Planet for Plunder

by Hal Clement

  At least, he had eliminated the last possible doubt that the things were non-metallic, non-electric machines, since he had actually seen them move in a manner which verified and complemented his seismic observations. This implied that the natives were not merely cultured, but had developed a physical science equal to, perhaps greater, than that of the agent’s own race. The latter was certainly possible, since he had not the faintest idea of what was the operative principle of the devices. It was a disturbing speculation, but he refused to enlarge upon it emotionally. Obviously they had some electrical equipment. The signal detector and broadcasting device, as well as the ionization cylinder, were quite evidently as artificial as his own ship. Their science, regardless of its development, could not be entirely alien. It might be possible for him to learn something about it. If so, it was important that he begin—for the equipment needed to stop the moles would have to be obtained from these people in rather short order.

  The agent examined once more, as precisely as his sensory equipment permitted, every detail of the things around him, which were now returning slowly, after their hasty withdrawal. He broadcast his “Hello” again, and carefully noted the way it affected the receiver. When the answer came, he checked with equal care the source of the modulating energy.

  The result was interesting. The receiver apparently did not consider the carrier waves important. It damped them out and used, through most of its circuitry, a secondary signal consisting of the original modulations. This was caused to vary the strength of a magnetic field which, as nearly as the agent could tell, was used to impart mechanical motion to an object principally non-metallic.

  He could get only a rough idea of its size and shape from the space left for it in the mechanism. The evidence seemed to indicate that the whole device simply rebroadcast the modulation of the original signal mechanically into the atmosphere.

  He knew, of course, that a gas could carry compression waves, though it had never occurred to him that they might be of any particular use. He had simply never stopped to wonder why his method of digging was more effective on a planet with atmosphere. It did no good to blame oneself for such oversights when the fat was in the fire. Anyway, he was sure of one thing. The waves were being used to carry the signals controlling the machines. Certainly no others were.

  They also served for communication, since similar waves appeared to be received by the same disc in the signal device, and were used to modulate its broadcast electromagnetic impulses. This process seemed pointless, except as a means of long-distance communication. Probably pressure waves did not transmit energy so effectively through a gas as electromagnetic radiation carried it through space. So far, so good.

  It all tied in, more or less, with the evident fact that these machines were not electrical, even if it did not begin to explain how they actually worked. Some sort of more precise analysis would, of course, be needed. The metal he could detect about the things seemed quite purposeless, and he did not see that it was likely to help.

  It was present in small, disconnected bits and was devoid of electrical energy, if you brushed aside the minute currents generated by its motion in the planet’s magnetic field.

  The machines, then, were made virtually entirely of nonconductors, and should be about as easy for the agent to examine as a device consisting exclusively of gas jets and magnetic fields would be for a human being.

  This meant that the analysis would have to be by highly indirect methods. A chemist, with his laboratory machine, might be able to do the job in microseconds. But a traveling device, like the scoutship, had no equipment designed with any such purpose in mind.

  He suspected that this was one of the situations where the sensile members of his race—the great majority—would leap at the chance to show their superiority over one who was bound to a machine. It had always been that way. It was a common enough feeling among those whose lives were primarily intellectual. The doers, like the agent, countered it with a clear recognition of the necessity for their work. At the moment, however, the agent rather wished that a normal person had been present, to show his intellectual superiority.

  Then he realized that his own possession of machinery did not disqualify him as an intelligent being. If a member of his race could solve this problem, it was as likely to be himself as anyone else. He would have to use all his knowledge, of course, not just the specialized information which was all the millennia of flight demanded.

  Enough knowledge should be there. He had, of course, been young when he had elected this life, but he had had much thinking time before his career was actually begun. Also, there had been a good deal of time to think as he drifted among the stars, and opportunities to gather data that planetbound thinkers had never possessed.

  He would have to go back to the most elemental principles of thought—if he could. First, he had decided, on the basis of what seemed adequate evidence, that the planet was inhabited—that its inhabitants used machines and, therefore, had freedom of motion—and that these machines were based on a technology almost, but not quite wholly, alien to his own.

  Nevertheless, the devices must operate under the same physical laws that obtained elsewhere in the universe. This meant that they must take in some form of energy, must perform a desired action, and must eventually account for the energy as heat.

  The energy was not electric or magnetic, since he could have detected the presence of that kind of energy directly. It was not gravitational, since the gravitational potential of these machines—when measured as a function of their distance from the planet’s center—had actually increased since he had first detected them. It was barely possible, of course, that some primary source beyond his detection-range might work on such a basis. But for the moment that hardly bothered him. It could be filed away for future reference.

  There was almost certainly no direct mechanical link with a distant energy source. He felt sure that he would have seen any such, during his brief trip aloft.

  Chemical energy, however, remained a distinct possibility. Normally—which usually meant, he reflected wryly, circumstances in which intelligence had not taken a hand—chemical reactions were too slow to provide useful energy, even though they were responsible for life. However, on a planet infested with such weirdly active carbon compounds, it would not do to be dogmatic on the matter.

