by Ian Stewart
He ran through the procedure again in his head. The wheelers on lo would be deactivated, thanks to the Elders' annoying perspicacity. The gravitic-repulsion machinery would be functioning, but locked into the current configuration. Reliant Robin had all the knowledge required to change the settings of the Diversion Engines, and it knew the location of the concealed entrance and how to get in and out again. Charles shuddered at the thought—no wonder their searches of the moons hadn't turned up anything. Best not to dwell on that, though: all he had to do was make sure the battered little wheeler gained access to the control center's consoles.
The OWL's screens showed awe-inspiring scenes: To rolling serenely across the far limb of Jupiter, dwarfed by the unblinking eye of the Great Red Spot and its ever-changing swirls of spun-off vortices; Skylark and the comet sparkling against a velvet backdrop. How long now? Eight hours, forty-two minutes . . . and a few seconds.
Charles patted the wheeler's snout. Reliant Robin could hear him, but it couldn't speak anything he could interpret. "Okay, Robin: time for a rehearsal. I'd hate to screw up now."
Jaramarana streaked across the Ganymedian skyline, following the curve of the planet, stealing some of its momentum. Its speed doubled.
Even though the autopilot was in charge, Charles kept a careful eye on the OWL's screens. Little relief was visible amid the glare from the whitish crust of Colchis Regio, but the views to the side became ever more spectacular as the OWL made a hasty descent. The giant volcano of Prometheus dominated the eastern skyline, spewing a fountain of silicate magma more than sixty miles into space. The magma, squeezed and melted by Jupiter's incessant gravitational kneading, burst upward from the moon's interior and fell back in a bouquet of graceful parabolic arcs. It was one of the most amazing sights in the Solar System, and despite their plight Charles had difficulty taking his eyes off it. To the north were the new plumes of Grendel and Heorot, their lower portions disappearing fast behind the mounds of ejecta that surrounded the now-dormant Volund. To the west, Colchis Regio shaded away to the horizon; to the south he could see the beginnings of the livid pale salmon of Mycenae Regio and the faltering plume of Marduk.
The area into which the ship was now descending was one of the more stable parts of the sulfurous worldlet, and the mottled yellows and pastel pinks mostly lay beyond the rapidly shrinking horizon. Not that it appeared to be shrinking—on the contrary, the landscape seemed to expand away from them in all directions as they plummeted toward it. Charles had set the autopilot for the quickest trajectory that wasn't going to cause permanent damage to any human occupant. The pressure of the deceleration, when it finally came, was frightening. Then the engines quit and they were down.
The autopilot had landed the OWL as close to their goal as the flimsy, crumbling crust of frosted sulfur dioxide would permit, leaving a trek on foot of about a quarter of a mile. Charles fastened his helmet, ran a final verification of his suit's integrity. The wheeler could survive in vacuum, and was proof against the thin traces of sodium-rich gas that still clung to lo's surface, mostly vented from its interior. He opened the hatch and the wheeler levitated itself outside: Charles followed it.
Underfoot, the encrusted surface felt a bit like snow that had melted and refrozen, a hard surface crust covering a softer layer beneath. Occasionally his boot would break through the crust, but in the low gravity this didn't happen often, and when it did there was a solid layer of sulfurous rock only inches below. He hoped that would continue: it wouldn't do to get trapped in the Ionian equivalent of a snowdrift.
Wisps of hot sulfur dioxide drifted up from innumerable blowholes, some six feet across, others half an inch. Reliant Robin floated serenely over them, but Charles had to pick his way carefully between the blowholes where the ground was less treacherous.
Soon they reached their objective—one of the larger blowholes, a good fifteen feet across, oddly quiescent. The wheeler floated out to the center and immediately sank from sight. Charles approached the edge, and peered in. The blowhole was smooth-sided, forming the top of a shaft that might be ten feet deep, or ten thousand. Wherever the scattered light from the Sun and its reflection from Jupiter failed to penetrate, the hole was pitch-black.
He found a fist-sized lump of solidified dioxide, hefted it, and carefully tossed it into the middle of the blowhole. It hovered for several seconds, bobbed up and down, and began to sink into the darkness. It disappeared.
