What it all added up to was the indisputable fact that life is incredibly resilient, amazingly adaptive, and as common as dirt throughout the cosmos.

"Europan life," Lieutenant Kemmerer said, "they're all heat eaters?"

Selby laughed. "Thermovores. Well, a lot of it is. We've been studying the Europan biome for almost a century and a half, and we've almost literally just scratched the surface. Most of the life forms we've catalogued so far appear to be thermovores, yes. We believe that there are chemovores in the great deeps, mainly because Europan life is based on sulfur, rather than carbon. We think they started off metabolizing chemical emissions around hot vents at the mantle, like the sulfur-metabolizing microbes around deep-ocean hydrothermal vents on Earth."

"But the Medusae are different, aren't they?" Dr. Montgomery said. "Not thermovores, but . . . what's the word? Kymovores?"

"Exactly."

"What the hell is a kymovore?" Garner wanted to know.

"They eat chemicals, of course," McKean said, mistaking the pronunciation for chemovore.

"Uh-uh. Kymovores," Selby said, stressing the y as more of an "oo" sound. "From kym, the Greek word for 'waves.' They get energy directly from the energy of waves in the water."

McKean reddened slightly, but didn't say anything. He didn't like being caught in the wrong.

"Besides tidal flexing," Selby went on, "there's a second force acting on Europa's ocean, keeping it warm. Europa has a very slight axial tilt-less than a tenth of a degree-but it's enough to respond to Jupiter's tide action and generate waves that pass through the ocean. They're called Rossby waves. They travel quite slowly, only a few kilometers per day, but they release a lot of energy into the water-maybe two hundred times what Europa gets from tidal forces alone, and some species in the Europan ocean use that energy directly for metabolism. That includes the Medusae."

As the conversation continued, I walked over to one of the big windows and looked down. The water was filled with small, drifting bits of white matter illuminated by the colony's external lights. The underside of the ice cap was covered by branching, whitish growths called Europafitoformes-Europan plant forms-and debris from the stuff constantly drifted down into Europa's ocean depths like snow. A lot of the biology down there depended on that organic rain.

I saw something rising out of the darkness.

It was large, it was round-a kind of flattened umbrella shape-and it looked as though it was manufactured out of spun glass. I was reminded of certain terrestrial jellyfish, and recognized the Europan Medusa from downloads I'd taken on Earth a year ago.

At the translucent core of the thing's body, there was a cluster of organic lights, and these were winking on and off in an obvious pattern as it rose. One light . . . two . . . four . . . eight . . . sixteen. Then they all winked off and the pattern began again: one, two, four, eight, sixteen. The Medusan Count, it was called, and it was the main reason xenosophontologists thought that the organism was intelligent.

"Dr. Selby?" I said. "Looks like you have someone trying to talk to you out here."

Selby joined me at the window. "Hah! Looks like. They come up and blink at us every so often. I think they're just saying 'Hi, there.' Or else they might just be reacting to our lights."

I noticed from the light showing in the water above the window that the station was flashing something in response. "You have a bank of lights on the outside of the building, sir?" I asked.

"That's right. We've been trying to respond to them."

"Responding how?" Kemmerer asked.

"By continuing the series," Selby replied. "We repeat the Medusa's pattern, then add thirty-two, sixty-four, and one hundred twenty-eight."

"Does it work?"

"Not really," Selby explained. "Or rather, not yet. We try to respond every time they signal. Unfortunately, all either we or the Medusae can learn from the exchange is that the other guy knows how to count in geometric series. There's no other exchange of information, no way to encode information. None that we've been able to discover, anyway."

"You've tried longer sequences?" McKean asked.

"We have," Selby said. "But the Medusae seem to only have those sixteen light-producing organs in their bodies, so that's apparently all the higher they can count. If the blinking lights are a conversation, we don't know how to continue it with them, and apparently neither do they."

"Do they even have brains?" Chief Garner asked. "That thing out there looks like a goddamn jellyfish."

