Even from twenty million miles away, Jupiter was already the most conspicuous object in the sky ahead. The planet was now a pale, salmon-hued disk, about 1/2 the size of the Moon as soon from Earth, with the dark, parallel bands of its cloud belts clearly visible.365Please respect copyright.ＰＥＮＡＮＡbCdIK4ywDA
Shuttling to and for in the equatorial plane were the brilliant stars of Io, Europa, Ganymede, and Callisto---worlds that elsewhere would have counted as planets in their own right, but which here were merely subjects of a gargantuan king.
Through the telescope, Jupiter was a glorious sight---a mottled, multicolored globe that seemed to fill the sky. It was not possible to grasp its true size; Dhala kept reminding himself that it was 11 times Earth's diameter, but for a long time this was a meaningless statistic.
Then, as he was briefing himself from the tapes in H.A.L.'s memory units, he found something that suddenly brought the appalling scale of the planet into focus. It was an illustration that showed the Earth's entire surface peeled off and then pegged, like an animal's skin, on the disk of Jupiter. Against this background, all the continents and oceans of Earth appeared no bigger than India on the terrestrial globe.
When Dhala used the highest magnification of Pesquisador's telescopes, he seemed to be hanging above a slightly flattened globe, looking down upon a vista of racing clouds that had been smeared into bands by the giant planet's fast rotation. Sometimes these bands congealed into wisps and knots and continent-sized masses of colored vapor, sometimes they were linked by transient bridges thousands of miles long. Hidden beneath those clouds was sufficient material to outweigh all the other planets in the Solar System. And what else, Dhala wondered, was also hidden there?
Over this shifting, turbulent roof of clouds, forever hiding the real surface of the planet, circular patterns of darkness sometimes glided. One of the inner moons was transiting the distant sun, its shadow marching beneath it over the restless Jovian cloudscape.
There were other, far smaller, moons even out here---twenty millions miles from Jupiter. But they were merely flying mountains---a few dozen miles in diameter, and the ship would pass nowhere near any of them. Every few minutes the radar transmitter would get its act together and send out a silent thunderclap of power; no echoes of new satellites came pulsing back from the darkness.
What did come, with ever growing intensity, was the roar of Jupiter's own radio voice. In 1955, just before the dawn of the (American) space age, astronomers had been astonished to find that Jupiter was blasting out millions of horsepower on the 10-meter band. It was only raw noise, associated with haloes of charged particles circling the planet like the Van Allen belts of Earth, but on a far greater scale.
Sometimes, during lonely hours on the control deck, Dhala would listen to this radiation. He would turn up the gain until the room was filled with a crackling, hissing roar; out of this background, at regular intervals, emerged brief whistles and peeps like the cries of insane birds. It was an eerie sound, for it had nothing to do with Man; it was as lonely and as meaningless as the murmur of waves on a beach, or the distant crash of thunder beyond the horizon.
Even at her present speed of over 100,000 m.p.h., it would take Pesquisador almost two weeks to cross the orbits of all the Jovian satellites. More moons circled Jupiter than planets orbited the Sun; the Lunar Observatory was discovering new ones annually, and the tally had now reached 36. The outermost--Celena---moved backwards in an unstable path nineteen million miles from its temporary master. It was the prize in an eternal tug-of-war between the Sun and Jupiter, for the planet was constantly capturing short-lived moons from the asteroid belt, and losing them again after a few million years. Only the inner satellites were its permanent property; the Sun could never seize them from its grasp.
Now there was new prey for the clashing gravitation at fields. Pesquisador was accelerating toward Jupiter along a complex orbit computed months ago by the astronomers on Earth, and constantly checked by H.A.L. From time to time there would be minute, automatic nudges from the control jets, barely perceptible aboard the ship, as they made fine adjustments to the trajectory.
Over the radio link with Earth, data was flowing back in a constant stream. They were now so far from home that, even traveling at the speed of light, their signals were taking fifty minutes for the journey. Though the whole world was looking over their shoulder, watching through their eyes and their instruments as Jupiter approached, it would be nearly one hour before the news of their discoveries reached home.
The telescopic cameras were operating constantly as the ship cut across the orbit of the giant inner satellites---each one of them larger than the Moon, each one of them uncharted territory. Three hours before transit, Pesquisador passed only twenty thousand miles from Europa, and all instruments were aimed at the approaching world, as it grew steadily in size, changed from globe to crescent, and swept swiftly sunward.
Here were fourteen million square miles of land which, until this moment, had never been more than a pinhead in the mightiest telescope. They would race past it in minutes, and must make the most of the encounter, recording all the information they could. There would be months in which they could play it back at leisure.
From a distance, Europoa had seemed like a giant snowball, reflecting the light of the faraway sun with remarkable efficiency. Closer observations confirmed this; unlike the dusty Moon, Europa was a brilliant white, and much of its surface was covered with glittering hunks that looked like stranded icebergs. Almost certainly, these were formed from ammonia and water that Jupiter's gravitational field had somehow failed to capture.
Only along the equator was bare rock visible; here was an incredibly jagged no-man's-land of canyons and jumbled boulders, forming a darker band that totally surrounded the little world. There were a few impact craters, but no sign of vulcanism; Europa had obviously never possessed any internal sources of heat. There was, as had long been known, a trace of atmosphere. When the dark edge of the satellite passed across a star, it dimmed briefly before the moment of eclipse. And in some areas there was a hint of cloud---maybe a mist of ammonia droplets, borne on tenuous methane winds.
