by Hal Clement
Well, that was a problem for the geologists; Zaino climbed aboard and settled to his task.
The trouble was that he could do very little more here than he could in the tractor. He could have improvised longer-wave transmitting coils whose radiations would have diffracted a little more effectively beyond the horizon, but the receiver on the missing vehicle would not have detected them. He had more power at his disposal, but could only beam it into empty space with his better antennae. He had better equipment for locating any projecting wisps of charged gas which might reflect his waves, but he was already located under a solid roof of the stuff—the Albireo was technically on Brightside. Bouncing his beam from this layer still didn’t give him the range he needed, as he had found both by calculation and trial.
What he really needed was a relay satellite. The target was simply too far around Mercury’s sharp curve by now for anything less.
Zaino’s final gesture was to set his transmission beam on the lowest frequency the tractor would pick up, aim it as close to the vehicle’s direction as he could calculate from map and itinerary and set the recorded return message going. He told Rowson as much.
“Can’t think of anything else?” the captain asked. “Well neither can I, but of course it’s not my field. I’d give a year’s pay if I could. How long before they should be back in range?”
“About four days. A hundred hours, give or take a few. They’ll be heading back anyway by that time.”
“Of course. Well, keep trying.”
“I am—or rather, the equipment is. I don’t see what else I can do unless a really bright idea should suddenly sprout. Is there anywhere else I could be useful? I’m as likely to have ideas working as just sitting.”
“We can keep you busy, all right. But how about taking a transmitter up one of those mountains? That would get your wave farther.”
“Not as far as it’s going already. I’m bouncing it off the ion layer, which is higher than any mountain we’ve seen on Mercury even if it’s nowhere near as high as Earth’s.”
“Hmph. All right.”
“I could help Ren and Dr. Burkett, I could hang on outside the tractor—”
“They’ve already gone. You’d better call them, though, and keep a log of what they do.”
“All right,” Zaino turned back to his board and with no trouble raised the tractor carrying Hargedon and the mineralogist. The latter had been trying to call the Albireo and had some acid comments about radio operators who slept on the job.
“THERE’S ONLY one of me, and I’ve been trying to get the Darkside team,” he pointed out. “Have you found anything new about this lava flood?”
“Flow, not flood,” corrected the professional automatically. “We’re not in sight of it yet. We’ve just rounded the corner that takes us out of your sight. It’s over a mile yet, and a couple of more corners, before we get to the spot where I left it. Of course, it will be closer than that by now. It was spreading at perhaps a hundred yards an hour then. That’s one figure we must refine. Of course, I’ll try to get samples, too. I wish there were some way to get samples of the central cone. The whole thing is the queerest volcano I’ve ever heard of. Have you gotten Eileen started back?”
“Not as far as I can tell. As with your cone samples, there are practical difficulties,” replied Zaino. “I haven’t quit yet, though.”
“I should think not. If some of us were paid by the idea we’d be pretty poor, but the perspiration part of genius is open to all of us.”
“You mean I should charge a bonus for getting this call through?” retorted the operator.
Whatever Burkett’s reply to this might have been was never learned; her attention was diverted at that point.
“We’ve just come in sight of the flow. It’s about five hundred yards ahead. We’ll get as close as seems safe, and I’ll try to make sure whether it’s really lava or just mud.”
“Mud? Is that possible? I thought there wasn’t—couldn’t be—any water on this planet!”
“It is, and there probably isn’t. The liquid phase of mud doesn’t have to be water, even though it usually is on Earth. Here, for example, it might conceivably be sulfur.”
“But if it’s just mud, it wouldn’t hurt the ship, would it?”
“Probably not.”
“Then why all this fuss about getting the tractors back in a hurry?”
THE VOICE which answered reminded him of another lady in his past, who had kept him after school for drawing pictures in math class.
“Because in my judgment the flow is far more likely to be lava than mud, and if I must be wrong I’d rather my error were one that left us alive. I have no time at the moment to explain the basis of my judgment. I will be reporting our activities quite steadily from now on, and would prefer that you not interrupt unless a serious emergency demands it, or you get a call from Eileen.
“We are about three hundred yards away now. The front is moving about as fast as before, which suggests that the flow is coming only along this valley. It’s only three or four feet high, so viscosity is very low or density very high. Probably the former, considering where we are. It’s as black as the smoke column.”
“Not glowing?” cut in Zaino thoughtlessly.
“Black, I said. Temperature will be easier to measure when we get closer. The front is nearly straight across the valley, with just a few lobes projecting ten or twelve yards and one notch where a small spine is being surrounded. By the way, I trust you’re taping all this?” Again Zaino was reminded of the afternoon after school.
“Yes, Ma’am,” he replied. “On my one and only monitor tape.”
“Very well. We’re stopping near the middle of the valley one hundred yards from the front. I am getting out, and will walk as close as I can with a sampler and a radiometer. I assume that the radio equipment will continue to relay my suit broadcast back to you.” Zaino cringed a little, certain as he was that the tractor’s electronic apparatus was in perfect order.
It struck him that Dr. Burkett was being more snappish than usual. It never crossed his mind that the woman might be afraid.
