dust,
which once, two billion years ago, after probable ejection from
volcanoes, had no doubt floated in a then palpable atmosphere. But now,
to a lone man down there, they would be bleak plains stretching to a
disconcertingly near horizon.

Frank Nelsen's view was one of fascination, behind which was the chilly
thought: This is my choice; here is where I will have to live for a
short while that can seem ages. Space looks tame, now. Can I make it all
right? Worse--_how about Lester?_

Frank looked around him. Like Rodan, Lester and he had both pivoted
around in their gimbaled seats--to which they had safety-strapped
themselves--to face the now forward-pointing stern jets.

Rodan, looking more trap-mouthed than before, had said nothing further
as he guided the craft gingerly lower. Lester was biting his heavy lip.
His narrow chin trembled.

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