Godlike Machines (16 page)

As for the crater lake I saw nothing but a plain, flatter and even more featureless than the average, covered with a thin scattering of ice sand. But the lake was there, hidden. Poole extracted radar images which showed the unmistakeable profile of an impact crater, right ahead of us, kilometers wide. Such is the vast energy pulse delivered by an infalling asteroid or comet—or, in Saturn’s system, perhaps a ring fragment or a bit of a tide-shattered moon—the water locally can retain enough heat to remain liquid for a long time, thousands of years. Such a lake had formed here, and then frozen over with a thin crust, on top of which that skim of sand had been wind-blown. But the briny lake remained, hoarding its heat.

And, studded around the lake’s circular rim, were more sponge-like masses like the one we had discovered wrapped up in silane film at the shore of the polar lake. These masses were positioned quite regularly around the lake, and many were placed close by crevasses which seemed to offer a route down into the deep structure of the ice rock beneath us. Miriam started gathering data eagerly.

Meanwhile Poole was puzzling over some images returned from the very bottom of the crater lake. He had found motion, obscure forms laboring. They looked to me like machines quarrying a rock deposit. But I could not read the images well enough, and as Poole did not ask my opinions I kept my mouth shut.

Miriam Berg was soon getting very agitated by what she was finding. Even as she gathered the data and squirted it up to Harry Poole in the
Crab
, she eagerly hypothesised. “Look—I think it’s obvious that Titan is a junction between at least two kinds of life, the silanes of the ethane lakes and the CHON sponges. I’ve done some hasty analysis on the CHON tissues.

They’re like us, but not identical. They use a subtly different subset of amino acids to build their proteins; and they have a variant of DNA in there—a different set of bases, a different coding system. The silanes, meanwhile, are like the life systems we’ve discovered in the nitrogen pools on Triton, but again not identical, based on a different subset of silicon-oxygen molecular strings.

“It’s possible both forms of life were brought here through panspermia—the natural wafting of life between the worlds in the form of something like spores, blasted off their parent world by impacts and driven here by sunlight and gravity. If the System’s CHON life arose first on Earth or Mars, it might easily have drifted here and seeded in a crater lake, and followed a different evolutionary strategy. Similarly the silanes at the poles found a place to live, and followed their own path, independently of their cousins ...”

The transfer of materials from the oily ethane lakes to the water crater ponds might actually have facilitated such creations. You need membranes to make life, something to separate the inside of a cell from the outside. As water and oil don’t mix, adding one to the other gives you a natural way to create such membranes.

She shook her head. “It seems remarkable that here we have a place, this moon, a junction where families of life from different ends of Sol System can coexist.”

“But there’s a problem,” Bill Dzik called from his shower. “Both your silanes and your sponges live in transient environments. The ethane lakes pretty much dry up every Titan year. And each crater lake will freeze solid after a few thousand years.”

“Yes,” Miriam said. “Both forms need to migrate. And that’s how, I think, they came to cooperate ...”

She sketched a hasty narrative of the CHON sponges emerging from the crater lakes, and finding their way to the summer pole. Maybe they got there by following deep crevasses, smashed into Titan’s ice crust by the impacts that dug out crater lakes like this one in the first place. Down there they would find liquid water, kilometers deep and close to the ammonia ocean. It would be cold, briny, not to terrestrial tastes, but it would be liquid, and survivable. And at the pole they would find the silane lilies floating on their ethane seas. The lilies in turn needed to migrate to the winter pole, where their precious life-stuff ethane was raining out.

Miriam mimed, her fist touching her flattened palm. “So they come together, the sponges and the lilies—”

“To make the Titan birds,” I said.

“That’s the idea. They come flapping up out of the lake, just as we saw, heading for the winter pole. And meanwhile, maybe the sponges get dropped off at fresh crater lakes along the way. It’s a true symbiosis, with two entirely different spheres of life intersecting—and cooperating, for without the migration neither form could survive alone.” She looked at us, suddenly doubtful. “We’re all amateurs here. I guess any competent biologist could pick holes in this the size of the center of Saturn’s rings.”

