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A Cold Dry Cradle
Gregory Benford and Elisabeth Malartre
Science Fiction Age
November, 1997
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Gregory Benford is one of the modern giants of the field. His 1980 novel Timescape won the Nebula Award, the John W. Campbell Memorial Award, the British Science Fiction Association Award, and the Australian Ditmar Award, and is widely considered to be one of the classics of the last two decades. His other novels include The Stars in Shroud, In the Ocean of Night, Against Infinity, Artifact, Across the Sea of Suns, Great Sky River, Tides of Light, Furious Gulf, and Sailing Bright Eternity. His short work has been collected in Matter's End. Recent books are a new addition to Isaac Asimov's Foundation series, Foundation's Fear, and a big novel, Cosm. Benford is a professor of physics at the University of California, Irvine.
Elisabeth Malartre is an environmental consultant and science writer with a doctorate in biology. This was her first sale.
Here they take us along with them on a mission to Mars, the kind of practical, hardheaded, nuts-and-bolt mission that might actually take place in the next few decades, the sort of mission that is actually on the drawing boards at NASA today…and show us that sometimes it's the things you're not looking for at all that are the most important things to find…
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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 1

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 com when he hit 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 com 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 cozy, carefully brought from Earth as part of her personal mass allowance. Nothing could've induced her to leave it behind—home was where the cozy 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 had 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 inflatable 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 continent. 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 had 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 L*I*F*E, 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 peroxide-laden 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.
She tried to envision how it must have been here, billions of years ago. Did life give way with a grudging struggle, trying every possible avenue before retreating into the diminished role of mere microbes?
The planet did not die for want of heat or air, but of mass. With greater gravity it could have held onto the gases its volcanoes vented, prevented its water vapor from escaping into vacuum. Split from hydrogen by the sun's stinging ultraviolet, the energetic oxygen promptly mated with the waiting iron in the rocks. The shallow gravitational well failed. Light hydrogen blew away into the yawning vastness of empty space. Had Mars been nearer the Sun, the sunlight and warmth would simply have driven water away faster.
So those early life forms must have fought a slow, agonizing retreat. There were eras when lakes and even shallow, muddy seas had hosted simple life—Marc's cores had uncovered plenty of ancient silted plains, now compressed into sedimentary rock. But no fossil forests, nothing with a backbone, nothing with shells or hard body parts. If higher forms had basked in the ancient warmth here, they had left no trace.
The squat hab came into view in the salmon sunset. Looking like a giant's drum, five meters high and eight meters across, it stood off the ground on sturdy metal struts. Long pink and white streamers of carbon dioxide and water vapor trailed from roof vents, signaling that Marc and Raoul were there. Inside, the two stacked decks had the floor space of a smallish condo, their home for the last two years. Not luxurious, but they would certainly be nostalgic for it in the cramped quarters of the Return Vehicle they would shortly be boarding.
By now the hab was familiar to billions of Earthbound TV viewers and Net surfers. Everyone on Earth had the opportunity to follow their adventures, which were beamed daily from Ground Control and carried on the evening news. Their Web page registered over a hundred million hits in the week following the landing. Mars had ceased to be Space and had become a place.
She told herself that she had done all anybody reasonably could. After finding the microbes, she had postulated that they used an enzyme like catalase to harvest the peroxides' energy. Then she had tested it in her small greenhouse set-up, found it worked. She would write that up on the half-year voyage home, squirt it e-mail to an eager audience of every biologist in the world. Heady stuff!
She had data on chemical and biological toxicity of Martian substances to terrestrial biota. Another paper there, too. Plus work on the suitability of local soils to support greenhouse agriculture. Marc had even tried to grow kitchen herbs, but none of the plants survived. Her long searches for fossil microbial mats in the paleoseas had turned up plenty of oddities that might bear fruit under rigorous inspection back Earthside. But she still felt she was just nibbling at the edges, but of what?
Raoul and Marc climbed down out of the hab as she approached, in the last slanting rays of a ruddy sunset, two chubby figures in dark parka suits. Only Raoul's slight limp distinguished them. The tracker system had alerted them, and they would have to carry Piotr in. Plus a little ceremony they had devised: salvaging water from the rover. The methane-oxygen burn made carbon dioxide, which the engine vented, and pure water. She backed the rover to the conical Return Vehicle, with its gaudy red-on-white Mars Consortium wrap-around letters, a meter high. Raoul and Marc hooked the water condensers to the input lines, so the chem factory inside could store it. They had full tanks of methane and oxygen for the liftoff, but water was always welcome, after the parching they had taken on the long flight here. The guys did this last task by way of saying "welcome home." In the bleak, rusty dusk, the cold of night biting already through her skinsuit, the symbolism was important. Mars was sharp, cold and unrelenting, and they all felt it to the bone.

