by Hal Clement
“The tanks were completely full, initially. We never touched them on landing. With those valves wide, the water would have boiled—we should have felt the vibration if we were in the ship. It must have been done while Ingersoll was on watch. Boiling water would spatter into the vents, and perhaps outside them, and as the evaporation pulled heat from it it would freeze. The valves are probably jammed with ice.
“You may not have lost much from the tanks, since a layer of ice would have formed sooner or later on the surface and cut down the evaporation rate. That must be what made the ship so cold—evaporation into a vacuum. I should think you could free the valves by melting the ice—you may have to do some improvising with electric heaters, but it shouldn’t be difficult. When you get the valves shut, keep the main thermostat up the way I left it. When the ship temperature really starts to climb, the ice inside the tanks will have melted and you can reset it to make the place comfortable. With liquid in the tanks, you can compute the amount of juice from the reading of any of the static pressure gauges—preferably Number One, the lowest. There’s a table in my kit for turning pressure readings into quantity for that tank under various acceleration conditions. We’d better go on, it seems to me. Whether or not there’s enough juice left to get us home doesn’t make much difference in what we can do about it.”
Imbriano interrupted. “Why go on, though? Ingersoll must have been raving mad to pull that trick. It would doom him as surely as it does us, if too much water really boiled from the tank. He’s probably driven himself over a cliff or opened his cab with his helmet off by this time, anyway!”
NO ONE IN the cab really heard Kinchen’s answer to this. It came through, but it came through mixed with another voice. It was a dry, clear voice, enunciated so perfectly that the words were plain even mixed with those of Kinchen, and clear enough to permit the mocking overtones to be grasped. All three listeners got every word of it; none of them could remember afterward what Kinchen had been saying at the same moment.
“That sounds like our good doctor!” the mocking voice came. “The doctor who knows so much. The doctor who shouldn’t really have come to moon at all, since he knows much about it—knows it hasn’t any life, and knows it hasn’t any water. Such a smart fellow! And he feels sure I’ve killed myself, so that I won’t have to starve on the moon like the others, because of course that dope Ingersoll could never find anything on the moon to replace water lost from the tanks! Oh, no!”
“Tell me, Dr. Imbriano, how, to you manage to live with your own brilliance? Doesn’t t overwhelm you at times? Of course, you’re right about one thing—you ought to go back. You won’t get to water with the fuel you have. I can wait, wait until you’re gone, and fuel up my tractor and come back, and refill the ship’s tank, too. And I can take off for Earth with a very sick group of friends, and they just might die en route, and be jettisoned in space, so no one could ever tell just what they died of. And maybe they were a little crazy, because they destroyed my life specimens—don’t you think that’s a reasonable chain of events, you self-righteous, pompous, know-it-all? Don’t you?” Ingersoll’s voice fell silent, and the men in the cab looked at each other.
“He’s really gone!” muttered Detzel. “Plant life—which I could and did swallow—but now water, which I certainly can’t!”
His attention was attracted by Kinchen’s voice, asking why the tractor had stopped broadcasting. Evidently Ingersoll’s waves were not reaching the ship, which was hardly surprising. Detzel extended the microphone to the doctor, so that he could explain what had happened, but Imbriano shook his head impatiently. He was obviously bothered by something, and didn’t want his thoughts interrupted, so Detzel himself explained to the commander. Kinchen listened silently.
“If he’s really out of range, you might as well come back,” he said when the engineer had finished. “I wish those fellows who gave us all the tests before takeoff had been able to pick that up. We’ve lost one man, may lose nine more, and the project itself can’t possibly be completed now. All that’s over and above the fact that I liked Ingersoll.”
DETZEL was about to acknowledge the order when the doctor held up a hand imperiously.
“Wait!” he exclaimed. “Can he possibly be out of range of the tractor yet, if we can hear him on the radio?”
“It’s hard to be sure, without knowing how far from a straight line the ground will force us to go, but I’d say it was unlikely. Why?”