The dropshaft seemed to be functioning. Charles hoped the symbiautic antigravity machinery stayed that way. He took a deep breath and stepped off the edge.
After the initial shock of not plummeting to one's death, the descent was almost pleasant, except for the darkness. His heart still thumping, Charles switched on his suit's helmet lamp, but all it showed was the shaft walls slowly sliding upward, so he switched it off again to conserve power. He counted the passing seconds and fretted.
Overhead, the circle of bright sky dwindled to a dot and vanished. He fell.
According to one theory of lo's vulcanism, a surface layer of frozen sulfur and sulfur dioxide less than a mile thick floated on a sea of the same material in liquid form, about two miles deep. Below was solid silicate subcrust. Charles fervently hoped this theory was false, and that the alternative—a fifteen-mile-thick solid crust that rose and fell in response to Jupiter's tidal forces—was nearer the mark. Presumably the Jovians and their wheeler construction teams had known what they were doing when they built the shaft and the installation at its foot.
A gentle upward tug warned him that their descent was coming to an end. The walls of the shaft began to glow with a muted pink light; so did the floor, only inches beneath his feet. Boots hit solid rock. To one side, the dim lighting revealed the arched opening of a wide tunnel: Reliant Robin was nowhere to be seen, but the tunnel was the only exit, so it must have gone that way. The comet was now less than two hours from its Europan rendezvous, a second slingshot that would speed it up by a further factor of five. If that was allowed to happen, all was lost. Charles set off at a run.
The tunnel stretched for perhaps fifty yards and opened out into a brightly lit chamber. A third of a billion years earlier, wheeler teams had excavated a huge cavern half a mile below lo's hyperactive surface. Since then, gravitic repulsion had kept it and its access shaft safe from seismic shocks, tremors, and ioquakes. And here the Jovians had installed their Diversion Engines. There were similar installations inside the other three Inner Moons, with equally obscure entrances. Between them, the Engines could reconfigure the orbits of all four Inner Moons.
Hundreds of wheelers littered the chamber, immobile. Charles knew he wouldn't be able to reactivate any of them in time to make a difference. He had to stop himself from looking back over his shoulder, so strong was the sense that the comet was rushing upon him. Stepping over several frozen wheelers, he headed for the far end of the chamber. There, so he had been told, were the control consoles, mounted on stubby plinths . . . and the information was accurate.
Reliant Robin was waiting beside them. As Charles approached, it levitated once more and settled itself on top of the fourth plinth. For a moment nothing happened, but then a curious pattern of indentations flowed into being, accurately matching the symbiauts wheels. The wheeler rolled forward a half turn and settled into the indentations.
A portion of wall flowed, forming a flat circular area. Lights flickered over its surface, then settled into crudely formed human letters, if you can read, affirm. Charles did so: now he and Robin could communicate in both directions, accessing repulsion FIELD CONFIGURATION ROUTINES. Charles called up his suit's head-up display to check the comet's progress. "Robin, we're running out of time!" he yelled, knowing that this was silly. The wheeler was doing its best. For several minutes the symbiaut displayed no further messages, and Charles couldn't help wondering whether something had gone wrong, until a new message appeared: canceling standby mode.
Standby mode? That wasn't in the script. "What's all this about standby mod
e?"
ENGINES PARTIALLY DEACTIVATED, ORDERS OF ELDERS. POWERTRAPS DISCHARGED. NOT ANTICIPATED, CONTRARY TO PRECEDENT. UNAVOIDABLE DELAY.
Delay? "How long?"
ONE HALF-DAY.
A Jovian day was just short of ten hours . . .five hours'. "Confirm delay of one half-day!"
CONFIRMED.
Before another five hours had passed, the comet would have shot past Callisto on its way back out of the Jovian system, with the Earth firmly in its sights. It would be too far away for the Engines' short-range antigravitic forces to have a significant effect.
Charles sank to his knees on the floor of the chamber. We've lost. It's all over. I should have acted sooner. Bitter self-recriminations surged through his mind.
Idiot.