PART 2

Despite Marc's best efforts, dinner was not a culinary success. Marc was the foodie among them, forever trying out new combinations of the limited range of kitchen stores. But they had long ago exhausted the narrow potential of the kitchen stores for new tastes, and now everything they ate was too familiar to the tongue, though Marc kept trying. He had even brought along spices as part of his personal mass allowance. Some of his infamous attempts had produced stomach-rumbling distress. The microwaved frozen vegetables especially resisted creativity. Still, the food was much better than the freeze-dried horrors of NASA days…or so some said.
They took turns in the tiny galley. On the outbound voyage Ann bowed to the public's expectation and dutifully did her time, but the others agreed that the results were definitely substandard, and she was relieved of cooking. Instead, she did extra cleanup. That didn't bother her, a dedicated non-foodie, who believed that eating was a somewhat irksome necessity. She went through school with a minimally equipped kitchen. Throwing a box of macaroni and cheese into boiling water stretched her limits. Piotr joked that he sure as Hell hadn't married her for her cooking. She actually liked good food, but wasn't interested in taking the time to produce it.
"So what did you two do while we were gone?" Ann asked later over very slightly grainy pudding. The chocolate color disguised any visible traces of Martian dust, but the tongue found its sting.
Marc licked his spoon carefully. "Well, we drilled another core. Found something…interesting."
"Where were you working?" asked Piotr.
"We took the runabouts back to the mouth of the big canyon in Long Ridge—you know, where we saw the fog a couple of months back on that early-morning trip." The base sported two open dune buggies that the crew used for short sprints of less than 10 klicks round-trip. By taking both buggies, it was possible to haul the drilling gear.
Ann shivered, remembering the biting cold that morning she and Marc had seen the fog, suit heaters cranked to the max, looking like quilted penguins. Their picture now graced the cover of the Lands' End catalogue, wearing the parkas and leggings now called Marswear, of course. It was the latest rage in macho-type clothes, and the underwriting helped pay for the mission.
As they'd prepared to leave the rover she'd grabbed her tea cozy and worn it like a knit ski cap. That was only the first time she'd used it as extra insulation.
Marc continued, "We were down about thirty meters, going pretty slow through some resistant stuff, then all of a sudden the drill started to cut down real fast. I stopped it then so we wouldn't lose the tip. But when we pulled out the drill stem and core, it was smoking."
"Uh-oh," said Ann, automatically sympathetic.
"That's what it looked like, anyway, but it wasn't hot, wasn't even warm." He smiled, looking at Ann and Piotr slyly.
"So how could it be smok—oh, wait, it was water vapor!" shouted Ann. "You found water!"
Marc grinned. "Yep. The drill tip was really wet, and making cloud like mad." It was so cold and dry on Mars that water on the surface never passed through a liquid stage, but sublimed directly from frozen to vapor. The team had concentrated their efforts to drill for water in places where early morning fogs hinted at subsurface moisture.
"So, the deepest core is always the wettest. Makes sense. There really must be frozen oceans down there," said Ann.
"What does Earth think?" asked Piotr.
"Well, with all the data from the other cores, first indications are that it's probably good enough."
"Good enough for the government, as they say," said Raoul with uncharacteristic levity. Raoul Molina, the compact and muscular fourth crew member, was the top mechanic on the team, and ritually cynical about governments. He even disliked the fact that NASA had separately contracted with the Consortium to supply some geological data.
"Too bad we're not working for the government, eh?" shot back Marc.
Ann looked over at him, surprised. The brief exchange left much unsaid, but all understood the shorthand. Tensions were definitely building as the launch date approached. No one wanted to be the cause of a delayed return. The search for subsurface water had gone slowly, disappointing some of the mission backers, and raising the specter that the team would be asked to stay longer to complete the mapping.
After dinner it was time for their regular video transmission to Earth. They pulled Consortium logo shirts over their waffle weave longjohns and prepared to look presentable. In fact, they wore as little as possible when in the hab—loose clothing didn't aggravate the skin abrasions and frostbite spots they suffered in the suits. They kept the heat cranked up to compensate, but then nobody had to pay the electric bill, Marc pointed out. Competition was keen for creams and ointments for their dry skin rashes.
"My turn, I think," said Marc.
Ann smiled. "Janet on the other end tonight, then?" Janet Burton was a former test pilot who had trained with them, and clearly had hoped to make the trip. The Consortium had made a careful selection: individual talents balanced with strategic redundancy. The crew of four had to cover all the basics: mission technical, scientific and medical. They fit together like an intricately cut jigsaw puzzle.
In the end it had come down to a choice between Janet and Piotr, and Ann was relieved at the final decision. She didn't know if she could have left Piotr behind so soon after their marriage, even for a trip to Mars.
For the thousandth time she wondered if that had figured in the crew choice. Adding a woman had inevitably made for tensions, but on the other hand, it also gave half the possible Earth audience somebody to identify with. And the Consortium could be subtle.
"Let's play up the water angle, not the ankle," Piotr said.
"Drama plays better than science," Ann said.
"So we must educate, yes?" Piotr jabbed his chin at Marc.
But Marc wasn't listening. The brief description of Piotr's accident had been squirted to Earth earlier, and he was downloading the reply. Due to the time delay of six minutes each way, normal back and forth conversations were not possible, and communications were more like an exchange of verbal letters. At times the round-trip delay was only a matter of four minutes, sometimes forty. Nonetheless, Earth and Mars teams agreed on a download at a specified time to preserve the semblance of a conversation. They did a short video sequence at the same time. It was great theater, but the Consortium also had a team of doctors scrutinize the footage.
At the short delay times Marc and Janet tended to handle the bulk of the communications. And there was a little spark in the transmissions.
The crew gathered around the screen to watch the latest video from Earth. It was Janet, all right, gesturing with a red Mars Bar. Waiting for a successful landing, Mars, Inc., the candy manufacturer, had agreed to become a mission underwriter, releasing a special commemorative wrapper—a red number featuring the four of them against a Martian backdrop. They had taken about twenty shots of each crew member holding up a standard Mars Bar before a scenic backdrop. They each got $5,000 per shot, with the Mars Bar people paying $10,000 per pound to ship a box of the bars out for the photo shoot. It would have been irritating after a while, except that they came to relish the damned things, keeping one for exterior shots, where it quickly got peroxide-contaminated, and eating the rest as desserts. The cold sopped up calories and the zest of sugar was like a drug to Ann. She was quite sure she would never eat another, back home, even if she did get an endorsement contract out of the deal.
Ann had dubbed the resulting red-wrapped candy the Ego Bar, unwilling to honor it with the name of a planet and an ancient god, and the team adopted the name. There had been some talk early on about producing another wrapper with Mars life pictured, but microbes weren't exciting enough, and the manufacturer had just decided to stick with the Ego Bar.
Somehow, the commercialism of it all still grated on her. But she had signed on with eyes open, all the same. She had known that market-minded execs ran the Consortium, but going in had thought that meant something like, If we do this, people will like it. Soon enough she learned that even exploring Mars was seen by the execs as, If we do this, we'll maximize our global audience share and/or optimize near-term profitability. Such were the thoughts and motivations on Earth. Still, Mars the raw and unknown survived, unsullied and deadly.

