The Year's Best Science Fiction: Fifteenth Annual Collection

by Gardner Dozois

It seemed ... that if he or some other lord did not endeavor to gain that knowledge, no mariners or merchants would ever dare to attempt it, for it is clear that none of them ever trouble themselves to sail to a place where there is not a sure and certain hope of profit.

  -Prince Henry the Navigator, assessing the motivations for sea exploration, circa 1480

  PART I

  He turned with a cry of surprise, falling helplessly with a silky slowness she would never forget. Piotr had caught his boot and when he tried to free it he managed to trip as well. His second yelp rang in Ann's suit corn when he bit the ground and his ankle snapped. His right arm smacked down vainly as he tried to break the fall. The impact sent plumes of red dust arcing up into the thin atmosphere. She trotted to him in the long, gliding steps that covered ground best in the deep gravel and low gravity. The dust began its lazy descent as she bent over Piotr and said, "How bad?"

  "Da ... Felt it go. Foot .. ."

  She unfastened the bottom of his insulated legging and ran her hands lightly over the ankle cuff of the thin pressure suit underneath. "Suit looks OK, no breaches. How's your air?"

  The damned dust had settled on his faceplate and she couldn't see him, but knew he would be checking the readouts on the inside of the helmet. "Normal."

  His voice was thin and strained. "Good. How do you feel?"

  He shifted slightly, groaned. "Like yesterday's blini. Light-headed. My right foot hurts like hell."

  Keep him talking. Can't risk shock.

  She kept her tone light. "That's what you get for doing cartwheels."

  "Unh. I can't move it."

  She frowned, wondering how difficult it was going to be to get him back into the rover. Help was more than 35 klicks away, and she was driving the only vehicle on the planet. So the two of them had to manage it on their own. From the rover she could contact the other two members of the team, for moral support if nothing else. If she could get him there.

  "Let's get you up."

  "Awright." His slightly slurred voice worried her. They were all worn down after months in this cold, raw landscape and shock could be setting in.

  She bent over and slipped her left arm clumsily around his waist, feeling like a kid in a snowsuit. Suit-to-suit contact had a curiously remote feel about it, with no feedback from the skin. Still, she liked hugging him, even this way. They slept together in a close embrace, ever since the launch from Earth orbit a year ago.

  "I've got some great stuff in the rover that'll make you feel like a new man."

  "Good. Aieee."

  He heaved himself up onto his left leg, leaning heavily on her. Together they struggled for balance, threatened to go over, then steadied. She had long ago stopped counting how many times the 0.38 gees of Mars had helped them through crucial moments. It had proved the only helpful aspect of the planet.

  "Whew. Made it, lover." Keep the patter going, don't alarm him. "Ready? I'll walk, you hop as best you can."

  Like a drunken three-legged sack-race team, they managed to stagger slowly up the crater slope. "You will work as a team," the instructor at mission training had said, but she hadn't anticipated this. Over corn came deep, ragged gasps. Hopping through gravel, even in the low gravity, was exhausting Piotr. Luckily the rover was just on the rim, about a dozen meters away.

  Not at all like the electric dune buggies used in the Apollo Lunar missions, the Mars rover resembled an oversized tank on wheels. It was really a mobile cabin that could keep a crew of two out in the field for two weeks. She got him into the lock and set the cycle sequence. No time to brush off the dust; the cab inside was hopelessly thick with the stuff anyway. She heard the cycler finish and felt the rover's carriage shift. Good; he had rolled out of the lock and was lying on the floor. She hit the pump switch and oxygen whistled into the cabin from half a dozen recessed ports.

  The chime sounded; they were pressurized. She turned off her suit oxygen, released the clamps on her helmet and as quickly as possible shucked her parka, leggings, and finally, her suit. She shivered as she stepped out into the chilly cabin: She had actually been sweating on Mars-a novel experience. A prickly itch washed over her face and neck and already she regretted their dusty entry. The usual routine was to brush the suits down outside with a soft brush. Some genius from mission prep with a lot of camping experience had thoughtfully stowed it aboard, and it quickly had become one of their prized possessions. The Martian surface was thick with fine, rusty dust heavily laden with irritating peroxides. Her skin felt like it was being gently sandpapered during the long months here, especially when she was tired, as now.

