Twice he reached the edge of the opening and failed to get a proper handhold, sliding back onto the floor both times. The third time he managed to tear away some of the algae around the rim of the opening for a better grip. He dug in and held on while he brought his feet beneath him, hoping to use them to drive himself up and into the opening. It nearly worked.

He gathered himself for the push and then let fly. His head rose to the level of the bottom of the opening and he thrust an arm forward while his feet kicked against the smooth, slick stone wall. Then he brought his other hand arround and grasped the lip of stone. It was then he felt himself fallling backwards to the tunnel floor below.

The fall progressed in slow motion. His hands raked the stone and then empty air as he twisted catlike in mid-fall, sank backward, and dropped in a heap to the floor.

The impact knocked the wind out of him. For one horrible moment he could not breathe, and then air rushed in in great windy gasps. His ribs felt as if they had{been staved in, and his shoulder throbbed where he landed on it.

What he failed to accomplish with strength and dexterity he achieved with patience and cunning.

Using every inch of body surface to, increase the amount of available traction, he imagined himself a slug and oozed up the curving side of the tunnel toward the opening. He felt his hand hold and pulled himself up centimeter by painful centimeter until he could lean into the opening and squirm in on his belly.

This new tubule also rose at a slight t upward grade which forced him to concentrate on every stele-one misstep would send him sliding out into the main tunnel like something expelled from a cannon. He doggedly placed one foot in front of the other and, arms outspread like a man walking a tightrope, labored up the passageway.

This tedious method of locomotion wore on him, taxing already tired muscles to the limit. He longed to sit and rest, but the incline offered no advantage there. He lowered his head and pressed on, ignoring the pain shooting through his thighs like fire.

A kind of benumbed melancholy overtook him, which he recognized as the sum of a number of factors-stress, fatigue, hunger, and pain not the least of them. Each step was a struggle against creeping despair; he longed to just sit down and let his fate roll over him like breakers upon a desolate shore. But he did not give in. …

HE SLEPT AGAIN AND awoke, still exhausted but clearheaded and with a gnawing emptiness in his stomach. He was fiercely hungry, but the prospects of doing anything significant about it appeared depressingly slim. He resolved to push all thoughts of food and eating out of his mind.

The attempt proved largely unsuccessful. Like the tongue that has just discovered the still tender gap where a tooth used to be, his mind returned again and again to probe the subject despite the pain it caused him.

Under such extreme conditions hallucinations were perhaps to be expected. Still, despite this knowledge and his training in the ways of the human brain, the hallucination stopped him dead in his tracks.

Unremarkable as hallucinations go, it nevertheless hit him with a wounding impact, as if the thing had exploded in his face. He tottered on his heels for a moment and then stepped backwards into the wall behind him where he slid slowly to the floor, eyes starting from his skull in shock and disbelief.

There before him, glimmering faintly across the corridor, stood a door.

No snarling, hydra-headed monster could have alarmed him more than this simple architectural object. At first he thought it must be an optical illusion, a trick played by overtired eyes. Then he knew he was experiencing a hallucination-seeing doors where he desperately wanted them to be.

Following this observation, it dawned on him that persons undergoing hallucinations did not perceive them as such while in the very grip of them.

A door! His mind reeled. What could it mean? Indeed, what else could it mean?

Feverishly Spence began tearing away the algae by handfuls digging it out with his gloved fingers from around the imagined threshold. What emerged was an object of stone, cut from the stuff as the surrounding walls, with no external markings of any kind. He would have considered it a novelty of nature the except its smoothness, roundness, and perfect symmetry against a natural artifact. But he could not be sure. argued He lifted off his helmet and smacked it into the slab. He listened to the echo pinging away to the dim recess of the tunnel. He also heard a hollow sound beyond the b Overcome by a burning curiosity to see it lay beyond the supposed door, he leapt at the slab and began pushing with all his might, succeeding only in shoving his feet out from under him. Then he knelt before the door and tried to worm his fingers into the cracks at the sides. He arched his back and strained until he thought his heart would burst-and the slab began to move.

It slid a few centimeters, and he felt a gush of warm air from behind the door. The algae on the floor around him flushed brightly. He smelled the stale dry air flowing out; it had an odd taste which he could not place-sweet, yet rancid. The air of a tomb.

Once more he attacked the door with a fury. He was rewarded for his labors when at last the stone rolled back another few centimeters and he was able to squeeze his shoulders through.

He forced himself through the narrow opening, dizzy from the lack of oxygen and gasping for breath. He collapsed on the floor and lay down, panting while waves of nausea from his overexertion slammed into him.

A faint, reddish-gold radiance fell over him as he lay gazing upward, though where this might come from he could not readily tell. The walls around him were smooth stone and dull red in the ruddy twilight of the mysterious light.

After a while the wracking nausea subsided and he was able to raise his head and look around. There was not much to see. The passage, bone dry and dusty, continued upward at a steep angle directly ahead of him. In order to find out more about his new surroundings, he would have to haul himself back onto his weary legs and climb that incline.

Shaking with fatigue he squirmed onto his side and made to push himself up. His hand brushed something in the dust-a small ridge of stone. He looked down and saw between his hands the faintly outlined depression of a footprint.

… THE FOOTPRINT LAY SQUARELY in his path, outlined in the red dust thick upon the floor. A trick of the light, he thought; some odd stone formation. But he stared at it as if he expected it to disappear.

Spence leaned down over the print and carefully, as any archeologist would, blew away the dust. Then, with the tips of his fingers, ever so lightly, he brushed away the thicker silt that had accumulated.

The print remained, inexplicably pressed firmly into the stone-a print of an upright creature: quasi-human. Narrower and longer-it looked like someone had taken a man's foot and stretched it out of proportion. And it had only four small toes. On close inspection he decided that it was not missing any of its toes, as from an accident; it had been designed that way.

He looked around to see if there were any other prints nearby, but there were none. He did discover that the print lay in the bottom of a slight depression boundaries by two smooth banks, as if at one time long ago an underground stream had trickled along this course.

Spence sat in the dust, his mind reeling.

This was the discovery of a lifetime-of several lifetimes. Probably the most important find in the last two hundred years. In the last thousand!

Life on Mars! He, Dr. Spencer Reston, had discovered life on Mars. Beyond a shadow of a doubt, Mars had once been home to something more significant than glowing algae. The thing that made that print walked upright like a man, perhaps thought as a man, was conscious of itself.