* * * * *

The spirit of getting to Mars on private capital was to shuck away all excess. No diversionary Moon base. No big space station to assemble a dreadnought fleet. No fleet at all—just missions launched from Earth, then propelled outward by the upper stage of the same booster rocket that launched them. They had then landed on Mars after a long gliding journey, as the Apollo shots had.
But the true trick was getting to Mars without squandering anybody's entire Gross National Product. When President Bush called in 1989 for a manned mission to Mars on the 50th anniversary of the 1969 Apollo landing, he got the estimated bill from NASA: 450 billion dollars.
The sticker shock killed Bush's initiatives in Congress. The price was high because everyone in NASA and their parasite companies tacked every conceivable extra onto the mission.
When evidence of ancient fossil microbes had turned up in 1996 and later, public interest returned. Soon enough, even Congress-creatures realized that the key to Mars was living off the land. Don't lug giant canisters of rocket fuel to Mars, just to burn it bringing the crew back to Earth. No fluids like water hauled along for an 18 month mission. Instead, get the basic chemicals from the Martian atmosphere.
The Mars Consortium had begun by sending an unmanned lander, the Earth Return Vehicle. It carried a small nuclear reactor for power, an automated chemical processor, the rovers, and the Return Vehicle, unfueled. Using the nuclear reactor power, it started its compressors. They sucked in the thin Martian carbon dioxide and combined it with a store of hydrogen hauled from Earth. This made methane and water. The chemical plant was compact, laboring for half a year to separate the methane into the rocket fuel tanks and clean some of the water for later human use. The rest of the water got broken into oxygen and hydrogen. The hydrogen went into the tanks, and the oxygen was reserved for later combination with the methane in the combustion chambers of the Return Vehicle. Nothing was wasted.
All this was simple chemistry: hauling to Mars only hydrogen as a feed stock for the process, the ship made 18 times as much rocket fuel as the mass of hydrogen it brought. Taking all that fuel to Mars would have cost billions, plus assembly of the mission in orbit. By going slim and smart, the Consortium saved all that. Had the early European explorers tried to carry all their food, water, and fodder to the New World, few could have gone.
Slightly over a year after the first launch, the refueled Return Vehicle awaited the crew. They had launched on a big Saturn-style booster rocket, the contribution of the Russian partner, Energiya. Their closed-loop life-support system had recycled the air and water.
As their upper stage burned out, it pulled away on a tether cable about 300 meters long. A small rocket fired on the habitation drum, setting it to revolving with the upper stage as its counter-weight. At two revolutions a minute, the hab drum had a centrifugal gravity of 0.38 Earth's, to get them used to Mars.
At the end of six months gliding along a curving trajectory close to the minimum-energy orbit, the hab cut the cable. Rather than firing its rocket right away, it used an aeroshell—a cone-shaped buffer—to brake itself as it swung around the planet. They targeted on the radio beacon set up for them and landed right beside the fueled Return Vehicle.
All this was risky; their loss of precious water on the way out had come close to doing them in. Making exploration super-safe was not only hugely expensive, it was impossible. Further, it was anti-dramatic: The public audience was thrilled all the more if lives truly were at stake.
Risks were both obvious—a blowup at launch, as with the Challenger shuttle—and subtle, as with radiation dosage. The voyage exposed them to the solar particle wind and to cosmic rays. They could shelter from solar storms, which were infrequent, but the rest of their exposure amounted to about a 1 percent increased probability of having a fatal cancer within their life span.
Further, Mars itself could do them in. Storms could collapse their habitat or blow over their return rocket. Dust could clog the pumps at the crucial blastoff.
But the 1970s Viking landers had been designed to last 90 days, yet one held out for four years against cold, wind and dust, and the other lasted six.
Multiple backup systems are the key to safety—but the more backups, the higher the cost. Bush's 450 billion dollar program showed that a NASA-run program could easily turn into an enormous government pork farm.
So a radical idea arose: The advanced nations could get this adventure on the cheap by simply offering a prize of 30 billion dollars to the first successfully returned, manned expedition.
This mechanism European governments had used for risky explorations centuries ago. The advantages are that the government puts out not a dime until the job is done, and only rewards success; investors lose if their schemes fail. Also, if astronauts died, it was on somebody else's head, not an embarrassment to a whole government.
So the Mars Consortium of Boeing, Microsoft, Lockheed and the Russian Energiya took the plunge. They originally wanted to use the name Mars, Inc., but discovered that a candy manufacturer had long ago beaten them to it. A Japanese partner bowed out, finally contributing only the smart-toilet, now dubbed the Marsbidet. At $10,000 to fly a pound to Mars, disposables were impossible. This went right down to writing paper—erasable slates served better, and could be digitally saved, even sent Earthside—and toilet items. Nobody had figured out how to recycle toothpaste, but toilet paper was dispensable. The smart toilet combined a bidet arrangement of water jets with a small blow-dryer. Since its inclusion on the mission it was the hottest piece of plumbing on two planets.
A second mission attempt was being made by Airbus Interspatiale, formed from the French Nationale Industrielle Aerospatiale, British Aerospace, the Spanish Construcciones Aeronauticas S.A. and Daimler-Benz Aerospace. The Airbus group had a more cautious method; their fully fueled Return Booster had arrived in Mars orbit four months before. The Airbus crew had launched 50 days later. They could win only if the Consortium's Return Vehicle failed at launch. The whole world was watching the race…which made the Consortium's nightly "Hello, Earth" show rake in the dollars.

* * * * *

They all snorted when the usual question came in from Janet. She looked embarrassed, but what could she do? "And how are you feeling, with Airbus getting nearer and your own launch—"
Marc started before Janet was finished. "We'll wave to them as we head home."
Everybody laughed, but there was a forced quality to it.
After the usual updating on Ann's foray, Janet wished Piotr a speedy recovery, transmitted some bland medical advice, and then turned to quasi-technical details about the upcoming liftoff test. Piotr's accident was one more mishap to be overcome. Janet didn't fail to mention the obvious: The broken ankle meant their captain would be less effective if anything went wrong with the liftoff of the Return Vehicle. What should have been a routine test in this part of the mission was looming as a potential crisis.
On arrival they had discovered that it was damaged. A failure in the aero-braking maneuver made the Return Vehicle come in a shade too fast, crushing fuel pipes and valves around the engines. None of the diagnostics had detected this, since the lines were not pressured. In some instances the damage went beyond mere repair and Raoul had been forced to refashion and build from scratch several of the more delicate parts. Working with Earthside engineers, he had been steadily making repairs.
In this he drew upon not only his technical training, but his family's tradition of Mexican make-do. His father and uncle ran a prosperous garage in Tecate, just below the U.S. border. He'd grown up in greasy T-shirts with a wrench in his hand. Coming from a country with a chronic shortage of hard goods meant that "recycle and reuse" was not just a slogan but a necessity. Raoul was good at creative reuse, making novel pieces fit, but never before had he worked under this kind of pressure. Their return, and quite possibly their lives, depended on his repairs.
They ended the transmission on an edgy note. It was 13 days and counting to launch.

* * * * *

There was plenty of grunt labor to get ready for the liftoff test. Gear they had used on the repairs, supplies dumped months ago while in a hurry, scrap parts—all had to be hauled away from the Return Vehicle. On the long glide back to Earth, every kilogram extra they carried made their fuel margin that much slimmer, and it wasn't that fat to begin with.
Ann didn't mind the heavy labor. The low gravity helped but the laws of inertia still governed. Man-handling gear into the unpressured rovers to stow it for the next expedition at least gave her a chance to think; simple jobs didn't absorb all her concentration. That was when all her frustrations surfaced and she decided to do some pushing of her own.

* * * * *

After the usual heavy-carbo lunch she found Marc in the hab's geology lab, packing a core for transport.
"What do we do now?" she asked, "Just you and me?"
Their last, long expedition in the rover was out—that much was clear. Safety protocols demanded two in the rover, and both mechanics, Raoul and Piotr, had to be working on the Return Vehicle. Marc was the backup pilot, so he would be needed to help Piotr, at least through the liftoff trial.
"You're going to tell me, right?" He grinned.
"I'm not going to sit around twiddling my thumbs on my last two weeks on Mars."
Marc said crisply, "You can't go out for a week by yourself, Ann."
"I know. Come with me, Marc. There's just enough time left for a vent trip."
The extensive Return Vehicle repairs had cut into all their schedules. For the week-long rover trips, mission protocol decreed that one of the pair be a mechanic—Raoul or Piotr. When the two of them were tied up with Return Vehicle repairs, Ann and Marc were restricted to day trips in the rover. Marc had filled his time setting off lots of small seismic blasts, and was surprised to discover extensive subterranean caverns several hundreds of meters down. So far they hadn't found a way in to any of them, and Ann knew Marc was itching to get down there.
Marc looked doubtful. "You did that already. I thought we agreed it was a bust. No life or fossils."
"Yes, but we picked a vent that was outgassing remnants of atmosphere—it had oxygen in the mix."
"So? We were looking in the most likely place for life."
"For Earth life, and ancient Mars life, but not modern Mars life. Oxygen is most likely poisonous to the organisms we're looking for."
Marc frowned, distracted by his chore. "Why so?"
"About four billion years ago, Earth's atmosphere was a byproduct of the early photosynthetic microbes…precursors of plants. They succeeded by learning how to make their own food, and by poisoning the competition, the anaerobes, with their wastes."
"Oxygen?"
"Right!" Ann nodded vigorously, caught up in her vision. "On Earth, anaerobes went underground or underwater to get away from the poisonous oxygen atmosphere. Here on Mars, oxygen-using forms would have been eliminated when the planet lost its atmosphere. Maybe it's their descendants under the soil, living off the peroxides. But the anaerobes only had to fight the cold and drought. They must have followed the heat and gone underground."
"Where d'you want to look?"
"The big vent about 55 klicks to the north is the closest."
Marc said, "We could maybe manage a few days in the rover, no more."
"Good enough. I'll start packing."
"Not so fast. We've all got to agree."

