—to slow and stop a safe distance from the bottom. Even if everything is all right, the first thing it’ll try to do is lift a couple of meters, and there isn’t that much room overhead—there! You watch it, too! I think it’s all clear, but I don’t know.”

  “Better shut the door again. If there’s still any ammonia, we want to get rid of it, and if there’s anything we know it’s that this outside air is pretty well saturated.”

  Carol hesitated; if anything were still wrong, delay in getting to the keys could be serious. Then she followed Molly’s advice. Both watched, tensely at first, then gradually relaxing as the cylinder floated obediently a few centimeters above the rock.

  “How much more time should we give it before we take out the can?” asked Carol. “We certainly don’t want to move it around with that liable to spill. We’d be worse off than before.”

  “We worry about that later,” replied the Human. “First things to the head of the line. Get up there and plug in your charging cable. I’ll lift you if you’re worried about jolting the cylinder.”

  “It won’t be bothered by me.” The small humanoid vaulted to the top of the robot, undipped the appropriate plug from her armor, and established connection with the fuser. Five minutes later—the unit could have produced all the energy their accumulators could hold in as many seconds, but conducting it was another matter—Molly took her place, and a few minutes after that her sigh of relief reached Joe’s translator.

  “I take it your immediate danger is over, Molly and Carol.”

  “Yes. Now I can start thinking about a bath and a good meal again.”

  “Or maybe about the job,” added Carol.

  “Even the job. I think we may as well take that can out and remove one more immediate worry. Also, I’d like to know if it’s liquid or not.”

  “Good,” said Joe. “Then as soon as you reach the boat, Jenny, please set Exit Lock Five—the little waste-disposal one near the shop—for automatic cycling, and the shop master inside for Activation Code Two. I may as well put the new machines to work. There should be about three hundred of them ready…” “What?” gasped Molly.

  “—and about two hundred more to be finished. That will be enough, I hope. I made the bodies out of silicon and carbon compounds instead of metal, so the only raw material shortage is in electrical contacts; we’re low on silver now. The shop equipment can handle them up to a few more than five hundred.”

  “But what are they?”

  “You will have guessed, Molly. Small mappers, each with its own model storage unit, all interconnected electromagnetically, all radar equipped. They will be spread out through these caverns, plotting as they go, assembling a model of the interior of Enigma. Charley’s estimate of the length of time it would take to do it by ourselves was very discouraging, and it seemed best to use equipment that wasn’t limited by having to carry living operators. As soon as Jenny gets to the boat, she’ll start sending them after me, and I can begin mapping from these incurrent caves inward. They should get to your end of the planet—I’ve programmed them to stay in touch, so they won’t diffuse and try to map the whole sphere, and to go as far down as possible to make the trip a minimum-distance one—in a couple of weeks.”

  “But…” Molly started to vent her feelings, and fell silent. Carol was less restrained.

  “You said this end was more likely to have the life forms that restored the gas. Why not send them here first?”

  “Jenny has specimens of those and will be able to tell us fairly soon whether that hypothesis is right. Charley and you two are already mapping the summer end. If you hadn’t managed to charge your batteries, naturally I’d have sent the new ones looking for you first. That was Activation Code One. Luckily, I was able to tell Jenny to key in Two; but I waited until I heard from you two, of course.”

  Chapter Twenty

  Of Course I Couldn’t Know

  Once again, Molly was unable to find the right words. The vision of hot food and hot bath went glimmering as it had before.

  Carol happily decided, aloud, that the next thing to do was resume their trip down the river toward Enigma’s heart. It was only a matter of time before Charley made contact with them, and if for some reason the Kantrick failed, the new mappers would do the job. Five hundred certainly ought to be enough. With their armor batteries charged and the robot and its fuser standing by, there was nothing to keep them from work. Her beautiful brown fur might be sticky, matted, or even starting to fall out, but her armor would take care of any that did. She could shampoo later.

  There were lots of questions to be answered. Was Enigma as spongy and cavernous as their experience was beginning to suggest, or was this something local? Were the caves really kames, and if so, were the original ice bodies that had molded them comet nuclei or something else? If they were comets, how had they incorporated themselves into Enigma’s mass without blowing up in the process, since the kinetic energy of a typical interplanetary collision is more than enough to vaporize iron? If they were comets, were there still some of them at greater depths to be found in their original state, to justify Molly’s ice hypothesis? If the basic idea was right, how had the silicates consolidated into rock hard enough to support these deep caves? Was Enigma really as young as its sun had to be? If so, how had it managed to develop highly complex life forms? Was biochemistry really the answer to the air-circulation problem? Was it also the answer to the problem of why the little world had air at all—their originally assigned research question? It could be; if gas precipitated as solid before getting far from the surface, it could hardly escape.

  Even Molly, thinking all this over, was able to forget her personal discomfort and join in the planning. Clearly, they had to go deeper. However good Joe’s new little robots might be, they would not be able to select biological specimens for detailed analysis; researchers would have to do that themselves. Furthermore, geochemical data were badly needed, too; the lasers and picks would have to be put to more use.

