I reported aboard the USRS J. B. S. Haldane late the next day, along with the rest of the Marine Special Expeditionary Platoon, now dubbed MSEP-Alpha. One of the Commonwealth's Scientist-class research ships, the Haldane was a no-frills ride, a minnow to the Clymer's whale when she docked alongside for the payload transfer. She was named for the twentieth-century British geneticist and evolutionary biologist who'd famously said, "[T]he universe is not only queerer than we suppose, but queerer than we can suppose."

And that had been long before we started meeting extraterrestrial species, or visiting the worlds they lived on.

The Haldane was only eighty-one meters long and thirty broad, and the trip out to GJ 1214 was going to be a bit on the cramped side. Technically, she was a civilian research vessel, but Commander Janice Summerlee was a Navy officer, and most of her crew personnel were Navy as well. Haldane was listed on the rolls as a research ship, which meant she served a wide range of roles. One of her most important missions, though, was transporting personnel and supplies to the far-flung science colonies across near interstellar space.

I floated out of the boarding tube and into her quarterdeck compartment, where I saluted the officer of the deck. "Permission to come aboard, sir."

"Granted," the man growled. You don't go through the military formalities on a civilian vessel, but if the Haldane was being pressed into military duties, the niceties of tradition were maintained. "Pre-screen records?"

I thoughtclicked the appropriate icon in my in-head, giving him access to the results of the med scan I'd gone through a few hours earlier. Purely routine stuff, that. Haldane would be out and on its own for at least a couple of months, and it wouldn't do for anyone on board to come down with something nasty while we were in deep space . . . especially something that might contaminate the entire crew.

That sort of screening is anything but simple, and it takes a pretty powerful AI to carry it out. The human body is host to thousands of species of bacteria, but in terms of sheer numbers, our bacterial hangers-on are overwhelming. The typical person has about 10 trillion cells in his or her body . . . and ten times that number of bacteria in their gut alone. Something like 3 percent of our body mass consists of microbiota: bacteria, archaea, and fungi. All of these actively help us and keep us healthy, in a symbiotic relationship with their human host. We couldn't digest stuff like carbohydrates without them, and for that reason they're known as the "forgotten organ."

Generally, when we get sick it's because our immune system has been compromised in some way-generally by stress of one sort or another-and that allows some otherwise innocuous organism that was there all along to get out of hand. So a screening for pathogens doesn't mean spotting Eschericia coli in the colon, for example, but determining whether the population of E. Coli is out of balance with all the rest, whether the patient's immune system is functioning properly, and whether normal body cells in the area are showing signs of inflammation are all part of the process. Picking up problems caused by viruses can be even tougher.

So the screening process concentrates on whether or not the person is showing an immunological response or not. It doesn't rule out the possibility of an infection breaking out later, but it helps spot trouble before it gets out of hand.

My scans had come up clean.

The OOD downloaded the scan results, then recorded my ID data on his e-pad. "Carlyle," he said. "Welcome aboard. I'm Lieutenant Walthers, the ship's exec." He jerked his thumb over his shoulder. "Says here somebody wants to see you. Mess bay."

Curious, I followed the thumb down a short passageway, swimming through the corridor in microgravity. There was technically a faint echo of spin gravity here. Starport was on the out-most end of the space elevator, and as the asteroid whirled about Earth on the end of its 70,000-kilometer tether, it created a six-hundredth of a gravity . . . scarcely enough to feel. Drop something, and it would "fall" a bit less than a centimeter in the first second.

The mess bay was the Haldane's common area, which served as mess deck, recreation lounge, briefing room, and social space for the small ship. Three Brocs were floating in front of the big viewall, which was set to look past the swell of the Clymer close alongside, and off along the line of other naval vessels entangled within a forest of docking ramps, boarding gantries, and connector cables, the business end of Starport.

My personal ID was pinged, checking my name and rank. Obviously, the M'nangat had as much trouble telling humans apart as we had with them.

YOU ARE DOCTOR CARLYLE. The translation flowed across my in-head. I could only tell which one was speaking by the almost spastic twitch of its tentacles. YOU SAVED D'DNAH. YOU SAVED OUR BUDS.