* * * * *

Raoul shook his shaggy head. All the men were letting their hair grow out to the max, then would shear it down to stubble just before liftoff, including beards. The "Mars Bald" look, as Earthside media put it, went for Ann, too. In the cramped hab of the return vehicle, shedding hair was just another irritant. If it got into their gear, especially the electronics, it could be dangerous. He gestured at the injured Piotr. "Without him, we'll take longer to complete checkout. Marc, I know it's not your job, but I'll need both you and Ann to help. I want to eyeball every valve and servo in the undercarriage."
"Okay, I can see why you need all of us for that. But once it's done—"
"Until we've done the liftoff, planning is pointless," Piotr said in a voice that reminded them all that he was, broken ankle or not, the commander. So far he had not needed to throw such weight around. Ann shot him a look and saw in his face the man who was the commander/mechanic first and her husband second. Which was as it should be at this moment, she knew, even if a part of her did not like such facts right now. She said slowly, "I have a quick run we could do."
Piotr called from his bunk, "For jewels, I hope."
She grimaced. Piotr was deeply marked by the bad years in Russian space science following the collapse of the Communist economy. She recalled his saying, "In those dark years, the lucky ones were driving taxicabs, and building spaceships on the side. The others just starved." Not only research suffered. Some years there had been no money, period. Faced with no salaries, staff members in some science institutes found new ways to raise money, sometimes by selling off scientific gear, or museum collections. It was like her grandparents, who had grown up during the Great Depression; they couldn't get money far from mind. So Piotr made a fetish of following Consortium orders about possible valuable items: he scrounged every outcropping for "nuggets," "Mars jade," and anything halfway presentable. They all got a quarter of the profits, so nobody griped. Still, Piotr's weight allowance on the flight back was nearly all rocks—some, she thought, quite ugly.
"No, for science."
Piotr gave her a satirical scowl.
"Your vent idea." Raoul eyed her skeptically.
"There are three thermal vents within a hundred kilometers. I want to try the closest one, to the north."
"We've studied their outgassing, the whole area around them," Marc said. The Consortium wanted information on water and oxygen; they could use it on later expeditions, or sell the maps to anyone coming afterward.
Raoul shook his head, scowling. "We've already got one injury. And we've looked in one vent already. Crawling down more holes isn't in the mission profile."
"True, but irrelevant," she said evenly. Raoul was the tough one, she saw. Piotr would support her automatically, though grumpily, if she could fit her plan into mission guidelines. Marc, as a geologist, had a bias toward anything that would give him more data and samples.
"It's too damned dangerous!" Raoul suddenly said.
"True," Marc said. "We could use our seismic sensors to feel if there are signs of a venting about to occur, though, and—"
"Nonsense," Raoul waved away this point. "Have you ever measured a venting?"
"Well, no, but it cannot differ greatly from the usual signs on Earth—"
"We do not know enough to say that."
She had to admit that Raoul was right in principle; Mars had plenty of nasty tricks. It certainly had shown them enough already, from the pesky peroxides getting in everywhere—even her underwear!—to the alarming way seals on the chem factory kept getting eaten away by mysterious agents, probably a collaboration between the peroxide dust and the extreme temperature cycles of day and night. "But our remote sensing showed that venting events are pretty rare, a few times a year."
"Those were the big outgassings, no?"
"Well, yes. But even so, they are low density. It's not like a volcano on Earth."
"Low density, but hot. Our pressure suits do not provide good enough insulation. I believe we all agree on that."
This provoked rueful nods. The biggest day-to-day irritant was not the peroxides, but the sheer penetrating cold of Mars. Raoul's style was to hedgehog on the technicals, then leap to a grand conclusion. She got ahead of him by not responding to the insulation problem at all, but going to her real point. "The vents must be key to the biology."
"We have done enough on biology," Raoul said adamantly.
"Look—"
"No," he cut her off with a chop of his hand, the practical mechanic's hand with grime under the fingernails. "Enough."
And they all had to agree. In Raoul's set jaw she saw the end of her dreams.

* * * * *

The liftoff test came after two days of hard labor. They had been burning methane with oxygen in the rovers for more than five hundred days, but that was with carbon dioxide to keep the reaction heat down, acting like an inert buffer much as nitrogen did in the air of Earth. But the Return Vehicle boosters would burn at far higher temperature. The many engineering tests said the system would withstand that, but those were all done in comfortable labs on Earth. And they did not use a system that had ruptured on landing and that Raoul had labored month after month to repair.
A warning call from Raoul made her crouch down. They had decided that this test liftoff, just to see if anything blew a pipe, would have only Raoul and Piotr aboard. Piotr could run the subsystems fine from his couch. She and Marc took shelter a few hundred meters away, ready to help if something horrible happened. The stubby Return Vehicle stood with its chem systems detached and gear dragged away, looking a bit naked against pink soil as thoroughly trod as Central Park in Manhattan, and with more litter.
She and Marc had nothing to do but pace to discharge all their adrenaline. The damned cold came through her boots as always and she stamped them to keep the circulation going. Even the best of insulation couldn't keep the cold from penetrating through the soles of the boots. It was early morning, so they would have a full day of sunlight to make repairs. She seldom came out this early into the biting hard cold left over from the night. Quickly enough they had learned the pains of even standing in shadow, much less of Martian night—skin stuck to boot tabs, frostbite straight through the insulation. Raoul's limp resulted from severely frostbitten toes after hours of making repairs in the shadow of the Return Vehicle.
She closed her eyes, trying to relax. They were about to land on Mars for the second and last time; think of it that way. Such odd ways of taking each moment, relieving it of its obvious heart-thudding qualities, had sustained her through the launch from Earth and their aerobraking. Months of tedious mission protocols and psychological seminars had given her such oblique skills.
"Ready," she heard Raoul through the suit com. "Starting the pumps."
Piotr responded with pressure readings, flow rates. She saw a thin fog form beneath the rocket nozzle, like the vapors that sometimes leaked from the soil as the sun first struck it.
More cross-talk between the pilots. Their close camaraderie had been so intensive the past few days that she and Marc felt like invisible nonentities, mere "field science" witnesses to the unblinking concentration of the "mission techs," as the terminology went. Then Raoul said, almost in a whisper, "Let's lift."
A fog blossomed at the Return Vehicle base. No gantry here, nothing to restrain it. The conical ship teetered a bit, then rose.
"Nice throttling!" Marc called.
"Wheeeee!" Ann cheered.
The ship rose 20 meters, hung—then started falling. A big plume rushed out the side of the ship. Crump! came to her through the thin atmosphere. A panel blew away, tumbling. The ship fell, caught itself, fell another few meters—and smacked down.
"All off!" Raoul called.
"Pressures down," Piotr answered, voice as mild as ever.
"My God, what—?"
Then she started running. Not that there was anything she could do, really.