  Fluffing her short black hair, she doffed a red Boeing cap and went over to help Piotr. She upped the pressure to get him more oxygen and together they gingerly peeled off his insulating layers and his suit. A look at his leg confirmed her guess: broken ankle, swelling fast.

  From there it was straight safety manual stuff: bind, medicate, worry.

  "I love you, even zonked on painkillers," she murmured to his sleeping face when she had checked everything five times. He had dropped off disturbingly fast. He kept up a front of invincibility; they all did somewhat or they wouldn't be here; it went with the psychology. But he had the bone-deep fatigue that came from a hard mission relentlessly pursued.

  She was suddenly very tired. Emotional reaction, she diagnosed wryly. Still, better tend to it.

  Time for a cup of tea. She looked around first for her tea cosy, carefully brought from Earth as part of her personal mass allowance. Nothing could've induced her to leave it behind-home was where the cosy was. She retrieved it from a corner of the cooking area. Originally light blue and cream colored, it was now stained irretrievably with the red dust of Mars. When things got tough she sought the comfort of a proper cup of tea made in a teapot. There were precious few emergencies that couldn't wait until after a cuppa.

  As the water heated she got on the AM channel and tried to reach the other two back at the hab, got no answer. They were probably deep in the guts of the Return Vehicle, starting the final checks for the approaching test fire. She left a heads-up on the ship's message system that they were coming back. No way could she get any more done out here on her own. Anyway, Piotr came first, and any solo work was forbidden by their safety protocols.

  She stared out of the forward view port at the pale pink hills, trying to assess what this accident meant to the mission. Maybe just a mishap, no more? But Piotr still had plenty to do, preparing for their return launch. No, this would screw up the schedule for sure. Her own work would get shoved aside. Face it, she thought-biology was not the imperative here any more. She had made her big discovery. To the world, their expedition was already a big success-they'd found life.

  The robot searchers of years before had fruitlessly tried to find evidence of life or even fossils. But in the iron peroxide desolation all traces were erased. The tiny robots had an impossible task, akin to dropping a toy rover into Montana and expecting it to find evidence of the dinosaurs that had once tramped through its hills. Mars was bone-dry, but without bones. Not even the algal mats some had hoped might be preserved from the ancient lake beds.

  The noxious peroxides bad a good side, though. In chem labs Earthside, hydrogen peroxide was a standard disinfectant, giving the Consortium a handy argument against those who said a human expedition would contaminate the whole planet, compromising the search for life. In closed-environment tests, the peroxides scavenged up the smallest microbes, making it quite clear why the Viking landers had found no signs of organic chemistry. For Earth life, Mars was like living in a chemical blowtorch.

  But Mars life had found a way to circumvent and vanquish the peroxides. Life here was widespread, subsurface microbes using the ubiquitous iron peroxides as their energy source. Within a week after landing, some of Marc's first exploratory cores had come up with streaks of a dark, crumbly soil-like layer less than a meter below the surface.

  Hoping to find something interesting, she set up a plastic inflatabl
e greenhouse dome outside the habitat, spiked samples of the Martian soil with water and nutrients, sealed them in small pressure vessels and incubated them. She could then check for any gases produced by the metabolism of life forms in the soil. She was essentially repeating the robot Viking biology program, but this time life was looking for life directly. To avoid the embarrassing possibility of introducing her own microflora into the experiment, she worked with the samples only outside, under the cold red-stained sky. In her pressure suit and insulating outerwear she was somewhat clumsy, and each step went slowly. But finally she was satisfied with the setup. The elevated greenhouse temperatures kept the water from freezing and speeded up the results enormously.

  Sure enough, as in the Viking experiments, there was an immediate response of dry surface peroxides to the water. A spike of oxygen. When that had run its course she bled off the gases and resealed the pressure vessels. And was rewarded in a few days with unmistakable signs of renewed gas production. Carbon dioxide this time. The microscope then confirmed living colonies of Martian microbes. The rest, as they say, is history. So why was she still restless, unsatisfied?