"We think they have a kind of a nerve net, similar to terrestrial sea jellies. There's also a node of tissue in there among the light organs that may be a brain of sorts. They have what appear to be fairly sophisticated ocelli, sixteen of them around the rim of the bell, so they can see. How well, we're not sure."

"They might not really be counting," Montgomery said. "The lights could be coming on as a kind of autonomous reflex, with more lights coming on successively as more and more neuron bundles fire."

"Quite a few xenosophontologists have come to that exact same conclusion," Selby told her. "Right now, we're at a complete impasse. We here at Chaos Base think the Medusae might be intelligent, but we have no way to prove it."

And that, I thought, was a hell of a note. We think we know what human intelligence is, but we still have trouble defining exactly what that is. And in a nonhuman species . . . well, if they build spaceships like the Brocs or the Qesh, and have a language we're able to translate, we have to assume that they are. But something like the Medusae are so damned different we may not have anything whatsoever in common . . .

. . . and we may never know for certain that they can think.

Outside, the solitary Medusa was going through some unusual acrobatics, the skirts of its bell coming up on all sides . . . and then the top appeared to split open, exposing a forest of furiously beating tendrils, like the cilia of a protozoan. The thing looked like it was trying to turn itself inside out.

"Chow time," Selby said. Indeed, the organism was rising closer to the ice ceiling outside. It appeared to be inhaling large quantities of the drifting organic snow.

"Wait, I thought you said it got metabolic energy from Rossby waves," Kari Harris said. "That thing is eating."

Selby smiled. "With our kind of life . . . okay, we ingest food, and breaking that food down-metabolism-provides us with the energy we need for life. The Medusae get their energy from waves passing through their bodies . . . but they still need to ingest food to get the raw material they need for growth . . . to add to their own mass, don't you see? It's actually an efficient way to do things, here. In an environment like this one, life would be very limited if it depended on chemical metabolism alone. The amount of energy in that organic snow out there just isn't enough . . . we say the energy is low density. It would take more energy than that material can provide in order to get energy out of it. So our Medusan friends have learned to get the energy they need another way, and just use solid food for growth, physiological repair, and reproduction."

"A grazer," Ortega said. "It seems an unlikely candidate for a sapient species, don't you think?"

"Maybe the question we should be asking," Montgomery said, thoughtful, "is why an organism like that would need intelligence in the first place."

It was, I thought, a damned good question. The thing drifted in the dark, absorbed waves moving through the cold water, fed on the local equivalent of plankton, and its slow movements suggested that it didn't have any major predators . . . none that it would be required to run from or outwit, at any rate. No spaceships, no buildings, not even any knowledge of the universe beyond the ice above. If the Medusae were intelligent, it would mean lives of unimaginable boredom.

Or did it simply mean that their mental lives, their imaginations, perhaps, their view of the world around them all were so alien, so inexpressibly different from those of humans, that we could not begin to understand them?

We watched the creature a moment more, and then Selby turned from the window. "So, you good people came by to pick up the Walsh?"

"An EDD Mark V, Doctor," Kemmerer said. "Yes. I gather you have spares."

"A few. Earth didn't give me any details when they lasered the orders last week. I take it you have some deep diving to do?"

"We don't know yet," Kemmerer replied, "but we want to be ready, just in case." She looked out the window. "What's the water pressure here?"

"Not too bad, actually," Selby replied. "Six hundred sixty meters . . . but at only point one three four of a G. And ice is only nine-tenths the density of water. Make it the equivalent of eighty meters on Earth . . . or about eight atmospheres. I gather you're going deeper than that?"

"Yes," Lieutenant Kemmerer said, her voice taking on a grim note. "A lot deeper . . ."

Chapter Eight.

I watched from the mess deck as a robot cargo tractor hauled the Walsh out to the landing area on the surface of Europa. Jupiter remained on the western horizon, huge and banded seemingly just beyond the horizon of tumbled blocks of ice. "You think we're even going to use that thing?" Charlie McKean asked.