* * * * *

At least the damage was clear. The panel had peeled off about a meter above the reaction chamber. Inside they could see a mass of popped valves.
"Damn, I built those to take three times the demand load," Raoul said.
"Something surged," Piotr said. "The readout shows that."
"Still, the system should have held," Raoul insisted, face dark.
"Over pressure was probably from that double line we made," Piotr said mildly.
"Ummm." Raoul bit his lip; she could see his pale face through his helmet viewer and wondered if he felt defeated. Then he nodded briskly. "Probably right. We should check with the desk guys, but I'll bet you're right."
"The double line was their idea."
"Right, Piotr. We'll go back to the original design."
Somehow this buoyed them. It had to, she reflected. Either they get the system working or they wouldn't dare lift. The Airbus crew would rescue them, maybe, getting the glory and the 30 billion dollars.
"Should I contact Ground Control now, or wait until you get back to the hab?" Marc asked.
"They control nothing," Raoul said. "We're in control."
"Is damned right," Piotr said, laughing in a dry way.
"Okay." She grinned uncertainly and Marc followed suit.
"I suppose we should wait, talk to Earthside before we pull anything out and start refitting," Raoul said.
Piotr's voice crackled in the radio, his accent more noticeable. "Nyet, nyet, no waiting. You do it. And Marc, tell them, the Airbus—we may need their wessel to get home."

* * * * *

She brought up the unthinkable as a way of edging her way around to her own agenda. What the hell, they were all exhausted from laboring on the repairs, and it had been three days. They were nearly done. Time to think the unthinkable again.
Ann turned to Marc. "Okay, suppose we can't get off at all. We've got months until Airbus gets here. What do you think we could do with the highest impact?"
Marc looked surprised. Nobody answered for a very long time. She could see in their faces a vast reluctance to face this issue. But they had to. Finally Marc said slowly, "Geology, maybe."
Piotr laughed sourly. "Scratch scientist, find fanatic. Geology we have plenty. A cold dry desert with red rocks and ancient water erosion. Not much better than the Viking pictures."
Raoul said reasonably, "Ann, this is an old argument. Of course the Viking landing spots were purposely picked to be flat and boring and dry. Not the best places to look for life, but the safest to land. Now we know Viking could never, anywhere on Mars, have found your microbes that retreated to their little layer when the seas and lakes dried up."
"Over a billion years ago, I estimate," Marc put in.
"We don't know that the microbe retreat model is the only one," she said.
Piotr called, "Ah, your new version of the old Sagan argument. While Viking was licking dust into the biology experiments, an undetected Martian giraffe walked by on the other side of the lander."
Ann bristled but did not show it. Sometimes she wondered if Piotr had to occasionally show that he was not just her husband, and thus an automatic ally. "I'm not really expecting Earth-type animals, but I'm keeping an open mind about other possibilities."
Marc blinked. "You really think we'll find more than microbial life in a vent?"
"I certainly think we should look. We're probably never going to be here again, any of us." She looked around at them. "Right?"
This they had never discussed. In some ways the surface mission was the least risky part of the expedition, the first four-fifths in days spent but not in danger. Their coming launch was risky, and the aerobraking into Earth's atmosphere would be more tricky than their rattling deceleration in the comparatively soft Martian atmosphere. Still, the sheer wearing-down of their labors in the harsh cold dryness of Mars had sobered them all somewhat. When they returned home—or if—they would be wealthy, famous. Would they do this again?
"I might come back," Marc said.
"I, too," Raoul said, though without the conviction he had before.
"I am honest enough to say that I will not," Piotr said, grinning at them. "I will have a wealthy wife, remember."
They all laughed, maybe more than the joke deserved. The laughter, after a filling meal, served to remind them that they were a team, closer than any contracts could bring them. This was a highly public, commercial enterprise, of course, but none of it would work without a degree of cooperation and intuitive synchronization seldom demanded anywhere.
Ann looked at the others, their clothes emblazoned with the logos of mission sponsors, all quite soiled. Through the Consortium's endless marketing they had endorsed a staggering array of products. They were destined to be a team forever, no matter what happened in the future.
Marc said, "The metals, that's why I'm here. They'll be more important than life, in the long run."
Piotr: "I disagree. The asteroid belt is where we will go for metals. Mars is where we build a base to mine the asteroids. Going to be much cheaper to boost from here than anyplace else."
Raoul appeared from the pint-sized galley toting a bulb of coffee. "So we've just wasted our time looking for metals on Mars? Suits me. If we jettisoned all of the damned ore samples there'd even be room to breathe on the return."
Ann said, "We shouldn't be limited by what we think we know. Or what we think we're going to find. A biologist named Lovelock pointed out before the Viking landings that there was probably no life because the atmosphere was in chemical equilibrium with the surface. Spectroscopy from Earth showed plainly that there was nothing in it but boring CO2 and nitrogen."
"Good argument, you have to admit," Marc said.
"But it assumed life would use the atmosphere as its buffering chemical medium. Unlikely, because it's so thin…
"That's what we found." Marc looked puzzled. They were co-authors on the microbial Nature paper, but they all knew the major work was hers.
"Other life may have many ways of holding on deep underground. We can't reach it except through the vents."
When her news of life was beamed to Earth, the public had chewed over it, and decided that it was not all that exciting. Just a bunch of microbes, after all. The deeper issue of its relationship to Earth life had to wait until they got the samples home. Until then, the issue was the province of learned talking heads chewing over the implications. Time for that later.
They had been through all of this before, of course. In the course of two years you get to know each other's views pretty damn well, she reflected, and Raoul had his set look, jaw solid and eyes narrowed, already announcing his position.

* * * * *

The second liftoff trial was grim. Their lives were riding on the plume of scalding exhaust. She fidgeted with the microcams—Earthside wanted four viewpoints, supposedly for engineering evaluation, but mostly to sell spectacular footage, she was sure.
"Let's go," Raoul called in a husky whisper.
The vehicle rose on a column of milky steam. The methane-oxygen burn looked smooth and powerful and her heart thudded as the ship rose into the burnt-blue sky. It was throttled down nicely, standing on its spewing spire as Raoul and Piotr made it hover, then drift sideways, then back.
"All nominal," Piotr said, clipped and tight.
"Control A 16 and B 14 integrated," Raoul answered. "Let's set her down."
And down they came, settling on the compressed column. The ship landed within 10 meters of the damp smear that marked the takeoff.
"Throttle down," came from Piotr in a matter-of-fact voice she did not believe for a minute.
Then she was running across the rocky ground, feet crunching, her cheers echoing in her helmet along with all the others, tinny over the com.

