Heavy Planet

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?”

“Turning,” Barlennan replied, gesturing Karondrasee toward the rotation lines. “I’m not sure, but I think we’re pretty close to where the test was made, only we’ve passed the cliff. If it still is a cliff. Can your eye see through fog? If it can, you’ll know better than I where we are when you look back. Where’s Dondragmer? I should be able to—”

“I can hear you, Captain. I can’t make a very good report. The falling of the cliff stopped a couple of miles after it passed us, but we can’t get back to where the ship was yet. It’s too hot. The Flyers say that’s to be expected, and at least the lower part of the fall is producing fog too dense to see through. Luckily the wind’s now blowing toward the rockfall and keeping fog and that heat away from us, but we can’t get really near the ship yet.”

“Can you see enough to guess whether it escaped?”

“No, sir. And if it’s still uncovered it may not stay that way long. If you and the balloon were here you could tell better than we can, but it looks to us as though the very bottom of the fall were still moving this way. More like flowing than falling.”

“I see the wind near the ground where we are is also moving toward the rocks, and now that you mention it, I think we can see that outward flow, too. We’ll see it better when we get closer; we’ve let down pretty far — more honestly, we were pretty low when Hars killed our drop — and yes, we’re blowing back toward the cliff now.” The conversation had been in Stennish, but Parkos had been able to follow it. “Then you’d better climb again, Captain!” she cried. “If you’re carried too close to the slope — well, I don’t know how much heat you can stand, but you’ll be cycling though that updraft again. You’ll be starting from lower down, where it should be a lot hotter!” Hars spoke as he manipulated the guides, without waiting for orders. “Worse than that, Captain. I don’t think we have enough fuel to manage another descent like this one. We’d better get up into the flow away from the plateau, get some more distance, and then land before we’re carried back in again. The fog up there is blowing out past us the way we need to go, so there’s a good wind not too far up.” Barlennan gestured assent to the fireman. “Don, you must have heard that. Unless something serious happens, we won’t call you again until we’re on the ground. You can tell me anything you think worth while. Jeanette, you must have had a good look at the fog yourself by now. Can you see through it?”

“Probably no better than you. We can see the stuff lifting from the rocks at the edge of the slope; they must be pretty hot. Did you smell anything, familiar or otherwise, while you were in it? We’re trying to guess what could be boiling.”

“There was some ammonia. Nothing else I could tell, but ordinary methane seems likely, too. How about the rest of you?” The others gestured negatively. “That’s interesting just the same. Have you smelled any ammonia since you left the equatorial regions?”

“No. Not that I can remember.” Once more the others agreed with him. “It’s hard to see how that stuff could be so far from the equator at this season,” remarked another human voice. “I’d expected most of the planet’s supply to be frozen in the other hemisphere right now.” Once more the captain focused his attention on his more immediate problems. Hars had found the wind they needed and was holding altitude with his usual skill, and the line of fog was once more receding; but the fuel was getting very low indeed. It would not be good to let down into the other wind too early, of course; but if it took them too long to reach a safe distance, there might not be enough fire to make the descent and landing safely. “Your judgment, Hars,” the captain said. “Get as far as you think will let us down without flattening us. Don’t wait for my orders.” The fireman gestured understanding without taking his attention from his levers. Barlennan had never learned to like situations where he wasn’t in personal control, but he had long ago learned to be a captain. There were situations which didn’t leave time for orders. In Barlennan’s