  Perhaps it was no longer really essential to follow the river, as there was now another way for the others to find them and get the group back together; but since they were now frankly seeking for a route down, the river seemed the obvious guide. Also, it would clearly be much easier for even the new robots to find rivers than explorers.

  With the anxiety about the robot allayed and the collecting can of ammonia water poured gratefully out on the rock where the machine had stood so long, Molly and Carol resumed their journey.

  Charley, too, was following a river—Jenny’s—but there was so far no evidence that it was either the same one as Molly and Carol’s or one of its tributaries. He, too, was finding much life. His verbal descriptions irritated Carol; the organisms were either decidedly different in structure from those she and Molly had been seeing, or he was doing a very poor job of describing. He was collecting specimens, of course, so there was no point in being critical until these could be examined, and the Shervah managed to restrain herself.

  Time went on, on the whole happily. Everyone but Jenny got deeper into the planet, though for Joe it was by proxy; he remained at the antarctic surface, finding and charting more and more wind-caves and sending a small swarm of mapping robots into each as he found it. The halo of fist-sized cylinders that accompanied his own craft was growing smaller, though replacements were still homing in on him from the boat’s shop.

  Even Carol and Molly were finding a gradual change in the
life forms around them, though not enough, the former insisted, to account for the discrepancies in Charley’s descriptions. The temperature was rising significantly, though their armor prevented them from noticing the fact through their own senses. The real warning was the appearance on the rock around them of a faint, white mold.

  Even Carol had reached the point where not every life form had to be examined closely, and neither had a container left in which to collect anything new, but this stuff got thicker as they progressed, and finally both felt that it deserved detailed attention. Molly scraped some from a convenient surface and spread it on her palm where they could both look at it. They saw a mass of needlelike crystals matted in a way that reminded the Human of the sparkling stuff she had seen in the first cavern.

  This, however, was glassy rather than metallic. There was something else familiar about it, and as the women watched, the mass abruptly lost most of its whiteness and then slumped into a tiny puddle of liquid on the palm of Molly’s glove. She didn’t feel the local heat loss, as her suit had very efficient distributing apparatus even at the thin gloves, but what had happened was suddenly plain enough.

  “Frost! Water!” the Human exclaimed. “What became of the ammonia? What’s the river made of now?”

  The river at the moment was a dozen meters away from the parked robot. Carol headed for it, eagerly but with caution bred by the low gravity, took a sample, and made the same standard test she had used on the stream so far above.

  “It’s not pure ammonia by a lot,” she reported after a moment. “This gadget makes it about seventy percent. I don’t know what the rest is.”

  Molly’s armor lacked comparable testing gear, but she had a thermometer probe. She dipped this into the liquid on her glove and held it away from her suit, watching sample and reading as the substance froze again.

  “Just under two seventy-two. Not pure, but mostly water. What’s going on here?”

  “What’s the air temperature?” asked Charley.

  “Wait a moment—it’s still dropping, now the stuff’s all frozen.” Charley waited, to Carol’s surprise. “About two sixty-four. Check, Carrie?”

  “That’s what mine’s been saying.”

  “And the river?” Another brief delay while the women made the test.

  “About two fifty-five. Much too high for pure ammonia, much too low for water. I couldn’t begin to calculate percentage composition because it’s probably not an equilibrium mixture, I don’t know the constants for either association or ionization in those mixtures, and I certainly don’t know what else may be there. So what’s going on?”

  “Very simple,” said Charley. Carol rolled her eyes wildly but managed to keep silent. “There’s heat below, warming the wind that comes up. Liquid is going down. The walls of the caves and passages connecting them give plenty of surface area and are rough enough for all sorts of turbulence. The planet is a countercurrent heat exchanger…”

  “Better yet, it’s a reflux condenser!” Molly jumped enthusiastically at the suggestion. Carol, with her conditioned skepticism for Charley-hypotheses, remained silent. “But there goes the last chance of my finding any ice—even water ice—down below. Wouldn’t you say, Joe?”

  “I gather you just found some.”

  “You know what I mean. Masses of it. Chunks that would explain these caves being kames, not just frost deposits on cold rock from vapor picked up from the river.”

  “I’m afraid so. I can’t yet guess how far down the caverns extend, and I don’t know how far down you are. My new robots have mapped downward a little over a hundred and fifty kilometers, but they’re not equipped to take pictures or specimens, and I regret to say they can’t measure temperature.”

  “Joe!” Molly hoped that Carol’s shocked tone was not meant seriously. The Nethneen seemed unaffected; at least, he offered no further apology.

  “To that depth,” he went on, “the crust remains about the same. Between a quarter and a third of its volume is open space, as measured by the radar of the small units.”

  “How do you keep in touch with them for such a distance through rock?” Molly asked.

  “I’ve programmed them to spread out in such a way as to be able to relay among themselves and all the way back to me. After the whole set of robots is completed and extended as far as practical, I’m going to have to go underground myself so that they won’t have to use so many units in relay to the surface that their mapping front is too greatly reduced.”