* * * * *

Celebration. Extra rations; they even ate the last Ego Bar. Joyful calls from Earth. The laconic way Piotr told the Airbus people that they would not be needing a ride home after all…
Then the next morning. Assessment.
Now they had five days until liftoff and it stretched like forever. The rush to do the second test had kept them at it 16 hours a day, pouring their anxious energy into the other preflight procedures. After two years they functioned smoothly together, anticipating one another's needs wordlessly. The efficiency of true teamwork bore fruit: Now they were ahead of schedule. Ann worked alongside them and judged their mood and dreamed her own dreams. Home! The call of it was an ache in the heart. The cool green hills of Earth…
Still, she could not let go her own itchy ideas. She lay beside Piotr in the cold darkness and thought.
Leaving Mars…
Behind her she felt the yearning of millions, of a whole civilization reaching out. Why had the issue of life here come to loom so large in the contemporary mind? It dominated all discussions and drove the whole prize-money system. Piotr and Raoul thought economic payoffs would be the key to the future of Mars, but they were engineers, bottom-line men, remorselessly practical. Just the sort you wanted along when a rocket had to work, but unreliable prophets.
She suspected that the biologists were themselves to blame. Two centuries before they had started tinkering with the ideas of Adam Smith and Thomas Malthus, drawing the analogy between markets and nature red in tooth and claw. The dread specter of Mechanism had entered into Life, and would never be banished after Darwin and Wallace's triumphal march across the theological thinking of millennia. God died in the minds of the intellectuals, and grew a rather sickly pallor even among the mildly educated.
All good science, to be sure, but the biologists left humanity without angels or spirits or any important Other to talk to. Somehow our intimate connection to the animals, especially the whales and chimps and porpoises, did not fill the bill. We needed something bigger.
So in a restless, unspoken craving, the scientific class reached out—through the space program, through the radio-listeners of the Search for Extraterrestrial Life—for evidence to staunch the wound of loneliness. That was why their discovery of microbes satisfied no one, not even Ann. Mars had fought an epic struggle over billions of years, against the blunt forces of cold and desiccation, betrayed by inexorable laws of gravitation, chemistry and thermodynamics. Had life climbed up against such odds, done more than hold on? To Ann, survival of even bacteria in such a hellish dry cold was a miracle. But she had to admit, it left an abyss of sadness even in her. And there was still time…

* * * * *

Morning. Four days to go. Over breakfast Ann signaled to Marc, took a deep breath, and made her pitch. The last few days' hectic work had pushed them hard. More than that, it had nudged them across an unseen boundary in their feelings toward the trip. Despite what Marc and Raoul had said about returning, they all realized that this was a one-time experience. Once they left it would be all over.
Raoul looked up. "The vent trip again? I thought we laid that to rest. You didn't find anything the first time."
"Absence of evidence is not evidence of absence," she shot back.
Raoul frowned, "Besides, there isn't time. We're not packed up yet."
"We're ahead of schedule," said Ann.
Piotr cut in quickly. "Under normal circumstances, yes." He gestured at his cast. "With this, I'm clumsy. It takes longer to do everything." He looked at Ann. "I need your help."
They all knew that a public admission of weakness cost him a lot, and it touched her, but she was determined not to be swayed. She refused to meet his eyes. Damn. Why did women always have to choose? He never would've asked that of a man.
In an impassioned tone, she used her Columbus argument—how could they go home when there was the chance they had only nibbled at the edges of discovery?
Marc came to her rescue. After days of grunt work, the scientist in him yearned for this last chance as much as she did. "We can do it in two days. We'll work here tomorrow morning, drive to the site and set up the pulleys by nightfall. Next day we'll explore the vent and come back. That gives us a full day to finish up here before liftoff." He looked at Piotr and Raoul. "We feel we have to do this."
Technically, the two scientists could amend mission plans if they felt it was warranted. Clearly they would do so this time.
Raoul looked pensive. "I want to go over the thruster assembly again. Something might need adjustment after the burn we just did." He hurried on, "But I can do it alone."
In a flash Ann understood that Raoul wished to take responsibility for the repairs, needed to have time alone with his handiwork. He would be just as happy not to have two itchy scientists underfoot. Then he could take as much time as he liked, obsess over every detail.
There was a long moment. They skirted the edge of a rift. Finally Piotr nodded agreement. He had followed Ann's arguments carefully, hoping to be convinced. Now he snapped back into mission commander mode. "Da. All right. Two days only."
Ann's heart soared. She flashed him a brilliant smile, leaned over and, ignoring mission discipline, gave him a big kiss. Spending one final night in a hellishly cold rover would be the price, but well worth it. She was going to explore the vent at last!

