Complete Short Fiction, page 142
“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.
IV
PERHAPS an hour later, after several more unanswered calls, they reached a spot where something seemed to have happened. There was a dark patch of irregular shape in the “snow.” The white deposit was now some half an inch deep on the plain; but here it seemed to have been cleared away. The edges of the bare region were sharp and well defined, though irregular. The men all reached the same conclusion at the same time; they had all shovelled too many snowy driveways to be fooled here.
“He scraped the stuff up to put in his tank!” exclaimed Frake. “That’s what he meant about water, all right—though he’ll spend a good long time getting up enough to make much impression on the ship’s tank, I should think. But hadn’t we better do the same? Our own fluid gauge is reading lower than I really like, at this distance from Moretus.”
“How about it, Al?” asked Imbriano. “Suppose this stuff is largely ammonia and/or methane? What would happen if we used it in the tractor?”
“Either one is all right so far as straight theory goes,” Detzel replied carefully. “They’re both low-boiling, low molecular weight compounds which would operate perfectly well in a turbine. I’m just afraid they might be a little too low boiling. That would cut down of efficiency, and at our working temperature their vapor pressures might be too much for our tank.”
“I was afraid of that. Is there any way we can make sure, safely?”
“I should think so. There are safety valves on the tanks—after all, even water is apt to get pretty hot if the tractor stands in the sun for long. The regular relief valves might keep things safe, but I could ease off their springs a bit to make them safer. If we don’t put too much of the stuff in at once, we might get away with it. After all, Ingersoll seems to have.”
“HE SEEMS to have loaded the stuff. We don’t know that he got away with it,” responded the doctor dryly. “I suggest, Al, that we quietly put one pinch of the stuff in the tank and see what happens—in fact, could we draw a bucket or can or something of water from the tank and put our pinch of snow in that, at some distance from the tractor? I admit I’d be happier that way.”
“I guess a cup of water would last long enough for that. We’ll try, anyway.” The three men donned their helmets, pumped a reasonable fraction of the cab’s air into the low-pressure economy tank, and opened up. Detzel found a paper drinking cup and stepped out, making his way around to the trailer which carried the, fluid tank. There he bent, held the cup under a stop-cock, and quickly opened and, closed the latter. Water squirted out violently; it was warm enough to have a vapor pressure of several centimeters of mercury. The stream of liquid hit the cup and splashed, but enough remained inside to be useful. Detzel grimaced behind his face plate.
“Offends my economical soul,” he remarked, staring at the bubbling, frothing liquid.
“You’ll be wasting more if you don’t get moving,” retorted Frake. “Get some of the snow in before everything boils away.”
Detzel obeyed. He took a small scraper from its place on the side of the trailer and walked over to the edge of the clear area. He set the cup on the ground where the men could see it; Frake was holding the beam of a flashlight on the scene. He picked up a bit of the snowy material on the end of the scraper, and tipped it into the cup.
The results were spectacular; as Imbriano said a moment later, “Water holds quite a bit of latent heat, doesn’t it?” The contents of the cup fountained skyward and failed to return, fading into invisible vapor before the moon’s feeble gravity could do much about it. The cup itself was intact, but the fact was rather surprising to the witnesses.
“I don’t think any valves made will take that, or let the tank take it,” Detzel remarked “I’m afraid we’ll have to depend on what’s still in the tank to get us back to the ship.”
“WHAT?” Even Imbriano was startled to hear the dry voice of Ingersoll in his headset once more. “What? Can’t the brilliant doctor solve such a simple problem? Even when he just mentioned the answer? But of course, you have a slight disadvantage. You have only one fuel tank, haven’t you? I very carelessly brought the spare with me. It was empty when I filled it—with snow, friends—no water. No stored heat to speak of. I’ve packed the snow into it, and we’ll just let it melt very slowly, and the methane can evaporate quietly through the valves, and the ammonia stay in solution if it wants . . .
“I’ll tell you what, good doctor: why don’t you just dump all your water out of that tank? Then in a little while it will be cool enough to take the snow safely, and you can go back to starve with your friends—for you can’t catch me, can you? I have two tanks, and that makes the big difference, doesn’t it? I’m going, by the way, and—I’m sure you can see me with your instruments, but you can’t follow. You don’t dare go any way but back to Moretus, do you? Of course, I’m not going far either—I’m not going to take this tank out into sunlight for a while—but you don’t dare even chase me around in circles, do you? Fuel is getting a little short.”
He broke off as abruptly as he had started. The drivers looked at the doctor. He shrugged invisibly in his suit, and led the way back inside the cab. There, with air once more about them and their helmets off, Frake finally spoke up.
“Well? Was he right?” He was looking at Imbriano as he spoke.
“I’m not the engineer,” the doctor said wearily. “So far as I can see, he is perfectly right. Personally, I’m optimistic about the fuel in the ship’s tanks. I don’t think we could possibly have lost much before the ice layer formed. But that doesn’t make me any happier about Ingersoll.”