"Don't know, Machine," I replied. "I imagine the skipper wants to have it on board just in case."

HM1 McKean was known by the nickname Machine at least in part from his meticulous nature. One of the stories about him was that he'd raced high-speed e-Cars for a living, back before he'd joined the Navy. It might be true. I think he was the guy who hung the "E-Car" moniker on me, though ever since FMF training I'd been trying to be accepted as "Hawkeye."

It had turned out to be a losing battle.

Moving slowly, the robot crawler positioned the EDDV beneath the Haldane, and then lifted it up into the research vessel's broad, flat storage bay. Captain Summerlee had given orders to shift the dynamic nanomatrix of the Haldane's cargo compartment to better accommodate the deep diver, which was over a quarter of the starship's length.

The Walsh was a research submersible designed to operate under extremes of temperature and pressure. A black compressed-matter cigar just twenty-two meters long, it massed almost 2,500 tons. CM explorers were relatively new, but they'd given us a powerful tool for investigating places like the upper atmospheres of Jupiter and Saturn, and the broiling, ninety-atmosphere surface of Venus.

Almost three centuries ago, in 1958, the U.S. Navy had purchased a bathyscaph, an Italian-made submersible named Trieste, and used her for a series of deep exploratory test dives. The series had culminated on January 23, 1960, when the Trieste reached the bottom of the Challenger Deep in the Marianas Trench, just less than eleven kilometers down, the deepest point of Earth's world ocean. On board, crammed into the bathyscaph's tiny pressure sphere, were two men-Jacques Piccard, the son of the craft's designer, and Lieutenant Don Walsh of the U.S. Navy. The pressure at that depth was about one and an eighth metric tons per square centimeter. The eighteen-meter-long float chamber above the pressure sphere was filled with gasoline-less dense than water, which made it buoyant, but incompressible, which meant that the float chamber didn't need steel walls 12.7 centimeters thick like the crew compartment. Nine tons of magnetic iron pellets served as ballast; at those pressures, the Trieste could not possibly have emptied ballast tanks like a conventional submarine.

Of particular interest was the fact that Piccard and Walsh spotted a sole or flounder swimming slowly along the floor of the trench. Though the sighting was controversial for many years after, with some biologists insisting that the creature must instead have been a sea cucumber, it ultimately was proof that vertebrate life could withstand and even thrive under the intense pressure at the bottom of the Challenger Deep. Life, it seemed, was unimaginably adaptable, resilient, and tough, a realization that would lead ultimately to the discovery of life within the ice-locked oceans of Europa and Enceladus, adrift in the Jovian and Venerean cloud tops, buried beneath the Martian permafrost, and swimming in lakes of ethane and methane on Titan.

And now, a vessel named for Lieutenant Walsh was being used within the Europan ocean.

But the Walsh now being jockied into Haldane's belly was a far cry from a twentieth-century bathyscaph. Where the original Trieste had had an estimated crush depth of over eighteen kilometers, the Walsh technically could not be crushed . . . at least, that was the theory.

CM-collapsed matter-is a special form of exotic, artificial material. It occurs naturally in neutron stars when the gravitational collapse of a dying sun of between 1.4 and 3.2 solar masses forces electrons to combine with protons, creating a neutron star, a fast-spinning sphere composed of degenerate matter so compact that a teaspoonful contains the mass of Mount Everest.

A century ago, materials engineers figured out how to artificially collapse matter down to a state just short of neutron star material, using the quantum dynamics of vacuum energy to remove a large fraction of the empty space among atoms. The result was artificial matter normally incompressible, so much so that even with inner compartments at standard surface atmospheric pressure, bulkheads constructed of this material remained rigidly inert even under pressures of tens of thousands of atmospheres.

At least, that was the theory. I wasn't sure I wanted to trust my life that completely to the materials engineers just yet, however. According to Dr. Shelby, the Walsh, or its sister vessels, had descended to depths of around fifty kilometers within the Europan ocean, going about halfway down toward the mantle, a depth that in Europa's scant gravity corresponded to a pressure of 690 atmospheres, or about a tenth of a ton per square centimeter. At a depth of ten thousand kilometers within Abyssworld, and in Abyssworld's gravity, the pressure would be considerably greater: 900,000 atmospheres, or almost a thousand tons per square centimeter.