"Not 'Doctor,' " I said. "I'm a Navy Corpsman. They just call me Doc."

DOC CARLYLE, THEN. WE WISHED TO THANK YOU FOR SAVING OUR BUDS.

"All in the line of duty," I said. The Broc in the middle of the three was D'dnah. I could tell by the patch of skinseal still glistening on herm's side. "How are you feeling, D'dnah?" I asked.

I AM WELL, the M'nangat said. YOUR PEOPLE TRANSPORTED ME TO THE NAVAL HOSPITAL IN SAN ANTONIO. WE WERE TOLD THAT YOU HAD DONE EVERYTHING NECESSARY, THAT NO FURTHER TREATMENT, SURGERY, OR NANOTECHNIC INTERVENTION WAS NECESSARY.

"Sometimes we get lucky," I said. "I'm glad to hear you're okay."

I'd not done anything for the M'nangat life carrier beyond pretty basic emergency first aid. Sure, I'd pulled the unexploded nano-D bullet out of herm's torso, which was something usually best left to well-equipped operating rooms, but there'd not been a lot of choice, there, and no leeway if I'd guessed wrong. Apparently, the nanobots I'd put into D'dnah's body had managed to seal off all of the internal bleeding, and the skinseal had taken care of surface bleeding. The M'nangat, evidently, had fairly robust biological repair and recovery systems. I'd slapped the equivalent of a bandage on D'dnah's wound, and the M'nangat's physiology had taken care of the rest.

Even so, it had only been three days since the battle on board Capricorn Zeta. "I'm surprised they released you so soon," I added. "I would have thought that they'd want to keep an eye on you for a few days, just to make sure you were healing okay."

THEY DID, the Broc on the right said. THEY STATED A DESIRE TO KEEP HERM UNDER OBSERVATION. OUR CONSULATE MISSION WAS ABLE TO CONVINCE THEM THAT THERE WAS NO NEED.

Well, the M'nangat would understand their own emergency medical needs better than we did.

I felt a bit awkward. Two of the M'nangat I'd met on Capricorn Zeta, of course, but the third had been on Earth during the attack. I recognized D'Dnah, but I had no idea which of the other two was which. I wondered how to ask for an introduction.

"So, D'dnah," I said. "I take it this is your triad?" It was a lame ploy, but it worked.

I AM D'DREVAH, the one on the left said. I AM EGG BEARER.

I AM D'DEEN, said the one on the right. I AM LIFE DONOR. FORGIVE US IF WE MISUSE YOUR PROTOCOLS OF SOCIAL INTERACTION. THEY ARE . . . AS YET UNFAMILIAR TO US.

"Not at all," I said. "You're doing great."

WE WERE DIRECTED TO COME TO EARTH AS POLITICAL LIAISONS, D'drevah told me, AND TO ASSIST YOUR PEOPLE WITH YOUR ACCESS TO THE DEEP TIME EPHEMERIS-WHAT YOU CALL THE ENCYCLOPEDIA GALACTICA. I WAS, UNFORTUNATELY, INVOLVED IN WORK AT OUR CONSULATE ON EARTH WHEN OUR LIFE BEARER WAS INJURED. BUT D'DEEN TOLD ME WHAT YOU DID ON THE MINING STATION, ABOUT HOW YOU SAVED OUR BUDS.

"I was glad to be able to help," I told them. If I'd felt awkward before, I was downright uncomfortable now. The introduction seemed to have released an avalanche of personal information, as if we'd passed some sort of privacy threshold to enter a new level of intimacy. More than that, I was increasingly aware that the male and female of the triad, D'drevah and D'deen, seemed much more concerned about the safety of their offspring than they were about their bearer, D'dnah.

Well, that's the thing about aliens. They're alien . . . different to the point of incomprehensibility.

In Corps School, when they were teaching us about alien cultures and social norms, they spent a lot of time hammering home the idea that just because a particular cultural belief set is different, it's not wrong. I've never necessarily subscribed to that notion, not wholeheartedly. I mean . . . look at radical fundamentalist Islam as practiced a couple of centuries ago during the Troubles . . . or even today in places like the Central Asian Caliphate that recognize only Sharia law. Ask the inhabitants of what once was Tel Aviv about the morality-or the validity-of a god who glories in murder, vengeance, and genocide.

