Arthur C Clarke's Venus Prime Omnibus

by Paul Preuss

  The gravity of Amalthea was so microscopic that walking was out of the questions; they were all roped together like mountaineers, and they blew themselves across the plain with gentle bursts from their backpack maneuvering systems.

  “What’s it like down there?” came Forster’s impatient query in their suitcomms.

  “Like an Italian ice,” said Blake.

  “The closer one looks, the more extraordinary the formations,” Hawkins said. “Infinitely recursively structured, probably down to the limit of the water molecule.”

  “What did he say?” McNeil muttered audibly.

  Blake and McNeil were at the two ends of the tether, so that any unwise eagerness on Hawkins’s part—he’d established a reputation as one given to disruptive enthusiasms—was restrained. After his companions had had to yank him back into line for the second time, Forster’s voice came over the commlink again. “How are you feeling, Bill?”

  “I know that some people think it must be very entertaining to walk around on an airless, low-gravity planet in a spacesuit. Well, it isn’t.”

  McNeil grumbled, “Strain getting to you?”

  “All these checks and precautions.”

  “Just think about the main points. Know where you are?”

  “What does it matter when I’m on this bloody rope?”

  “Have enough air?”

  “Well of course, Angus, really…”

  “Then just don’t forget to breathe.”

  For five minutes they moved on in silence until their objective, one of the arrays of black circles they had seen from space, was a quarter of a kilometer away, and they could just make out a hazy sketch of lines in the mist.

  McNeil said, “Maybe we’re dealing with a relay, an amplifier. Maybe some of these antennas are aimed at the home star of the ones who built them.”

  “Why six antennas?” Hawkins asked. “Even with one to point at Jupiter—seems like four extra to me.”

  “Rotation,” said Blake.

  “It couldn’t have taken long for Amalthea to become tidally locked to Jupiter,” Hawkins protested. “So it must have been in this orientation a billion years.”

  “You’re overlooking its revolution around Jupiter.”

  “Right,” McNeil said. “With six arrays, they can cover the whole sky all the time.”

  “Well, whatever it is, there it is,” Hawkins said.

  The line of half-drifting, half-flying spacesuited men rebounded to an awkward halt, like a Slinky toy falling off a stairstep. Out of the white mist ahead of them the thing loomed up, black and spidery, furred with icicles weirdly splayed in every direction.

  It was unquestionably an artificial object—very possibly a radio antenna, as seemed likely—but it was unutterably foreign in its details. It could have come from beneath the sea.

  An hour went by. Blake exhausted himself trying to prize a chunk of stuff off the structure, but there was nowhere to get a purchase. Nothing was rusted; the thing didn’t appear to be made of iron or any metal susceptible to corrosion, but of something resembling an indestructibly tough black plastic. There were no seams big enough to slip a knife-blade into. He couldn’t unscrew anything or shear off anything, because there were no screws or bolts or rivets. As for the base of it, that was apparently still buried meters deep in the ice.

  The huge circular rig was a shallow, bowl-shaped mesh more than a kilometer across, a paraboloid with a central mast terminating at its focus. But Angus McNeil pointed out that it seemed the wrong shape, too flat in the Z-axis, for the electromagnetic radiation it was supposed to detect. “If it’s an antenna, okay, but it would be damned inefficient,” he said. “I can’t believe these aliens were sophisticated enough to set up a listening post here but not sophisticated enough to design an efficient receiver or transmitter.”

  “Maybe it’s not a transmitter. Maybe they didn’t worry about the home star,” said Blake. “Maybe Amalthea houses some kind of memory device, recording data intended to be picked up later.”

  “But this whole thing was supposed to be under ice for a billion years, right?” Hawkins said.

  Looking at the huge construction which loomed like a spider web in the mist, it was hard to remember that the fragile snow around them hadn’t always been there, that not long ago the surface of Amalthea had been higher than their heads—high enough to completely engulf the alien antenna.

  “You mean its geometry compensates for the speed of light in water?” McNeil’s tone conveyed what he left unsaid: either you don’t know anything at all about physics, young Dr. Hawkins—or you’re not so dumb after all.

