Earthlight

Chapter XVI

It would never have happened had Jamieson been thinking more of driving and less of politics—though, in the circumstances, he could hardly be blamed. The ground ahead looked level and firm—exactly the same as the kilometers they had already safely traversed.

It was level, but it was no firmer than water. Jamieson knew what had happened the moment that Ferdinand’s engine started to race, and the tractor’s nose disappeared in a great cloud of dust. The whole vehicle tilted forward, began to rock madly to and fro, and then lost speed despite all that Jamieson could do. Like a ship foundering in a heavy sea, it started to sink. To Wheeler’s horrified eyes, they seemed to be going under in swirling clouds of spray. Within seconds, the sunlight around them had vanished. Jamieson had stopped the motor; in a silence broken only by the murmur of the air circulators, they were sinking below the surface of the Moon.

The cabin lights came on as Jamieson found the switch. For a moment, both men were too stunned to do anything but sit and stare helplessly at each other. Then Wheeler walked, not very steadily, to the nearest observation window. He could see absolutely nothing: no night was ever as dark as this. A smooth velvet curtain might have been brushing the other side of the thick quartz, for all the light that could penetrate it.

Suddenly, with a gentle but distinct bump, Ferdinand reached the bottom.

“Thank God for that,” breathed Jamieson. “It’s not very deep.”

“What good does that do us?” asked Wheeler, hardly daring to believe there was any hope. He had heard too many horrifying tales of these treacherous dust bowls, and the men and tractors they had engulfed.

The lunar dust bowls are, fortunately, less common than might be imagined from some travelers’ tales, for they can occur only under rather special conditions, which even now are not fully understood. To make one, it is necessary to start with a shallow crater pit in the right kind of rock, and then wait a few hundred million years while the temperature changes between night and day slowly pulverize the surface layers. As this agelong process continues, so a finer and finer grade of dust is produced, until at last it begins to flow like a liquid and accumulates at the bottom of the crater. In almost all respects, indeed, it is a liquid: it is so incredibly fine that if collected in a bucket, it will slop around like a rather mobile oil. At night one can watch convection currents circulating in it, as the upper layers cool and descend, and the warmer dust at the bottom rises to the top. This effect makes dust bowls easy to locate, since infra-red detectors can “see” their abnormal heat radiation at distances of several kilometers. However, during the daytime this method is useless owing to the masking effect of the sun.

“There’s no need to get alarmed,” said Jamieson, though he looked none too happy. “I think we can get out of this. It must be a very small bowl, or it would have been spotted before. This area’s supposed to have been thoroughly marked.”

“It’s big enough to have swallowed us.”

“Yes, but don’t forget what this stuff’s like. As long as we can keep the motors running, we have a chance of pushing our way out—like a submarine-tank making its way up on to shore. The thing that bothers me is whether we should go ahead, or try and back out.”

“If we go ahead, we might get in deeper.”

“Not necessarily. As I said, it must be a pretty small bowl and our momentum may have carried us more than halfway across it. Which way would you say the floor is tilted now?”

“The front seems to be a bit higher than the rear.”

“That’s what I thought. I’m going ahead—we can get more power that way, too.”

Very gently, Jamieson engaged the clutch in the lowest possible gear. The tractor shook and protested, then lurched forward a few centimeters, then halted again.

“I was afraid of that,” said Jamieson. “I can’t keep up a steady progress. We’ll have to go in jerks. Pray for the engine—not to mention the transmission.”

They jolted their way forward in agonizingly slow surges, then Jamieson cut the engine completely.

“Why did you do that?” Wheeler asked anxiously. “We seemed to be getting somewhere.”

“Yes, but we’re also getting too hot. This dust is an almost perfect heat insulator. We’ll have to wait a minute until we cool off.”

Neither felt like making any conversation as they sat in the brightly lit cabin that might well, Wheeler reflected, become their tomb. It was ironic that they had encountered this mishap while they were racing for safety.

