A faint whisper had begun. As far back as the 1940s, astronomers had begun to suspect that the Moon was, after all, not entirely airless. There would be traces of heavy gases--argon, neon, xenon, krypton, and volcanic carbon dioxide. It would be expanded far upward above the surface, because the feeble lunar gravity could not give it sufficient weight to compress it very much. So it would thin out much less rapidly with altitude than does the terrestrial atmosphere. From a density of perhaps 1/12,000th of Earth's sea level norm at the Moon's surface, it would thin to perhaps 1/20,000th at a height of eighty miles, being thus roughly equivalent in density to Earth's gaseous envelope at the same level! And at this height was the terrestrial zone where meteors flare! This theory about the lunar atmosphere had proven to be correct. The tiny density was still sufficient to give the Moon almost as effective an atmospheric meteor screen as the Earth's. The relatively low velocity needed to maintain vehicles in circumlunar orbits, made its danger to such vehicles small. It could help reduce speed for a landing; it caused that innocuous hiss of passage. But it could sometimes be treacherous. Frank thought of these things as the long minutes dragged. Perhaps Rodan, hunched intently over his controls, had reason enough, there, to be silent... The actual landing still had to be made in the only way possible on worlds whose air-covering was so close to a complete vacuum as this--like a cat climbing down a tree backwards. With flaming jets still holding it up, and spinning gyros keeping it vertical, the rocket lowered gradually. The seats swung level, keeping their occupants right side up. There was a hovering pause, then the faint jolt of contact. The jet growl stopped; complete silence closed in like a hammer blow. "Do you men know where you are?" Rodan asked after a moment. "At the edge of Mare Nova, I think," Frank answered, his eyes combing the demons' landscape beyond the thick, darkened glass of the cabin's ports. The dazzling sun was low--early morning of two weeks of daylight. The shadows were long, black shafts. "Yes--there's Tower Rock," Lester quavered. "And the Arabian Range going down under the dust of the plain." "Correct," Rodan answered. "We're well over the rim of the Far Side. You'll never see the Earth from here. The nearest settlement is eight hundred miles away, and it's Tovie at that. This is a really remote spot, as I intimated before." He paused, as if to let this significant information be appreciated. "So that's settled," he went on. "Now I'll enlighten you about what else you need to know... Come along." Frank Nelsen felt the dust crunch under the rubberized boot-soles of his Archer. There was a brief walk, then a pause. Rodan pointed to a pit dynamited out of the dust and lava rock, and to small piles of greyish material beside six-inch borings rectangularly spaced over a wide area.