Heavy Planet

by Hal Clement

  LECTURE DEMONSTRATION

  The wind wasn’t really strong enough to blow him away, but Estnerdole felt uneasy on his feet just the same. The ground was nearly bare rock, a grayspeckled, wind-polished reddish mass which the voice from the tank had been calling a “sediment.” It was dotted every few yards with low, wide-spreading, rubbery bushes whose roots had somehow eaten their way into a surface which the students’ own claws could barely scratch. Of course the plants themselves could provide anchorage if necessary. The ex-sailor’s nippers were tensed, ready to seize any branch that might come in handy if he did slip. While the gusts of hydrogen sweeping up from the sea at his right wouldn’t have provided much thrust for a sail, the feeble gravity of Mesklin’s equator — less than two percent of what he was used to in the higher latitudes — made Estnerdole feel as though anything at all could send him flying. It took a long time, as he had been warned, to get used to conditions at the world’s Rim; even the bulky metal tank crawling beside him seemed somehow unsteady. He was beginning to wonder whether he had been right to sign on for the College — the weird establishment where beings from the sky taught things that only the most imaginative Mesklinites had ever dreamed of. It would be fine to be able to perform miracles, of course, but the preliminaries — or what the aliens insisted were necessary preliminaries — got very dreary at times. This walk out on the peninsula, for example. How could the aliens know what the rocks below the surface were like, or what kind would appear at the surface at a given place, and how they had been folded up to make this long arm of dry land? And, most of all, why was any of this worth knowing? True, he had seen some of the holes drilled near the school and had even examined the cylinders of stone extracted from them; but how could anyone feel even moderately sure that things were the same a few cables away? It seemed like expecting the wind to blow from the north on one hilltop merely because it was doing the same on the next one. Well, the alien teachers said that questions should be asked when things weren’t clear. Maybe one would help here — if only Destigmet wouldn’t cut in with his own version of the answer. That was the worst of asking questions. You couldn’t be sure that everyone else didn’t already know the correct answer … But Estnerdole had learned a way around that. “Des!” he called, loudly enough to be sure that the other students would also hear. “I’m still not straight on one thing. The human said that this exercise was to tell whether the peninsula is a cuesta or a hogback. I still don’t see the difference. It seems to me that they could be pretty much the same thing. How do you know that anything you call a cuesta isn’t a small part of a hogback, or wouldn’t be if you looked over enough ground?” Destigmet started to answer in a self-assured tone, “It’s simply a matter of curvature. A cuesta is a flat layer of rock which has a softer layer under it which has eroded away, while a hogback—” He paused, and Estnerdole’s self-esteem took an upward turn. Perhaps this know-it-all was going to run aground on the same problem. If Des just had to give up and ask the instructor, everything would be solved. If he didn’t, at least there would be the fun of hearing him struggle through the explanation; and if it didn’t come easily, there would be nothing embarrassing about checking with the tank driver. The voice which came suddenly from the vehicle was therefore an annoyance and a disappointment. Estnerdole did not blame a malicious power for interfering with his hopes, since Mesklinites have little tendency toward superstition in the mystical sense, but he was not pleased. “We will turn south now,” the alien voice said in perfectly comprehensible, though accented, Stennish. “I haven’t said much yet, because the ground we’ve been covering is similar to that near the College. I hope you have a clear idea of what lies underneath there. You remember that the cores show about twelve meters of quartz sandstone and then over twenty of water ice, followed by several more layers of other silicate sediments. It shouldn’t have changed much out here. However, you will recall that along the center of this peninsula the surface looks white from space — you have been shown pictures. I am guessing, therefore, that erosion has removed the sandstone and uncovered the ice at the top of a long fold. This is of course extrapolation, and is therefore a risky conclusion. If I’m right, you will get some idea of what can be inferred from local measurements, and if I am wrong we will spend as much time as we can to find out why. “It will take us only a few minutes to reach the edge of the white strip. Any of you who don’t mind the climb may ride on the tank. Now, I want each of you to think out in as much detail as your knowledge and imagination permit just what the contact area should be like — thickness of sandstone near it, smoothness of the two surfaces, straightness of the junction, anything else which occurs to you. I know you may feel some uncertainty about making predictions on strictly dry-land matters, but remember I?m taking an even worse chance. You?re sailors, but at least you?re Mesklinites. I?m from a completely different world. There, I?m stopping; any of you who wish, climb on. Then we?ll head south.? Estnerdole decided to ride. The top of the tank was seven or eight body lengths above the ground and acrophobia is a normal, healthy state of mind for a Mesklinite; but College students were expected to practice overriding instinct with intelligence wherever possible. There would obviously be a better view of the landscape from the top of the vehicle. Estnerdole, Destigmet, and four of the remaining ten class members made their way up the sides of the machine by way of the ladderlike grips provided to suit their pincers. The other six elected to remain afoot. They took up positions beside and ahead of the tank as it resumed motion, the flickering legs which rimmed their fifteen-inch wormlike bodies barely visible to the giant alien inside as they kept pace with him. Visibility dropped as night fell, and for nearly nine minutes the tank’s floodlights guided the party. Then the sun reappeared on their left. By this time the edge of the dark rock they were traversing was visible from the tank roof, only a few hundred yards ahead. The teacher slowed, and as the ground party began to draw ahead, he called its members back. “Hold on. We’re almost close enough to check predictions, and I’d like to get a few of them on record first. Has anyone seen details yet which surprised him?” Estnerdole remained silent; he had made no predictions he would trust, and did not expect to be surprised by anything. Destigmet also said nothing, but his friend suspected that it was for a different reason. None of the others had anything to say either, and the teacher sighed inaudibly inside his machine. It was the same old story, and he knew better than to let the silence last too long. “There’s something I didn’t guess,” he finally said. “The edge of the dark rock isn’t as straight as I had expected — it looks almost wavy. Can anyone suggest why?” Destigmet spoke up after a brief pause. “How about the bushes? I see them growing along the edge. Could they have interfered with the erosion?”