  The crackle of the radio startled her. "Home team here. Got your heads-up, Ann. How is he?" Marc Bryant's crisp efficiency came over clearly, but she could hear the clipped tenor anxiety, too.

  "Stable." She quickly elaborated on Piotr's symptoms, glancing at his sleeping face. They had each taken a month of medical training but Marc had more. She felt relieved when he approved of her treatment. "Got to think what this means," he said laconically.

  "We'll be there for supper. Extra rations, I'd say."

  A small, very small joke. They had celebrated each major find with a slightly excessive food allotment.

  So far, they had not marked disasters this way. And they were having their share.

  The first was the vent failure on the flight out. They found they had lost a big fraction of their water reserve, four months out from Earth, from a blown valve. There had been no time to console themselves with food, and good reason not to. They had landed bone-dry, and lived on the water manufactured by the Return Vehicle's chem plant ever since. That accident had set the tone for the others. Celebrate the triumphs, overcome the disasters.

  "My night to cook, too," Marc said, transparently trying to put a jovial lilt to it. "Take care, gal. Watch the road."

  Here came the heart-squeezing moment. She turned the start-up switch and in the sliver of time before the methane-oxygen burn started in the rover engine, all the possible terrors arose. If it failed, could she fix it? Raoul and Marc could come out in an unpressured rover and rescue them, sure, but that would chew up time ... and be embarrassing. She wasn't much of a mechanic, but still, who likes to look helpless?

  Then the mixture caught and the rover chugged into action. Settling in, she peered out at the endless obstacles with the unresting concentration that had gotten her on this mission in the first place. To spend 550 days on Mars you wanted people who found sticking to the tracks a challenge, not boring. She followed the auto-tracker map meticulously, down a narrow valley and across a flood plain, then over a boulder-strewn pass and down a narrow valley and across a flood plain, then over a pass ... Here, a drive back to base that proved uneventful was even pleasant. Mars was always ready to thunk a wheel into an unseen hole or pitch the rover down a slope of shifting gravel, so she kept exactly to the tracks they had made on the way out, no matter how enticing a distant flow pattern in the rocky shelves might be. She had seen enough of this red-hued terrain to last a lifetime, anyway. Nothing more out there for a biologist to do.

  In the distance she caught sight of the formation she and Piotr had dubbed the Shiprock on the way out. It looked like a huge old sailing ship, red layers sculpted by eons of wind. They'd talked about Ray Bradbury's sand ships, tried to imagine skimming over the undulating landscape. The motion of the rover always reminded her a little of being on the ocean. They were sailing over the Martian landscape on a voyage of discovery, a modern-day Columbus journey. But Columbus made three voyages to the new world without landing on the continent. He "discovered" America by finding islands in the Caribbean, nibbling on the edges of a coast. A sudden thought struck her: was that what they were doing-finding only the fringes of the Mars biology? Many people had speculated that the subterranean vents were the most likely places for life on this planet. The frontier for her lay hundreds of meters below, out of reach. She sighed resignedly. But it bad been great fun, at first.

  She slurped more tea, recalling the excitement of the first months. Some of it was pure fame-rush, of course. Men on Mars! (Uh, and a woman, too.) They were household names now, the first Mars team, sure bets for all the history books. Hell, they might eventually eclipse Neil Armstrong.

  She was first author on a truly historic paper, the first submitted to Nature from another world. Barth, Bryant, Molina & Trevinski's "Subsurface Microbial Life on Mars" described their preliminary findings: It would rank with Watson & Crick's 1952 paper nailing the structure of DNA. That paper had opened up cell biology and led to the Biological Century.

  What would their discovery lead to? There was already a fierce bidding war for her samples. Every major lab wanted to be the first to crack the Martian DNA code, and determine the relationship between Martian and terran life. Her simple chemical tests, staining samples of thin-sectioned Mars colonies under the microscope, had shown that the basic constituents of life-proteins, lipids, carbohydrates, nucleic acids-were the same here, or at least close enough to respond to the same chemical tests.

