He maintained his rate of fall, dropping far beneath the level of the browsing medusae and through the yielding floor of cloud bank D. Now he was a hundred and fifty kilometres down, the pressure was up to eighteen atmospheres—and he was certain that today he would fall deeper than ever before. His internal monitors showed complex displays. Soon, as the pressure and density increased, his craft would adopt a new configuration. The balloon envelope would collapse and be drawn back into the gondola—but the buoyancy of the gondola itself would now be enough to draw it upwards. So a band of small fusor-powered ramjets would start up to drive the ship deeper into the thickening murk—and the main asymptotic-drive engine could be called on too if necessary. And then the strengthening of the hull by the Springers’ technicians would be thoroughly tested.
Overhead, the sky was darkening through shades of purple. This was not the onset of evening—dusk was still hours away—but the gradual filtering out of solar illumination. Much the same thing happened in the depths of Earth’s oceans. The main difference here was that the external temperature was steadily rising, even as the iron crush of the atmosphere redoubled its hold on the gondola. Above him, he knew, the buoyancy envelope was adjusting, narrowing, controlling its own internal temperature and pressure to match the external conditions, and provide the lift he needed.
Two hundred kilometres deep. There were still complex molecules floating in the crushing air, but nothing that met the usual definitions of a living organism. It was already too hot and dark for life: too hot for the right chemical cycles, too dark for photons to pump energy into any sort of food chain. Falcon, believing that he had “seen” all he was going to, prepared to switch from his visual system to a composite overlay stitched together from radar, sonar and infrared channels . . .
Wait.
To his astonishment—and consternation, for it contradicted all he knew of the Jovian cloud layers—a faint, milky glow was rising up from the depths.
He needed the maximum amplification of his enhanced eyes to see it at all, but nonetheless there it was. It shimmered and strobed, like a neon tube struggling to light. The glow was coming from a fixed depth, perhaps three hundred kilometres down, and when he looked further out he saw that it came from all directions. There was an oddly regular patterning to it—like a quilt, stitched together from square swatches of slightly varying radiance—a quilt stretched wide and deep across this Jovian sky. And there were hints of solid forms embedded in that surface of textured light, nodes defining the boundaries of those quilted squares. Each node was separated from its four nearest neighbours by a hundred kilometres of clear air.
Something associated with the glow was confusing his radar and its interpretive software. Falcon reverted to optical/sonar, abandoning the radar. The milky glow was tenuous, but there was sufficient contrast to enable him to pick out the rough forms of the nodes. Each was an upright spindle, like two sharp-tipped cones joined base to base. Each was huge, about as tall as Kon-Tiki and its balloon. And there were hundreds, thousands of them . . .
The spindles were floating in that layer of milky light—but they were also creating it, he saw now. Sweeping out from the spindles’ midsections were moving beams, pinwheeling like searchlights. The beams must be intense electromagnetic projections: ultraviolet lasers or something analogous. They were exciting the layer of air between the spindles, heating it into plasma. The whole exercise was choreographed with tremendous precision, the plasma layer billowing around the spindles, and the spindles rising and falling with the undulations. They made him think of buoys floating on a roiling, angry sea of their own making.
A dark intuition convinced him that these were elements of a sentry system, primed to deter intruders. And, falling at random into the planet, surely he had not simply chanced on one concentration of defences. It must spread far, perhaps across all of Jupiter. A planetary-scale structure: a thing of wonder in its own right. And if so, no wonder the upper cloud layers had shown such large-scale disruption.
And at least he had resolved one mystery: this plasma curtain was surely the radio/radar scattering surface which had prevented any recent study of the Jovian interior, cloaking the work of the Machines . . .
“You have been busy little bees,” he murmured.
Now he must think of his own continued survival.
Falcon quickly decided that the plasma curtain was not going to hurt him; Kon-Tiki would pass through it without damage. And nor would he approach a node so closely as to risk collision. The lasers, though, were something else. If one of those beams should choose to linger on the gondola or the balloon . . .
But there, suddenly, was a way through. Four of the spindles had become inert, no longer exciting the air between them, creating an aperture in the plasma curtain—a single black chessboard square. It was not directly below him, but exactly on his projected path, given his angle of drift and descent speed.
It was a door with Falcon’s name on it. “Come on in, the water’s lovely,” he murmured.
And then it occurred to him to wonder if the open square was no more than a lure to guarantee his easy destruction. Nothing for it now, one way or the other.
He fell towards the gap, on edge all the while.
“This is Falcon,” he sent back to Io, and he sent back a stream of hastily compiled imaging and other data. “I’m still here, but I’m close to the depth of the scattering surface—you’ll see what I’ve found down here, which is probably the cause of that scattering—I expect that this is likely to be the last you’ll hear from me for a while. Try not to do anything rash . . .”