“Maybe we’d better tell him about the ice stopping the evaporation,” suggested Frake.
“You do it. He certainly wouldn’t believe me,” the doctor replied wearily. Frake took the microphone.
HE CALLED Ingersoll’s name several times, without answer; then he told about the freezing in the tank, sure that the other was listening. He ended with an air of frankness.
“I admit we don’t know there’s enough to get us home,” he said, “but you know I’m talking sense when I say there’s a good chance of it. If you want to take that chance, just stay where you are and watch. You can probably see the takeoff from here. You’ know about when it will be—you can guess how long it will take us to get back. We’re starting now. You can stay or come, as you please.”
He hung up the microphone and Detzel started the tractor out toward the sunlight, slanting back toward the foot of the trail leading down from the rim. Imbriano rode with head turned over his shoulder, in the general direction that he believed the other vehicle to be. There was sound from the radio.
But it was Detzel who saw the other machine, and called their attention to it. It was parallelling their course, half a mile to the north, and gradually pulling ahead of them. It was just barely visible; almost all that could be seen was scattered light from its lenses, and the streak of illumination stretching over the ground ahead of it. Detzel took the microphone.
“Glad you’re coming, Milt,” he called. “Want to lead? You must know this road enough better than we do, so you can go faster safely.” There was a brief pause.
“All right. Pull over this way, and fall in behind me.” The voice had lost all trace of emotion. Detzel slanted obediently to the left, and relaxed a trifle—he had been giving close thought to the problem of navigation. Imbriano did not; and it was just as well.
THEY WERE a scant hundred yards from the other machine, and were just about able to make it out in the light now reflected from the mountains, when Detzel’s attention was jerked back to full operational level. With a turn that threatened to snap the couplings of its trailers, Ingersoll’s tractor was whipping around; its lights glared directly into their eyes, and Imbriano and Frake ducked instinctively. Fortunately, Detzel’s reactions were of a more constructive nature; he wrenched their own vehicle to the right, and managed to avoid the first charge.
“Get your helmets on!” he snapped to the others. “Then take the wheel, Bill, while I do mine. If he even grazes us there’ll be no air in this cab!”
“We can outrun him. He’s pulling a bigger load,” the doctor pointed out as he fitted his helmet in place.
“We could on the straight—but we’re not sure we can go straight. If anyone knows the crevasses around here, it’s Ingersoll, not me.”
“Even he shouldn’t know them too well. He can’t have spent all his time exploring cracks,” Frake put in optimistically.
“He doesn’t have to know them at all to have a big advantage,” snapped Detzel. “The sad fact is that we’re going first. If we can keep going, he can. We can keep ahead just as long as I don’t have to detour.”
“Head out into the sunlight!” cried Imbriano. “He won’t dare take that trailer of snow out there. It would boil too fast.”
“We don’t know what he’d dare. It’s a metal tank, and would take a while to heat up. And if he’s willing to risk his own life in a collision, he can’t be very rational anyway. I’m already on the way toward sunlight, in case you hadn’t noticed.”
“Put on more juice! He’s catching up!” called Frake. Detzel tried, but the turbine was already whirling at its safe limit.
“Something’s wrong. Our trailer must be dragging,” he snapped. “We didn’t take time to service it properly before we set out on this junket.”
“That’s not it. I can see now. The back right tire is flat. Either it picked a gruesome time to hit something sharp, or Milt nicked it on that first pass.”
“IF WE CAN’T outrun him, we’ll have to outmaneuver him,” grunted Detzel. “We should still be able to make tighter turns than he can, tire or no tire. Tell me when he’s about twenty yards back.”
“He’s closer than that already, I’d say, though it’s hard to be sure with the lights right in my eyes.” Detzel’s answer was another twist to the right. At the same moment Imbriano started the economy pump since they all had their helmets sealed by this time. Neither of the others noticed. Detzel would probably have objected to the waste of power if he had.
The turn was almost, but not quite, successful. The other machine grazed the rear of the trailer, some projection on it ripping their other back tire. Fortunately, the fuel tank front made the trailer’s center of gravity a trifle ahead of middle pair of wheels, so it didn’t settle too badly on back ones except under acceleration; but the additional flatting of the middle tires added quite a bit of drag.
For a moment, it looked as though Detzel might be overcoming this disadvantage. He held his turn, and the other train was unable to match it, as he had hoped. Slowly he drew ahead; then he was parallel, going the other way; then drawing up behind as he lapped Ingersoll. Then they were traveling only a yard or two away from the back trailer of the other machine, and matching its angular speed. As they reached this point, Imbriano opened the door by his seat and swung out.
For a moment, neither of the others noticed. By the time they did, he was climbing across the back of the cab and almost within reach of Ingersoll’s rear trailer. He reached, but couldn’t quite make it.
