Hal Clement - Heavy Planet

“You know,” cut in another alien voice, “this will be the first chance we’ve ever had to get a close look at the rock making up that cliff. We could see it was sedimentary, if horizontal layering means anything, but all we could tell was that the bottom fifty feet or so was light gray in color, the next layer up was a lot darker, and for the rest of the way up there were variously light and dark bands up to the nearly black one at the top. That one’s silicate — mostly amphibole, the gear on the rocket told us years ago right after the landing, but this will be the first time we’ll be able to tell anything about the other layers.”

“ What will we be able to tell?” snapped another. “Just what will color tell us, and what else will we be able to see?” Dondragmer, like the captain, tuned out the argument. He had more important problems to face. There was no more visible rock motion anywhere along the fall; the stuff must, indeed, have reached some sort of equilibrium. There was no more sound even from the left, where falling material must presumably have taken a little longer to fill space around the new corner. But something — the “smoke” described a little while before? well, maybe ordinary fog — was rising from the far side of the river, over the newly fallen material. Even after watching balloons, the sight of something flowing upward was startling. Explanation would have to wait, though. There were fragments of all shades and several colors at the bottom of the fall, but the mate was more concerned with what might be under it. What had happened to the Bree? And for that matter, what might have happened to the river? He didn’t worry about the captain, who had presumably been almost as much out of danger as the Flyers. After a few moments’ thought, he headed toward where the ship had been, ordering a few of the crew to come with him carrying the communicator, and sending off others to examine the edge of the fall both up and down stream. Almost immediately he had a question to ask the aliens above. “It’s getting a lot warmer as we get near the fallen stuff. Can you suggest why?” Even Jeanette could, but one of the scientists undertook the explanation. Not even Dondragmer had really grasped much thermodynamics yet, but many of the natives had a fairly clear idea of energy. Every falling pebble had lost a lot of potential— Quite a lot. More than enough, for the stuff originally near the top, to bring its temperature above the melting point of water, one of the aliens figured. Not that any of the natives knew what water was, or that there was any reason to believe there was any around. “Better stay away for a little while,” the alien concluded his or her remarks. “It shouldn’t take long to cool again; your air is a very good conductor of heat. Actually, it must be radiation you’re feeling; there ought to be a pretty strong wind from where you are toward the cliff.”

“There is. It’s still uncomfortable, but we can stand more if we have to.”

“Just wait a while.” The mate saw nothing else to do. Barlennan would have done the same, if the choice had been offered. Hars had worked the balloon rather jerkily downward from its ceiling until the basket was only a few yards above the tallest boulders, but at every level the wind was now toward the cliff edge. It was carrying them far too rapidly for a safe landing; hooking the car on a boulder and tipping the crew out was not acceptable. They could easily have fallen several body lengths. The cliff edge — or rather, the nearest point of the new slope — was less than half a mile away; much less, now. It seemed safest as well as unavoidable to go out beyond it and drop below the level of the plateau, a maneuver which should at least provide a wider choice of wind directions. It didn’t. There still was only one choice, it turned out. A little later, after his quick physics lesson, Dondragmer could have told his captain what the choice would be, but the information would have been of little help. As Bree Three neared the top of the slope, the temperature rose abruptly, the balloon started upward, and the surroundings faded from sight. Neither the need nor the possibility of instrument flying had ever occurred to Barlennan or any of his crew. They had felt the upward surge, tiny as the acceleration was compared to the local gravity, and the captain could tell from the tracker readings that the climb was continuing. The instrument had been the first one salvaged from the very top of the rocket; its main purposes had been to help guide the original landing, with the additional hope that if the south pole were not found exactly its distance from the rocket could be determined and, possibly, seismic measurements be secured later. To Barlennan, the temperature rise plus the upward acceleration suggested an upward air current heated from below and outside the balloon; Hars judged the same and reacted at once, slanting the vanes to waste hot air to the sides. The captain’s first thought was that this was the proper reaction; then he realized that the climb couldn’t possibly last long, but might very well take them above the balloon’s normal ceiling. If the upward impulse ceased at some point, which it could hardly help doing, even full fire might not be enough to keep a catastrophic descent from following. “Keep it hot! Hot as you can!” he hooted. The fireman reversed the slope of the guides without question, though perhaps not without uneasiness. For several seconds the crew remained without reference points, though the figures on the instrument showed they were still climbing; then the surrounding fog began to thin, and sun and sky could once again be seen. The ground directly below could not, nor that along the former line of the cliff edge; they were still in fog. Toward the plateau, however, boulders were visible once more. In the opposite direction the less rugged area of the lowland showed fuzzily at first, but quickly cleared. Evidently they were still traveling in the same direction. A glance at the inertial reading confirmed this. The readout was reliable to fourteen places, even here; it had been made visible on the surface of the baseball-sized sphere to permit initial calibration, and Barlennan was not the only member of his crew to have learned to interpret the characters. Hexadecimal readings weren’t too difficult for people who normally used base eight. The tracker was completely solid, with no moving parts larger than electrons, and the gravity had produced no readable change in its behavior, the Flyers had reported. It had, after all, been designed for such a field. It quickly became just as evident that the expected descent had started, and Hars, without further orders, heaped more fuel on the fires. Karondrasee sprinkled a contribution from his juice tank. Barlennan looked upward rather than at the approaching ground; wrinkling of the balloon fabric from rising pressure would mean more than the narrowing of the space still below them, however read. It occurred fleetingly to him that a small sealed balloon at regular temperature might serve as an even quicker method of determining rate of descent. One could watch it swell toward full or crumple toward flatness. It would also be something they should be able to make themselves. There would be no other inertial instruments until they got back to the equator, where Flyers could land. But that could be thought out later, if he were alive to think about it. They were descending fast now, as even vision could tell when he glanced downward, but at least the skin was still smooth. The balloon was maintaining its volume in spite of the rising outside pressure; Hars was doing his job. The possibility of the bag’s bursting during a climb had bothered the crews during the earliest flights, but the Flyers had assured them that the opening through which hot air entered it would never let the pressure get too high inside. Again fleetingly, Barlennan wondered whether they might be wrong again. They weren’t, this time. The descent slowed and stopped, though it was fortunate they were no longer over the plateau. The cliff now was hidden by the same fog which had concealed the rest of the world on the upward surge, and the numbers said they were over a hundred feet lower than the rocket. At this point the voice of Jeanette, which had been surprisingly silent for the last few minutes, sounded again. “Captain, what’s happened? Where are you? We can’t see anything but the sort of ground across the river from the cliff, and it doesn’t have enough features for any of us to recognize. We can read the tracker, but can’t match figures with landscape yet. Can you turn the eye so we can see the cliff and the boulder country?”