And then Kon-Tiki was level with the plasma surface, and passing through, and the lasers held their fire.
He looked up, peering beyond the curve of the balloon, and watched as the plasma square snapped back into existence. A door had opened. He had come through. Now it had slammed shut behind him.
And still he fell.
* * * *
Three hundred and twenty-five kilometres. Three hundred and fifty. Gradually the milky surface faded away, too far above him for detection. Cracks, pops and groans came from around the gondola as it adjusted to the strain, like the uneasy dreaming of a large animal. One or two of the craft’s more fragile instruments gave up the ghost.
But still he fell.
Four hundred kilometres. Now he was approaching the thermalisation layer, with a temperature at which no organic material could survive—and a pressure equivalent to the deepest of Earth’s oceans—yet he had not travelled even one percent into Jupiter’s interior.
The radar was working reliably again now. And it told him that, below, there were more solid objects coming up, bigger than the spindles and, so it seemed, rather fewer in number. The nearest was about two hundred kilometres to port. He studied the composite overlay, tracing a dark floating form the size of a small mountain, shaped like a highly cut gem with a tapering point aimed back at the sky.
It was like no weapon that Falcon had ever seen before, and he could only guess at its functional principles. But it was clearly a weapon—he did not need to understand how a gun worked to recognise one. That floating engine was surely a cannon, its barrel focused in the only possible direction from which an aggressor might approach. And there were many other such weapons, stretching to the limits of his sensors. Like the scattering surface, did the guns spread all the way around Jupiter . . . ?
How was it even possible to make so much stuff, down in this super-compressed hydrogen ocean?
At about four hundred and fifty kilometres down he passed, without harm, through the layer of weaponry—and then descended through more layers, at four hundred and sixty metres, four hundred and seventy. More floating guns, stacked at different depths, but all aimed out at space. No human attack or invasion could have overcome those mighty defences, Falcon decided.
But they would be no use when Io fell.
Five hundred kilometres, four thousand atmospheres—deeper than he could ever have gone in the original gondola. He descended at last through the weapon garden, and into empty hydrogen-helium air.
And now his sensors picked up something new again. Emerging below him was a landscape of solid, geometric surfaces, stretching out in all directions. As his sensors gathered more data, Falcon studied a veritable cityscape of blocks and plazas, of planar forms and rectangular masses, the structures mathematically angular, their surfaces laser-smooth. Orpheus had seen quasi-solid clouds near these depths—probably the objects that had once been mistakenly interpreted as a solid surface of Jupiter—but this could not be the same phenomenon, or not just that. Falcon was seeing something artificial. A city, mostly a dark and windowless city, as befitted these bleak fathoms. But there were glowing red lines around the bases of the rectangular forms, and similar glowing traceries branching between them.
The scale of it made him shudder. None of those rectangular forms were less than dozens of kilometres across, and the plane in which they were constructed—interrupted as it was by shafts and canyons—stretched away for tens of thousands of kilometres, with barely a hint of curvature. Neither the spindles nor the guns had prepared him for such effortless, daunting immensity. It had been one thing to conjecture that the spindles might encompass the planet, a comparatively simple, repetitive arrangement—but this?
Now a blocky form detached itself from one of the larger rectangles. It was rising to meet him—a solid object with the proportions of two cubes jammed side by side. It was the tiniest thing in Falcon’s field of view, but was still hundreds of times larger than Kon-Tiki and its balloon.
The object floated up to his level. Falcon was still descending, but a few bursts from the asymptotic drive soon slowed him to a hover.
The black mass slid next to him. Though it was dwarfed by the greater structures of the city, this was a mirror-perfect cliff that soared above and plunged below, mocking Falcon’s flimsy little craft and its even flimsier occupant. Outside, it was hot enough to melt lead, and the hydrogen-helium atmosphere was now under so much pressure that it was behaving more like a fluid than a gas. And yet this skyscraper-sized block just floated, impervious, disdainful, daring him to question its total superiority of form and function. Unlike the buildings below, it gave off no red glow along its base or edges. Without his instruments’ sensory overlay, he would have been quite unable to see it. He could have been drifting down that sheer flank, oblivious . . .
The rectangular surface began to deform. Something was pushing out from the smoothness, a series of stepped contours made from the same black material as the rest of the structure. The contours gathered into an oval, and the oval gained a nose, a mouth, a pair of sightless black eyes. It was a monstrous face, like a black mask pushing through an oil slick.
The mouth moved and shaped a series of sounds, projecting them into the surrounding medium of hydrogen-helium. The liquid medium conveyed those sounds to the Kon-Tiki’s acoustic sensors—and a voice boomed through the cabin’s speakers, adjusted by the ship’s systems to human-hearing frequencies, while through the gondola’s walls, Falcon felt more than heard the raw sounds: a deep bass report.
“Are you impressed, Falcon?”
“Adam,” Falcon whispered.