  “Did I say that?” Hawkins asked.

  The former, McNeil decided. Ah, well. “Radio waves don’t travel far in water,” he growled.

  “It wasn’t that far under water,” Blake said, siding with Hawkins. “Only a few meters.”

  “Well, it’s a hypothesis,” McNeil said. “I’ll have to run some calculations.”

  “Still … if these are antennas, where’s the power source?” Hawkins added, still playing devil’s advocate, taking delight in complicating matters further.

  “If this were my rig, I’d make it self-contained, fit it with superconducting batteries and capacitors,” McNeil said. “Field measurements will tell us. If you want to worry about power, think about whatever’s driving those geysers.”

  “Could be, their power source isn’t on Amalthea at all,” Blake said.

  “What do you mean, Blake?” Professor Forster’s voice sounded in their helmets.

  “Until a year ago, Amalthea was thought to be a rigid body. If the rigidity was artificial, maybe the medusas’ signal somehow turned off the gizmo—so now Amalthea is feeling the tidal forces from Jupiter. In that case Jupiter would be the heat engine.”

  “As with the volcanoes of Europa,” Forster said.

  “Yes sir,” Blake said. “If Amalthea is really mostly water, expansion and contraction as it whips around Jupiter would be enough to start it boiling away, so long as nothing prevents it.”

  “Meaning we still don’t know what we’re looking for,” Angus McNeil grumbled.

  Later, when it was arbitrary night aboard the Ventris, McNeil displayed the results of his measurements and calculations on the graphics plate. Indeed, the structures had just the right geometry to function as antennas under a moderate layer of ice.

  The team was supposed to use the night hours to sleep, but the day’s events left few of them calm enough. After dinner in the wardroom, Blake left the others arguing about how and with whom the antennas communicated and went back to the ship’s cramped but well-equipped laboratory.

  Having finally resorted to a laser probe and an ion trap to get a few sample molecules from the alien structure, he spent the early evening hours trying to find out what the stuff was. Spectrometry didn’t help him much: no exotic elements showed up in the peaks and valleys of the spectrum—a few common metals, plus carbon and oxygen and nitrogen and other light elements—and not even any unusual ratios among them. Whatever had given the structure its extraordinary strength and durability was surely due to its crystalline structure—but that had been reduced to molecular chaos when Blake blasted it with his laser.

  He gave up and turned to the ice cores they had collected. These were more … suggestive.

  He was peering at the readouts, shaking his head glumly, when he became aware that Forster was watching him from the hatch of the cramped, padded laboratory.

  “Hello,” Blake said, “have you come to watch me learn basic college chemistry?”

  “What are you doing?” Forster asked, eyebrows vibrating.

  “Well, sir, I could give you a list of failed experiments. Structure and composition of the ice. Age of the ice—trying to do age determinations on these core samples we took today and not succeeding.”

  The surface of Amalthea, subliming into space, was constantly exposing fresh layers of material. The long-buried ice had been affected by particles in
Jupiter’s radiation belt and by solar and cosmic rays. By measuring isotope ratios in the fresh ice, it was theoretically possible to calculate how long each layer had rested undisturbed.

  “What’s the problem?”

  “The readings are crazy. Neighboring samples give values that differ by five or six orders of magnitude.”

  “You’ve calibrated the instruments?”

  “Yes sir. Maybe I’m misreading the manuals—maybe they were translated from Eskimo or Finno-Ugrik or something.”

  “Why not believe the instruments? One sample’s old, another’s young.”

  Blake said, “We’re not talking old and young here, sir, we’re talking young and very young. Most of the samples date this ice to a billion years BP. Compare that to ice from Ganymede or Callisto or Europa, which is a respectable four-point-five billion years BP.”

  Forster sounded gruff, but there was a smile in his voice. “Meaning Amalthea didn’t form as part of the Jupiter system. Perhaps it was captured later.”

  “Meaning Amalthea didn’t form as part of the solar system.” Blake grunted. “Listen to me, I sound like Sir Randolph-Loudmouth-Mays.”