PART 3

She woke to the bitter tang of black Colombian perking in the pot, the scent mingling with a buttery aroma of pancakes, the sizzle of bacon in its lake of fat, all lacing in their steamy collaboration to make a perfect moist morning—
And then she snapped awake, really awake—on the hard rover bunk, hugging herself in her thermoelectric blanket. Once all her waking dreams had been about sex; now they were about food. She wasn't getting enough of either, especially not since Piotr's ankle.
The break would heal by the time they were on the long glide Earthward; their rations would not improve until they were back eating steak. She pushed the thought of meat out of her mind and sat up. First feelers of ruddy dawn laced a wisp of carbon dioxide cirrus high up; good. Today she got to burrow, at last.
"Hey, Marc! I'll start the coffee."
No dallying over breakfast, though the hard cold that came through the rover walls made her shiver. A ruddy sunup was just breaking, giving them one final day of exploration. She peered out the viewport as she munched. They would run on in-suit rations today, no returning to the Spartan comforts of the rover.
They had set up the cable rig at the edge of the vent before sundown. By early light it still looked secure, anchored to three boulders. Marc didn't trust the soil here to hold so they had arranged cross-struts of their monofilament-based cabling to take their weight as they went down the steep incline. Metal cable was much too heavy to fly to Mars, and not necessary under the lighter gravity.
The first part was easy, just backing over. The rock was smooth and of course dry. Even if vapor had spouted last night, it would never condense for long. The Martian atmosphere was an infinite sponge.
The vent snaked around and steepened as the pale light of late dawn from above lost out to the gloom. The rock walls were smooth and still about 10 meters wide. They reached a wide platform and the passage broadened farther. Every 10 meters down they checked to be sure the cable was not getting fouled. They were both clipped to it and had to time their movements to keep from getting snarls.
They edged along the ledge cautiously, headlamps stabbing into the darkness. She was trying to peer ahead but her eyes were cloudy for some reason. She checked her face-plate but there was no condensate on it; the little suit circulators took care of that, even in the cold of full Martian night. Still, the glow from Marc's suit dimmed.
"Marc, having trouble seeing you. Your lamp die?"
"Thought I was getting fogged. Here—" He clambered over on the steep slope of the ledge and shone his handbeam into her face. "No wonder. There're drops of something all over your face-plate and helmet. Looks like water drops!"
"Water…?"
"We're in a fog!" He was shouting.
She saw it then, a slow, rising mist in the darkness. "Of course! It could be a fog desert in here."
"A what?"
"Ever been out in a serious fog? There's not much water falling, but you get soaked anyway. There are deserts where it doesn't rain for years, like the Namib and the coast of Baja California. Plants and animals living there have to trap the fog to get water." She thought quickly, trying to use what she knew to think about this place. In fact, frogs and toads in any desert exploited a temperature differential to get water out of the air even without a fog. When they came up out of their burrows at night they were cooler than the surrounding air. Water in the air condensed on their skin, which was especially thin and permeable.
Ann peered at the thin mist. "Are you getting a readout of the temperature? What's it been doing since we started down?"
He fumbled at his waist pack for the thermal probe, switched it to readout mode. "Minus 14, not bad." He thumbed for the memory and nodded. "It's been climbing some, jumped a few minutes ago. Hm. It's warmer since the fog moved in."
They reached the end of the ledge, which fell away into impenetrable black. "Come on, follow the evidence," she said, playing out cable through her clasps. Here the low gravity was a big help. She could support her weight easily with one hand on the cable grabber, while she guided down the rock wall with the other.
"Evidence of what?" Marc called, grunting as he started down after her.
"A better neighborhood than we've been living in."
"Sure is wetter. Look at the walls."
In her headlamp the brown-red rock had a sheen. "Enough to stick!"
"I can see fingers of it going by me. Who woulda thought?"
She let herself down slowly, watching the rock walls, and that was why she saw the subtle turn in color. The rock was browner here and when she reached out to touch it there was something more, a thin coat. "Mat! There's a mat here."
"Algae?"
"Could be." She let herself down farther so he could reach that level. The brown scum got thicker before her eyes. "I bet it comes from below."
She contained her excitement as she got a good shot of the scum with the recorder and then took a sample in her collector rack. Warmer fog containing inorganic nutrients would settle as drops on these cooler mats. Just like the toads emerging from their burrows in the desert? Analogies were useful, but data ruled, she reminded herself. Stick to observing. Every moment here will get rehashed a million-fold by every biologist on Earth…and the one on Mars, too.
Marc hung above her, turning in a slow gyre to survey the whole vent. "Can't make out the other side real well, but it looks brown, too."
"The vent narrows below." She reeled herself down.
"How do they survive here? What's the food source?"
"The slow-motion upwelling, like the undersea hydrothermal vents on Earth?"
Marc followed her down. "Those black smokers?"
She had never done undersea work but was of course aware of the sulfur-based life at the hydrothermal vents. Once it was believed that all life on Earth depended on sunlight, trapped by chlorophyll in green plants and passed up the food chain to animals. Then came the discovery of sunlight-independent ecosystems on the ocean floor, a fundamental change in a biological paradigm. The exotic and unexpected vent communities were based on microbes that harnessed energy from sulfur compounds in the warm volcanic upwelling. Meter-long tube worms and ghostly crabs in turn harvested the bacteria. The vent communities on earth were not large, a matter of meters wide before the inexorable cold and dark of the ocean bottom made life impossible. She wondered how far away the source was here.
In the next 50 meters the scum thickened but did not seem to change. The brown filmy growth glistened beneath her headlamp as she studied it, poked it, wondered at it.
"Marsmat," she christened it. "Like the algal mats on Earth, a couple of billion years ago."
Marc said wryly, puffing, "We spent months looking for fossil evidence, up there in the dead sea beds. The real thing was hiding from us down here."
The walls got closer and the mist cloaked them now in a lazy cloud. "You were right," Marc said as they rested on a meter-wide shelf. They were halfway through their oxygen cycle time. "Mars made it to the pond scum stage."
"Not electrifying for anybody but a biologist, but something better than individual soil microbes. It implies a community of organisms, several different kinds of microbes aggregated in slime—a biofilm." She peered down. "You said the heat gradient is milder here than on Earth, right?"
"Sure. Colder planet anyway, and lesser pressure gradient because of the lower gravity. On Earth, 1 klick deep in a mine it is already 56 degrees C. So?"
"So microbes could probably survive farther down than the couple of klicks they manage on Earth. They're stopped by high heat."
"Maybe."
"Let's go see."
"Now? You want to go down there now?"
"When else?"
"We're at oxy turnaround point."
"There's lots in the rover."
"How far down do you want to go?"
"As far as possible. There's no tomorrow. Look, we're here now, let's just do it."
He looked up at his readouts. "Let's start back while we're deciding."
"You go get the tanks. I'll stay here."
"Split up?"
"Just for a while."
"Mission protocol—"
"Screw protocol. This is important."
"So's getting back alive."
"I'm not going to die here. Go down maybe 50 meters, tops. Got to take samples from different spots."
"Piotr said—"
"Just go get the tanks."
He looked unhappy. "You're not going far, are you?"
"No."
"OK then. I'll lower them down to the first ledge if you'll come back that far to pick them up. Then I'll come down, too."
"OK, sounds fine. Let's move."
He turned around and started hauling himself up the steep wall. "Thirty minutes, then, at the first ledge."
"Yeah, fine. Oh, and bring some batteries, too. My handbeam's getting feeble."
"Ann…"
"See you in 30 minutes," she said brightly, already moving away. Marc kept going. The slope below was easy and she inched down along a narrow shelf. Playing out the cable took her attention. Methodical, careful, that's the ticket. Especially if you're risking your neck deep in a gloomy hole on an alien world.
She felt a curious lightness of spirit—she was free. Free on Mars. For the last time. Free to explore what was undoubtedly the greatest puzzle of her scientific life. She couldn't be cautious now. Her brother Bill flashed into her mind. He took life at a furious pace, cramming each day full, exuding boundless energy. They went on exploring trips together as children, later as nascent biologists. He was unstoppable: up and out early, roaming well after dark. There was never enough time in the day for everything he wanted to see. "Slow down, there's always tomorrow," people would tell him.
But his internal clock had served him well, in a way. He was cut down at age 22 when his motorcycle slid into a truck one rainy night when sensible people were home, warm and dry. Looking around the church at his funeral, Ann felt he'd lived more than most of the middle-aged mourners. Bill would've approved of her right now, she was sure.
A flicker from her handbeam brought her back. She looked down, shook it. The beam brightened again. Damn, not now.
The mat was thicker here, as she'd guessed it would be closer to the elusive source.
She landed on a wide ledge, moved briskly across it, mindful of time passing. The floor was slippery with Marsmat but rough enough so she could find footing. Sorry, she said silently to the mat, but I've got to do this.
Her handbeam flickered again, died. She shook it, bent her head to look at it with the headlamp, then felt a sudden hard blow to her forehead, heard the headlamp shatter. She fell backward, in slow-motion but inexorably, nothing to grab.
Her wrist hit first as she landed and she dropped the handbeam. She lay there for a moment, waiting for the surprise to go away. Must've run into an overhang. It was pitch dark. Where was her damned lamp? There was a faint glow to her left. That must be it. She started to get up, noticed a feeble luminescence ahead of her. Confused, she sat back down. Take this carefully.
All around her, the walls had a pale ivory radiance.
She closed her eyes, opened them again. The glow was still there.
—No, not the walls—the Marsmat. Tapestries of dim gray luminosity.
She reviewed what bits she remembered about organisms that give off light. This she hadn't boned up on. Fireflies did it with an enzyme, luciferase, an energy-requiring reaction she had done in a test-tube a few thousand years ago in molecular bio lab. Glow worms—really fly larvae, she recalled—hung in long strands in New Zealand caves. She remembered a trip to the rainforest of Australia: Some tropical fungi glow in the dark. Hmm. Will-o'-the-wisps in old graveyards, foxfire on old wooden sailing ships…could there be fungi here? Unlikely. Wrong model. She shook her head. Waves breaking at night into glowing blue foam during red tides in California. Those are phosphorescent diatoms. What else? Thermal vent environments…
Deep sea fish carried luminescent bacteria around as glowing lures. That's it. The lab folks had fun moving the light-producing gene around to other bacteria. Okay. So microbes could produce light, but why here? Why would underground life evolve luminescence?
Bing bing. The warning chime startled her out of her reverie. She flicked her eyes up. The oxygen readout was blinking yellow. Thirty minutes reserve left. Time to go back.
As she picked herself up she brushed against her handbeam. She picked it up but left it off. Navigating by the light of the walls was like hiking by moonlight.
Pulling herself up gave her time to think, excitement to burn in muscles that seemed more supple than usual. Yes, it was warmer here. She turned her suit heater down. Life hung out in the tropics.
Before she reached the tanks, she heard Marc's impatient voice. "Ann, where are you?"
"On my way. Pretty close." She rounded a jut in the vent walls, into the glare of his lights. The walls faded into black.
"Where were you? You're way late, damn it. The tanks were here on time—hey, where's your headlamp?"
"Ran into an overhang. Smashed it. Marc—"
"Handlamp too? What'd you do—grope your way back? Why didn't you call?" He was clearly angry, voice tight and controlled.
"I found, I found—"
"Ann, calm down, you're—"
"Turn off your lamps."
"What?"
"Turn off your lamps. I want you to see something."
"First we switch your tank."
She sighed. It was just like Marc to fuss over details. Looking down at the sidewalk for pennies and missing the rainbow.
When she finally got the lamps off he could see it too. There was a long moment of utter shock and he seemed to know it was better to say nothing.
Then she heard something wrong. The faint hissing surprised her. Mission training reasserted itself.
"What's that? Sounds like a tank leaking." Automatically she checked her connections. All tight. "Marc?—check your tank."
"I'm fine. What's the matter?"
"I hear something, like a leak."
"I don't hear anything…"
"Be quiet. Listen." She closed her eyes to fix the direction of the sound. It came from near the wall. She shone her handbeam on the empty tank, bent down low and heard a thin scream. Oxygen was bleeding out onto the Marsmat.
"Damn. Valve isn't secured." She reached down to turn it off. Stopped—"What?"
The Marsmat near the tank was discolored. A blotchy, tan stain.
"Damn! We've damaged it." She knelt down to take a closer look, carefully avoiding putting her hand on the wall.
"What happened?" Marc took one long step over, understood at a glance. "The oxygen?"
"Uh-huh. Looks like it."
"What a reaction. And fast! No wonder there was nothing in the first vent. You were right about that."
"Oxygen's pure poison to these life forms. It's like dumping acid on moss. Instantaneous death."
He looked around wonderingly. "We're leaking poison at them all the time in these suits."
She nodded. Stupid not to see it immediately, really. Like SCUBA gear, their suits vented exhaled gases at the back of the neck, mostly oxygen and nitrogen with some carbon dioxide. A simple, reliable system, and the oxygen was easily replaceable from the Return Vehicle's chem factory.
Marc shook his head, sobered. "Typical humans, polluting wherever we go."
"If the stuff is this sensitive, we'll have to be really careful from now on." Ann straightened up carefully and backed away from the lesion.
They stood for a long moment in inky blackness, letting their retinas shed the afterimage of the lamps. Finally Marc asked, "Where's the light coming from?"
"Marsmat glows. Phosphoresces, is more correct."
"How can it do that?"
"Don't know. The more interesting question is why."