  “Possibly. How could you check on that possibility?”

  “See whether the rock where they’re growing is any higher or lower than where they aren’t.”

  “All right. Let’s see.” And that was why the group was all together when the shell of sandstone gave way under the tank. The human teacher observed less of the event than his pupils. The yielding ledge freed his vehicle for a fall of some fifty feet under three times his normal gravity, and one second was not long enough for him to appreciate the situation. His safety clamps, padded and reinforced though they were, had not been designed for any such shock, though it was just as well they were there. Neither was the shell of the tank, and even the students least familiar with the alien machinery could tell that something was wrong with it. The evidence was not visual; a stink of oxygen permeated the neighborhood and for a moment sent the Mesklinites scurrying as far as they could. Even a creature which doesn?t actually breathe because it is small enough for high-pressure hydrogen to reach all its tissues by direct diffusion may have evolved a sense of smell. The space into which they had dropped was windy, and the oxygen quickly became imperceptible. Estnerdole crept back to the side of the motionless tank; like his fellows, he was of course uninjured. The fall had meant no more to
them physically than a similar one on Phobos would have to a human being, though any fall can be expected to provide an emotional jolt to a Mesklinite. “Teacher! Dr. LaVerne! Can you answer us?” There was no response, and after a moment the sailor began to examine the machine in detail, looking for visible damage. The process was hampered by the fact that it was three quarters buried in white powder — the ammonia snow which had been blowing from the north for weeks as winter for Mesklin’s habitable hemisphere drew on. The snow formed a slope of about thirty degrees, extending into a hollow which reached east and west as far as Estnerdole could see. The cavern’s north face was walled by a nearly vertical cliff of clear, glassy material. The roof, now pierced by the hole through which the party had fallen, was rock. Sunlight slanting through the hole was reflected by the ammonia which formed the south side and illuminated the immediate area for the moment, though the light changed constantly as the beam scanned along the slope. The exposed portion of the tank showed no visible cracks; the oxygen must have leaked from some place below. Light was shining from the exposed windows, and Estnerdole made his way to the nearest of these by means of the climbing grips which studded the shell. Destigmet was close behind. Neither was really familiar with the vehicle’s interior, so neither could be sure whether the apparent chaos of objects within was normal or not. The form of the teacher was visible, motionless in the control seat. His armor, which they had seen often enough to know well, appeared intact; but the transparent front of the headpiece seemed to have colored liquid over part of its inner surface. The human being’s head could not be discerned in detail. Neither sailor was familiar with the appearance of human blood, but both had good imaginations — even though they lacked real circulatory systems of their own. “We’ll have to get in somehow and get him out of there,” Destigmet said. “He’ll have to get back to the College somehow, and we certainly can’t carry the tank.”

  “But if we break in or open the door, our air will get in too, and he can’t stand that. Shouldn’t we, or some of us, go back ourselves and bring human help?”

