The Diamond Moon (20 page)

The sub came down to within a few meters of the gleam-ing surface. It showed no sign of plates or rivets, no hint of a seam or even an irregularity. It was perfect. They flew over it with stately wing-flaps as if over a landscape plated with a film of diamond. The horizon was curved as gently as a moon’s, and the black-water sky was spangled with living, darting stars.

“What if we
can’t
get in?” said Blake.

 

Forster’s reply was uncharacteristically tentative. “Diffi-cult to imagine anything more . . .
tantalizing
than to be locked out of the greatest archaeological find in all history.”

 

Sparta was silent, almost contemplative, as if nothing that happened could upset or surprise her.

The objective of the school of glittering squid seemed to be a broad, low dome at least a kilometer in circumference. Soon they were over it; far off on the diamond plains stood the great bright towers, evenly spaced in rows around then, catching them in a reticule of shimmering reflection.

Now the school of squid spiraled above them like bright-colored autumn leaves caught up in a whirlwind, soaring into the sky and falling, only to be swept aloft again in the swirling dance. The Manta flapped its way to the middle of the spiral of ascending transparent animals. There below them in the center of the otherwise flawless dome the three submariners saw the first interruption in Amalthea’s perfect surface, a circular hole some two meters across.

“Too small to get in,” said Forster, crestfallen.

 

Sparta let the Manta settle toward the dark opening, probing it with the sub’s lights. Inside were other bright structures, a tunnel-like opening whose walls were fretted and filigreed in bright metal.

 

“This doesn’t look artificial,” Forster said, with increas-ing pessimism.

 

“Could be a meteor strike,” Blake said brightly, leaning forward to peer between their heads at the opening below.

 

“Mighty lucky hit,” said Sparta. “Awfully round hole, wouldn’t you say?”

 

“Big meteors always produce circular holes, unless they strike very glancing blows.” It was as if Blake wanted to convince them of the worst.

 

“I doubt that a meteor would make a round hole in this material,” Sparta said, “This is the same stuff as the Martian plaque.”

 

“But look at the edges,” Blake persisted. “You can see there’s been an explosion of some kind.”

 

“I don’t think so. That etching looks too intricate to have been done by an explosion.”

 

Forster cleared his throat with a growl. “What do
you
think it is, Troy?”

 

“I think they left the door open for us.”

 

“
They?
This is a machine,” Forster exclaimed hoarsely. “A billion-year-old machine.”

 

She nodded. “A very smart one.”

 

“You think it’s programmed to let us in?” He was transparent; he wanted her to tell him what he wanted to believe.

 

She nodded again, obliging him at least partly. If he wanted her to say that
they
were still inside, however, she would have to disappoint him.

 

Sparta studied the interior of the round hole and its scal-loped and serrated surfaces; she fixed it in memory and then, for an imperceptible moment—

—she fell into a trance, into a mathematical space of unpicturable dimensions where no real-world sensations penetrated—only the chittering squeaks of the squid, still echoing inside her head. Her soul’s eye performed the anal-ysis and the computation and suddenly she saw how the thing worked. Her eyes flickered—

—and she was back in the strangely lit underwater world—partly bright, partly dark, partly cold, partly hot. The Manta bobbed sensuously in the dark water. Without both-ering to explain herself to Blake or the professor, Sparta manipulated the Manta’s waldos, brushing its sensitive ti-tanium fingers along the complex inner surface of the cy-lindrical hole, brushing and stroking the textures that could as easily have been melted slag or fine jewelry by their appearance but were really something as straightforward and purposeful as a mathematical constant, like the writtenout expansion of pi.

“Something’s happening,” said the professor.

 

“I don’t see anything,” Blake said. “Or hear anything.”

 

“I feel it—I mean, somehow I
sense
it.” Forster’s eyes widened. “Look there, what’s that?”

 

The low dome over which they hovered seemed somehow less adamantine, less perfect in its reflection of boiling incandescent towers.

 

“It’s brighter here,” he said excitedly.

 

“Really?” Sparta’s voice was teasing.

 

“The ground—I mean the hull, or whatever it is—it’s glowing.”

 

“The instruments don’t show any increase in tempera-ture,” said Blake.