I'm all for modern technology, yeah . . . and I was relying on modern materials engineering now to keep me alive in Europa's near-vacuum atmosphere, with a radiation flux outside the Haldane's hull that would have killed me in a few days. But CM-hulled ships had never been tested under such insane conditions, and I wasn't sure that I wanted to be the guinea pig.

Still, Lieutenant Kemmerer said we were only taking the Walsh along as a precaution, just in case our search for the missing research colony took us into the Abyssworld's deeps. Besides, I'd teleoperated a deep-sea high-pressure probe on Niffelheim-e. I assumed that we would be pulling the same trick with the Walsh.

At least I hoped that would be the case.

Half a Europan day after our arrival at Europa, Haldane lifted into the tenuous atmosphere, hesitated a moment as though getting her bearings, and then began to accelerate. That atmosphere, I'd been surprised to learn, was molecular oxygen, O2, though at a pressure so low as to seem like hard vacuum to an Earth-evolved air breather. Rather than having an organic source, as oxygen did on Earth, the O2 sputtered off the ice as incoming solar radiation plus high-energy particles from Jupiter's magnetosphere hit the surface and dissociated the oxygen from the hydrogen. The lighter hydrogen vanished into space; the oxygen was just heavy enough to hang around, though its pressure at the surface was just 10-12 of the surface atmospheric pressure on Earth: 1 trillionth of a bar.

Jupiter, the opposite hemisphere now in sunlight, hung off our port side . . . and this time I could make out the deep salmon pink of the Great Red Spot, just south of the equator and close to the dawn terminator. Minute points of lightning flashed and pulsed across the planet's nightside.

Then we accelerated, and Europa-and then Jupiter-dwindled away, a single bright star falling into the glare of the distant sun.

Harris, Dubois, and McKean were with me in the mess bay. "So why the hell wasn't Kirchner with us when we went down to the base?" Dubois asked.

"Don't know," I said. "He didn't see fit to fill me in."

"Ah," McKean said, shrugging. "The poor bastard's ghost-ridden."

"So?" Dubois said, sounding skeptical. "Dr. Francis on the Clymer handles his ghosts okay. Most doctors do."

Ghost-ridden, in Corps parlance, referred to doctors and some other personnel who were permanently linked through their implants to Net expert systems. No one, not the best doctor in the world, can keep everything in his head that he needs to know-about chemistry, pharmacology, anatomy, bacteriology, pathology, biochemistry, nanotechnic programming, holistics, medical imaging, cybernetics, psychology, and the gods of medicine know what all else. Most doctors had a kind of glassy, faraway stare, and usually that was because they were listening to the voices in their heads.

"Well, sure," McKean said. "Most doctors can handle it. But Kirchner, he's kind of old, y'know? Maybe it's starting to wear him down."

"How old is he, anyway?" Kari Harris wanted to know.

"One hundred twelve," I told them. "This is his second round of anagathic treatments."

"How the hell do you know that?" McKean demanded.

I shrugged. "I looked up the Sam-Sea records on-line the day before we left Earth," I told them. You weren't supposed to do that, of course. Personnel records were private, accessible by others only with specific authorization, and peeking at an officer's records was a definite no-no.

But there are always ways around the safeguards. Mine was a bit of software residing in my cerebral implants called Lockpick, courtesy of my father and General Nanodynamics. I wasn't going to tell them about that, however.

But there was something about the way Kirchner had looked at us that morning at the briefing with Chief Garner that had given me hot-and-cold running willies, and that's when I'd decided to check him out.

"I rest my case," McKean said. "Paranoia . . . schizophrenia . . . the ghosts'll do that to you."