“Beacuse we’ll have to get him—have to. He’s not crazy the way you think. I’m no psychologist, I admit, but I think I know what’s wrong, and it’s my fault. Sure, he’s a bit paranoid—but I rode him too hard. If anything pushed him over the edge into this nonsense, it was the way I treated him—you could read that, in the way he was talking just now. I’m the one, he’s down on, and—well, let’s not go into it. We’ve got to get him.”
“I can’t see it,” retorted Frake. “What difference does the cause make? Even if you feel guilty, and want to rescue him, what difference does it make if he’s killed us all? I don’t blame you, but . . .”
“That’s not it—at least, not all of it. Sure, I feel pretty rotten about what I’ve done to Milt, but that’s not the whole story. He’s not raving mad. He wants revenge on me. How can he get it unless he’s telling the truth about the water?”
“THERE was a moment of silence; then Detzel spoke.
“Either you’re speaking from knowledge ‘way outside your field, or you’re filling in a graph with a lot of guesswork, or you’re nuttier than Ingersoll,” he remarked. “Just how do you get the notion of water on the moon? Every part of the blasted rock ball gets above the boiling point of water, or even what the boiling point would be at sea level on Earth. And the moon can’t hold any gas with a molecular weight of less than about sixty. Hydrate minerals like gypsum form from the evaporation of salt solutions, and if the moon ever had seas I’ll drink an equivalent quantity as soon as it’s proved.”
“Never mind the cosmology,” snapped Imbriano. “It’s irrelevant. Ingersoll, remember, is a geologist. I don’t think he’s a very good one, and it’s my own fault that I didn’t keep that to myself. But he’s not a complete dope and I never said he was. He claims, indirectly, that he’s found water. He should be competent to know whether he has or not. If you don’t want to stay on the moon to be discovered by the next expedition, then get back to the controls and start us along that trail once more. Ingersoll may be really crazy, but I’m betting he isn’t. Give me the mike.”
The engineer obeyed, muttering something about “wishful thinking,” and started up the turbine. Imbriano called the commander.
“We’re not coming back gas just yet,” he said. “I can’t explain why over the radio. Expect us when you hear from us.” He snapped the microphone onto its hook with a gesture of finality, and settled an back into his seat with an expression on his face which prevented either of the others from speaking. The tractor nosed its way along the small crater rim and began to switchback down into the incredibly broken country between Moretus and Short. The trail was clear enough, here; most of the ground was not only too rough for a tractor but too steep for dust, and everywhere a vehicle could go there was enough dust to take its tracks. More than once the marks showed multiple; evidently Ingersoll was retracing his earlier path.
FOR SOME fifteen miles projectile distance, which the torturous way made into more like forty, they followed westward between Moretus and Short. Then the trail led up the outer slopes of a ten-mile crater which overlapped the northern rim of Short, and down a terrifying ridge where the two merged out onto the somewhat smoother floor of the latter. The trail was more difficult to see here, but the drivers were catching on to the logic Ingersoll seemed to have used in finding the passes; and between this and the occasional tracks, they were able to follow almost straight across the thirty-mile walled plain of Short to another intruding pit on its southern rim. They sloped up along the latter, and eventually emerged on the eas
tern brink of Newton. They were perhaps ninety miles from the ship in a straight line, but had ridden considerably more than twice that distance.
The scene below them was something Earth could not offer, and even the moon would have had trouble in equalling. Newton comes the closest of any ringed plain of its size to having the entire floor visible from one of the walls. Usually the far side is well below the horizon; but Newton is deep. The men were not at the highest point of the rim; that was nearby, a four-and-a-half-mile peak more impressive than any mountain of Earth, since the four and a half miles was above the nearby plain rather than a sea several hundred miles away. Even from the point where the tractor was parked, the drop to the central plain was stomach-wrenching—something better than twice the depth of Arizona’s Grand Canyon.