  “And the other sample?” Forster demanded.

  “Somewhere between a thousand and ten thousand years old.”

  “Not quite as old as the solar system,” Forster said, smiling openly now.

  “Well sir, if you were a Creationist…”

  “Where did that sample come from?”

  “Right under the alien antenna,” Blake said.

  “Might be an interesting place to start looking.” Forster sighed softly. “Too bad Troy’s not with us. Could be, that cult of hers would have something to say about these matters.”

  “She wouldn’t like to hear you call the Free Spirit her cult, Professor.”

  “Salamander, then, or whatever you call yourselves. Professor Nagy attempted to enlighten me, but I’m afraid I was never able to get it all straight.”

  “Besides, the Knowledge is hardly complete. It doesn’t make any reference to Amalthea,” said Blake, evading the topic.

  “Rather odd, then, that Troy always seems to know more than this so-called Knowledge. Too bad she never stays in one place long enough to make herself useful.”

  Blake felt his ears glowing. “She usually manages to arrive when she’s needed,” he said defensively. Forster of all people knew that better than most.

  “Quite. What is she about, back there on Ganymede? Did she drop any hints in your hearing?”

  “Sorry. I don’t know any more about it than you.”

  “Hm, well… I wish she’d let us know earlier. Saved ourselves a week or two in that gloomy cavern.” Forster turned his attention to the lab bench, tapping the laser spectrometer’s little flatscreen. “What else have you got to show, my boy?”

  “Take a look at the basic composition of this stuff. Look at these ratios.” Blake first showed Forster close-ups of ice crystals on the big screen, then a chemical analysis of the foreign minerals trapped in the crystals.

  Looking at the colored graphics and spiky charts on the flatplate, J. Q. R. Forster’s face broadened into a truly happy grin. “Golly, Mr. Wizard.”

  “What are you onto, sir?” Blake demanded, for it was obvious the older man was not surprised.

  “You first, young man—what does it all mean to you?”

  “Well, the crystalline structure’s common enough. Ordinary Ice I, so we know it froze at low pressure.”

  “Surely that’s what you’d expect.”

  “Yeah, unless Amalthea was a leftover chunk of the core of a much larger ice moon.”

  “You considered that, did you?” Forster said appreciatively.

  “It crossed my mind. See, I don’t think this stuff froze in vacuum. How could you explain these dissolved minerals—salts, carbonates, phosphates, others…” He pointed to the graphic on the plate.

  “What does it look like to you?” Forster prodded.

  “How about frozen seawater?”

  13

  The Michael Ventris slowly settled out of orbit under the feathery tug of Amalthea’s gravity, until its flat tripod feet sank deep into the frothy surface. In the equipment bay the ice mole hung lightly in its shackles, lit by the metallic glare of worklights. Blake and Forster pulled themselves into its cockpit and methodically strapped themselves in. The gingery professor was seething with impatience.

  “Quaint old gadget,” Blake muttered placidly, regarding the gaudy display panel now lit up like a carnival midway. He fiddled interminably with the instruments while Forster, who had been edgy throughout the tedious pre-launch, grew increasingly tense.

  “Got an old mole here, do we?” came Josepha Walsh’s hoarse and cheerful voice over the comm.

  “This Old Mole’s still got plenty of get up and go,” Blake said at last. “Diagnostics give us a clean slate. Ready to launch.”

  “Let’s get on with it,” Forster said.

  “All set, Jo?” Blake said in the general direction of the mike.

  For a moment there was silence on the commlink before Walsh replied. “That’s a roger. You may proceed.”

  Blake brought the clear bubble down over their heads and sealed it. “Confirming full atmospheric pressure, no discernible leaks.”

  “You’ll be fine as long as you’ve got your E-units,” came Walsh’s reply. Against sudden pressure loss they wore emergency soft-suits, with the faceplates of their head-fitting helmets left open. The mole was of too early a vintage to be equipped for Artificial Reality suits, with which a pilot could feel wholly a part of the machine.

