The Best of Hal Clement

by Hal Clement

  Oddly enough, there wasn’t. Ridging was moderately surprised; Shandara seemed to take it as a matter of course. The cartographer had eaten, slept, and taken his turn at driving with only an occasional remark. Ridging was beginning to believe by the time they reached their goal that his companion was actually as bored with the Moon as he claimed to be. The thought, however, was fleeting; there was work to be done.

  About six hundred pounds of assorted instruments were attached to the trailer which had been improvised from discarded fuel tanks. The tractor itself could not carry them; its entire cargo space was occupied by another improvisation—an auxiliary fuel tank which had been needed to make the present journey possible. The instruments had to be removed, set up in various spots, and permitted to make their records for the next thirty hours. This would have been a minor task, and possibly even justified a little boredom, had it not been for the fact that some of the “spots” were supposed to be as high as possible. Both men had climbed Lunar mountains in the last four weeks, and neither was worried about the task; but there was some question as to which mountain would best suit their needs.

  They had stopped on fairly level ground south and somewhat west of Plato—“sunset” west, that is, not astronomical. There were a number of fairly prominent elevations in sight. None seemed more than a thousand meters or so in height, however, and the men knew that Plato in one direction and the Teneriffe Mountains in the other had peaks fully twice as high. The problem was which to choose.

  “We can’t take the tractor either way,” pointed out Shandara. “We’re cutting things pretty fine on the fuel question as it is. We are going to have to pack the instruments ourselves, and it’s fifty or sixty kilometers to Teneriffe before we even start climbing. Plato’s a lot closer.”

  “The near side of Plato’s a lot closer,” admitted Ridging, “but the measured peaks in its rim must be on the east and west sides, where they can cast shadows across the crater floor. We might have to go as far for a really good peak as we would if we headed south.”

  “That’s not quite right. Look at the map. The near rim of the crater is fairly straight, and doesn’t run straight east and west; it must cast shadows that they could measure from Earth. Why can’t it contain some of those two-thousand-meter humps mentioned in the atlas?”

  “No reason why it can’t; but we don’t know that it does. This map doesn’t show.”

  “It doesn’t show for Teneriffe, either.”

  “That’s true, but there isn’t much choice there, and we know that there’s at least one high peak in a fairly small area. Plato is well over three hundred kilometers around.”

  “It’s still a closer walk, and I don’t see why, if there are high peaks at any part of the rim, they shouldn’t be fairly common all around the circumference.”

  “I don’t see why either,” retorted Ridging, “but I’ve seen several craters for which that wasn’t true. So have you.” Shandara had no immediate answer to this, but he had no intention of exposing himself to an unnecessarily long walk if he could help it. The instruments to be carried were admittedly light, at least on the Moon; but there would be no chance of opening spacesuits until the men got back to the tractor, and spacesuits got quite uncomfortable after a while.

  * * *

  It was the magnetometer that won Shandara’s point for him. This pleased him greatly at the time, though he was heard to express a different opinion later. The meter itself did not attract attention until the men were about ready to start, and he had resigned himself to the long walk after a good deal more argument; but a final check of the recorders already operating made Ridging stop and think.

  “Say, Shan, have you noticed any sunspots lately?”

  “Haven’t looked at the sun, and don’t plan to.”

  “I know. I mean, have any of the astronomers mentioned anything of the sort?”

  “I didn’t hear them, and we’ll never be able to ask until we get back. Why?”

  “I’d say there was a magnetic storm of some sort going on. The intensity, dip, and azimuth readings have all changed quite a bit in the last hour.”

  “I thought dip was near vertical anyway.”

  “It is, but that doesn’t keep it from changing. You know, Shan, maybe it would be better if we went to Plato, instead.”

  “That’s what I’ve been saying all along. What’s changed your mind?”

  “This magnetic business. On Earth, such storms are caused by charged particles from the sun, deflected by the planet’s magnetic field and forming what amounts to tremendous electric currents which naturally produce fields of their own. If that’s what is happening here, it would be nice to get even closer to the local magnetic vertical, if we can; and that seems to be in, or at least near, Plato.”

  “That suits me. I’ve been arguing that way all along. I’m with you.”

  “There’s one other thing—”

  “What?”

  “This magnetometer ought to go along with us, as well as the stuff we were taking anyway. Do you mind helping with the extra weight?” Shandara had not considered this aspect of the matter, but since his arguments had been founded on the question of time rather than effort he agreed readily to the additional labor.

  “All right. Just a few minutes while I dismount and repack this gadget, and we’ll be on our way.” Ridging set to work, and was ready in the specified time, since the apparatus had been designed to be handled by spacesuited men. The carrying racks that took the place of regular packs made the travelers look top-heavy, but they had long since learned to keep their balance under such loads. They turned until the nearly motionless sun was behind them and to their right, and set out for the hills ahead.