  “So they each carry complete diagrams of the volume covered, and so does your own carrier.”

  “Right. I’ll be able to follow down very quickly, when the time comes.”

  “Fine,” said Molly happily. “Then downward to the warmth of the Underworld. This is starting to be fun. Oh—Carol, how about your armor’s refrigerator? Is it all right? Is there any reason to worry about it? What sort of backup does it have?”

  “It’ll work. Standard equipment. No moving parts bigger than electrons to get out of order; I never heard of one failing. And I do wish you’d never given that word worry to my translator. Come along, and even if you can’t help worrying about yourself, stop fretting over me.”

  Molly made no answer, though she wondered whether Carol or her own translator had come up with “fret”. She came along.

  No one had bothered Jenny for a long time. Joe would not have dreamed of it, since she was presumably working; Molly would not have as long as Joe might notice; Carol had managed to resist by reminding herself that any questions would have made her look too much like Charley; what had held the Kantrick back no one wanted to ask.

  When the Rimmore finally did speak, Carol immediately keyed the robot to a stop; she wanted to give full attention.

  “There’s obviously a lot yet to check” came the grating tones, “but you’ll all want to hear this much right away. The organisms I picked up represent at least two basically different life forms—that is, different in genetic coding. They are cellular in structure, which is not surprising, since that is the easiest way to engineer the nutrition-in and waste-out problem for any creature above microscopic size. The interesting point is that they do contain high energy compounds, as was suggested. There are hydrazine and hydrazine derivatives in all of them, nitrates in some, hydrogen peroxide in others with some overlap, and azides in a few. One had so much hydrazoic acid I’m a little surprised I’m not scattered around the cavern where I found it, so watch yourselves, all of you.”

  Carol reacted gleefully. “The next step is to find how they make the compounds. The primary energy source practically has to be the sun, but…”

  “It’s getting hotter as you go down,” Charley interjected. Carol was silenced for a moment.

  Molly decided to play safe, and made the obvious answer. “Another point to check as we go. I wonder how hot it will really get. Even in this gravity, there must be a limit before the rock creeps and these caverns close.”

  “Well, it’s a young planet, we’ve been assuming. Maybe the creeping is still going on.” Molly looked uneasily at the sections of cavern wall that her light and Carol’s allowed them to see.

  “I’m not sure I really like that thought. If you must dwell on it in conversation, please stress the word creep. Anyway, we’ll look for more life, now that the liquid has changed to water. Things certainly ought to be different.”

  “But it isn’t all water,” Carol reminded her. “Ammonia from above is still mixing with it—which I suppose contributes to some of the heating that’s been worrying us. The pure water has been vapor, condensing on cold walls.”

  “Right. Right. But do you know any life forms that operate anywhere near fifty-fifty ammonia-water mix? All I’ve ever heard of are either one or the other, with the one not the main solvent usually quite poisonous in more than trace amounts. My own body produces ammonia, but I have a couple of very complex organs we call kidneys whose main job is to get rid of it and some chemical machinery to turn it into something less toxic un
til they do. There are plants, if they are plants, growing in that river, Carrie. Are they water-based with evolutionary provision to avoid the ammonia, like me, or the other way around, or what?”

  “Collect them. We’ll see.” Carol actually examined her own carefully labeled cans, selected one, discarded its contents, and replaced it with material from the river. She re-sealed the cover and redid the label, looking almost defiantly at Molly with one eye as she did so.

  The Human said nothing to the implied challenge, but after a moment remarked, “We’ll be back, you know.”

  “I know. Specific answers are more interesting than general ones, though.” The giant had to agree, at least for the moment. They remounted the robot, and continued down river and through caves, sometimes more or less horizontally, quite often chasing another fall from top to bottom—much more cautiously now. They had less to go on but were inclined to agree with Joe’s estimate that a quarter to a third of Enigma’s volume was open. At the thought of the increasing thickness of planet above, Molly found herself less and less resentful of the negligible gravity. Maybe it was just as well that the rock didn’t weigh much.

  Wherever enough wall area could be seen, she checked carefully for evidence of faulting, hoping it would not appear. Sometimes she went to the length of sweeping mud out of the way to get a better look at underlying rock. She kept reminding herself that some of the laboratories on Think were over two hundred kilometers below the surface, and Think was an ice body, presumably less rigid than Enigma’s silicate structure, and unless the hollows weakened the latter ...

  She put that possibility out of her mind, firmly. After all, Enigma had presumably had a million years or so to collapse in, if it were going to do any such thing; why should it pick the moment she was visiting the place?

  “The last of the little mappers has arrived,” Joe finally reported. “I’m going underground to get as wide a search front as I can. Things aren’t going quite as fast as I hoped; apparently my machines aren’t spreading out as widely as I had planned. Don’t worry, though, the diagram is growing fast enough, and if it seems to slow too much, I’ll come out and hit the planet from your end.”