The Year's Best Science Fiction: Fifteenth Annual Collection

by Gardner Dozois

  "Right."

  They descended again, quickly; time was narrowing. The image of the lesion repeated on successively lower mats twice more, five meters apart.

  She gazed back up. The blurred gleaming above had faded. So it was not just a simple copying, for some pointless end. "It's following us down."

  "Tracking us?"

  "See for yourself, up there-the image is nearly gone, and the one next to us is brightening."

  "Are you implying it knows we're here?"

  "It seems to sense what level we're on, at least."

  "This one is stronger than the others."

  "I think so too. Brighter the deeper we go. The glow is purely chemical, some signaling response I would guess, and the denser vapor here deep in the vent helps it develop."

  "Signaling?" Marc sounded puzzled.

  "Maybe just mimicking. Light would be the only way to do it here. It couldn't use chemical packets to signal downwards because of the updrafts of vapor. Sound could go either up or down, but it doesn't carry well in this thin an atmosphere."

  His voice was strained in the blackness. "There's got to be a simple explanation."

  "There is, but it doesn't imply a simple organism."

  "Maybe it's ... signaling something else .. ."

  "And if it's brighter the deeper we get, maybe that means ... something below."

  They went one more time down into the darkness. Her muscles ached and her breath came in ragged gasps. At the next ledge down the lesion image began to swell into a strong, clearer version.

  Something beyond comprehension was happening here and she could only struggle with clumsy speculations as she worked. Somehow the mat could send signals within itself. There were many diaphanous flags and rock-hugging forms and somehow they all fit together, a community. They used the warmth and watery wealth here and could send signals over great distances, tens of meters, far larger than any single mat. Why? To sense the coming pulse of vapor and make ready? A clear survival value in that, she supposed. Could organisms evolve such detailed response in this harsh place?

  And how did these fit with the peroxide-eating microbes? Could they somehow work together? Darwin had his work cut out for him here ... With their lamps off she took video shots of the ghostly lesion images with her microcam, though she was pretty sure the level of illumination was too low to turn out. She would memorize all this and write it down in the rover. Careful notes ... "We're out of time."

  She gazed down and saw at the very limit of the weak lamplight bigger things. Gray sheets, angular spires, corkscrew formations that stuck out into the upwelling gases and captured the richness ... She blinked. How much was she seeing and how much was just illusion, the product of poor seeing conditions, a smudged helmet view, her strained eyes "Hey. Time."

  She felt her fatigue as a slow, gathering ache in legs and arms. Experience made her think very carefully, being sure she was wringing everything from these minutes that she could. "How far down are we?"

  Marc had been keeping track of the markings on the cable. "Just about one klick."

  "What's the temperature?"

  "Nearly 10. No wonder I'm not feeling the cold."

  "The thermal gradient here is pretty mild. This vent could go down kilometers before it gets steam-hot. And we've just reached the cavern level."

  "Ann .. ."

  "I know. We can't go farther."

  "It'll be a long, tough climb out. Must be dusk up there by now."

  Getting deathly cold on the surface, and fast, yes. Automatically she cut a small sample out of the closest mat and slipped it into the rack. A strange longing filled her.

  "I know. I'm not pushing for more, don't worry. Biologists need oxygen, too."

  They got the rover back just before they could've been accused of being late, tired and cold but still elated by their discoveries. Over a late dinner they briefed Piotr and Raoul, then squirted a summary Earthside, along with the digitized readout from her microcam. Now, whatever happened to them at liftoff, the information was safe.

  Ann and Piotr made love one last time on Mars. Piotr had been worried about her: He held her close afterward long after she drifted into sleep. After a few hours they were all up again, in a hurried rush to get ready. There was plenty more to do for launch, and months to cancel the sleep debt.

  As she worked alongside the others, she was struck again at how well they all worked together. Even under enormous time pressure they partitioned the duties with little or no overlap. It all went so smoothly that by noon they were just about finished. They celebrated at lunch, finishing up with a few saved delicacies.

