Charles Sheffield - Proteus in the Underworld

Maybe that was also the answer to the problem of air supply. There could be a steady absorption and accumulation of oxygen during a night period of dormancy, followed by expenditure during daytime activity. Could the surface forms be using some new method for body storage under pressure? They would in any case need high tolerance for carbon dioxide.

Bey thought of the great whales, back on Earth. They took in air on the surface and dived cheerfully to a depth of a mile or more. The pressure change on their bodies during that descent and ascent was hundreds of atmospheres. During their half hour in the depths, the oxygen/CO 2ratio in their bodies steadily decreased. It did not trouble them. Bey could imagine ways that the modified alveolar patterns of whale lungs, together with their pressure change tolerance, might be achieved in humans. Embodying those ideas into a form-change program was tricky, but it did not sound impossible.

In fact, it was clearly not impossible. Someone had done it. All Bey had to do was find that someone, and ask how.

He roused himself and stared down at the ground. Its temperature was cold enough to burn bare flesh instantly, but the insulated boots of his suit protected him totally. There was no reason why a changed human form could not do just as well, making use of normal organic materials.

It was still too early to distinguish between the dusty reds and stark blacks of the Mars surface, but Bey could see well enough to pick his way across the broken ground. The hangar for the aircar was already visible as a darker hulk against a purple-black sky. He made his way to it, wondering if his surface quest was totally unrealistic.

How many surface forms were there? And what was the chance of encountering one or more of them today in an almost blind search, as Trudy Melford had done last time?

Bey’s natural skepticism kicked in. How much of a blind search had it been? Why should he believe that Trudy had done any such thing? Suppose the whole event had been a set-up, of BEC-funded forms planted at a particular place and time so that he could see them and be lured to work on Mars?

There was only one way to find out. Bey went across to the hangar and climbed into the car. He checked that it was fully powered, then gave the command to take off. There was the same gut-wrenching twenty seconds of rough motion across the torn surface. Finally they became airborne, with the car circling steadily and waiting for Bey’s next instruction.

He set the course that he remembered from the last time, cruising slowly north at low altitude. He would not dare to fly too far in that direction at this time of day. With dawn came the diurnal bombardment of comet material, the fragments hurtling in to strike at twenty degrees latitude and beyond. The first fireball had already streaked across the sky ahead of the car.

Would the surface forms remain hidden until the barrage was over? Or did the spectacle exercise for them, as it did for Bey, the awful fascination of world-building by planetary turmoil?

The sun was well above the horizon now. Its clean bright disk of early morning started to streak and blur with plumes of dust and steam rising from the shattered surface. Bey forced himself to ignore the rain of comets and focused his attention on the rock structures ahead of the floating car.

Even that proved disconcerting. Like most Earth-dwellers, Bey’s knowledge of Mars geography was rudimentary. He knew that the smaller size and mass of the planet must permit steeper rock structures. He also knew that the horizon was closer, and the atmosphere much thinner. What he had not expected was the way that those variables conspired, to produce the effect of a circle of crisp, jagged mountains that sharply vanished at a certain distance, as though the world came to an end there.

He tried to ignore that illusion of a circular cookie-cutter world with the car at its center, and concentrated only on what lay directly ahead. There was little to reward his attention. He was creeping along above a dry, rusty terrain populated with anonymous cliffs, shallow screes, and black boulders. After an hour’s flight he had had his fill of sand, rock, and green- black lichen, and had seen nothing that was significant. He became convinced that he had mistaken the direction of his earlier flight; and then, when he was on the point of giving the command to circle back, the unmistakable and contrasting shapes of the Chalice and the Sword popped suddenly into view over the forward horizon.

Bey instructed the car to set down between them. He could not tell if the terrain was rough or smooth, but there was little risk. If the ground was too broken for a safe landing the car’s sensors would determine that. It would balk at the command to descend.

Apparently the car had a high regard for its own durability. Even with a surface gravity less than two-fifths of Earth’s, the landing-touch-down was surely the wrong word-rattled Bey’s teeth. He held on tightly to the arm-rests until they at last shuddered to a halt “You have air and power sufficient for twenty-one hours of moderately strenuous activity,” said a warning female voice as Bey slid open the aircar door. “It is recommended that you return here for replenishment after no more than fifteen hours.”

“Sure. Fifteen hours.” It was stupid, offering conventional and polite responses to a machine; but everybody did it. Bey found himself standing on a surface rather more rocky and uneven than the one he had started from. There was another and more major difference. The dark-green lichens near the surface exit point from Melford Castle had been no more than a thin varnish, a painted coating on the grains of rock. Here the surface cover comprised recognizable plants, their hair-thin central stems reaching up a few centimeters to try to grab a few photons more than their neighbors.

He oriented himself using the Chalice and the Sword as reference points. The ledge of rock where he and Trudy had seen the surface forms lay about a kilometer to the north- west; the sunlight, striking in at a low angle, marked a faint track in that direction where vegetation did not grow. It could be a natural structure, a fault line in the underlying rock where plant nutrients were missing; or it just might be a trail, worn by the passage of many feet.

Bey turned slowly to his left. There was another marked path heading off to the west, and it was much better defined than the first one. It led to an overhanging scarp face about thirty meters high, maybe half a kilometer away. Later in the day the sun would move to illuminate the side of the rocky mass facing Bey, but at the moment it formed a dark impenetrable shadow.

Should he go to the place where he had seen them before, or pursue what seemed like the stronger trail? When you got right down to it, every important decision in life was made with inadequate information. The tough times were the ones when die decision was irrevocable. This one didn’t seem to be. Bey made the mental toss of the coin, and headed west.

The vegetation scrunched slightly under his boots. Looking behind him, he could see his progress marked by thin broken stems. It made him feel slightly guilty. He tried to walk where the path was already well-defined because plants were not growing as thickly. Vegetation on Mars had enough to cope with from natural conditions, without a blundering human adding to the hardships.

Soon he was at the edge of the shadowed rock. The track he was following went right up to the shadow and vanished into it. Bey could do the same, but he would have to use his suit light. Presumably the car had allowed for such a thing when it quoted him his power and air limits. He set the light to broad beam and turned it on. And froze. Right in front of him, standing no more than ten meters within the shadow, a white form was silently waiting.