time: and all
over this planet's surface were found remnants of a vast and intricate
civilization--from the canals that laced its surface, to great cities
with mighty buildings still standing. But of life there was none. The
atmosphere was too rare to support it; and the theory was that it had
constantly thinned through thousands of years till the last Martian
had gasped and died in air too attenuated to support life even in
creatures that must have grown greater and greater chested in eons of
adaptation.

Then Jupiter had been reached: and here the methodical planet by
planet work promised to be checked for a long time to come. Jupiter,
with its mighty surface area, was going to take some exploring! It
would be years before it could be plotted even superficially.

* * * * *

Brand had been to Jupiter on four different trips; and, as he walked
toward his quarters from Stone's office, he reviewed what he had
learned on those trips.

Jupiter, as he knew it, was a vast globe of vague horror and sharp
contrasts.

Distant from the sun as it was, it received little solar heat. But,
with so great a mass, it had cooled off much more slowly than any of
the other planets known, and had immense internal heat. This meant
that the air--which closely approximated Earth's air in density--was
cool a few hundred yards up from the surface of the planet, and dankly
hot close to the ground. The result, as the cold air constantly sank
into the warm, was a thick steamy blanket of fog that covered
everything perpetually.

Because of the recent cooling, life was not far advanced on Jupiter.
Too short a time ago the sphere had been but a blazing mass. Tropical
marshes prevailed, crisscrossed by mighty rivers at warmer than blood
heat. Giant, hideous fernlike growths crowded one another in an
everlasting jungle. And among the distorted trees, from the blanket of
soft white fog that hid all from sight, could be heard constantly an
ear-splitting chorus of screams and bellows and whistling snarls. It
made the blood run cold just to listen--and to speculate on what
gigantic but tiny-brained monsters made them.

Now and then, when Brand had been flying dangerously low over the
surface, a wind had risen strong enough to dispel the fog banks for an
instant; and he had caught a flash of Jovian life. Just a flash, for
example, of a monstrous lizard-like thing too great to support its own
bulk: or a creature all n