  It was known that reactions, in such circumstances, did go with enormous speed, though little actual quantitative work had been done on the matter of the energy involved. It was quite conceivable, in any case, that there might be some method of turning chemical directly into mechanical energy, without involving electricity as an intermediate stage.

  Looked at from this viewpoint, several more possibilities as to the planet became evident. Its natives could survive, either by nature or intelligent adaptation, in an oxygen-rich atmosphere. Oxygen was one of the most virulently active elements in existence. Hence, it might not be too surprising to find such a people developing a chemical technology and bypassing the electricity a living creature should logically use—but wait. They had not bypassed electricity.

  There were auxiliary machines, among the vehicles facing him, which did use it. Perhaps, these people had originally developed a normal technology, but, for some unaccountable reason, had never mastered space-flight! That was more than likely, if one assumed they did not merely tolerate oxygen, but needed it.

  In that case, they would inevitably exhaust, in a relatively short time, the metal resources of a single planet.

  They would be faced with the choice of developing machines that did not make demands on the metal supply, or of sinking to barbarism during the millions of years it would take new metal deposits to concentrate to usability.

  This race might have succeeded in accomplishing the former—in which case, the exhaustion of the local ore veins could not be blamed on the poachers after all. The marauder might have planted the torpedoes in momentary pique, believing that a regular freighter had been there first and
hoping to throw the production schedule of this planet out of step with that which had been recorded for it.

  It was a very attractive idea, but the agent decided he should not go quite so far in pure speculation. There should be other possible sources of energy besides chemical activity, promising as such energy appeared to be. He could, for example, detect a pressure against his hull which seemed to be due to currents in the atmosphere. These must necessarily carry energy, though it seemed, at first estimate, that it could hardly be quantitatively adequate to run these machines.

  There was nuclear energy. Obviously, these aliens did not use it directly, yet the possibility remained that it was their primary source and was stored in some non-self-destructive form within them. Strength was lent to this possibility by the presence of the ionization tube, which might well be used to locate radioactive materials. If, of course, the normal senses of the creatures were inadequate for the task. Atomic energy not under rigid control was always a rather frightening thing to contemplate, and he did not dwell on certain other unlikely possibilities concerning it.

  He had already thought of solar energy, but had seen nothing to offset any of his earlier objections to this theory. On the whole, the chemical idea seemed the most worth following up.

  He searched his memory for the little he knew about the highspeed chemical reactions of free-oxygen environments, and found a few helpful items. For one, they did involve solar energy—they employed it usually in breaking down water. The oxygen was freed to the surroundings, and the hydrogen combined with oxides of carbon to produce carbohydrates.

  These, in turn, could react upon each other, with simple compounds and with some of the free oxygen, to produce incredibly complex substances whose detailed structure had never been worked out by any chemist of his people. This situation should, of course, result in a continual increase of free oxygen in the planet’s atmosphere at the expense of the water.

  Observation indicated that, actually, an equilibrium was usually attained in this respect. Whether the oxygen re-combined spontaneously with the hydrogen in the compounds, or whether still other high-speed reactions, of the same general type as the photosynthetic ones, did the trick, was still a matter of debate. Even the agent could understand, however, that the combination of oxygen with almost any of the complex carbon-hydrogen compounds would return the energy originally supplied by the sun.

  If the compounds had any reasonable density, it should be possible to store quite a fuel supply in a very small space that way, using atmospheric oxygen to combine with it whenever desired. Even without precise figures, he felt sure that this would constitute an adequate energy-source for the machines he had been watching.

  Was there anything he had overlooked? No—he was nothing if not thorough when he undertook a task of objective scientific analysis. A doer had his own pride to safeguard, and if he was not an intellectual in a strict sense, he did possess a first-rate mind.

  How could this theory be checked experimentally? If it proved correct, there should be, somewhere on or within these machines, a store of hydrogen-carbon compounds. They should be absorbing atmospheric oxygen at a fairly high rate. And they should be exhausting water and, possibly, oxides of carbon.

  He had no means for recognizing the hydrogen-carbon compounds, even if he found them, so there seemed little point in trying to take one of the mechanisms apart. No point even if its operator proved willing to allow it. However, there seemed to be a possible way of attacking the problem through the other facts. If an oxidizing reaction of the sort he had envisioned went on in a confined space, what would happen to the pressure? He pondered the problem.

  Producing solid oxides would reduce pressure by removing oxygen. The formation of carbon dioxide would leave it unchanged, for there would be the same number of molecules after the reaction as before. Making water or carbon monoxide would give a pressure increase, since each molecule of oxygen would go into two molecules of the product.