  These elevations were not the peaks they expected to use; the Moon’s near horizon made those still invisible. They did, however, represent the outer reaches of the area which had been disturbed by whatever monstrous explosion had blown the ring of Plato in the Moon’s crust. As far as the men were concerned, these hills simply meant that very little of their journey would be across level ground, which pleased them just as well. Level ground was sometimes an inch or two deep in dust; and while dust could not hide deep cracks it could and sometimes did fill broader hollows and cover irregularities where one could trip. For a top-heavy man, this could be a serious nuisance. Relatively little dust had been encountered by any of the expedition up to this point, since most of their work had involved slopes or peaks; but a few annoying lessons had been learned.

  Shandara and Ridging stuck to the relatively dust-free slopes, therefore. The going was easy enough for experienced men, and they traveled at pretty fair speed—some ten or twelve miles an hour, they judged. The tractor soon disappeared, and compasses were useless, but both men had a good eye for country, and were used enough to the Lunar landscape to have no particular difficulty in finding distinctive features. They said little, except to call each other’s attention to particularly good landmarks.

  The general ground level was going up after the first hour and a half, though there was still plenty of downhill travel. A relatively near line of peaks ahead was presumably the crater rim; there was little difficulty in deciding on the most suitable one and heading for it. Naturally the footing became worse and the slopes steeper as they approached, but nothing was dangerous even yet. Such crevasses as existed were easy both to see and to jump, and there are few loose rocks on the Moon.

  * * *

  It was only about three and a half hours after leaving the tractor, therefore, that the two men reached the peak they had selected, and looked out over the great walled plain of Plato. They couldn’t see all of it, of course; Plato is a hundred kilometers across, and even from a height of two thousand meters the farther side of the floor lies below the horizon. The opposite rim could be seen, of course, but there was no easy way to tell whether any of the peaks visible there were as high as the one from which the men saw them. It didn’t really matter; this one was high enough for their purposes.
>
  The instruments were unloaded and set up in half an hour. Ridging did most of the work, with a professional single-mindedness which Shandara made no attempt to emulate. The geophysicist scarcely glanced at the crater floor after his first look around upon their arrival, while Shandara did little else. Ridging was not surprised; he had been reasonably sure that his friend had had ulterior reasons for wanting to come this way.

  “All right,” he said, as he straightened up after closing the last switch, “when do we go down, and how long do we take?”

  “Go down where?” asked Shandara innocently.

  “Down to the crater floor, I suppose. I’m sure you don’t see enough to satisfy you from here. It’s just an ordinary crater, of course, but it’s three times the diameter of Harpalus even if the walls are less than half as high, and you’ll surely want to see every square meter of the floor.”

  “I’ll want to see some of the floor, anyway.” Shandara’s tone carried feeling even through the suit radios. It’s nice of you to realize that we have to go down. I wish you realized why.”

  “You mean … you mean you really expect to climb down there?” Ridging, in spite of his knowledge of the other’s interests, was startled. “I didn’t really mean—”

  “I didn’t think you did. You haven’t looked over the edge once.”

  Ridging repaired the omission, letting his gaze sweep carefully over the grayish plain at the foot of the slope. He knew that the floor of Plato was one of the darker areas on the Moon, but had never supposed that this fact constituted a major problem.

  “I don’t get it,” he said at last. “I don’t see anything. The floor is smoother than that of Harpalus, I’d say, but I’m not really sure even of that, from this distance. It’s a couple of kilos down and I don’t know how far over.”

  “You brought the map.” It was not a question.

  “Of course.”

  “Look at it. It’s a good one.” Ridging obeyed, bewildered. The map was good, as Shandara had said; its scale was sufficient to show Plato some fifteen centimeters across, with plenty of detail. It was basically an enlargement of a map published on Earth, from telescopic observations; but a good deal of detail had been added from photographs taken during the approach and landing of the expedition. Shandara knew that; it was largely his own work.

  As a result, Ridging was not long in seeing what his companion meant. The map showed five fairly large craterlets within Plato, and nearly a hundred smaller features.

  Ridging could see none of them from where he stood.

  He looked thoughtfully down the slope, then at the other man.

  “I begin to see what you mean. Did you expect something like this? Is that why you wanted to come here? Why didn’t you tell me?”

  “I didn’t expect it, though I had a vague hope. A good many times in the past, observers have reported that the features on the floor of this crater were obscured. Dr. Pickering, at the beginning of the century, thought of it as an active volcanic area; others have blamed the business on clouds—and others, of course, have assumed the observers themselves were at fault, though that is pretty hard to justify. I didn’t really expect to get a chance to check up on the phenomenon, but I’m sure you don’t expect me to stay up here now.”

  “I suppose not.” Ridging spoke in a tone of mock resignation. The problem did not seem to concern his field directly, but he judged rightly that the present situation affected Shandara the way an offer of a genuine fragment of Terrestrial core material would influence Ridging himself. “What do you plan to take down? I suppose you want to get measures of some sort.”

  “Well, there isn’t too much here that will apply, I’m afraid. I have my own camera and some filters, which may do some good. I can’t see that the magnetic stuff will be any use down there. We don’t have any pressure-measuring or gas-collecting gadgetry; I suppose if we’d brought a spare water container from the tractor we could dump it, but we didn’t and I’d bet that nothing would be found in it but water vapor if we did. We’ll just have to go down and see what our eyes will tell us, and record anything that seems recordable on film. Are you ready?”

