off his oxygen bottle, subsisting entirely by the satellite’s atmosphere. A normal man, avoiding exertion, could breathe such stratosphere-thin air for a limited period of time without ill effects.
“Bet the air has a bite to it,” Traft shivered, glancing at the thermo-scale that showed the outside temperature at minus 102 degrees. The overhead, midget sun did little to dispel such cold. “But of course he has the nose tube warming coils taking most of the chill out.”
“Lucky guy!” sighed Greeley. “Bottled air always tastes so stale after a few hours.”
A click sounded in the stillness of the ship. Traft was training a small, compact camera—a marvel of perfection that took colored pictures under almost any conditions—out of the port, snapping the outside scenery.
“A candid camera fiend, if there ever was one,” Greeley said, grinning. “The breed hasn’t died out in a hundred years.”
“It’s a great hobby,” said Traft simply. “I have pictures taken on ten worlds, and I’m proud of the collection.”
The group outside strode to the top of a low hillock overlooking the surrounding territory. Benning kneeled suddenly, grabbing up handfuls of coarse soil to peer at it closely. He seemed startled and was evidently telling the others what a fortune in ore lay at hand.
“It’s a wonder private interests haven’t been here,” Traft reflected aloud, “to sneak away a few million dollars’ worth, as they did on Callisto. Remember that case, some years ago? They got away with a fortune in radium ore before Government exploitation moved in.”
Captain Harvey’s deep voice issued startlingly from the radio speaker, kept open and tuned to his helmet radio.
“Traft,” called the captain, “we are making our way to the nearest cliff at the right. Benning suggests the richest deposits may be there. We are all breathing the air now. Very sweet and fresh. Keep the radio open.”
“Aye, sir!” said Traft.
Then he and Greeley, from the aft port, watched the party move toward the sharp, upflung cliff to the right from the ship’s nose. They could make out the cliff’s details easily, no more than a quarter-mile away. At the base of it showed the black, uneven cut-out of a natural cave leading into the solid rock. Anemic sunlight failed to penetrate within its depths.
The exploring party had seen the cave, too. They were approaching it, with the curiosity that all men have for the mysterious. Guns up in instinctive wariness, they clambered to its mouth and peered in. Benning climbed to a flat, overhanging lip for a closer look.
To the two watching pilots there was no thought of danger. A deserted world, uninhabited by inimical life-forms, could offer little uncertainty. Their stay on Iapetus promised to be as routine and safe as on the more well known planets.
And then it came!
They saw the men out there stagger drunkenly, then start to stumble toward the ship, fumbling at their open visors. Their movements were stiff, awkward.
“Something’s happened!” gasped Greeley in startled alarm.
Traft, moving with tigerish swiftness for all of his size, was already at the radio, shouting into it.
“Captain Harvey! What’s wrong? What—”
“Something—freezing—choking us!” came back the captain’s hoarse tones. And more weakly: “Gas—cold—in the air. Traft, Greeley—help!”
The voice died away in a strangling moan. The men were dropping now, one after another, bouncing like rubber balls in the light gravity. They twisted convulsively. Traft and Greeley glanced at one another for an instant of horrified wonder.
“Vac-suits!” roared Traft, whirling to the rear supply compartment.
They fairly dived into their vac-suits, snapped the oxygen valves, and entered the lock. They plunged from it a moment later and bounded for the fallen men. Exerting full muscular effort in the reduced gravity, they were able to cover the quarter-mile in less than a minute. The fallen men were lying still now, with eyes closed behind their visors.
Traft knelt at the side of Captain Harvey and quickly unstrapped his leaden shoe weights. He did the same for another, then picked up the limp bodies, one under each arm. He was still able to run faster than he could have on Earth, carrying nothing but his own weight. Greeley followed with two more of the stricken men.
They made another hurried trip, but Greeley came back with only one man. Inside the cabin he hastily unfastened his visor. “Benning is missing!” he shouted at Traft. “He must have fallen into the cave mouth.”
Traft nodded grimly, grabbed up a hand flash and dashed out again. Greeley wriggled out of his vac-suit and began stripping the others.
Traft returned in a few minutes, his face strained.
“Benning is lost!” he announced with a note of finality. “That cave is a monstrous place, full of pits that haven’t any visible bottom.” He shrugged, not with indifference, but with hopelessness.
“Good Lord!” groaned the co-pilot. But he was staring numbly at the bodies of the rescued men. “They aren’t even breathing. They’re d—” He gulped, unable to bring the word out.
“Not necessarily,” snapped Traft, though his eyes held the daze of shock. “They were exposed only a short time to whatever was in the air. People don’t die so suddenly, even when their hearts stop beating and their lungs collapse. They found that out back in the Twentieth Century. We’ve got to hurry, though. Slip an oxygen mask over their faces and pump their diaphragms like you would for a drowned person. Come on, we’ve got work to do.”
They labored like slaves at this, changing from one limp form to another, hoping to revive them all. But no signs of returning life rewarded them. No color came to the faces that seemed drained of all blood. The clammy fingers of fear gripped their hearts.
Gradually the hopelessness of it stole into their minds, but they doggedly continued their efforts, unwilling to admit defeat. Several hours later, dog-weary and with aching muscles, they stared at one another pantingly.
“They’re dead,” Greeley declared, shudderingly. His voice held a grating edge from frayed nerves.
Traft looked haggard. But his eyes were puzzled. He raised the arm of one of the limp forms. Then he released it. The arm dropped back loosely.
“No rigor mortis!” he whispered hoarsely.
“What do you mean?” gasped Greeley.
The giant pilot sprang up. “This is a case for the Extra-Terra Bio-Institute.” Sudden resolve flared in his eyes. “The sooner we get there, the better. We’ll refuel at Titan and head for Earth.”
“What good will that do?” moaned Greeley. “It’ll take at least four or five days to get there. By that time they’ll be dead for sure, if they aren’t already.”
“Maybe they aren’t—and won’t be.”
Traft stared down at the bodies queerly, trying to tell himself he was mad for the thought. Yet his pulses hammered with an insistent hope that he might be right. He leaped for