  Despite a mountain of last-minute details, Ann's thoughts kept flashing back. Something about the team related to the puzzle of the vent life, but she couldn't quite get it. Oh well, she'd have six months to think about it, starting in just a few hours.

  Piotr made her stick to their deal on mass allowance. She spent pointless time worrying about which of her sample racks to leave and fretted and even begged Piotr (with no luck)-and then thought of a last trick.

  Once they had the old hab stripped and their gear transferred, she did the last rites of sealing up the worn little apartment they had now lived in for over two years. She would be perfectly happy to never set foot in it again. Piotr had already set the power reactor to low, so it could still drive the communications with Earth. She made sure the TV micro-cameras were pointed to follow the liftoff. If they crashed at least Earthside would see what had gone wrong. She brought the last personal gear over and then-her idea-had the men pass their pressure suits out through the ship's lock. Leaving the suits behind saved a hundred kilos, neatly taking care of all her sample racks.

  They had to lift at night to make their launch window. Escape energy for Mars was less than twenty percent of Earth's, which made the entire process of making their fuel from Martian carbon dioxide workable-they didn't need to make a lot. But even making the five km/sec escape velocity took a lot, so the entire flight plan, including the final boost to Earth, cut matters fairly fine. They had stayed the full 550 days to make this minimum energy window.

  She was strangely calm, waiting in her couch in the cramped Return Vehicle hab when Piotr started the engines.

  "Pressurizing all OK."

  "Flow regular."

  "Max it."

  "On profile."

  Cottony clouds billowed outside, licking up past the square port. She could see their liftoff by turning her head and the hills seemed close in the deep blackness of Martian night.

  They climbed quickly in a roaring, rattling rush, a feeling like being pressed down by a giant, yet she knew that meant it was all going well. Raoul called out altitudes, speeds, voice calm and flat.

  She felt a sadness as they angled over at several kilometers up. Mars lay in its frigid night below. Then she saw it.

  The entire moment lasted probably no more than five seconds. In memory it became a long, stretched syllable of time to which she was the sole witness.

  Her microcam was irretrieveably tucked away. The others were busy with the launch, shouting with relief and joy and the boundless releasing pleasure of knowing that after two years they were going home. No witnesses.

  She had no time to think about what she had seen because the trouble started as soon as they were in orbit. It came through her earphones in Piotr's pinched voice: "Losing pressure, Tank 2."

  The methane tank had a rupture. "Damn plumbing again," Marc said, trying to be casual, but they all knew this was bad.

  In the end it was their teamwork that saved them again.

  Resealing the tank using what few tools they had left from Raoul's kit was a tense, precise operation. She had to go outside in the light, full-vac suit and serve as general gofer while Raoul and Marc blocked the venting of methane, then made a makeshift repair. Meanwhile, Piotr made orbital calculations.

  The story of those days would make Raoul into the true media hero of the expedition. Not that she minded in the
least, for indeed, he had saved them all.

  But they had lost a lot of methane. Calculations showed they could not boost for Earth out of Mars orbit.

  So they rethought, frantically. Piotr was the first to see the only plausible solution: the booster fuel prepositioned in high Mars orbit by their competitors, Airbus. He put together a sequence of five burns that took them into a long, elliptical matching orbit with the Airbus tanks.

  Earthside was aboil with negotiations between the Consortium and Airbus, with lawyers angrily slapping writs on each other, over fuel four hundred million miles away. Airbus argued that the Consortium team failed if it could not get home without Airbus's help: They should at least split the $30 billion prize money. This provoked a brief flurry within the government. NASA announced that the terms of the contest only specified that the first team returning successfully from Mars would be the winner. Anything else was between Airbus and the Consortium.

  Intense public interest greased the negotiations. Airbus couldn't refuse the team their only chance home with the whole world watching. And none of the negotiators could have stopped the team from taking the fuel anyway. It was like piracy on the high seas two hundred years before.