  “Our air is already inside — at least, his came out, and ours has much higher pressure. Either his armor saved him, or it’s too late already. Certainly if any of us can get out, one should go for help; but the rest must get to him and at least do our best to see that — well, to see whether we can do anything. Come on, everyone — dig out the door and try to get it open while we can still see. One of you climb the hill.” The snow was loose and powdery, defeating any attempt to dig a narrow hole. The door of the tank was on the downhill side, which helped some. The bulk of the vehicle kept the entire mass of white dust from sliding down. Legs working at near-invisible speed hurled the stuff away from the metal in clouds, and as the minutes passed, the lower part of the vehicle grew more and more visible. The five minutes or so of daylight left when they started was not nearly enough to let them shift all those cubic yards of material, but enough light came from the windows to let the Mesklinites work through the night; and within two days the door was uncovered. There would have been no difficulty in opening it, but even Destigmet was a little uneasy about doing so in spite of his earlier logic. “Let’s check the window once more,” he said. “Maybe—” He left the sentence unfinished and began the climb to the nearest window. He had scarcely started, however, when the hull of the tank shifted slightly, tilting toward the cluster of watching Mesklinites. Destigmet had never jumped in his life — the concept was alien to a being reared in nearly three hundred Earth gravities — but his reflexes did something. Suddenly he found himself over twenty yards away from the tank, close to the glassy cliff which formed the other wall of their prison. His fellows had also scattered, but not quite so abruptly. They were delayed mostly by bad traction, the fluffy material under their claws doing most of the initial moving. Destigmet had been on the tank. The latter did not complete its threatened fall, for the moment. It was resting entirely on the loose, white dust which had saved it from flattening like an egg under an elephant’s foot, and most of this had been removed from the downhill side; but it did not yet fall. The Mesklinites approached again with caution. Even they, in a place where everything’s weight seemed negligible to them, had no wish to be underneath that mass if it really did topple. “I thought your weight must have shifted it, but something else must be moving inside,” remarked Estnerdole. “Maybe the teacher is in better shape than we thought.”

  “A person’s weight doesn’t mean a thing here,” returned Destigmet. “It must be him moving. Let’s get to that window.”

  “If he is moving around, the climb will be pretty risky. Nothing but luck is keeping that thing from rolling the rest of the way down the slope now.”

  “No matter. We have to find out. Come on.” Destigmet led the way up the loose material, but before any of the Mesklinites had reached the tank, it became evident that its occupant was once more active. Its outer lights suddenly flashed on. Estnerdole gave a hoot of relief, and followed it with words. “Dr. LaVerne! How can we help you?” For several seconds there was no answer, but the tank wavered even more alarmingly. Then the door opened, and the giant figure of the armored alien appeared in the opening. It tottered a moment, then fell outward into the snow. The tank rocked away as the man’s weight left it, swung forward again in a way which would have brought Estnerdole’s heart to his mouth if he had possessed a heart, and then stopped once more. The Mesklinites swarmed forward with the common intent of dragging the human being away from the dangerous neighborhood, but before they reached him he started crawling under his own power. His voice came haltingly from his helmet speaker. “Stay back — all of you — I can make it — you couldn’t move me in this stuff anyway.” Estnerdole and two of the others kept coming; with Mesklinites as with other intelligent races, some customs override selfish caution. The three tiny figures swarmed around the struggling monster, trying to speed its faltering trip away from the danger zone, but they promptly found that the teacher had been right; they couldn’t help. It was not that the five hundred kilograms of weight were too much for them — any one of them could have lifted that. The trouble was the footing. A Mesklinite’s legs end in insectlike claws, except for the nippers on the fore and aft pairs; the claws provide excellent traction on the wooden deck of a ship or the hard-packed soil which covers much of Mesklin. But a sand dune or a heap of ammonia snow is a different matter. The students’ efforts to push the huge bulk of their teacher simply drove their own bodies into the loose fluff. LaVerne was only partly aware of their presence. He had more or less recovered from the shock of his fall, and had seen enough to evaluate the situation fairly well; but he was not really in full possession of his faculties. He knew he was on a sloping surface of loose material, and that the tank was rather likely to roll over on him at any moment; his whole attention was focused on getting out of the way. The warning to the students had been little more than reflexive, like their own move to help him, and he did not follow up the order. He simply crawled as well as the situation permitted. A human observer might have had trouble deciding whether his mode of progress should have been called crawling or swimming, but he did make progress. He never was sure whether it took him five seconds or a whole minute, but presently he found himself on smooth, solid rock with the white slope safely behind him. He relaxed with a sigh, and only slowly became aware of the dozen caterpillarlike figures around him. With an effort he managed to lever himself to a sitting position. His students waited silently. He took in the nearly buried tank, the cliff in the opposite direction, the rock roof above with sunlight slanting through the jagged hole, and the darkness which swallowed the seemingly endless cavern to east and west. The Mesklinites were reasonably familiar with human facial expression and tried to read his, but they could make out little in the poor light through the face plate, which was partly obscured by blood from his nose. They waited for him to speak, and were not surprised when his first words formed pertinent questions.?How long did it take you to do that digging job? Ho
w long has that fellow been trying to climb the hill?? Destigmet answered, “Only a few days; we didn’t keep close count.”

  “Hmph. He hasn’t gotten very far. I’m reminded of an animal on my own world which traps its prey in pits rather like this — loose stuff at its angle of repose. Climbing such a surface is nearly impossible. What will he do if he gets to the top? That hole is twenty of your body lengths away from the bank.”

  “But, Doctor!” pointed out Estnerdole, “the stone itself is not very thick. If we can reach the top, we know the stone comes to an end only a short distance to the south. We can dig our way out from under the edge easily enough.”