Charles was still berating his own stupidity The comet was smack on course—unfortunately—and was halfway toward the orbit of Leda. Reliant Robin had coaxed the Diversion Engines back out of standby mode and was recharging the powertraps. It was also succeeding in overcoming the Elders' disruption of interwheeler communications. Another half an hour, and everything important would be back on line.
Fat lot of use that was. The comet had come, and gone, and was beyond the range of the gravitic repulsion-beams. Nothing now could stop—
Unbidden, a sliver of hope. Bloody hell.
It was wild, it was crazy, it was the ultimate act of vandalism—and it might just work. "Robin? Can you hear me?"
LISTENING.
"I've got an idea."
Halfholder was screaming at Defier. They had been receiving regular news of the comet's progress, and to her horror the Inner Moons had remained in their current configuration throughout its passage. Already the gigantic snowstone was on its way back out of the Jovian system, beyond the Inner Moons, fast approaching the Outer Moons, soon to pass the Outermost Moons—and still exactly on the course that the Elders had intended: destination Poisonblue.
She was half mad with frustration because the rest of Defier's revolutionary plans were succeeding . . . but not the only part that mattered. How could the Lifesoul Cherisher permit such an obscenity? Her faith was in tatters. So she blamed Defier, who was the only one within earshot.
He waited for the tirade to end. She might even he right. Now that the extrajovians' last desperate opportunity had been missed, he felt strangely tarnished. There would be no joy in sky diver power over Secondhome.
Halfholder began to run out of breath and inspiration, and sank to the floor of the sanctum, her trunks quivering. Then a new report came in. Finally, the projectors were shining their repulsion beams and the moons were starting to reconfigure. But— too late, too late!
In any case, whatever the Inner Moons were doing, it certainly was not the planned reconfiguration. Instead, only one of the moons was moving.
Fivemoon.
The effect of the motion on its volcanic plumes was astonishing. Some had increased their height tenfold. Remarkable. What does this mean? Defier calmed Halfholder down and drew her attention to the new development. Baffled, they digested the reports as they came in. Not only was the moon starting to move—it was accelerating to an astonishing velocity. Why? What was Charred Lea of the Dun Moor up to now? If that went on, Fivemoon would soon fly free of the Secondhome system alto-geth—
Comprehension dawned.
The radio operator at Europa Base switched channels frantically, trying to find a wavelength that was not obscured by static. Once they caught a few snatches of conversation, but it was too brief for their signal-processing routines to clear into recognizable words. Every channel was obliterated by the electromagnetic storms created as lo stirred in its orbit, distorting like a peeled hardboiled egg as the repulsion beams pried it loose from Jupiter's grip. Minutes earlier, lo had boasted a dozen active volcanoes; now there were more than a hundred. Vast fountains of silicate magma jetted into space as lo's molten core changed shape and material escaped through newly formed canyons in the moon's fragile crust. The reaction forces that the vents created made fine control a nightmare—on Europa Base's readouts, lo fizzed and wobbled like a giant knuckleball.
Prudence refocused her scope on the polar approaches to the tortured worldlet, trying to pick out the tiny speck of Charles's returning OWL. It was hopeless: the seething brimstone fog blotted out everything.
The gravitic repulsors continued their relentless pressure, lo edged outward from its motherworld, trailing a lengthening cloud of sickly yellow vapor. The gas began to spread along the plasma torus that linked lo to Jupiter, until it looked as though the moon had sprouted horns. Truly, sulfur was the element of hell.
Suddenly the leathery hide of Bright Halfholder of the Violent Foam appeared on one of the monitors. The image flickered and dissolved; strange blotches of electronic noise gnawed at its edges. Halfholder's voice was half swamped by static, but Moses could just about make out what she was saying.
"She says—she says there has been something bad on the"— his voice dropped as he mumbled, half to himself—"shell-that-dives, child of shell-that-arrived from nosuchplace . . . Something bad on the OWL." The alien's features fragmented into a dozen zigzag bands, then locked together once more. "I think she's trying to tell us that the OWL has exploded."
Prudence closed her eyes to shut out visions of horror. It only made them all the more vivid. She tried to think clearly, but it was hard when your stomach felt as though you were plummeting down a mine shaft. "What sort of explosion? Was Charles on hoard?"