  Finally they agreed. Overnight, a billion dollars changed hands. Deep in the bowels of a Swiss bank, a dolly heavily loaded with gold bars was wheeled from one vault to another.

  The two-bulbed booster looked surprisingly like a huge metal insect as they approached. Hanging below it was the rusty dry abyss of Mars, ripe for exploration.

  Ann shot the docking sequence with her microcam, a concession to the publicity-mad Consortium. Ground Control had wanted her to take extensive footage of the whole incident, but she had refused so far. It was too much to ask that they star in a home movie that might end in their deaths, and besides, she was too busy helping with the repairs.

  The team offloaded tons of methane from the booster reserves. That did not leave enough for the Airbus crew to return, which meant that Airbus had to send a second, smaller methane tank to rendezvous-no mean feat of orbital mechanics and navigation. That drama would play out years later, of course, for the Airbus team had a year and a half, just like the Consortium, to explore the surface of Mars before risking return.

  The refueling worked, though just barely. Bedeviling details such as incompatible couplings in the hoses and frozen joints in high vacuum cost them time and nerves. They alternately cursed the hardware and cajoled each other through the rough spots.

  But they got the methane they could not live without. The entire return orbit had to be recalculated, and of course they had missed their optimum time to catch the lowest-energy trajectory. That would cost them more fuel at Earth rendezvous, but at least they had it to burn.

  When they were under way they all slept most of the first week, not wholly from fatigue, but from the need to escape the sense of a closing vise around their lives. Recovery was slow. But then she had time to think, to recall those first moments of liftoff.

  They had half a year of waiting before their aerobrake into Earth's swampy air. As soon as they could they got the ship spinning, using the last stage rocket as counter-weight. This brought back Mars-level gravity and in the months ahead they gradually spun it to higher angular speeds, building up for the return to Earth.

  Ann thought a lot without talking to the others. Marc processed his data from the vent and they were all pleased to discover that the vapor boiling out had plenty of hydrogen and methane-a ready resource for later expeditions. If somehow they could land a robot vehicle next to a vent and trap its exhalations, Earthside wouldn't even need to ship hydrogen to make fuel here.

  Her samples were sealed away, her equipment on the planet below, so she could not work on the mat tissues or the shrimp or any of the rest of it. A treasure for others, though of course she would get to direct a lot of the work. They sure as hell owed her that; better, it was in her contract. There was no place in the Return Vehicle hab to rig a sealed work vessel for even simple studies. So she was left to her hypotheses.

  Back to basics, she decided. Try to see the whole planet from a Darwinian perspective.

  She couldn't prove any of her speculations, of course.

  Not without knowing more about Martian DNA. She suddenly realized what to look for, once she reached the labs of Earth.

  The DNA code might just hold the answer. Earth's code was degenerate: a mistake in the coding was like a change in spelling that didn't always alter the meaning. In a sense, there were alternate spellings for the same amino acid. And of course proteins themselves have regions where a substitution of a different amino acid doesn't really matter. Room for error, with no consequences.

  She had always thought that was a response to a rapidly evolving planet with lots of mutagens: a Darwinian hotbox world. So a rich world struck a balance between conservatism and experimentation, achieved over billions of years on a planet where evolution's lathe was always spinning.

  Climatic fluctuations changed the rules of survival, flipping from warm to cold and back again. It led some to postulate the Red Queen hypothesis: You have to keep running to stay in the same place, the entire biota evolving in fast lock step to avoid being left behind. The pace was grueling, and a species lasted on average only a million years or so before running out of steam.

  What would happen on Mars, where there may have been only one golden age of evolution, and a long twilight of one-way selective pressure? The environment got ever colder, ever drier, the atmosphere ever thinner. But there were also brief eras of warmth, when water or at least mud flowed on the surface. What then?