“Ren, don’t get any closer with the tractor unless I call. I’ll get a set of temperature readings as soon as I’m close enough. Then I’ll try to get a sample. Then I’ll come back with that to the tractor, leave it and the radiometer and get the markers to set out.”
“Couldn’t I be putting out the markers while you get the sample, Doctor!”
“You could, but I’d rather you stayed at the wheel.” Hargedon made no answer, and Burkett resumed her description for the record.
“I’m walking toward the front, a good deal faster than it’s flowing toward me. I am now about twenty yards away, and am going to take a set of radiation-temperature measures.” A brief pause. “Readings coming. Nine sixty. Nine eighty. Nine ninety—that’s from the bottom edge near the spine that’s being surrounded. Nine eighty-five—” The voice droned on until about two dozen readings had been taped. Then, “I’m going closer now. The sampler is just a ladle on a twelve-foot handle we improvised, so I’ll have to get that close. The stuff is moving slowly; there should be no trouble. I’m in reach now. The lava is very liquid; there’s no trouble getting the sampler in—or out again—it’s not very dense, either. I’m heading back toward the tractor now. No, Ren, don’t come to meet me.”
There was a minute of silence, while Zaino pictured the space-suited figure with its awkwardly long burden, walking away from the creeping menace to the relative safety of the tractor. “It’s frozen solid already; we needn’t worry about spilling. The temperature is about—five eighty. Give me the markers, please.”
Another pause, shorter this time. Zaino wondered how much of that could be laid to a faster walk without the ladle and how much to the lessening distance between flow and tractor. “I’m tossing the first marker close to the edge—it’s landed less than a foot from the lava. They’re all on a light cord at ten-foot intervals; I’m paying out the
cord as I go back to the tractor. Now we’ll stand by and time the arrival at each marker as well as we can.”
“How close are you to the main cone?” asked Zaino. “Not close enough to see its base, I’m afraid. Or to get a sample of it, which is worse. We—goodness, what was that?”
Zaino had just time to ask, “What was what?” when he found out.
IV
FOR A moment, he thought that the Albireo had been flung bodily into the air. Then he decided that the great metal pillar had merely fallen over. Finally he realized that the ship was still erect, but the ground under it had just tried to leave.
Everyone in the group had become so used to the almost perpetual ground tremors that they had ceased to notice them; but this one demanded attention. Rowson, using language which suggested that his career might not have been completely free of adventure after all, flashed through the communication level on his way down to the power section. Schlossberg and Babineau followed, the medic pausing to ask Zaino if he were all right. The radioman merely nodded affirmatively; his attention was already back at his job. Burkett was speaking a good deal faster than before.
“Never mind if the sample isn’t lashed tight yet—if it fails off there’ll be plenty more. There isn’t time! Arnie, get in touch with Dr. Mardikian and Dr. Marini. Tell them that this volcano is explosive, that all estimates of what the flow may do are off until we can make more measures, and in any case the whole situation is unpredictable. Everyone should get back as soon as possible. Remember, we decided that those big craters Eileen checked were not meteor pits. I don’t know whether this thing will go in the next hour, the next year, or at all. Maybe what’s happening now will act as a safety valve—but let’s get out. Ren, that flow is speeding up and getting higher, and the ash rain is getting a lot worse. Can you see to drive?”
She fell silent, Zaino, in spite of her orders, left his set long enough to leap to the nearest port for a look at the volcano.
He never regretted it.
Across the riven plain, whose cracks were now nearly hidden under the new ash, the black cone towered above the nearer elevations. It was visibly taller than it had been only a few hours before. The fountain from its top was thicker, now jetting straight up as though wind no longer meant a thing to the fiercely driven column of gas and dust. The darkness was not so complete; patches of red and yellow incandescence showed briefly in the pillar, and glowing sparks rather than black cinders rained back on the steep slopes. Far above, a ring of smoke rolled and spread about the column, forming an ever-broadening blanket of opaque cloud above a landscape which had never before been shaded from the sun. Streamers of lightning leaped between cloud and pillar, pillar and mountain, even cloud and ground. Any thunder there might have been was drowned in the howl of the escaping gas, a roar which seemed to combine every possible note from the shrillest possible whistle to a bass felt by the chest rather than heard by the ears. Rowson’s language had become inaudible almost before he had disappeared down the hatch.
For long moments the radioman watched the spreading cloud, and wondered whether the Albireo could escape being struck by the flickering, ceaseless lightning. Far above the widening ring of cloud the smoke fountain drove, spreading slowly in the thinning atmosphere and beyond it. Zaino had had enough space experience to tell at a glance whether a smoke or dust cloud was in air or not. This wasn’t, at least at the upper extremity . . . And then, quite calmly, he turned back to his desk, aimed the antenna straight up, and called Eileen Harmon. She answered promptly.
THE STRATIGRAPHER listened without interruption to his report and the order to return. She conferred briefly with her companion, replied “We’ll be back in twelve hours,” and signed off. And that was that.
Zaino settled back with a sigh, and wondered whether it would be tactful to remind Rowson of his offer of a year’s pay.