She waited in an agony of suspense while Moses translated. "Um . . . failure, mechanical—no, no, mechanism . . . Absence of. . . pressure? Did the shuttle decompress? No, not pressure— deathsong."
"Charles is dead?"
Moses stared at her, only now becoming aware of her emotional state. "Sorry, Aunt Pru. I've scared you. No: absence of deathsong. Charles is still very much alive. But he's stranded on lo—the OWL's fuel tanks blew up while he was still in the wheeler control complex." Jagged images came and went on the screen. lo trailed its ghastly yellow halo. Spurts of magma spiraled crazily in the distorted field of the gravity beams. "Nobody could survive that."
"Not for long," Prudence muttered. "Let's see if I can improve the odds." Then she was gone.
Tiglath-Pileser hummed uncomfortably as Prudence flipped its flight systems into readiness, bypassing the usual safety procedures, omitting anything that she could manage without. She'd borrowed an OWL and used it to transfer to her own ship—it would be quicker that way. This time, no one had tried to stop her. It was her ship, her life, and—she'd clearly decided—her responsibility.
The cruiser's main thrusters ignited. Balanced on an arc of flame, Tiglath-Pileser began to maneuver for a rendezvous with the hellworld that now was lo.
Prudence flew the ship with an unhurried and unnatural calm, lo's orbit was closer to Jupiter than Europa's: the direct route was down, and that would be the fastest. An OWL would lack the power to decelerate from such a trajectory, but Tiglath-Pileser was made of sterner stuff.
Now that she knew Charles might still be alive, she could think properly again. He had risked death to save his home planet—possibly the first unselfish act in his life, and very likely the last . . . unless the fates were in an uncharacteristically kindly mood and Tiglath-Pileser was capable of a task that far exceeded its designers' expectations.
She guided the rugged little ship toward lo, planning to come in from the polar direction where less junk was being vented. She flew the cruiser like a maniac, expending fuel recklessly if it would save a minute. Now Tiglath-Pileser was itself enveloped in a sulfur haze. The meteorite hazard-warning light was going berserk. Prudence switched it off.
No point in praying. She'd never believed in any kind of god anyway. Foolish idea. Random acts of chaotic universe, those made sense. She could live with those. Considered acts of an allegedly benevolent supernatural being? My ass. She kind of wished she did have faith in something more personal than the mindless unfolding of ra
tional laws ... It would be nice to imagine that the universe might want to take care of you . . . She snarled. Idiot! Imaginary entities won't help you here! You're going to have to pull this one off with nothing hut your own resources!
In an odd way, that was comforting. The only thing she'd ever had any real confidence in was her own resources. She swallowed, her mouth suddenly dry . . . What if her confidence was misplaced?
Reliant Robin relayed news to Charles.
Jaramarana had passed the orbit of Leda.
lo was ten hours behind, on track, catching up, but slowly. The massive rotors of its Diversion Engines howled with the strain; if lo did not catch the comet in time, the Earth would be destroyed.
The OWL had been wrecked by flying debris; they were trapped on lo. Charles had scarcely dared hope otherwise, given the calamity that he had unleashed.
It would be a small price to pay.
Outside the control complex the world had gone mad. Peles normal fountainlike jets had quadrupled in volume, now subject to wild bursts of activity as millions of tons of liquid silicates spurted into space, escaping lo's feeble gravity, trailing behind the moon in a turbulent cloud that condensed into tiny particles as it cooled. Jupiter was growing a new ring, a ring of sulfur-silica dust. Every few seconds the complex shook under a new ioquake, or a chaotic rebound of an earlier one, or an aftershock of an earlier one still.
lo rang like a cracked, doomed bell. Like the shell of a gigantic turtle's egg, its surface was breaking up into a hundred fragments, tectonic platelets that jostled and spun with an awful, ponderous deliberation as the beast within fought to escape its fragile prison.
An especially violent tremor shook the cavern, and Charles fell heavily to the floor. Even though he knew he was already a dead man, the thought came unbidden: My helmet! If it cracks —
Then the main shock hit.