"Bullshit," I told him. "His records also say he had a brilliant career at SMMC, teaching path, materia medica, and A and P. I never had him myself, but he's got commendations in his jacket."

"I did have him," McKean said, his expression sour. "Officious, picky, OCD bastard. Cost me my four-oh a couple of times. I was lucky to graduate."

"Well there's your problem," Harris said, grinning. "You just don't like the guy!"

"Hell no, I don't like him. They need to retire his ass . . . or promote him out of the classroom."

"He's only a lieutenant commander," Dubois said. "At a hundred and twelve? He must have pissed someone off."

"Yeah," McKean said. "Maybe he got caught fucking an admiral's daughter."

"He's only been a Navy physician for fifteen years," I told them. "This is his second career . . . third if you count his being Medical Corps as separate from being a civilian doctor."

With life extension, people could expect to live to be two or three centuries old, assuming they had the money to swing the treatments. Most people didn't. Those who did were expected to switch careers five or six times through a long life span.

I say expected because we've only been able to carry out major anagathic treatments for the last century or so. Hell, we didn't pick up the trick of telemeric engineering from the X'ghr until just thirty-five years ago. The oldest person alive right now is only somewhere in his mid-hundreds-150, 160, something like that.

But people like Dr. Kirchner got tired of the same job decade after decade. According to the records I'd seen, Lyman Kirchner had started off as a nanotechnics program designer, and switched to medical nanotechnics in 2188. He went from there to med school at Bethesda Medical Center in 2195, about the time he received his first anagathic treatment at age sixty. He'd had his second overhaul at age ninety, joined the Navy Medical Corps in 2232 at ninety-seven, and been a Navy doctor ever since.

Oh . . . yeah. The guy had made a fortune in the nanotech boom. That was how he'd been able to afford the tune-ups. I didn't share that much with the others, though. I guess I was feeling guilty for having peeked.

"He probably didn't show up at Europa because he already knows everything!" Harris said.

"That's certainly the way he acted when he was teaching pathology at Sam-Sea," McKean said with considerable feeling. "Damn him!"

Machine McKean's vehemence surprised me . . . and it worried me a bit, too. Any expedition to a new world, into an alien environment, required that the members work smoothly with one another, and they had to trust their department heads. Normally, Machine was pretty laid-back, though he could be intensely focused when he needed to be. I'd never known him to be this angry.

From the little I'd seen of Kirchner, he wasn't making himself easy to trust . . . but he certainly deserved the benefit of the doubt.

Haldane accelerated out-system at one gravity, using her Plottel Drive to crawl up the sun's far-flung magnetic field, seeking that region, a billion and a half kilometers out, where the gravitational metric of spacetime was flat enough to make the transition to FTL. Eventually, shortly after evening mess, the warning came down from the bridge. "Now hear this, now hear this. Zero-gravity in thirty seconds. I say again, zero-gravity in thirty seconds. Stand by to engage the Alcubierre Drive."

Half a minute later, as promised, weight vanished. In another moment, the Haldane gathered up her figurative skirts-if by "skirts" you mean the intangible field of space-time within which she was moving-and dropped into her very own pocket universe.

Mexican physicist Miguel Alcubierre had worked out what became known as the Alcubierre metric in 1994, though it had taken over a century to work out how to transform theory into fact. In particular, it had taken the Vacuum Energy Tap to liberate enough power to create a warp bubble, continually contracting the space ahead of a ship and expanding it behind. The vessel within the warp bubble was in free fall, and motionless in relation to the pocket of space within which it rested, while the bubble holding that pocket traveled at many times the speed of light. The laws of physics still prohibited both matter and energy from moving faster than light . . . but there was nothing at all in those laws prohibiting space from doing so. Indeed, current inflationary models of the big bang demanded that the expansion of space had vastly exceeded the speed of light in the first instants after Creation itself.

"Now hear this, now hear this. Stand by to initiate spin gravity." There was a measured pause, as if for dramatic effect, and I knew what was coming. "All hands commence attitude adjustment. Spin gravity will initiate in ten minutes."