All four vehicles were now homeward bound; all one had to worry about was whether any of them would make it. Hargedon and Burkett were fighting their way through an ever-increasing ash rain a scant two miles away—ash which not only cut visibility but threatened to block the way with drifts too deep to negotiate. The wind, now blowing fiercely toward the volcano, blasted the gritty stuff against their front window as though it would erode through; and the lava flow, moving far faster than the gentle ooze they had never quite measured, surged—and glowed—grimly behind.
A hundred miles or more to the east, the tractors containing Mardikian, Marini and their drivers headed southwest along the alternate route their maps had suggested; but Mardikian, some three hours in the lead, reported that he could see four other smoke columns in that general direction.
Mercury seemed to be entering a new phase. The maps might well be out of date.
Harmon and Trackman were having no trouble at the moment, but they would have to pass the great chasm. This had been shooting out daughter cracks when Zaino and Hargedon passed it hours before. No one could say what it might be like now, and no one was going out to make sure.
“We can see you!” Burkett’s voice came through suddenly. “Half a mile to go, and we’re way ahead of the flow.”
“But it’s coming?” Rawson asked tensely. He had returned from the power level at Zaino’s phoned report of success.
“It’s coming.”
“How fast? When will it get here? Do you know whether the ship can stand contact with it?”
“I don’t know the speed exactly. There may be two hour, maybe five or six. The ship can’t take it. Even the temperature measures I got were above the softening point of the alloys, and it’s hotter and much deeper now. Anyway, if the others aren’t back before the flow reaches the ship they won’t get through. The tractor wheels would char away, and I doubt that the bodies would float. You certainly can’t wade through the stuff in a space suit, either.”
“And you think there can’t be more than five or six hours before the flow arrives?”
“I’d say that was a very optimistic guess. I’ll stop and get a better speed estimate if you want, but won’t swear to it.”
Rowson thought for a moment.
“No,” he said finally, “don’t bother. Get back here as soon as you can. We need the tractor and human muscles more than we need even expert guesses.” He turned to the operator.
“Zaino, tell all the tractors there’ll be no answer from the ship for a while, because no one will be aboard. Then suit up and come outside.” He was gone.
TEN MINUTES later, six human beings and a tractor were assembled in the flame-lit near-darkness outside the ship. The cloud had spread to the horizon, and the sun was gone. Burkett and Hargedon had arrived, but Rowson wasted no time on congratulations.
“We have work to do. It will be easy enough to keep the lava from the ship, since there seems to be a foot or more of ash on the ground and a touch of main drive would push it into a ringwall around us; but that’s not the main problem. We have to keep it from reaching the chasm anywhere south of us, since that’s the way the others will be coming. If they’re cut off, they’re dead. It will be brute work. We’ll use the tractor any way we can think of. Unfortunately it has no plow attachment, and I can’t think of anything aboard which could be turned into one. You have shovels, such as they are. The ash is light, especially here, but there’s a mile and a half of dam to be built. I don’t see how it can possibly be done . . . but it’s going to be.”
“Come on, Arnie! You’re young and strong,” came the voice of the mineralogist. “You should be able to lift as much of this stuff as I can. I understand you were lucky enough to get hold of Eileen—have you asked for the bonus yet?—but your work isn’t done.”
“It wasn’t luck,” Zaino retorted. Burkett, in spite of her voice, seemed much less of a schoolmistress when encased in a space suit and carrying a shovel, so he was able to talk back to her. “I was simply alert enough to make use of existing conditions, which I had to observe for myself in spite of all the scientists around. I’m charging th
e achievement to my regular salary. I saw—”
He stopped suddenly, both with tongue and shovel. Then, “Captain!”
“What is it?”
“The only reason we’re starting this wall here is to keep well ahead of the flow so we can work as long as possible, isn’t it?”
“Yes, I suppose so. I never thought of trying anywhere else. The valley would mean a much shorter dam, but if the flow isn’t through it by now it would be before we could get there—oh! Wait a minute!”
“Yes, sir. You can put the main switch anywhere in a D.C. circuit. Where are the seismology stores we never had to use?”
Four minutes later the tractor set out from the Albireo, carrying Rawson and Zaino. Six minutes after that it stopped at the base of the ash cone which formed the north side of the valley from which the lava was coming. They parked a quarter of the way around the cone’s base from the emerging flood and started to climb on foot, both carrying burdens.
Forty-seven minutes later they returned empty-handed to the vehicle, to find that it had been engulfed by the spreading liquid.
With noticeable haste they floundered through the loose ash a few yards above the base until they had outdistanced the glowing menace, descended and started back across the plain to where they knew the ship to be, though she was invisible through the falling detritus. Once they had to detour around a crack. Once they encountered one, which widened toward the chasm on their right, and they knew a detour would be impossible. Leaping it seemed impossible, too, but they did it. Thirty seconds after this, forty minutes after finding the tractor destroyed, the landscape was bathed in a magnesium-white glare as the two one-and-a-half kiloton charges planted just inside the crater rim let go.
“SHOULD WE go back and see if it worked?” asked Zaino.
