So time sped by. And outward, ever toward the fringes of Sol's empire, flashed the _Liberty_ on her all-important mission. The sun which but a few short weeks ago had been a blazing furnace threatening fiery annihilation to the space venturers had now dwindled to the apparent size of a tiny, glowing pea, half lost in the black depths behind them. A small, feebly glistening body whose heat at this great distance was scarce sufficient to make its presence felt. And as this great luminary shrunk, its offspring grew ever larger in the _Liberty's_ vision plate. Now the fifth planet was a heaven-filling orb scant hours away. Already the cruiser had whisked through the orbit of Jupiter's nine satellites and now, on a course carefully set by Lark O'Day, Skipper Warren was preparing to drop the _Liberty_ to Jupiter's surface. Muldoon, standing beside the space patrolman as he fingered the studs, said wonderingly, "Boy, that's one big planet, ain't it? Only--" His brow furrowed--"there's one thing I don't understand. How far away from it are we?" "'Bout twenty thousand," answered Warren. "Well, then, how come it hasn't gripped us yet? I should think a thing as big as that would have a grav-drag strong enough to clamp hold of us about three or four times this far away." Warren chuckled. "Appearances are deceiving, Flick. Don't let the apparent size of Jupiter fool you." "Huh? What do you mean?" "Simply," explained the pilot, "that the true planet Jupiter is not much larger than Earth." "What? But I can see for myself--" "What you see is Jupiter's tremendous atmosphere belt. For some reason never satisfactorily explained, Jupiter's gaseous protective envelope is more than a thousand times deeper than that of any other planet. That's why Earth's astronomical instruments always show Jupiter's mass to be so tenuous; with a specific gravity, in fact, less than that of water. Jupiter is a gigantic cosmic fake; a huge bubble of semi-viscous atmosphere in the heart of which is embedded only a tiny, normal-sized core of the more cohesive elements which go to make up a planet." "Why, the big quack!" said Muldoon indignantly. Then another thought struck him. "But say, if that's the case it must be colder than Tophet on that planet? Those miles upon miles of cloudbank should completely blot out the sun." O'Day nodded. "And so they do. But on the other hand, they completely blanket the cold of interstellar space. You'll find Jupiter a dark, murky planet, but one with a very pleasant and equitable climate. Well--" He nodded to Warren as the vision plate before them was suddenly befilmed with writhing tendrils of moisture-laden atmosphere--"we're diving into the cotton. From now on it's blind flight. Co-ordinates O.Q.?" "O.Q.," said Warren briefly, and concentrated on the task of dropping the _Liberty_ through unfathomable miles of enswaddling cloud to the tiny core within. * * * * *