Jupiter's crushing gravity dropped away, and the Diver fell like a brick to the cloud floor below. The unfamiliar weightlessness lasted for seconds, the wind wailing in an alien voice as Phoenix accelerated through the sound barrier.
Norman Kayden, atmospherologist at Callisto-U, saw the moons lined up across the sky. They raced through flurries of fog, flickering illusions at this speed. Ennis Bond, the pilot, increased the dive angle to the maximum. The outside view came through diamond shielded cameras. The Diver's two meter thick armor didn't have windows.
   Through the buffeting, Norman watched the airship that had dropped them recede overhead, a shrinking sphere in the high blue sky, their last link with the known universe. Then it was gone.

   Very few people came here; this planet belonged to the machines. Jupiter was the prime fuel source of the Solar System. Its atmosphere was rich in heavy hydrogen and helium isotopes worth more than their weight in gold. Every hour tankers dropped from orbit behind heavy shields, scooping up and refining the thin air as they lifted off again. It was a wasteful process. They had to expel most of their cargo to return to orbit.
   Norman had arrived in the midst of a great evacuation. Just above the top of the atmosphere, Jupiter's horizon had been strangely flat, quite unlike Earth orbit. It had felt like flying at sea level.
   Large factories orbited there, rows of automated transfer stations. The cheap fuel they exported was making history. For the first time energy was available in almost unlimited quantities, within the Solar System and beyond. Space colonies multiplied, and the first starships left for points unknown.
   The Inversion had come without warning. Jupiter woke from its ancient slumber with a series of massive quakes. Shockwaves raced through the atmosphere at undreamt of speeds. Some of the sounds were even audible to human ears, like an endless howl.
   Over the familiar cloud bands interference fringes spread like falling dominos. The tropical and temperate belts bent at odd angles. The Inversion didn't confine itself to the planet. The lowest space stations were knocked out of orbit by the wildly oscillating atmosphere.
   After a month, the planet showed no signs of calming. Spots appeared near both poles, blazing with infrared energy. Standing on Io, you could feel the heat they radiated. All atmospheric descents had been canceled. Some said it was man's fault for tampering with the planet.
Norman intended to prove them wrong. He had second thoughts spying the cloud wall ahead.
   Long ago Jupiter had briefly shone as bright as the sun, but any remaining contraction heat and residual fission was supposed to leak harmlessly into space. Who knew what hid under these deep clouds? Heat had accumulated somehow.
   This caused concern in high circles. What was the worst that could happen? Jupiter's fuel was vital. The fusion conglomerates didn't want to relocate to Saturn. Someone had to take a closer look.
The toughest exploration craft ever built, Phoenix was a streamlined Deep Diver designed to surf through air almost as thick as water, an ultra-sleek cross between a shuttle and a submarine.
One sleepless night two weeks ago, Norman had agreed to volunteer in return for tenure immortality.
   His sense of scale was distorted. Norman's perspective flipped without warning. Now the clouds seemed close enough to touch, then they were immeasurably distant.

