A misty darkness closed around him, narrowing his field of vision, blurring the edges with a velvet softness. But the stars above, in the center of his sight, still burned hard and bright. Untwinkling, unmoving, unlike stars at all. It was as if the eyes of the universe watched him to see how a man died.

"No!" he shouted, hearing the empty ring of his voice in his helmet. "No," he said again; his voice was but a murmur.

Watching the stars he saw a pale white mist pass over them like a diaphanous veil. He thought it a trick of his failing eyesight. Then he saw it again-just the faintest trace of color against the night, the frailest of silken threads.

Odd, he thought. What could produce such a phenomenon?

His scientist's brain turned over this bit of novelty. He raised his head and saw, a little below him on the slope, a silver tracery on the rocks, glowing in the light of the moon.

On nerves and determination alone he stirred his useless limbs and half-slid, half-swam to the spot. He touched a gloved hand to the faint white outline of the stuff on the rocks. It gleamed in the clear light. "Crystals," he muttered to himself. "Ice crystals. Frost."

All around the immediate area he noticed the white hoarfrost, and below, the wisps of mist rising out of the ground.

Scarcely thinking or attending to what he was doing, he scrambled further down the slope and found himself peering into a pitch-dark hole. A fissure in the canyon wall had opened up, perhaps due to the rock slide earlier. Out of this fissure the slightest trace of pearly mist rose into the deathly cold Martian atmosphere.

The crack was just large enough for a man to squeeze head and shoulder through. Without thinking a second time, Spence thrust himself into the opening.

He found the hole beyond somewhat wider as he wriggled awkwardly into the opening. He inched forward into the blackness bit by bit and discovered the crevice dropped away at a sharp downward angle. He sat down and used his heels to pull himself along, sliding on his seat.

Down and down he went.

I have chosen my own grave, he thought. My bones will not be blown to dust on the winds.

The thought strangely cheered him. …

DEEPER INTO THE BRITTLE crust of the Red Planet he went. Sometimes sliding, sometimes walking nearly upright, calling on his will alone to move his body. Blind as a cave bat he moved, abandoning himself to all else but the moving. Onward; deeper and deeper still.

How long he walked, how far he burrowed, he did not know. The blackness around him penetrated his mind, covering it with itself, removing all thought, all memory, leaving only the present moment and the raw will to move on.

When the first ghostly glimmer reached his eyes out of the darkness around him, he thought it a trick of his failing mind: his faltering brain cells firing off minute electrical charges and somehow producing light in the cortex or optic nerve.

But the faint greenish glow did not fade. Instead it grew stronger. Spence, shuffling forward like a zombie, willing his legs to carry him along, stumbling over the uneven downward pathway, stayed on his feet and moved toward the gleam he saw in the distance.

He reached a spot where the glow seemed brightest and found as he came upon it that the faint light was a reflection on a blank wall of stone. He placed his hand upon the stone and saw the green cast on his glove.

He turned to see what produced the glow, as one reeling in a dream. What he saw rocked him back against the wall in disbelief: a wide tunnel glowing with interlacing veins of living light stretched before him. The thin green color glistened on the walls and roof of the gallery like a luminous dew.

Spence tottered into the tunnel and pressed his face close to the rock surface, as close as his helmet would allow. The glowing stuff oozed from the rock, clinging there like a slime. He thought of the phosphorescent plankton and algae in the oceans of Earth.

Can it be? he wondered. Have I discovered life on Mars?

2

… THE TUNNEL, GLOWING SOFTLY with the light of the tiny green organisms, stretched beyond Spence's sight. It was smooth and round, and large enough for a man to walk erect without touching the top or sides. Its circular symmetry reminded him of a water conduit; the notion occurred to him that the shaft had been formed long ago by the water which had once run in the arroyo above.

He stepped into the shaft and started walking, not knowing or particularly caring where it led. As he moved along he saw that the green light wavered as he passed, as if his passing disturbed the tiny luminescent creatures. The glow dimmed as he drew near and then flashed brighter behind him. The creatures, if creatures they were, apprehended his presence.

He moved on; it seemed like hours that he pursued the unbending downward course of the shaft before he noticed a slight curving of the tunnel walls ahead.

When he reached the place where the curve began he noticed a gap in the floor of the shaft. Not a large crack-one he could jump across if he were careful about it, but dark so that he could not see how far down it went.

Spence reached out over the edge of the hole and after a few moments felt a tingling sensation in his fingers as warmth began to seep through his gloves.

The fissure was a natural vent which carried heat from a deep reservoir beneath the crust of the planet, perhaps from some ancient volcanic source or, reasoned Spence, from the molten core of the planet itself.

With shaking hands he grasped his helmet and gave it a sideways twist and lifted it off his head. He felt the warmth drift out of the hole and wash over his frozen features. This was perhaps the source of the fragile mist he had seen on the slope of the arroyo trough.

He replaced his helmet momentarily and took a lungful of air; then, stepping away from the crack he blew it out and watched the steam roll away in great billows. Clearly, the tunnel was still desperately cold, but by contrast with the surface it was tropic. It was at least warm enough to keep the tin alive. He doubted whether it was enough to keep himself a vlrtual any length of time. Without real warmth the c Y glowing alive ally get to him, if more slowly than it would at the surface.

Spence, balancing himself carefully, leaped with extreme caution over the crack and trudged off, feeling every weary deep in his bones. He wondered how much longer he would be able to keep going and feared that if he stopped to sleep Would not wake up. The cold would overcome him. Pushing the thought aside he gritted his teeth and moved on. he After a while he noticed that the green glow shining around him grew brighter. Looking at the walls of the tunnel he saw that the strange organisms grew in greater profusion. Perhaps it meant that the shaft was becoming warmer. He continued on. at Soon he walked, not in a faint glow, but in the green ha light of a moon-bright night. The light-making creatures clustered in thick colonies over every available inch of surface, radiating a steady green fluorescence which made him feel as if he walked inside a beam of light.

He welcomed the illumination, but the floor of the tunnel was now so covered with the algae-like organisms that walking became a hazard, His unsteady feet, aching with the rigors of his ordeal, slid as on glare ice while he propelled himself along the shaft. He fell often, each fall wearing him down further; it took him longer to regain his feet each time. He began to think that the next time he would not rise again.

But he did rise again. Something urged him on, kept him climbing back onto legs wobbling with pain and fatigue. Again and again he rose, sliding, stumbling, staggering ever downward into the bowels of the planet.