But the rule is that alien environments, alien physiologies, alien psychologies produce worldviews that are fundamentally different from ours. The M'nangat would have developed ways of thinking, patterns of beliefs, that fit their particular evolutionary backgrounds.

And according to the xenosoc downloads I'd taken in school, it was wrong to judge them for simply being what they were.

"So . . ." I said, "was that what you wanted to see me about?"

TO THANK YOU, YES, D'deen told me, AND TO MAKE A SPECIFIC REQUEST.

"Oh?"

THE THREE OF US HAVE BEEN ASSIGNED TO THIS MISSION, D'drevah said. WE ARE TO HELP YOUR SCIENTISTS WITH ACCESS TO PORTIONS OF THE EPHEMERIS DURING THIS EXPEDITION TO THE PLACE YOU CALL ABYSSWORLD.

There'd been M'nangat in the Murdock colony, too, I remembered. The chances were good that they were also there to look after their own.

D'DNAH IS DUE TO RELEASE OUR BUDS IN ANOTHER THREE OF YOUR WEEKS, D'deen said. WE WILL REQUIRE MEDICAL ASSISTANCE. WE WISH FOR YOU TO PROVIDE THAT ASSISTANCE.

I gaped at them. They wanted me to deliver their young.

And from what I'd learned so far of M'nangat physiology, that would mean allowing D'dnah, the being whose life I'd saved, to die.

Chapter Seven.

I'd hoped for a last chance to say good-bye to Joy, but it didn't happen. I was still on restriction, which now meant I couldn't leave the Haldane, and security had been stepped up and no one was allowed to come on board who wasn't part of her assigned crew or an appropriately tagged member of the Starport work crew. War fever-the worsening situation in the Caliphate-had everyone on edge, and the CAC's views on scientific research were well known. Privacy would have been an issue on board the cramped science vessel in any case. We had a final in-head conversation late at night. "Damn it, you come back to me, Elliot," she told me. "That's a goddamn fucking order."

"You don't outrank me, Sergeant," I said, grinning into the darkness. A Marine sergeant and a Navy second class both were E-5, the same rank. "But I'll be back for you. Promise . . ."

We departed from Starport at 0700 the next morning.

Our immediate destination, though, was not the world of GJ 1214 I, some forty-two light years distant. Instead, we used our Plottel Drive to tack on the sun's magnetic field out-system to Jupiter, making the passage of 9 AUs in eight and a half days.

During the outbound passage, I pulled down the ephemeral data. I'd actually been scheduled to deploy to Europa at the end of my FMF training, but the deployment to Bloodworld had intervened.

Commonwealth Planetary Ephemeris Entry: Europa, Jupiter II Star: Sol Planet: Sol V, Jupiter Satellite: Sol Vf, Jupiter-f Name: Europa Type: Ice-covered world ocean, kept liquid by tidal heating; rocky core Mean orbital radius: 670.900 km; Orbital period: 3d 13h 13m 42s Orbital eccentricity: 0.009; Inclination: 0.47o Rotational period: 3d 13h 13m (tide-locked with primary) Mass: 4.7988 x 1025 g = 0.008 Earth; Equatorial diameter: 3,121.6 km = 0.245 Earth Mean planetary density: 3.01 g/cc = .545 Earth; Surface gravity: 0.134 G Surface temperature range: ~ -160o C to -220o C Surface atmospheric pressure: 0.1 Pa, or 10-13 bar [0.000000000001 Earth average]; Percentage composition: O2 100 [Molecular oxygen]

Age: 4.6 billion years Biology: Diverse marine forms; no surface forms present Human presence: Conamara Chaos research colony, established 2110. Fifty scientists, xenobiologists, and technicians in residence as of 2247. The base is an inverted cone hanging from the underside of the ice cap, at the bottom end of a 600-meter access tube from the surface. Further human presence in Europa is prohibited pending additional study of Europan biosphere, and in particular of the Medusae, which show evidence of being sapient. . . .