As swiftly as it had rushed out of the sky ahead, Europa dropped astern; and now Jupiter itself was only two hours away. H.A.L. had checked and rechecked the ship's orbit with infinite care, and there was no need for further speed corrections until the moment of closest approach. Yet, even knowing this, it was a strain on the nerves to watch that giant globe ballooning minute by minute. It was hard to believe that Pesquisador was not plunging directly into it, and that the planet's immense gravitational field was not dragging them down to destruction. Now was the time to drop the atmospheric probes--which, hopefully, would survive long enough to send back some information from below the Jovian cloud deck. Two stubby, bomb-shaped capsules, enclosed in ablative heat-shields, were gently nudged into orbits which for the first few thousand miles deviated barely at all from that of Pesquisador. But they slowly drifted away; and now, at last, even the unaided eye could see what H.A.L. had been asserting. The ship was in a near-grazing orbit, not a collision one; she would miss the atmosphere. True, the difference was only a few hundred miles---a mere nothing when one was dealing with a planet 90,000 miles in diameter---but that was enough.365Please respect copyright.ＰＥＮＡＮＡHiD0CVOoTL
Jupiter now filled the whole sky; it was so huge that neither mind nor eye could grasp it anymore, and both had abandoned the attempt. If it had not been for the extraordinary variety of color--the reds and pinks and yellows and salmons and even scarlets---of the atmosphere beneath them, Dhala could have believed that he was flying low over a terrestrial cloudscape.
And now, for the first time in all their journeying, they were about to lose the Sun. Pale and shrunken though it was, it had been Pesquisador's constant companion since her departure from Earth, 5 months ago. But now her orbit was diving into the shadow of Jupiter; she would soon pass over the night side of the planet.
1000 miles ahead, the band of twilight was hurtling toward them; behind, the Sun was sinking swiftly into the Jovian clouds, its rays spread out along the horizon like two flaming, down-turned horns, then contracted and died in a brief blaze of chromatic glory. Night had fallen.
Yet the great world below was not totally dark. It was awash with phosphorescence, which grew brighter minute by minute as their eyes got used to the scene. Dim rivers of light were flowing from horizon to horizon, like the luminous wakes of ships on some tropical sea. Here and there they gathered into pools of liquid fire, trembling with vast, submarine disturbances welling up from Jupiter's hidden heart. It was such an awe-inspiring sight that Dhala and Quarlos could have stared for hours; was this, they wondered, simply the result of chemical and electrical forces down there in that bubbling cauldron--or was it the by-product of some fantastic life-form? These were questions which scientists might still be debating when the century drew to its inevitable close.
As they drove deeper and deeper into the Jovian night, the glow beneath them grew steadily brighter.
Once Dhala had flown over northern Canada during the height of an auroral display; the snow-covered landscape had been as bleak and brilliant as this. And that arctic wilderness, he reminded himself, was more than 100 degrees warmer than the regions over which they were hurtling now.
"Earth signal is fading rapidly," announced H.A.L. "We are entering the first diffraction zone."
This was not unexpected--indeed, it was one of the mission's objectives, as the absorption of radio waves would give valuable information about the Jovian atmosphere. But now that they had truly passed behind the planet, and it was cutting off communication with Earth, they felt a sudden overwhelming loneliness. The radio blackout would only last one hour; then they would emerge from Jupiter's eclipsing screen, and could resume contact with the human race. That hour, unfortunately, would be the longest of their lives.365Please respect copyright.ＰＥＮＡＮＡkj8Noro33p
Despite their relative youth, Dhala and Quarlos were veterans of 12 space voyages, but now they felt like amateurs. They were attempting something for the first time; never before had any ship traveled at such speeds, or braved so intense a gravitational field. The slightest error in navigation at this critical point and Pesquisador would go speeding on toward the far limits of the Solar System, beyond all hope of rescue.365Please respect copyright.ＰＥＮＡＮＡtBL83MTf8N
The slow minutes dragged by. Jupiter was now a wall of phosphorescence stretching to infinity above them---and the ship was climbing straight up its glowing face. Though they knew that they were moving far too quickly for even Jupiter's gravity to take them, it was hard to believe that Pesquisador had not become a satellite of the King of Planets.365Please respect copyright.ＰＥＮＡＮＡ6okfqKG1dq
Finally, far ahead, there was a blaze of light along the horizon. They were emerging from shadow, heading out into the Sun. And at almost the same moment H.A.L. announced: "I am in radio contact with Earth. I am also happy to say that the perturbation maneuver has been successfully completed. Our time to Saturn is one hundred and sixty-seven days, five hours, eleven minutes."
That was within a minute of the estimate; the flyby had been carried out with impeccable precision. Like a ball on a cosmic pool table, Pesquisador had bounced off the moving gravitational field of Jupiter, and had gained momentum from the impact. Without using any fuel, she had increased her speed by several thousand miles per hour. 365Please respect copyright.ＰＥＮＡＮＡxBNwwsJpPd
Yet the usual laws of mechanics had not been broken. Nature always balances her books, and Jupiter had lost exactly as much momentum as Pesquisador had gained. The planet had been slowed down, true, but, because its mass was a sextillion times greater than the ship's, the change in its orbit was far too small to be detectable. The time had not yet come when Man could leave his mark upon the Solar System.365Please respect copyright.ＰＥＮＡＮＡAvJLT9Unqs
As the light grew swiftly around them, and the shrunken Sun lifted once more into the Jovian sky, Dhala and Quarlos reached out silently and shook each others hands.
Though they could barely believe it, the first part of their mission was safely over!365Please respect copyright.ＰＥＮＡＮＡfTBFvglzZL