   Their dive was bottoming out at the top cloud level. "Circling once," Ennis said.
Both crewmembers had been selected for their experience. Pausing at various altitudes, they would sample the atmosphere. Phoenix's weight would carry them as deep as they dared to go.
   Norman looked around. The cloud banks were vaster than anything hanging in the skies of Earth, their colors and shapes enhanced with exotic materials from deeper layers. They seemed unusually solid. Phoenix crossed great floating terraces, their leisurely drift belying the Diver's speed. It was as if they could land there, and spend a lifetime exploring the rolling curves and valleys. Odd shapes balanced in midair. They passed hovering balls and halls of foam. Some of the fragments were the size of asteroids, and cast dark shadows.
   Norman knew these clouds were less substantial than the water vapor over Earth. Still, the illusion was convincing.
"We're on course," he said. "Subharmonic levels increasing steadily."
   They approached the main cloud body, an overhanging cliff receding as far as they could see, like a wave about to crest. He noticed increasing details in the seconds before they hit the wall.
   Instantly everything went gray. The Diver never stirred.
   "Almost at room temperature," Ennis said. "You could go outside without a space suit. Hold your breath unless you want to burn."
   Norman couldn't feel it, but they were diving again, their helical flight path undetectable to his inner ear.
They emerged from the bottom of the clouds. There was an equally spectacular layer far below.
   Norman was startled by a metallic groan. Hull pressure was rising.
   Soon Phoenix was midway between the two layers, the floor and the ceiling extending in all directions. Distant lightning bolts bridged the levels, relieving the gloom. The clouds below were less defined, like a stormy sea. Norman didn't have a good view of the turmoil, but great forces were waiting. Visibility was worse than expected. The light was draining from the world. Phoenix was entering the darkness ahead of schedule.
   Norman heard a tap, then another. In seconds it escalated to a torrential downpour. Their forward lights illuminated a head-on snowstorm blown up from the clouds.
   "An inverted Buran," Ennis said. "Polysaccharides and nitrates"
   The flakes looked like snow, but were hot enough to burn skin.
   When they entered the bottom layer, the darkness was less than total. They were surrounded by an infrared glow, with intensity changes too steady to be lightning. At this depth chemical cycles generated light.
   "We're deeper than anyone has ever been," Ennis announced cheerfully.
   This cloud bank had no well-defined base, but it changed color as they crossed layers of turbulence. Things floated at the borders between strata, dim shadows too far to investigate.
   The air calmed, and through the gloom Norman could see an unknown distance. They had entered a stable zone. After a moment of foolish nostalgia for a sun they might never see again, he concentrated on the mystery of the illumination.
   "Oxygen levels rising," he said. "We may get an Ozone Flare if we're lucky."
   Now it was Ennis's turn to worry. The first Jupiter probes hadn't found enough water in the atmosphere. Self-catalyzing reactions had evolved to resemble primitive life. The same process that created the bizarre manna-like substances blowing through the storms also generated bursts of oxygen. All around them, long chains of carbohydrates were breaking down in the heat, releasing the oxygen trapped within them. The level was almost one part in a thousand. All it took was a spark . . .
   The heat of their passage was ample. Norman saw huge fireballs expanding behind Phoenix. Riding a burning wave, they watched the inferno catch up, and were engulfed. They were going too fast for flames to be visible around them. The air itself was luminescent. Ennis tried not to imagine the heat. Fire was a spaceman's great fear. Then something turned off the light.
   "Adjusting filters," Norman said. Still they saw nothing, only a fading glow above.
"Right on the dial. Tracking UHF bands ahead."
   This time there was turbulence and they plunged downward. Something hit the hull, and Ennis deployed the vanes to stabilize.
   "Welcome to the Smokestack," he said. "We'll ride it down."