Well, that's the sort of information you can download from the ship's library to your in-head memory. But how do you convey the sense of an entire, living world . . . even one as small, as bleak, and as ice bound as Europa? Like many moons and tide-locked planetary bodies of this type, the world has a very slight eccentricity to its orbit-0.009 in this case. When Europa is closest to Jupiter, it's stretched slightly by Jove's massive gravitational grip. A little less than two days later, at its farthest point from the gas giant, the squeezing relaxes. This constant stretch-relax cycle through every three and a half Earth days creates internal heat, kneading the core like a lump of clay in a potter's hands.

There's a second set of tidal forces at work too-Europa's resonances with both Io and Ganymede. Europa circles Jupiter once for every two orbits of Io, and twice for every one orbit of Ganymede. These Laplace resonances, as they are called, help pump up Europa's interior temperature by ultimately stealing energy from Jupiter's rotation through the tidal interactions between the planet and Io.

The combined effects are strong enough that even though the surface temperature is a frigid two hundred below zero, it turns out that there's a liquid ocean between ice and the rocky mantle a hundred kilometers down.

And liquid water always means there's a good potential for life.

During the last few hours of the approach, I watched the banded, slightly flattened disk of Jupiter swelling on the viewall in the mess bay. Three stars were visible to either side of the giant planet-two to the left and one on the right-three of the four classic Galilean satellites. First glimpsed through his primitive telescope by Galileo Galilei in 1610, those four moons shuttling around Jupiter rather than around a geocentric Earth had sounded the death knell of Aristotelian Cosmology. Four centuries later, the discovery of an induced magnetic field around one of those moons, Europa-a discovery made by a spacecraft named Galileo-had demonstrated for the first time that an actual liquid saltwater ocean existed somewhere other than on the planet Earth. In 2107, the Olympus Expedition to Jupiter had drilled down through the ice and discovered the Medusae. Three years later, exactly half a millennium after Galileo's observations, the base beneath Conamara Chaos had been built, primarily to study them.

I was interested to see in the ephemeris data that "Jupiter II" is an alternate name for Europa. Until the mid-nineteenth century, only the four Galilean satellites were known. Europa was the second out from Jupiter after Io, and was followed by Ganymede and Callisto, Jupiter I through IV. Not counting Jupiter's dark and mostly invisible ring system, though, we now know there are five moons closer to Jupiter than Europa; hence, "Jupiter f."

The Haldane continued decelerating as we dropped deeper and deeper into Jupiter's titanic gravity well. The missing moon of the quartet turned out to be Io, which eventually appeared as a tiny red disk visible against the backdrop of the Jovian cloud decks closely paced by the black dot of its own shadow. Hour by hour, the view slid off to the left as the turbulent colored bands of Jupiter's upper atmosphere filled the viewall. The mess bay was filled now with Marines and off-duty naval personnel who'd wandered in to see the show.

Eventually, though, Jupiter drifted out of frame, and we were bearing down on the inner of the two stars to the left. Another hour, and Europa resolved as a gleaming blue-white sphere, as smooth faced as a billiard ball, and thickly webbed by darker, brownish streaks and lines. Those lines, properly called lineae, reminded me of the supposed "canals" once thought to have crisscrossed the deserts of Mars, thanks to a nineteenth-century English mistranslation of the Italian word for "channels," canali.

One crater on that icy surface stood out more brightly than any other-a 26-kilometer-wide hole called Pwyll, looking like the starred impact of a hammer against a sphere of glass crystal. A thousand kilometers to the north, two particularly dark lineae crossed in a giant X, and just below was a tangle of broken and jumbled ice terrain darker than the surrounding areas. This was the Conamara Chaos, and the location of Humankind's sole outpost within the vast Europan ocean.

It takes some getting used to . . . the idea of an ocean more than a hundred kilometers deep covering the entire Jovian satellite. Europa is slightly smaller than Earth's moon, with a diameter of just over three thousand kilometers. Between its rocky, silicate mantle below and its shell of ice above lies that ocean of liquid water, but because of its depth, it's an ocean that actually and surprisingly holds more than twice the volume of water of all of the oceans on Earth.