Dzik said, “No competent biologist would even be hypothesising this way, not with so few facts.”

“No,” Virtual Harry said tinnily. “But at least you’ve come up with a plausible model, Miriam. And all without the need to evoke even a scrap of sentience. Good job.”

“There are still questions,” Miriam said. “Maybe the sponges provide the birds’ intelligence, or at least some kind of directionality. But what about power? The lilies especially are a pretty low-energy kind of life form . . .”

Michael Poole said, “Maybe I can answer that. I’ve been doing some analysis of my own. I can tell you a bit more about the silane lilies’ energy source. Believe it or not—even on a world as murky as this—I think they’re photosynthesising.” And he ran through the chemistry he thought he had identified, using entirely different compounds and molecular processing pathways from the chlorophyll-based green-plant photosynthesis of Earth life.

“Of course,” Miriam said. “I should have seen it. I never even asked myself what the lilies were
doing
while they were lying around on the lake’s surface . . . Trapping sunlight!”

Harry was growing excited too. “Hey, if you’re right, son, you may already have paid for the trip. Silane-based low-temp photosynthesisers would be hugely commercially valuable. Think of it, you could grow them out of those nitrogen lakes on Triton and go scudding around the outer System on living sails.” His grin was wide, even in the reduced Virtual image.

Poole and Miriam were smiling too, staring at each other with a glow of connection. Theirs was a strange kind of symbiosis, like silane lily and CHON sponge; they seemed to need the excitement of external discovery and achievement to bring them together.

Well, there was a happy mood in that grounded gondola, the happiest since we had crashed. Even Bill Dzik as he showered was making grunting, hog-like noises of contentment.

And just at that moment there was a crunching sound, like great jaws closing over metal, and the whole bus tipped to one side.

Poole and Miriam staggered and started shouting instructions to each other. I had my helmet over my head in a heartbeat.

Then there was another crunch, a ripping sound-and a scream, gurgling and suddenly cut off, and an inward rush of cold air that I felt even through my exosuit. I turned and saw that near the shower partition, a hole had been ripped in the side of the gondola’s flimsy hull, revealing Titan’s crimson murk. Something like a claw, or a huge version of Miriam’s manipulator arm, was working at the hull, widening the breach.

And Bill Dzik, naked, not meters from the exosuit that could have saved him, was already frozen to death.

That was enough for me. I flung open the hatch in the gondola roof and lunged out, not waiting for Miriam or Poole. I hit the Titan sand and ran as best I could, the exosuit laboring to help me. I could hear crunching and chewing behind me. I did not look back.

When I had gone 100 meters I stopped, winded, and turned. Poole and Miriam were following me. I was relieved that at least I was not stranded on Titan alone.

And I saw what was becoming of our gondola. The machines that had assailed it—and they were machines, I had no doubt of it-were like spiders of ice, with lenticular bodies perhaps ten meters long, and each equipped with three grabber claws attached to delicate low-gravity limbs. Four or five of these things were laboring at the wreck of our gondola. I saw that they had gone for the wheels first, which was why we had tipped over, and now were making a fast job of ripping the structure apart. Not only that, beyond them I saw a line of similar-looking beasts carrying silvery fragments that could only be pieces of the gondola off up the rising ground towards the summit of the cryovolcano. Some of the larger components of the wreck they left intact, such as the GUT engine module, but they carried them away just as determinedly.

In minutes, I saw, there would be little left of our gondola on the ice surface-not much aside from Bill Dzik, who, naked, sprawled and staring with frozen eyeballs, made an ugly corpse, but did not deserve the fate that had befallen him.

Harry Poole’s head popped into Virtual existence before us. “Well,” he said, “that complicates things.”

Michael swatted at him, dispersing pixels like flies.

X

Spiders

“Dzik is dead,” I said. “And so are we.” I turned on Michael Poole, fists bunched in the thick gloves. “You and your absurd ambition-it was always going to kill you one day, and now it’s killed us all.”

Michael Poole snorted his contempt. “And I wish I’d just thrown you into a jail back on Earth and left you to rot.”