“Do you hear that noise?” said Jamieson suddenly. He switched off the air-circulator, so that complete silence fell inside the cab.

There was the faintest of sounds coming through the walls. It was a sort of whispering rustle, and Wheeler could not imagine what it was.

“The dust’s starting to rise. It’s highly unstable, you know, and even a small amount of heat is enough to start convection currents. I expect we’re making quite a little geyser up at the top—it will help anyone to find us if they come and look.”

That was some consolation, at any rate. They had air and food for many days—all tractors carried a large emergency reserve—and the Observatory knew their approximate position. But before long the Observatory might have trouble of its own, and would be unable to bother about them…

Jamieson re-started the motor, and the sturdy vehicle started to butt its way forward again through the dry quicksand that enveloped them. It was impossible to tell how much progress they were making, and Wheeler dared not imagine what would happen if the motors failed. The caterpillar treads were grinding at the rock beneath them, and the whole tractor shook and groaned under the intolerable load.

It was almost an hour before they were certain they were getting somewhere. The floor of the tractor was definitely tilting upward, but there was no way of telling how far below the quasi-liquid surface they were still submerged. They might emerge at any moment into the blessed light of day—or they might have a hundred meters still to traverse at this snail-like pace.

Jamieson was stopping for longer and longer intervals, which might reduce the strain on the engine but did nothing to reduce that on the passengers. During one of these pauses Wheeler asked him outright what they should do if they could get no further.

“We’ve only two possibilities,” Jamieson answered. “We can stay here and hope to be rescued—which won’t be as bad as it sounds, since our tracks will make it obvious where we are. The other alternative is to go out.”

“What! That’s impossible!”

“Not at all. I know a case where it’s been done. It would be rather like escaping from a sunken submarine.”

“It’s a horrible thought—trying to swim through this stuff.”

“I was once caught in a snowdrift when I was a kid, so I can guess what it would be like. The great danger would be losing your direction and floundering around in circles until you were exhausted. Let’s hope we don’t have to try the experiment.”

It was a long time, Wheeler decided, since he had heard a bigger understatement than that.

The driving cab emerged above the dust level about an hour later, and no men could ever have greeted the sun with such joy. But they had not yet reached safety; though Ferdinand could make better speed as the resistance slackened, there might still be unsuspected depths ahead of them.

Wheeler watched with fascinated repulsion as the horrible stuff eddied past the tractor. At times it was quite impossible to believe that they were not forcing their way through a liquid, and only the slowness with which they moved spoiled the illusion. He wondered if it was worth suggesting that in future Caterpillars have better streamlining to improve their chances in emergencies like this. Who would ever have dreamed, back on Earth, that that sort of thing might be necessary?

At last Ferdinand crawled up to the security of the dry land, which, after all, was no drier than the deadly lake from which they had escaped. Jamieson, almost exhausted by the strain, slumped down across the control panel. The reaction had left Wheeler shaken and weak, but he was too thankful to be out of danger to let that worry him.

He had forgotten, in the relief of seeing sunlight again, that they had left Project Thor three hours ago, and had covered less than twenty kilometers.

Even so, they might have made it. But they had just started on their way again, and were crawling over the top of a quite gentle ridge, when there was a scream of tearing metal and Ferdinand tried to spin round in a circle. Jamieson cut the motor instantly and they came to rest broadside-on to their direction of motion.

“And that,” said Jamieson softly, “is most definitely that. But I don’t think we’re in a position to grumble. If the starboard transmission had sheared while we were still in that dust bowl ” He didn’t finish the sentence, but turned to the ob servation port that looked back along their trail. Wheeler fol lowed his gaze.

The dome of Project Thor was still visible on the horizon. Perhaps they had already strained their luck to the utmost, but it would have been nice could they have put the protecting curve of the Moon clear between themselves and the unknown storms that were brewing there.