  Ten days later they finally celebrated their victory over lunch. They had stopped holding their breaths and were beginning to relax in the tiny social room of the circular hab. The others had begun to write their memoirs. There would be four solid best-sellers out of this, no problem, already under contract with fat advances paid.

  Amateur writers all, they were trying out titles on each other.

  "I think I'll call mine Mars or Bust," said Marc.

  That got a laugh from Raoul. "More like Mars and Busted, don't you think?"

  "I know. Mars overstrike and Busted." They howled with laughter, delayed release from earlier terrors.

  "What about The Long Glide Home?" said Marc when they had calmed down. "Together on Mars," suggested Piotr, grinning at Ann.

  Something about the titles caught Ann's attention. Mars had a long cold drying out ... She sank back into her thoughts. Now that you can't grab any more samples, let the theory lead you ... On Mars, maybe the DNA code would become more conservative, simpler and more precise? After all, the direction of evolution for a billion years had been the same: colder and drier. Without sudden climatic shifts, the need for degeneracy disappeared.

  Every error would be significant. The price was that evolution must be slower. Even on Earth, most mutations were unfortunate, spelled gibberish, and killed the organism. Only a very few were useful.

  On Mars, the chance of a successful mutation would be much smaller, in the unchanging harsh conditions. Then what would happen if Marc was right, and there had been a few brief intervals of warmer, wetter conditions? Evolution couldn't work fast enough to take advantage of the new conditions.

  So ... what else?

  Could cooperation have become the winning rule? She looked around the tiny room at her teammates. Four tough-minded types with different skills, fitting together into an efficient whole. They had survived two near-disasters and a grueling 18 months in a freezing, near-vacuum rustbowl because of that efficiency. Piotr had finally been picked, instead of Janet, because his range of talents, his characteristics, were what the rest of the team needed. That's what her subconscious had been trying to tell her.

  Could it work on a planet-wide scale?

  Find a partner with the desired characteristic, instead of trying to evolve it yourself.

  A short period of wet and warm brought the mats out of the vents and into the
lake beds, where they interacted with the peroxide forms, perhaps incorporating them into the biofilm. Photosynthetic organisms loosed from the matthose shrimp?-could colonize the seas, making hay in the brief summer while the atmosphere lasted.

  Life that found partners to help it maximize the wet-era opportunities would be successful. Glowing mats and photosynthetic microbes, free-swimming forms and protective films, peroxide eaters and watery membranes, all somehow trading their resources.

  An entire ecology, driven far underground, nonetheless finding a path through the great Darwinnowing ... She did some quick calculations and saw that the available volume of warm, cavern-laced rock below Mars was comparable to the inhabitable surface area of Earth. Room to try out fresh patterns.

  But always meshed into the spreading network of organisms great and small ... evolution in concert. Organisms still died their pitiful deaths, genes got erased-but the system could be more interlaced, she saw, deep in the guts of a slumbering world. Maybe that explained what she had glimpsed at liftoff.

  Her last look down at the frigid Martian night had caught a smudge of light toward the horizon. A pale white cloud, linear, fuzzier at one end. It seemed to point downward. Then she saw that she was looking less north, and the cloud glowed. A pale ivory finger of illumination spiked up from the surface, broadening.

  From the vent, she knew instantly-an impossibly brilliant out-pouring. Then the ship took them up and away and Mars fell into its long cold night again.

  To poke such a glistening probe of light into the sky must have cost the matting enormous energies, she thought. To make it, the vent would first have to be expelling a gusher of vapor. Then the mats would all have to pour their energy into the pale glow, coherently.

  What coordination ... and what control, over the venting of vapor itself?

  Could life have attained such levels?

  On Earth, the anaerobic forms had never evolved beyond simple forms, bacteria. They had been competing with the hefty, poisonous oxygen-users, of course. On Mars that was no issue; the creatures of methane and hydrogen had prevailed, for billions of years, beneath the steady, cruel press of a world slowly bleeding its air and water into the hard vacuum above.