"The more conservative astronomers have always been right," I said. "We knew almost as much about the moon back in the eighteenth century as we do now. We get daily weather reports from Tycho now, and there are fifty-six Earth colonies beneath the lunar Apennines. But the astronomers knew that the moon was a sterile, crater-pitted world a hundred years ago. They knew that there was no life or oxygen beneath its brittle stars generations before the first space vessel left Earth. "The astronomers said that Venus was a bleak, mist-enshrouded world that couldn't sustain life and they were right. They were right about Mars. Oh, sure, a few idle dreamers thought there might be life on Mars. But the more conservative astronomers stood pat, and denied that the seasonal changes could be ascribed to a low order of vegetative life. It's a far cry from mere soil discoloration caused by melting polar ice caps to the miracle of pulsing life. The first vessel to reach Mars proved the astronomers right. Now a few crack-brained theorists are trying to convince us that Jupiter may be a solid, cool world." Joan turned, and frowned at me. "You're letting a few clouds scare you, Richard," she said. "No man on Earth knows what's under the mist envelope of Jupiter." "A few clouds," I retorted. "You know darned well that Jupiter's gaseous envelope is forty thousand miles thick--a seething cauldron of heavy gases and pressure drifts rotating at variance with the planet's crust." "But Ganymede is mist-enshrouded too," scoffed Joan. "We're hurtling into _that_ cauldron at the risk of our necks. Why not Jupiter instead?" "The law of averages," I said, "seasoned with a little common sense. Eight vessels went through Ganymede's ghost shroud into oblivion. There have been twenty-six attempts to conquer Jupiter. A little world cools and solidifies much more rapidly than a big world. You ought to know that." "But Ganymede isn't so little. You're forgetting it's the biggest satellite in the solar system." "But still little--smaller than Mars. Chances are it has a solid crust, like Callisto, Io, and Europa." There was a faint, rustling sound behind us. Joan and I swung about simultaneously, startled by what was obviously a space-code infraction. A silvery-haired, wiry little man was emerging through the beryllium steel door of the pilot chamber, his face set in grim lines. I am not a disciplinarian, but my nerves at that moment were strained to the breaking point. "What are you doing here, Dawson," I rapped, staring at him in indignation. "We didn't send for you." "Sorry, sir," the little man apologized. "I couldn't get you on the visi-plate. It's gone dead, sir." Joan drew in her breath sharply. "You mean there's something wrong with the cold current?" Dawson nodded. "Nearly every instrument on the ship has gone dead, sir. Gravity-stabilizers, direction gauges, even the intership communication coils."