This book was first published in 1954, and the description of the surface of Venus was in accordance with astronomic beliefs of the period.

Since 1954, however, astronomical knowledge of the inner Solar system has advanced enormously because of the use of radar beams and rockets.

In the late 1950s, the quantity of radio waves received from Venus made it seem that the surface of Venus might be much hotter than had been thought. On August 27, 1962, a rocket probe called "Mariner II" was launched in the direction of Venus. It skimmed by within 21,000 miles of Venus on December 14, 1962. Measuring the radio waves emitted by the planet, it turned out that the surface temperature everywhere was indeed considerably higher than the boiling point of water.

This meant that far from having a worldwide ocean, as described in this book, Venus had no ocean at all. All of Venus's water is in the form of water vapor in its clouds, and the surface is exceedingly hot and is bone-dry. The atmosphere of Venus is, moreover, denser than had been thought and is almost entirely carbon dioxide.

Nor had it been known, in 1954, how long it took Venus to rotate on its axis. In 1964, radar beams bounced off Venus's surface showed that it was turning once in every 243 days (eighteen days longer than its year) and in the "wrong" direction as compared with other planets.

I hope that the readers enjoy this story anyway, but I would not wish them to be misguided into accepting as fact some of the material which was "accurate" in 1954 but which is now outdated.

Isaac Asimov

November, 1970

Lucky starr and john bigman jones kicked themselves up from the gravity-free Space Station No. 2 and drifted toward the planetary coaster that waited for them with its air lock open. Their movements had the grace of long practice under non-gravity conditions, despite the fact that their bodies seemed thick and grotesque in the space suits they wore.

Bigman arched his back as he moved upward and craned his head to stare once again at Venus. His voice sounded loudly in Lucky's ear through the suit'sf radio. "Space! Look at that rock, will you?" Every inch of Big-man's five-foot-two was tense with the thrill of the sight.

Bigman had been born and bred on Mars and had never in his life been so close to Venus. He was used to ruddy planets and rocky asteroids. He had even visited green and blue Earth. But here, now, was something that was pure gray and white.

Venus filled over half the sky. It was only two thousand miles away from the space station they were on. Another space station was on the opposite side of the planet. These two stations, acting as receiving depots for Venus-bound spaceships, streaked about the planet in a three-hour period of revolution, following one another's tracks like little puppies forever chasing their tails.

Yet from those space stations, close though they were to Venus, nothing could be seen of the planet's surface. No continents showed, no oceans, no deserts or mountains, no green valleys. Whiteness, only brilliant whiteness, interspersed with shifting lines of gray.

The whiteness was the turbulent cloud layer that hovered eternally over all of Venus, and the gray lines marked the boundaries where cloud masses met and clashed. Vapor moved downward at those boundaries, and below those gray lines, on Venus's invisible surface, it rained.

Lucky Starr said, "No use looking at Venus, Bigman. You'll be seeing plenty of it, close up, for a while. It's the sun you ought to be saying good-by to."

Bigman snorted. To his Mars-accustomed eyes, even Earth's sun seemed swollen and overbright. The sun, as seen from Venus's orbit, was a bloated monster. It was two and a quarter times as bright as Earth's sun, four times as bright as the familiar sun on Bigman's Mars. Personally, he was glad that Venus's clouds would hide its sun. He was glad that the space station always arranged its vanes in such a way as to block off the sunlight.

Lucky Starr said, "Well, you crazy Martian, are you getting in?"

Bigman had brought himself to a halt at the lip of the open lock by the casual pressure of one hand. He was still looking at Venus. The visible half was in the full glare of the sun, but at the eastern side the night shadow was creeping in, moving quickly as the space station raced on in its orbit.

Lucky, still moving upward, caught the lip of the lock in his turn and brought his other space-suited hand flat against Bigman's seat. Under the gravity-free conditions, Bigman's little body went tumbling slowly inward, while Lucky's figure bobbed outward.

Lucky's arm muscle contracted, and he floated up and inward with an easy, flowing motion. Lucky had no cause for a light heart at the moment, but he was forced into a smile when he found Bigman spread-eagled in mid-air, with the tip of one gauntleted finger against the inner lock holding him steady. The outer lock closed as Lucky passed through.

Bigman said, "Listen, you wombug, someday I'm walking out on you and you can get yourself another…"

Air hissed into the small room, and the inner lock opened. Two men floated rapidly through, dodging Big-man's dangling feet. The one in the lead, a stocky fellow with dark hair and a surprisingly large mustache, said, "Is there any trouble, gentlemen?"

The second man, taller, thinner, and with lighter hair but a mustache just as large, said, "Can we help you?"

Bigman said loftily, "You can help us by giving us room and letting us get our suits off." He had flicked himself to the floor and was removing his suit as he spoke. Lucky had already shucked his.

The men went through the inner lock. It, too, closed behind them. The space suits, their outer surface cold with the cold of space, were frosting over as moisture from the warm air of the coaster congealed upon them. Bigman tossed them out of the coaster's warm, moist air on to the tiled racks, where the ice might melt.

The dark-haired man said, "Let's see, now. You two are William Williams and John Jones. Right?"

Lucky said, "I'm Williams." Using that alias under ordinary conditions was second nature to Lucky by now. It was customary for Council of Science members to shun publicity at all times. It was particularly advisable now with the situation on Venus as confused and uncertain as it was.

Lucky went on, "Our papers are in order, I believe, and our luggage is aboard."

"Everything's all right," the dark-haired one said, "I'm George Reval, pilot, and this is Tor Johnson, my co-pilot. We'll be taking off in a few minutes. If there's anything you want, let us know."

The two passengers were shown to their small cabin, and Lucky sighed inwardly. He was never thoroughly comfortable in space except on his own speed cruiser, the Shooting Starr, now at rest in the space station's hangar.

Tor Johnson said in a deep voice, "Let me warn you, by the way, that once we get out of the space station's orbit, we won't be in free fall any more. Gravity will start picking up. If you get space-sick…"

Bigman yelled, "Space-sick! You in-planet goop, I could take gravity changes when I was a baby that you couldn't take right now." He flicked his finger against the wall, turned a slow somersault, touched the wall again, and ended with his feet just a half-inch above the floor. "Try that someday when you feel real manly."