Europa's ice varies considerably in thickness. South, where Pwyll Crater punched deep into the surface in the recent past, the crust is more than fifty kilometers thick. Elsewhere, though, as at Conamara Chaos, the ice is much thinner-in places only a few hundred meters thick. There's evidence that the ice doesn't rotate at the same speed, quite, as the moon's central core . . . and even that the entire shell has shifted, rotating independently of that core by as much as eighty degrees, many times throughout its history.

The base itself was invisible from space. Europa's disk filled the viewall, continuing to expand as the Haldane zeroed in on the navigation broadcasts from the colony's surface facility.

The Conamara Chaos looks chaotic from above-a vast, sprawling tumble of ice blocks and floes, all frozen together now, but quite obviously the product of some major melting and jostling at some point in the not-so-distant past. We think there's a collection of hot vents opening from the rocky core a hundred kilometers down, that major eruptions in the past actually broke through the ice cap at this point, and that continuing upwellings of hot water keep the ice at Conamara relatively thin. That's what they were looking for when they began probing beneath Europa's icy roof, of course-thin ice.

And they found it, here amid ten-kilometer floes and bergs that looked like they'd been jumbled together, spun about, and even flipped upside down before being refrozen, broken, and refrozen yet again. The dark reds and browns mixed in with the ice were organic chemicals from the sea below, organics that had worked their way up and onto the surface each time the ice cracked all the way through, a clue both to the presence of life and to the richness of that life down in that chill, lightless void.

Eventually, we were close enough to see a kind of navigational marker, a vast, twin plume or cloud hovering above its shadow. The Europan surface is cold-about minus 160 degrees Celsius near the equator, and much lower, minus 220C, at the poles. Conamara Base is heavily insulated to avoid damage to the local environment, and that means they need to dispose of excess heat as efficiently as possible, venting it as sterile plumes of steam from a pair of hundred-meter stacks north of the facility. The steam cools high above the surface, crystallizing as ice that eventually falls back across the chaotic terrain as a blanket of fresh, white snow.

The landing zone was well south of the plume, a flattened-out rectangle a kilometer across with a couple of other spacecraft resting there in the open. Nearby was a surface blockhouse, heavily insulated, and the array of dish antennas that maintained communications-through a satellite network orbiting Jupiter-with Earth.

Conamara Chaos is about a quarter of the way east around the moon from the sub-Jovian point; Jupiter at half-phase dominated the bleak, ice-block tumble of the western horizon, an enormous dome with pale red and pink, brown, white, gray, and salmon-hued stripes running up and down, with detail enough at this distance to see the swirls, eddies, and storm spots within the various fast-rotating cloud bands. I looked for the Great Red Spot, the south hemisphere superstorm two to three times as broad as Earth herself, but didn't see it. I did see the small, flattened oval of Io's shadow, though, close to the planet's limb, and above, a tiny red disk that was Io itself.

We settled to ground, and the elevator tube rose up out of the ice to meet us. The expedition's five Corpsmen, as technical staff, plus our two civilian passengers, the ship's skipper, and Lieutenant Kemmerer would make the journey down to the base. Dr. Kirchner had been invited, I understood, but had opted to stay in his office on Haldane.

The radiation at Europa's surface is fierce-about 540 rem per day, enough to kill an unprotected human in fairly short order. Haldane's rad shielding had protected us down to the surface; from there on, the ice itself would keep us safe from being fried by Jupiter's intense radiation belts.

I felt a spring in my step as I entered the elevator. We'd been accelerating at one gravity for a week, now, but the surface gravity on Europa was only a bit more than a tenth of that. Drop something and it will fall half a meter in the first second, so there is a clear up and down, unlike on the tethered asteroid at Starport, but you need to watch your reflexes. Jump, and you could bang your noggin against the overhead.

"Welcome to Chaos," a voice said from a hidden speaker as we gathered within the elevator. "We're bringing you all the way down to Level Three. Please hang on to the handrails beside you. Enjoy the ride!"

The elevator ride was a long one-well over half a kilometer straight down. The warning about handrails was a good one. With a surface gravity of only 1.314 meters per second squared, our downward acceleration through that tunnel more than canceled our weight. I don't know how fast we were going, but we were in zero-G for most of the descent. The trip was also boring, with nothing to see but the gray metal of the shaft sliding up around us through the clear transplas of the car.