  “Ready as I ever will be.” Ridging knew the remark was neither original nor brilliant, but nothing else seemed to fit.

  * * *

  The inner wall of the crater was a good deal steeper than the one they had climbed, but still did not present a serious obstacle. The principal trouble was that much of the way led through clefts where the sun did not shine, and the only light was reflected from distant slopes. There wasn’t much of it, and the men had to be careful of their footings—there was an occasional loose fragment here, and a thousand-meter fall is no joke even on the Moon. The way did not lead directly toward the crater floor; the serrated rim offered better ways between its peaks, hairpinning back and forth so that sometimes the central plain was not visible at all. No floor details appeared as they descended, but whatever covered them was still below; the stars, whenever the mountains cut off enough sidelight, were clear as ever. Time and again Shandara stopped to look over the great plain, which seemed limitless now that the peaks on the farther side had dropped below the horizon, but nothing in the way of information rewarded the effort.

  It was the last few hundred meters of descent that began to furnish something of interest. Shandara was picking his way down an unusually uninviting bit of slope when Ridging, who had already negotiated it, spoke up sharply.

  “Shan! Look at the stars over the northern horizon! Isn’t there some sort of haze? The sky around them looks a bit lighter.” The other paused and looked.

  “You’re right. But how could that be? There couldn’t suddenly be enough air at this level—gases don’t behave that way. Van Maanen’s star might have an atmosphere twenty meters deep, but the Moon doesn’t and never could have.”

  “There’s something between us and the sky.”

  “That I admit; but I still say it isn’t gas. Maybe dust—”

  “What would hold it up? Dust is just as impossible as air.”

  “I don’t know. The floor’s only a few yards down—let’s not stand here guessing.” They resumed their descent.

  The crater floor was fairly level, and sharply distinguished from the inner slope of the crater wall. Something had certainly filled, partly at least, the vast pit after the original explosion; but neither man was disposed to renew the argument about the origin of Lunar craters just then. They scrambled down the remaining few yards of the journey and stopped where they were, silently.

  There was something blocking vision; the horizon was no longer visible, nor could the stars be seen for a few degrees above where it should have been. Neither man would have had the slightest doubt about the nature of the obscuring matter had he been on Earth; it bore every resemblance to dust. It had to be dust.

  But it couldn’t be. Granted that dust can be fine enough to remain suspended for weeks or months in Earth’s atmosphere when a volcano like Krakatoa hurls a few cubic miles of it aloft, the Moon had not enough gas molecules around it to interfere with the trajectory of a healthy virus particle—and no seismometer in the last four weeks had registered crustal activity even approaching the scale of vulcanism. There was nothing on the Moon to throw the dust up, and even less to keep it there.

  “Meteor splash?” Shandara made the suggestion hesitantly, fully aware that while a meteor might raise dust it could never keep it aloft. Ridging did not bother to answer, and his friend did not repeat the suggestion.

  * * *

  The sky straight overhead seemed clear as ever; whatever the absorbing material was, it apparently took more than the few feet above them to show much effect. That could not be right, though, Ridging reflected, if this stuff was responsible for hiding the features which should have been visible from the crater rim. Maybe it was thicker farther in. If so, they’d better go on—there might be some chance of collecting samples after all.

  He put this to Shandara, who agreed; and the two start
ed out across the hundred-kilometer plain.

  The surface was fairly smooth, though a pattern of minute cracks suggestive of the joints formed in cooling basalt covered it almost completely. These were not wide enough even to constitute a tripping danger, and the men ignored them for the time being, though Ridging made a mental note to get a sample of the rock if he could detach one.

  The obscuration did thicken as they progressed, and by the time they had gone half a dozen kilometers it was difficult to see the crater wall behind them. Looking up, they saw that all but the brighter stars had faded from view even when the men shaded their eyes from the sunlit rock around them.

  “Maybe gas is coming from these cracks, carrying dust up with it?” Shandara was no geologist, but had an imagination. He had also read most of the serious articles which had ever been published about the Moon.

  “We could check. If that were the case, it should be possible to see currents coming from them; the dust would be thicker just above a crack than a few centimeters away. If we had something light, like a piece of paper, it might be picked up.”

  “Worth trying. We have the map,” Shandara pointed out. “That should do for paper; the plastic is thin enough.” Ridging agreed. With some difficulty—spacesuit gloves were not designed for that purpose—he tore a tiny corner off the sheet on which the map was printed, knelt down, and held the fragment over one of the numerous cracks. It showed no tendency to flutter in his grasp, and when he let go it dropped as rapidly as anything ever did on the Moon, to lie quietly directly across the crack he had been testing. He tried to pick it up, but could not get a grip on it with his stiff gloves.

  “That one didn’t seem to pan out,” he remarked, standing up once more.

  “Maybe the paper was too heavy—this stuff must be awfully fine—or else it’s coming from only a few of the cracks.”

  “Possibly; but I don’t think it’s practical to try them all. It would be smarter to figure some way to get a sample of this stuff, and let people with better lab facilities figure out what it is and what holds it off the surface.”