 

“I didn’t say . . . look at that!” Forster scooted himself forward and practically shoved his nose against the Manta’s polyglas window. “I can see right through it!”

For indeed the low dome had begun to glow, like an immense light fixture on a very slow rheostat; the whole surface of the bulge in the diamond moon was a rosy pink, as of a soft neon sign. But it swiftly grew brighter, and suddenly what had appeared to be a solid—an opaque, pol-ished metal surface—had become as transparent as lead crystal.

For the first time in several minutes, Jo Walsh’s voice came to them over the sonarlink. “We’re seeing a change in the seismic profile of the core, Professor.”

 

“What change?” Forster asked.

 

“Computer can’t make sense of it. But the core’s no longer opaque to sound. It’s uncertain we have the appro-priate programs to interpret what we’re seeing. . . .”

 

“Just record. We’ll analyze later.”

 

“As you say, sir.”

 

Forster and Blake and Sparta were staring in wonder, straight through the perfectly clear kilometer-wide dome into a glowing open space, far bigger than Earth’s biggest cathedral.

 

“It’s an airlock,” said Forster. “Big enough for whole spaceships.”

 

“Not an airlock, I think,” said Sparta.

 

“What? Oh, of course . . . what’s inside isn’t air.”

 

“How do you suppose they open the hatch?” Blake asked.

As if on cue, the crystal dome beneath them began to melt visibly away. First the lock mechanism immediately below them—which had retained its shape although it had grown as fragile-looking as a spun-sugar sculpture—visibly quivered and dissolved. From the place where it had been, a gossamer gyre peeled off, Fibonacci-like; it was as if the material of the hull had grown thinner, losing layer after layer, faster and faster, down to the final layer of mole-cules—and then even these had been stripped away.

There was a great inpouring of water. Caught in the tur-bulence, the Manta tumbled inside, into the liquid arena.

A moment later it was all over: the gossamer window reformed overhead, layers of invisibly tiny molecular tiles relaid themselves in reverse order, and—even faster than it had become transparent—the great dome was once more opaque. The last sight that the three in the Manta saw through it, as the submarine tumbled inside in the eddies, was a bright school of squid flashing away in every direc-tion, like a shower of meteors.

Sparta took a moment to stabilize the rolling submarine, orienting the weightless craft with its belly toward the cen-ter of Amalthea, the “floor,” and its roof toward the center of the dome, the “ceiling.”

Eerie silence closed on them. The clattering rush and roar of the boiler towers outside had vanished, along with the subsonic phasing that had sounded so like a giant heartbeat. All the sub’s hydrophones picked up was the rhythmic wa-tery fizz of its own respiration.

“Jo, do you read us?” Sparta said into the sonarlink.

 

She was neither surprised nor concerned when there was no answer. She glanced at Forster, whose shiny face regis-tered excitement but no fear.

 

“Whatever’s damping the seismic signature of this thing is back in place,” Blake said.

 

“As long as we’re in here we won’t have any commu-nication with the surface,” said Sparta.

 

“I expected as much,” said Forster. “Walsh and the rest will know what’s happened. We’ll keep to our prearranged schedule.”

Sparta didn’t think the crew would realize what had hap-pened, but she knew they were disciplined enough not to depart from the mission plan. She glanced at the console. “Outside pressure is dropping rapidly.”

“Good trick,” said Blake.

Forster was surprised. “Must be some rather large pumps at work. But it’s perfectly silent.” “Rather small pumps, I think,” Sparta said. “Molecular pumps, like a biological cell’s, all over the surface of the lock.”

They were a tiny speck adrift in the center of a huge bowl, smaller than a guppy in a fish tank. A pale blue light, like that a dozen meters below the surface of the tropical seas of Earth, came from the softly glowing walls and floor of the chamber itself. On the roof of the dome, a random scatter of blue-white pinpricks shone more brightly.

While the spectrum did not extend either to the infrared or the ultraviolet, the ubiquitous glow was bright enough to allow Sparta to make out the graceful architecture of the vault. The space was sparsely filled, the shell lavishly dec-orated with Gaudi-like, apparently melting pilasters and sagging arches, all fretted about with a network of fractal piping, as intricate as the branching alveoli of a mammalian lung.