Phoenix had entered a conduit between the planet's abysmal ocean and its upper atmosphere.
   The flurries cleared, and Norman could see very far. Wisps of debris were carried along with them and fell away. To human eyes, this place would be pitch black, but enhanced infrared revealed a smooth tube of clouds twisting counterclockwise, a kilometer-wide corridor bending down. Visibility came not from the fast-streaming walls but from the hot gas flowing up from the depths. There were intermittent vapor streams at the center, and heavy wind shear at the edges.
   "Like a tunnel," Norman said. "Who could have imagined."
   At this depth, most structures were illusions caused by varying hydrogen percentages, but the sky river was real. Phoenix's descent slowed. If they hit the conduit's side, they would be thrown off course.
   The twisted shaft widened into a curved ceiling. Norman saw remote entranceways to other vortices.
   "The Boiler Room, ahead of schedule," Ennis said proudly.
   Here many forces converged. The Diver had entered an immense chamber filled with turbulence and longwave radiation. Too wide for the infrared cameras, its boundaries were lost in the haze.
   Until last month, this had been Jupiter's strangest phenomenon. First discovered by deep radar, a labyrinth of ephemeral conduits transported heat to the upper atmosphere. The Great Red Spot used to have dozens of Boiler Rooms before it had been absorbed by the greater Inversion. Some of the wilder branches were shaped like trees. Other tubes continued perfectly straight for hundreds of kilometers, then bent at sharp angles for no apparent reason. All emerged from "deep geysers".
   Ahead, rows of twisters lined up in a regular pattern. There were no shadows here. Every artifact constructed by humankind would fit inside this chamber.
   Their trajectory still felt level, but they had resumed their descent. The normal geometry of the Boiler Room had been disturbed by older forces whose domain they were approaching. The temperature neared the melting point of lead. They were flying almost sideways, but Ennis stayed on course using the plasma thrusters.
   "Hull pressure at 97% of rated capacity," Norman said tonelessly.
   "No worries," Ennis said. "We're here."
   At this level, the atmosphere should be relatively pure; instead Norman measured the densest smog ever seen. Ahead was the rising roar of a bottomless waterfall. Norman used the Diver's powerful radar to see through the burning fog. With difficulty, he could make out the edges of a spiral vortex the size of Australia.
   The scientists called them subcritical bubbles, the cause of the Inversion. When they went critical, Jupiter's atmosphere suddenly got much more interesting. This was the smallest bubble. Most of the flow leaked out the side streamers; but not for much longer. Phoenix's magnetic compass pointed straight down.
   Now it was Norman's turn to take control. "Releasing the probes," he said. The small pods were lost in the maelstrom, but sent data for several minutes. "We've covered .5% of the distance to the core."
   The Diver's control surfaces were almost useless. It tumbled through the storm, still losing altitude. Norman doubted even the most powerful fusion thruster could get them home now.
   "Outer hull developing hairline cracks," he said, feeling the strain of tens of thousands of atmospheres.
  " "If your predictions are right, that shouldn't matter," Ennis replied.
   For days, the subcritical bubble had been holding steady, connected to greater depths by tenuous tentacles. Now it was ready to erupt. Up in space, the satellites would see something extraordinary. Norman wished he could be there himself.
   The atmosphere had started to cool overhead, as shockwaves from other bubbles forced it to rise and expand. Heat from below evaporated ammonia ice crystals, causing rising thermals. There was the poorly understood interaction with the planet's tangled magnetic field lines. This was the closest thing Jupiter would have to a sunspot.

   Nightfall was the final straw. The roof was about to blow.

   "Now!"
Norman watched the three second collapse for many ages. All motion in the clouds stopped.
Then they shattered.
   "Going up," Ennis said nonchalantly.
   Norman felt the acceleration in his very cells, but maintained consciousness. He had to look back. He would never see anything like this again.
The walls of the bubble raced inward at incredible speed, its rotation reversing and then accelerating again, further heating the gas. The center glowed like the sun, but Norman could still look down.
Everything lined up, and for a few seconds he saw ever greater depths. Radar waves bounced down the tube like down a fiberoptic cable as layer after layer was revealed. Before the shaft closed, he thought he glimpsed something extraordinary. It couldn't be.
   Far below was the Kubla Sea, the ocean of metallic hydrogen no man could ever visit. It was extremely active: Jupiter's magnetic field had tripled in the past month. The Sea was somehow causing Jupiter's Inversion. A balance had been disturbed.
Who knew what metallic hydrogen was really like in its natural state? Large currents were set in motion, brushing against the solid core. Rocked by quakes, heat built up, changing the fluid's resistance.
At its heart, the Inversion remained a mystery. There was something unknown down there.
   Norman was glad to leave the final analysis to others, as they climbed with the hurricane. Lightning strikes escalated to an apocalyptic storm. Phoenix's counter registered 354 hits before it melted.
   Ennis didn't even try using the thrusters, only the trim tanks to maintain vertical pitch while playing "Riders on the Storm". Rising through the final shocked layers, Norman enjoyed a perfect sunrise before the surrounding sky darkened to the deeper blue of the stratosphere. They climbed until the stars came out, a perfect fury below, the fusion drive roaring as they lifted to orbit.
   Ennis asked, "want to do this again tomorrow?"
   "No thanks," Norman said. "I'd rather not lose my neck again."

   Norman looked forward to getting his body back. Phoenix's heavily armored life support capsule was barely big enough for both their brains.

* By 2008, Jupiter had THREE Red Spots. Similarities between this story and 'A meeting with Medusa' are purely coincidental.



The hard SF novel: Infinite Thunder by Jack Arcalon.
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