“Oh, Lethe,” Miriam said with disgust. She was sifting through the scattered debris the spiders had left behind. “Do you two have any idea how ridiculous you look in those suits? Like two soft toys facing off. Anyhow you aren’t dead yet, Jovik.” She picked up bits of rubbish, rope, a few instruments, some of her precious sample flasks, enigmatic egg-shaped devices small enough to fit in her fist—and food packs.

Michael Poole’s curiosity snagged him. “They didn’t take everything.”

“Evidently not. In fact, as you’d have noticed if you weren’t too busy trading insults with your passenger, they didn’t take
us
. Or Bill.”

“What, then?”

“Metal. I think. Anything that has a significant metal component is being hauled away.”

“Ah.” Poole watched the spiders toiling up their volcano, bits of our ship clutched in their huge claws. “That makes a sort of sense. One thing this moon is short of is metal. Has been since its formation. Even the core is mostly light silicate rock, more like Earth’s mantle than its iron core. Which maybe explains why every surface probe to Titan across 1600 years has disappeared without a trace-even the traces of your illegal sample-collectors, Emry. They were taken for the metal.”And,” he said, chasing the new idea, “maybe that’s what we saw in the radar images of the deeps of the crater lake. Something toiling on the floor, you remember, as if quarrying? Maybe it was more of those spider things after the metallic content of the meteorite that dug out the crater in the first place.”

“Well, in any event they left useful stuff behind,” said Miriam, picking through the debris. “Anything ceramic, glass fiber, plastic. And the food packs. We won’t starve, at least.”

Poole had homed in on theory, while she focused on the essentials that might keep us alive. That tells you everything about the man’s lofty nature.

“But they took the GUT engine, didn’t they?” I put in sharply. “Our power source. Without which we’ll eventually freeze to death, no matter how well fed we are.”

“And, incidentally,” Miriam said, “the identity-backup deck. We cached the backups in the GUT engine’s own control and processing unit, the most reliable store on the gondola. If we lose that, we lose the last trace of poor Bill too.”

I couldn’t help but glance at Dzik’s corpse, fast-frozen on the ice of Titan.

Not Poole, though. He was watching those receding spiders. “They’re heading down into the volcano. Which is a vent that leads down into the mantle, the ammonia sea, right? Why? What the hell are those things?”

Miriam said, “One way to find out.” She hefted one of those ceramic eggs in her right hand, pressed a stud that made it glow red, and hurled it towards the nearest spider. It followed a low-gravity arc, heavily damped in the thick air, and it seemed to take an age to fall. But her aim was good, and it landed not a meter from the spider.

And exploded. Evidently it had been a grenade. The spider shattered satisfactorily, those ugly claws going wheeling through the air.

Miriam had already started to run towards the spider. You couldn’t fault her directness. “Come on.”

Poole followed, and I too, unwilling to be left alone with Bill’s frozen remains. Poole called, “What did you do that for?”

“We want to know what we’re dealing with, don’t we?”

“And why are we running?”

“So we can get there before the other spiders get rid of it.”

And sure enough the other spiders, still laden with bits of the gondola, had already turned, and were closing on their shattered fellow. They didn’t seem perturbed by the sudden destruction of one of their kind, or of our approaching presence. They seemed to perceive only what was essential to them—only what was metallic.

We got there first, and we squatted around the downed spider in a splash of suit light. The spider hadn’t broken open; it was not enclosed by a hull or external carapace. Instead it had shattered into pieces, like a smashed sculpture. We pawed at the debris chunks, Miriam and Poole talking fast, analyzing, speculating. The chunks appeared to be mostly water ice, though Poole speculated it was a particular high-pressure form. The internal structure was not simple; it reminded me of a honeycomb, sharp-edged chambers whose walls enclosed smaller clusters of chambers and voids, on down through the length scales like a fractal. Poole pointed out threads of silver and a coppery color—the shades were uncertain in Titan’s light. They were clearly metallic.

“So the spiders at least need metal,” Miriam said. “I wonder what the power source is.”

But we weren’t to find out, for the other spiders had closed in and we didn’t want to get chomped by accident. We backed off, dimming our suit lights.

Miriam asked, “So, biological or artificial? What do you think?”