A little ahead of them, the wall curved in and descended toward and even beyond the center of the ring, almost as though Newton were two partly-fused craters. It seemed likely that the trail they were following would go down this way; the fugitive had certainly come this way before, and it seemed unlikely that he would have resisted the temptation to make the descent along what looked like a God-given path.
NORTH and south the walls curved westward, finally swinging back together and meeting some seventy miles away. Inside, they alternated stretches of appalling steepness with what amounted to broad terraces; on the far side, the lowest of these could just barely be seen above the bulge of the moon’s curvature. The curve itself showed plainly on the floor of Newton, though even allowing for this the “plain” was far from level. The northern half seemed deeper than the southern, carrying on to some extent the impression of two merged craters; much of the deeper floor was invisible in the shadow of the north rim, the sun being less than fifteen degrees above the northern “horizon.” It was less than a day past local noon.
“This is a bad place to park if we don’t want Milt to know we’re coming,” remarked Detzel after absorbing the scenery for some minutes. “This metal buggy must be gleaming all over the crater. If he’s anywhere inside, he must know we’re here already.”
Imbriano didn’t answer directly. He was scanning every dark patch he could see within Newton’s ring with the infra-red viewer, and the northern part of the floor was a lot to cover with the narrow-field instrument. “I should think that even a man in a space suit would radiate visibly against that background,” he muttered. “It’s cold. Not a flicker on the screen, at any gain this thing can take. Any metal reflection in the sunlight areas?”
“Nothing so far.” Both the other men spoke together.
Frake added, “You want a spell on that snooper?”
“All right.” Imbriano removed his face from the visor, and handed the gear forward. For some time there was little sound as Frake very slowly and methodically scanned the impenetrable darkness be1ow. Then he stopped, and played with the gain control for a moment or two.
“That should be it,” he said. “It’s about the right temperature for a condenser radiator. I can’t see any motion, but he’s a long way off—forty miles, I’d guess, though it’s hard to be sure when we can’t see the bottom contour. He could be on a hill a lot closer.”
“Where?” both the others asked simultaneously.
“SEE THAT peak just coming up into sunlight on the floor, just below another on the far rim? There. It’s warm enough to show on the screen. Now, swing the viewer to the right slowly—just a couple of degrees—that’s it; you should have him.”
“There’s a spot on the screen, all right,” Imbriano admitted. “I can’t read these colors well enough to judge temperature, but you should know this gadget better than I. If you say it’s the right temperature, it must be Milt. I can’t imagine any other source of warmth down there. Let’s go.”
“Which way?”
“Keep along the trail. I know it takes us farther away from that radiation source, but I can’t see diving straight down hill toward it”
Detzel nodded, started the turbine again, and sent the vehicle crawling forward. As they had expected, the trail led out onto the spur which merged into the floor miles across the plain. It was impossible to follow rapidly; on the original trip, Ingersoll must have been amazingly lucky to find the way down in the time he had, been away. It turned out that the trail reached the floor well before the buttress did, switching down the north side so they were able to keep the radiation source in sight nearly to the bottom. On the floor itself, of course, the curve of the moon put the other machine below the horizon.
The trail now, led almost straight toward the northern shadows; the sun crawled visibly toward the scarp miles above as they advanced.
“We’re going to need lights here,” remarked Frake. “There’s reflection from the peaks, all right, but I wouldn’t trust it to keep us out of a crack.”
Detzel grunted agreement; Imbriano was silent. A faint memory was crawling up into his consciousness. He kept sweeping the darkness ahead of them, hoping the other tractor would show on the screen; but the minutes crawled by with nothing appearing.
THE SUN vanished at last. The ground about them could just be seen in the light reflected from the ring of peaks, but as Frake had predicted, the lights of the tractor were needed. If the other vehicle were still in shadow, it must be using lights too; but of course these would be almost impossible to see unless pointed straight at the pursuers. Imbriano kept the viewer in use.