Blake could see it almost as well as she, and—“Some-thing about this place”—he noticed what she did, although he could not pin down his impression—“looks very . . . fa-miliar.”

 

To Sparta—allowing only for severe foreshortening—it was a familiar pattern indeed. “You saw the holos of the Free Spirit temple under Kingman’s place?”

 

“Yes.”

 

“Put that in a graphics program and flatten the Z axis about four hundred percent.”

The crypt beneath Kingman’s English manor was built in the high-flying Perpendicular style of the 14th century, while this space bulged outward more extravagantly than the central domes of the Blue Mosque. Yet the architectural elements—the graceful arches, the eight-fold symmetry, the interlocking ribs, the radiating foliate patterns from the cen-tral boss overhead—made for a sort of squashed High Gothic.

Forster craned his head to look up through the Manta’s bubble. “And those white lights overhead? Almost like stars.”

 

“Crux,” she said. “Perhaps they were sentimental. The center of the hatch, where we came in, marks the position of their home star.”

 

“And directly beneath it, the inner sanctum,” said Blake.

 

“Yes.” She nodded at Forster. “Directly beneath, sir, is the way in.”

She steered the Manta down into the blue water. The floor beneath was as intricate as a coral reef, encrusted with multi-armed and multi-tentacled creatures. Directly below lay a forest of frozen metallic tentacles, baroquely curled and bent, like the arms of a basket starfish. In the center of the array, where the sea star’s mouth would be, there was a dark opening. Sparta plunged the tiny Manta toward it.

Moments later they were in black water.

Sparta played the searchlights on the roof above; the ovals of light danced away into the distance until they were too diffuse to be visible. The Manta hovered in the midst of a space so vast and dark its light beams reached nothing below it.

“I feel like a spider suspended beneath the dome of St. Peter’s,” said Forster, peering around him in the gloom.

 

“I didn’t know you were a religious man, Professor.” Sparta’s cool tone did not betray her amusement.

 

“Oh, well . . . it’s a very large construction, that’s all I meant.”

 

“Surely this is exactly what you expected to find? The ship that brought Culture X to our solar system.”

 

“Yes, certainly. I’ve even argued it in papers that no one seems to have read—or if they did, they thought they were doing me a favor by pretending I hadn’t committed the indiscretion.”

 

“I recall one in
Nature
in ’74,” Blake said. “It got some attention.”

 

“You were hardly old enough to read in ’74,” said For-ster.

 

“I came across it in files later,” Blake said.

Forster admitted he was flattered. “It
was
rather a good statement of the thesis, wasn’t it? Suppose a civilization wanted to cross interstellar space—how would it attack the problem? I argued that it would build a mobile planetoid—a world-ship I called it—taking perhaps centuries over the task.”

“At least centuries, I should think.” Sparta’s tone of voice subtly encouraged him to keep talking as she nosed the Manta lower into the water below them—crystal clear and utterly devoid of light.

“Since the ship would have to be a self-contained world which could support its inhabitants for generations it would need to be as large as . . . as
this
. I wonder how many suns they visited before they found ours and knew that their search was ended?”

“So you guessed all this before we started,” Blake said. “Oh, not all of it.”

 

“No?” Sparta glanced at him curiously.

“I never thought they would be sea creatures,” said For-ster, his soft voice full of wonder. “Even with all we’ve encountered, the ice and the temporary sea outside—full of life—it never occurred to me that they would
live
in water. When we came into the inner lock, my first thought was that the vessel had sprung a leak, that all of them were dead and that the melting ice had filled their world-ship with water.”

“What changed your mind?”

 

“You knew it right away,” he said sharply. “The pressure and temperature in here are like the shallowest seas of Earth.”

 

“Yes. And like the seas that once covered Mars and Ve-nus,” said Sparta.

“The
salt-worlds
, that’s what the Martian plaque calls them. We knew that must mean ocean worlds, but we didn’t know how important oceans were to them. Oceans with just the right mix of nutrients to sustain their own kind.”

Something loomed out of the darkness below them, a vast and lacy strutwork of crystalline vaulting. Farther down, according to the Manta’s sonar, there was another smooth shell.