  “I hardly think we’re going to die of depressurization,” Forster said sharply.

  Blake gave him a quick glance. Perhaps it was the sense of separation, the need for layers of protection and interpretation between him and the environment, that made the professor so irritable. Perhaps he was reminded of his near-disastrous expedition to Venus.

  “I’ll not hold you up any longer then,” said Walsh. The clamshell doors of the equipment bay peeled away—

  —opening upon stars above and unearthly white mist below, and on the horizon a ruddy glow, Jupiter itself riding unseen beneath the moon’s edge.

  The whine of a miniature electric crane conveyed itself through the grapple to the roof of the vehicle as the mole was lifted ever so slowly out of the hold and held poised, outside the ship. The whine ceased. There was a click as the last magnetic grapple let go. Then another click, as springs uncoiled and gently propelled the machine away from the ship. Almost but not quite weightless, the massive machine slowly began to drop, nose down. It fell a long time into the mists, like a sagging helium balloon, interminably.

  An edge of the huge alien antenna came out of the milky whiteness on the port side. The Ventris had purposely dropped the mole beside the antenna, for here the ice samples showed patches anomalously younger than Amalthea’s otherwise uniform age of a billion years.

  Blake and Forster hardly felt the slow collision with the delicate ice when they hit the surface—but outside there were sudden snowdrifts, halfway up the cockpit window.

  Above and behind them, barely visible through the frosty window, two white shapes gleamed like portly angels, drifting down the black sky—Hawkins and Groves, checking the fat, half-coiled electrical cables that would power the mole from the Ventris’s auxiliary power units. They did what they had to behind the ice mole, securing the cable attachments.

  “Okay, you should be mobile,” came Hawkins’s jolly voice over the commlink. He had gotten over his awkwardness in spacesuits; indeed, with a day’s practice he’d become quite the athlete of the vacuum.

  “We’re all go here,” Blake reported to the Ventris.

  “And all links look good on our boards,” said Walsh from the flight deck.

  Forster said tensely, “You may go ahead when ready.”

  Blake eased the pots forward.

  Below them opposed twin bits began an intricate d
ance, slowly at first, then with rising speed. A cloud of ice crystals engulfed the mole. The top ten or twelve meters were spongy froth, then there was a bump, and the machine abruptly descended through a pocket of vacuum-pocked ice. Finally, with a screech, diamond-edged titanium blades engaged old, hard ice, and the mole began to drill straight into the heart of Amalthea.

  Forster suddenly relaxed, releasing a long sigh, as if he’d been holding his breath. The center of Amalthea tugged at his heart, harder the closer he got to it—like gravity, the force of his obsession increased with decreasing distance from his goal. But at least he was moving as fast as he could toward the object of his desire.

  The big screen in the middle of the console gave Blake and Forster a clear three-dimensional image of their sector of the moon’s structure—where they were and where they were going. Along with information from a year’s worth of passive observation by Space Board satellites, the results of the Ventris’s recent seismic studies had been fed into the mole’s data banks. Had Amalthea been anything but a thoroughly surprising place, the image on the screen might have been unexpected…

  For over a century, since it was first photographed close up by the primitive robot probe Voyager 1, Amalthea had been thought to be low in volatile substances—certainly a reasonable hypothesis, for the moon had no atmosphere, was rigid, seemed inert. By contrast, its much larger neighbor, Io, was a moon so rubbery, so rich in mutable liquids and gases, that remarkable sulfur volcanoes had been in constant eruption somewhere upon its surface ever since they had been discovered by the same Voyager 1, the first artificial observer to reach Jupiter’s orbit and the first, upon returning images of Io to its controllers, to reveal that the Earth was not alone in the solar system in being geologically active.

  But Amalthea was in fact about as volatile as a small body can be, consisting almost entirely of water; yet even while bathed in Jupiter’s radiation belts and racked by the tidal forces of the giant—a planet so massive it fell not far short of self-ignition into a star, and thus had often been described as a failed rival to the sun—Amalthea had remained frozen solid.