The ground, when they firs entered the shadow, was the typical, dark, dusty lunar plain. At first, they saw an occasional track; then they must have wandered a little off the line, for no more of these appeared. When Detzel finally pointed this out, and asked the doctor which way to go, Imbriano answered, “As you are. Keep angling west, and toward the north rim. That’s about the direction to the spot where he was, and there’s something else I want to see, anyway.”
“You won’t see much with these lights,” replied the driver. “You’d better wait until the sun gets here. It looks as though we might be waiting, anyway; turbine juice is running low. We’re about to the halfway mark on the gauge, and there’s a big hill to climb the way back.” Imbriano smiled, seemed about to speak, but didn’t.
Then, slowly, the ground changed. Its color under the lights was paler, as though more feldspar were showing in the predominantly basaltic rock, and the doctor began to nod slowly. At last the surface seemed almost white.
“Bear a little to the left—five degrees or so,” he said abruptly. Detzel obeyed without asking why, and silence fell again for another ten minutes. Then something appeared on the ground ahead.
“Tracks!” exclaimed Erake, the first to see them. “We’ve found the trail again!”
“I thought we’d be pretty sure to cross it,” Imbriano said quietly, “and of course, it would show up well here.”
“Why of course? Because the dust is so light-colored? I’m surprised it’s deep enough, on this flat surface. The trail looks almost like marks in snow.”
“Uh-huh.” Imbriano drawled the answer in a manner which would not have been tolerated even in a child actor, but the tone got his hearers’ attention. They whirled in their seats to face him.
“Are you implying it really is snow?” gasped Detzel.
“EEYES FRONT, driver. I am too much of an ignoramus to dare imply anything. I think I owe Milt Ingersoll a profound apology, though. If one of you will switch on the radio, I’ll try to make it. He might be close enough for diffraction to get him even if he isn’t quite line-of-sight from here.”
“Wait a minute.” Detzel made no move toward the radio. “I don’t care what the stuff out there looks like. If it has a boiling point much below that of feldspar, I’ll melt and drink it. You know as well as I that even ice has a respectable vapor pressure near its freezing point, and when the sun gets on his stuff it’s a darned sight hotter than the freezing point of ice.”
“Minor catch, Al. When does the sun get on it?”
“Why—in the daytime, of course. It . . .”
“I hate to be a party popper, but isn’t it daytime right now, on this part of the moon? Correct me if I’m wrong.”
Detzel whistled gently. “You’re right. Some of this shadow would get light when the sun was farther east or west, but most of it, right against the wall particularly—but wait. What about seasonal changes?”
“On the moon? With its axis about one degree from the perpendicular to its heliocentric orbit? Sorry. I don’t know how permanent that axial orientation is—with all the perturbations there must be—but I’ll bet it hasn’t wandered very far from its present line since the moon’s rotation matched its geocentric revolution. Some of this area may have been dark for only a few thousand or a few million years, but right in against the cliffs it’s been more like two or three billion, I expect”
“I see what Milt didn’t like about you. You’re too darned right. All right, I concede, drink the stuff. But wait a minute. Granting that it could stay here, how did it get here: I don’t buy rain, springs, frost, dew, rivers, or any other normal way.”
“You’d better not drink it. I expect it’s ice only by courtesy. I wouldn’t be surprise if a good healthy lacing of ammonia and perhaps methane were there; as well as water. As far as how goes, I don’t really know. But as a working guess, the moon must have passed through quite a few comet tails in the last couple of billion years.”
“But comet tails are thin—a ton to the million miles of length, or something like that . . .”
“Two billion years is a long time. But I don’t insist on that. I haven’t tried to work it out quantitatively; and wouldn’t be able to get an answer if I did try. Maybe the solar system went through a nebula or something—I don’t know. I just say there’s something like snow out there, and Ingersoll seems to have convinced himself that’s what it is, judging by his remarks a few hours ago. That’s why I say—give me the radio. I want to apologize to him.” Detzel obeyed in dazed silence, and Imbriano sent a call pulsing out over the crater floor, but there was no answer. He stopped after a few minutes, judging that he either wasn’t being heard or was being snubbed, and they kept on along the trail.