  She used standard techniques and extracted what seemed to be DNA from the microbes. So how similar was it to Earth-style DNA? She ran some hybridization tests with the dried DNA of terran microbes she'd brought along. Basically, you unzip the double-stranded DNA helix by heating, then mix the soup of single strands with strands of a different DNA. When the mixture is cooled down again, strands that are similar enough pair up. She got just enough pairing between Martian and terran microbial DNA to conclude that life on both planets at least used the same four-letter alphabet.

  That was exciting, but not conclusive. In other words, all DNA might have to be composed of the same four bases just for molecular structural reasons.

  But the DNA code was something else. DNA spells out the amino acids, which then construct the cellular proteins-both the structural brickwork and the busy enzymes that do the cell's business. If Martian DNA spelled in the same language as on Earth, it would mean unequivocally a common origin for life.

  When she tried sequencing the Martian DNA, it came out gibberish. It looked like Earth-style DNA, but she couldn't match it to known gene sequences. It was, once again, an ambiguous result. And that was as far as she could go with her equipment. The rest would have to wait.

  Assuming that life emerged only once for the two planets, where did it start?

  If Mars cooled first, life would arise here while Earth was still a pool of hot lava. And come to Earth via the meteorite express. The Martian meteorites with their enigmatic fossils had tantalized scientists for years. When they were first discovered, the big question had been whether they actually contained fossils, because most people thought they knew that Mars was lifeless. Now we know about that part, at least, she thought.

  Organized life forms from Mars seeding Earth's primitive soup of basic organic molecules would quickly dominate. Martians come to harvest Earthly resources. H. G. Wells with a twist. We may yet be Martians. Pretty heady stuff for the scientific community, and it would change our essential world view. Full employment time for philosophers, too, and even religious theorists.

  But deep down she realized she'd wanted to find life, not microbes. The ghosts of Carl Sagan's giraffes had shaped her expectations. Marc was jazzed by the discovery of deeper layers of microbes, separated by layers of sterile peroxideladen sediments in the old ocean beds. That implied periodic episodes of a wet and warm climate. But so far she had not found anything other than the soil
microbes. Even the volcanic vent they had explored had no life, only peroxide soil blown into it from the surface, like a dusty old mine shaft. And now they were about to leave and the subterranean caverns were still unexplored. Damn!

  After five hours Piotr was doing well, and had regained his energy and good spirits. They even managed a clumsy but satisfying slap and tickle when she stopped the rover for lunch. They weren't going to get any more privacy, not with just two weeks to go until the return launch. She felt nervous and skittish but Piotr was a persistent sort and she finally realized that this just might do both of them more good than anything in the medicine chest back in the habitat.

  The route began to take them-or rather, her, since Piotr crashed again right after sex; this time she forgave him-through familiar territory. She had scoured the landscape within a few days of the hab. Coming down in the Chryse basin, they got a full helping of Mars: chasms, flood runoff plains, wrinkled canyons, chaotic terrain once undermined by mud flows, dried beds of ancient rivers and lakes, even some mysterious big potholes that must be mini-volcanoes somehow hollowed out. Her pursuit of surface fossil evidence of life had been systematic, remorseless-and mostly a waste.

  Not a big surprise, really, in retrospect. Any hiker in the American West was tramping over lands where once tyrannosaurus and bison had wandered, but seldom did anybody notice a bone sticking out of the ground. Ann was more systematic and probed deeper in the obvious places, where water had once silted up and could have trapped recently dead organisms. Algal mats, perhaps, as with the first big life forms on Earth. But she had no real luck, even in a year and a half of snooping into myriad canyons and promising beds of truly ancient lakes. That didn't mean life wasn't somewhere on the planet. A billion years was a long time, enough for life to evolve, even if Mars had not supported surface life for perhaps three billion or more.

  She stamped her feet to help the circulation. Space heaters in the rover ran off the methane-oxy burn, but as always, the floor was cold. When the outside was tens of degrees Centigrade below zero, gradients in the rover were steep. Mars never let you forget where you were.