The Diamond Moon (12 page)

“Anybody got any ideas about what we’re looking at?” Forster asked.

 

“Well, sir, I’d venture . . .”

 

“No fair, Angus, you can tell at a glance. Bill? Tony? Any guesses?”

 

Tony Groves shook his head and smiled. “No idea. Although they do look a bit like giant dartboards.”

 

“Some dartboards,” McNeil snorted. “Some darts.”

 

“Bill?” the professor prompted.

 

Bill Hawkins said rather sullenly, “I’m a linguist, not a planetologist.” He seemed genuinely hurt by Forster’s evi-dent decision to withhold his prior knowledge of the mark-ings.

 

“What about you, Blake?”

 

Blake smiled. “Could they have something to do with the fact that when Falcon aroused the medusas, they aimed a radio blast right at Amalthea?”

 

“Is that really true?” Hawkins asked sharply. “Mays claimed it, but the Space Board never confirmed it.”

 

“It’s true, Bill,” Forster said. “I’ll show you my analysis of that signal. I think you’ll come to the same conclusion about its meaning I did.”

 

“Which is what?” Hawkins demanded.

 

“A message that translates, ‘They have arrived.’ I believe the medusas were announcing the arrival of visitors in the clouds of Jupiter.”

 

“The medusas!” Hawkins protested. “They’re not intelli-gent, are they? Aren’t they merely simple animals?”

“Well, we really have no idea how intelligent they are. Or even how to apply the concept of intelligence to alien lifeforms. But given the right sort of training, or program-ming, it takes no particular intelligence for an Earthly or-ganism to emit a complex-seeming behavior, upon the right stimulus. Trained parrots for example.”

“Assuming the medusas
were
signalling, there would have to be receivers to pick up the signal,” Blake said.

 

“
Radio
antennas, you mean?” said Hawkins, incredulous.

 

“So I’d bet,” said Forster.

 

Angus McNeil nodded. “That’s just what they are, by the look of ’em. Suitable for meter wavelengths, same as the markings on the medusas. What I wonder is why nobody ever noticed ’em before.”

“Until a year ago—until the geysers erupted—Amalthea was covered with reddish black dirt,” Forster said, “the color of a carbonaceous body rich in organics, and incidentally the perfect color to hide these artificial structures.”

“You think they were deliberately disguised, then?” asked Tony Groves, sounding skeptical.

“I don’t know,” Forster replied simply. “I suppose the dirt layer could have accumulated over the millenniums from random collisions with meteoroids.” He looked at Blake. “What do you say?” “What seems irrational to a human might make perfect sense to an alien,” Blake answered. “Yet I don’t see the point in hiding the antennas, if the idea is to alert some . . .
pres-ence
on Amalthea that visitors have arrived at Jupiter. What difference would it make if the visitors saw these things and chose to land on Amalthea before going to Jupiter?”

“Unless this presence, as you call it, didn’t want to be discovered accidentally,” said Forster.

 

“What does that mean?” Hawkins blurted, still nursing his resentment.

“A year ago nobody knew there were medusas living in the atmosphere of Jupiter,” Forster said to him, “despite a century’s worth of probes—over three hundred robot probes. Until somebody goes back down there and tries to interview a medusa, we won’t know how intelligent they are—your point, Bill—or what kind of intelligence we’re dealing with. Perhaps this—
presence
—doesn’t want to talk to robots. Or to trained parrots. Perhaps it doesn’t want to talk to entities that have merely stumbled upon some sign or mark of ar-tifice on the surface of Amalthea. Perhaps this presence only wants to talk to those who know exactly what they’re look-ing for.”

“Those who’ve found and deciphered the Martian plaque?” Hawkins asked, adding a bit acidly, “People like yourself?”

 

Forster smiled disingenuously. “The Martian plaque—or its equivalent.”

 

“According to Sir Randolph-Bloody-Mays, the Free Spirit claims to have preserved from antiquity such an
equivalent
.” Hawkins almost spat the words. “They call it the
Knowledge
.”

 

“I’m not one of the Free Spirit, Bill, and I’m not in league with them,” Forster said quietly. “Whatever Mays may claim.”

 

Blake broke the awkward silence that ensued. “Our turn to quiz you, Professor. What are we looking for out there?”

“Good question.” Forster paused, tugging at a stray hair in one of his thick brows. “Answering it is the essence of our task. I have my notions, but in fact I don’t know anything with certainty. No more than any of you,” he added, with a nod to Bill Hawkins. “We’ll begin with a close-in survey from orbit.”

They flew through a fantastic cloudscape, a corona of gases standing straight out from the surface of the moon like electrified hair. Instead of entangling itself in these ev-anescent tresses, the
Ventris
sailed through them without leaving so much as an eddy, except where the cage of its superconducting radiation shield temporarily bent the charged particles around the ship in curves of mathematical precision.
Coming over the leading half, blown bare of gas, they looked down upon a blinding whiteness that appeared as smooth and hard as a billiard ball; but when they bounced radar signals off the surface, a mushy signal came back. They charted the locations of the geysers and found that while they were not exactly equidistant from one another, they marked out the interstices of a regular imaginary grid pattern over the entire ellipsoidal surface of the moon. They found six of the giant “dartboards,” one at each pole of the long axis, and four evenly spaced around the equator.

When they were safely parked back in the radiation shadow, Tony Groves, who was in charge of the survey, neatly summed up the results: “Friends, there’s absolutely nothing natural about this so-called moon.”

The first exploratory team—Blake, Angus McNeil, and Bill Hawkins—went out twelve hours later. In that time Amalthea and its flea-sized parasite, the
Michael Ventris
, had raced all the way around Jupiter once and come back approximately to where they had been with respect to Ju-piter and its planet-sized, slower-moving Galilean moons, when they’d first made moonfall.

The hatch swung open and the three explorers, spot-lighted by a circle of yellow light from the airlock, floated out into the shadow of Amalthea. McNeil had done this sort of thing more times than he could count, on hundreds of asteroids and moonlets, although he’d never done it quite like this—

—diving into a white fog as bright and opaque as dry ice vapor but more tenuous, gauzier, harder to disturb, less skittish; it was as if the fog were no more substantial, no easier to cup in the hands or disturb with a vigorous swing of the arm, than the diffuse and omnipresent light that had existed in the photon era of the early universe.

When Forster had announced the roster, McNeil had muttered to Tony Groves that Hawkins was too inexperi-enced for the tricky extravehicular activity. But Forster made it clear that he wanted Hawkins to be on the first team.

Nor was Blake exactly an old hand; his experience in space was, putting it politely, eclectic. He’d once had fun jumping around on Earth’s moon, and he’d had plenty of practice with Martian pressure suits, but aside from one brief episode in an old-fashioned soft-suit near the Martian moon Phobos, he was new to work in deep space.

McNeil was appointed their shepherd. In thirty years of space travel, there were few emergencies he had not faced and managed.

When they got close enough to the surface they discov-ered beneath their booted feet a froth of pure and delicate water ice, fantastically carved by forces no more powerful than sublimation into a fluffy crystalline universe of branching miniaturized snowflake-structures—the scale and complexity of deep coral reefs, yet as insubstantial as a puff of talc.
The gravity of Amalthea was so microscopic that walk-ing 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 for-mations,” 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 estab-lished 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 enter-taining 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 am-plifier. 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 knifeblade 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, tak-ing 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’ sig-nal 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