But then the elevator emerged at the bottom level, we stepped out onto the main deck, and I gasped at the view.

Okay, so I'm easily impressed. But the others were speechless, too, even the usually unflappable Dubois, who said, "Fuck me," the words spoken very, very softly. Nearby, Dr. Ortega muttered something that sounded like, "Sweet holy Mother of God."

Conamara Base is upside down, as humans think of things, literally growing down from the underside of the ice ceiling overhead. Level One, with the hab quarters, is at the top, then Level Two with the lab spaces, with Level Three and the command center at the bottom, a broad, circular compartment fifty meters wide with instrument consoles and deck-to-overhead viewalls looking out into the abyss. The walls leaned out at a sharp angle, giving a clear view almost straight down.

Down . . .

The ocean here was just over a hundred kilometers deep. Lights on the outside of the base illuminated the water around us, as well as the eerily inverted icescape ceiling hanging above our heads. The light faded away swiftly with distance, however, and below, there yawned only a vast and empty night.

And yet, there were stars in that night. . . .

The year before, during the Bloodworld op, I'd spent some time on a gas giant moon-Niffelheim-e-my first experience with a hydrosubglacean world like Europa. On Niffelheim-e, the moon circling gas giant Gliese 581 VI, I'd linked in to a teleoperated submersible, cruising beneath the ice and encountering a variety of life forms there. Like abyssal forms in Earth's oceans, many created their own light; one titanic species, the five-kilometer-wide Luciderm gigans, had looked like the night view of a city seen from the air.

There were lights here as well, clouds of soft-glowing phosphorescence speckled by thousands of harder points, like stars, shining yellow and green. All were in motion, the whole giving an irresistible impression of vibrant, thriving life.

We now suspect that the majority of life across the Galaxy may live in environments like this one, locked in the eternal darkness of an ocean between rock and ice. Life, it seems, appears anywhere the conditions are at all favorable-and that frequently means liquid water. There are far more ice-locked moons and worlds in the Galaxy, possibly on the order of thousands to every one, than there are temperate, habitable-zone planets like Earth. Humans and Brocs are the exceptions, not the rules.

"Welcome aboard, folks," a civilian in white utilities said. "I'm Dr. Selby. I see you like the view."

"Spectacular," Lieutenant Kemmerer said. "And here I thought it would be boring, not having Jupiter in the sky all the time."

"You do get used to it after a while. But we keep discovering new species out there, and that keeps us on our toes."

"What's the outside temperature here?" Dr. Montgomery wanted to know.

"About five Celsius. That's actually pretty warm. We have some major convection currents rising beneath us at this point."

"The warmest water is in the deeps, am I right?" Ortega said.

"Exactly. The interior of Europa's core and deep mantle are still molten, and tidal interactions with Jupiter keep the mantle fairly plastic. The water near the mantle's surface is close to five hundred degrees, most places, but the pressure a hundred kilometers down is so high the water stays liquid, and can't turn to steam."

"And convection currents heat the entire ocean, keep it liquid," Ortega said, nodding.

"Correct. If Europa was a bit closer to Jupiter, she'd be like Io-kneaded and squeezed so hard by old Jove that the surface would be covered by volcanoes and flows of molten sulfur, and with all of the water driven off long ago. But out here the heating is just enough to maintain a liquid ocean."

"And Ganymede's mantle is all ice?" Ortega said.

"Right: ice, and a kind of warm ice slush down deep, above the inner silicate mantle. We have robots exploring Ganymede, looking for enclosed pockets of subsurface water like the deep lakes in Antarctica, and those might have evolved life as well, but so far at least, Europa is where all the biology is happening out here."

"Well, Europa," Montgomery said, "and the Jovian atmosphere."

Selby grimaced, and looked uncomfortable. "Of course."

We know precious little about life within Jupiter's atmosphere, and that still made exobiologists like Selby uncomfortable. Collector robots skimming through Jupiter's upper cloud layers have picked up organic molecules and what appear to be something like single-celled algae, the Jovian aeoleaprotistae. There was just a hint from these in their biochemistry that there might be more complex life existing deeper within the Jovian atmosphere, but at temperatures and pressures that made it unlikely that we'd be meeting it face to face anytime soon.