  All this, of course, assumed that water and the oxides of carbon were gases at this temperature. The method offered him two out of three chances of learning something—better, really, since it was likely that two, or all three, of the reactions occurred together. Only if CO2 alone were produced, would there be a negative result. The catch seemed to be how one was to seal one of these devices in a gas-tight container, with a limited amount of atmosphere?

  The container, of course, was available. His own ship had a good deal of waste space, left deliberately to allow for later modifications, if and when they were developed. He could open his hull for maintenance at virtually any point, and the openings were naturally designed to seal gas-tight, since his occupation was more than likely to lead him into corrosive atmospheres such as this.

  He would have to be sure that he let the planet’s air only into chambers where it could not reach either his own tissues or the ship’s circuitry. No, wait. The test should take only minutes or hours, not years. Both his flesh and the silver wires could stand oxygen that long, and he could get rid of it later by opening the hull to the vacuum of space. That made matters easier—much easier.

  But how could he detect the change in pressure, if it did occur? He did have manometers, of course. But they were vented to the outside of his hull. No one had foreseen a need for measuring internal pressure. He would have to do some more hard thinking.

  What effects would pressure produce, besides merely mechanical ones? There would not be enough change, in the electrical properties of the exposed wires, for even the agent to detect. The change would probably not be fast enough to alter the temperature noticeably. And even if it did alter it, he would not be able to tell whether the change were due to gas laws, or simply the operation of the machine.

  In the temperature range of this world, it was not really certain that all the products were gaseous, anyway. The mere fact that he had detected them in that form, during his approach, meant nothing. The infra-red spectrographic equipment he had used would have picked up trace quantities. It was unfortunate that its receivers were also aimed outward.

  The agent could not, for the life of him, recall the vapor-pressure curves of any of the expected products—though, come to think of it, something was liquid here. The clouds he could see proved that, as did their precipitation on his half. He could not assume that it was one of the products he sought, however, and his best bet was still to maintain pressure change. If he could do it . . .

  VIII

  STUNNED, SHAKEN, shaken, the three humans stared at the star-traveler which had now so unbelievably and unexpectedly revealed itself in full. And the star-traveler stared back at them through its dull, opaque vision windows.

  It was Candace Parsons who spoke first. “Why!” she exclaimed in a strained, oddly small voice. “Why—it looks like a gigantic bathysphere! Maybe . . .” she fell silent.

  Hal Parsons, ignoring the rain that streamed down his face, said, “Maybe what, baby?”

  “I don’t know.” Candace’s voice remained off-pitch, tremulous. “I guess I was thinking that maybe—if he is from outer space—our atmosphere is like an ocean to him. Maybe he is a bathysphere.”

  “Why do you refer to that thing as he?” her husband asked sharply. “Whatever is inside probably has no more concept of sex as we know it than an amoeba.”

  “I don’t know. I really don’t know, Hal.” Candace mopped the rainwater from her face with a khaki towel she had brought from the jeep. “I don’t know, but he—just seems masculine somehow.”

  “If that’s a bathysphere,” put in Truck MacLaurie, with a forced attempt at levity, “I’d surer than hell hate to take a bath in it. How would I ever get out?”

  “Truck!” said Candace, biting her underlip. “Don’t you honestly know what a bathysphere is?”

  “Isn’t it a round bathtub?” Truck asked.

  “For your information,” Candace said, more to herself than to the young man who had blundered, “A bathysphere is a globular device designed by Willi
am Beebe for deep underwater observation. Professor Piccard later used an improved model to—”

  Her husband, who kept his eyes riveted on the alien visitor, suddenly leapt at her and pushed her flat on her face against the hillside. As he did so he yelled at Truck, “For God’s sake, flatten out!”

  The alien was on the move. There could be no doubt about it this time. Candace, her face ashen, felt the near-earthquake vibration emanating from the advancing sphere and looked up, barely in time to see it zoom skyward, leaving boiling earth and mud in its wake.

  The alien’s rise was as rapid as the pursuit-foiling lifting processes attributed to flying saucers in the nation’s press. He shot up a thousand feet—two thousand—and again they smelled the acrid aroma of metal heating up unbearably from friction with the atmosphere.

  Feeling a sudden, shocking, incongruous disappointment, Candace cried, “Oh—he’s getting away! He’s leaving Earth”

  “No he isn’t,” said Truck, staring grimly up into the rain. “Get a load of that!”

  That proved to be a sudden lateral maneuver on the part of the alien. It moved several hundred yards sideways and again was immobile. It was apparently as capable of remaining immobile in the atmosphere as it had been immediately following its self-burial in the rocky soil.

  Candace could see the great round eyes, reduced to mere dots in the distance, trained steadily upon the three of them. She experienced paralyzing fear. It was obvious now that the alien failed to welcome close contact with humans, and was determined to resist investigation.

  Secondarily—but no less frightening—was the thought that, being an alien, it could scarcely be expected to have humanitarian sympathies. It would probably be no more hesitant about wiping them out than most people were about destroying bothersome insects.