* * * * *

They knew now that time and oxygen would set the limits. They had this day and were to return to the ship tomorrow. Team loyalty.
"Plenty of oxy up there," Marc said as they rested and ate lunch—a squeeze-tube affair she hated, precisely described in one of her intervideos as eating a whole tube of beef-flavored toothpaste.
"So we trade tanks for time."
"Piotr's gonna get miffed if we don't check in at the regular time."
"Let him." She wished they had rigged a relay antenna at the vent mouth. But that would have taken time, too. Tick tick tick.
"I don't want us to haul out of here dead tired, either."
"We'll be out by nightfall."
"We won't be so quick going out."
Field experience had belied all the optimistic theories about working power in low gravity. Mars was tiring. Whether this came from the unrelenting cold or the odd, pounding sunlight (even after the UV was screened out by faceplates), or the simple fact that human reflexes were not geared for 0.38 gee, or some more subtle facet—nobody knew. It meant that they could not count on a quick ascent at the end of a trying day.
"You want geological samples, I want biological. Mine weigh next to nothing, yours a lot. I'll trade you some of my personal weight allowance for time down here."
He raised his eyebrows, his eyes through his smeared faceplate giving her a long, shrewd study. "How much?"
"A kilogram per hour."
"Ummm. Not bad. Okay, a deal."
"Good." She shook hands solemnly, glove to glove. A fully binding guy contract, she thought somewhat giddily.
"Piotr's counting on using some of your allowance to drag back more nuggets and 'jewels,' y'know."
"It's my allowance."
"Hey, just a friendly remark. Not trying to get between you two."
Innumerable nosy media pieces had dwelled on the tensions between a crew, half married and half not, complete with speculations on what two horny, healthy guys would feel like after two years in a cramped hab with a rutting couple just beyond the flimsy bunk partition. All that they had scrupulously avoided.
So far the answer was, nothing much. Raoul and Marc undoubtedly indulged in gaudy fantasy lives and masturbated often (she had glimpsed a porno video on Raoul's slate reader) but in the public areas of the hab they were at ease, all business.
There was no room for modesty in the hab, four people in a small condo for two years. So they unconsciously adopted the Japanese ways of creating privacy without walls. They didn't stare at each other, and didn't intrude on another's private space unless by mutual agreement.
Nobody had thought much about what the hab would be like if the newlyweds—well, it had been well over two years now, most of that time in space—got into a serious spat. Maybe on the half-year flight home they would find out. She would worry about that then; for right now—
"Hey, we're eating into my hard-bought hours."

* * * * *

They returned to the ledge where Ann had her accident, two hundred meters farther in. On the other side of the fortuitous overhang they found a pool covered with slime on a ledge. It was crusty black and brown stuff and gave reluctantly when she poked it with a finger.
"Defense against the desiccation," she guessed.
Marc swept his handbeam around. The mat hung here like drapes from the rough walls. "Open water on Mars. Wow."
"Not really open. The mat flows down, see, and covers this pool. Keeps it from drying out. Saving its resources maybe?"
She scooped out some of the filmy pool water and put it under her hand microscope. In the view were small creatures, plain as day.
"My God. There's something swimming around in here. Marc, look at this and tell me I'm not crazy."
He looked through the 'scope and blinked. "Martian shrimp?"
She sighed. "Trust you to think of something edible. In a pond this small on Earth there might be fairy shrimp, but these are pretty small. And I don't even know if these are animals."
She hurried to get some digitals of the stuff. She scooped some up in a sample vial and tucked it into her pack. Her mind was whirling in elation. She studied the tiny swimming things with breathless awe.
So fine and strange and why the hell did she have to peer at them through a smudged helmet? They had knobby structures at one end: heads? Maybe, and each with a smaller light-colored speck. What?
Could Mars life have taken the leap to animals—a huge evolutionary chasm? These could be just mobile algal colonies—like volvox and other pond life on Earth. Whatever they were, she knew they were way beyond microbes. She bent down over the pool again, shone her handbeam at an angle. The swarm of creatures was much thicker at the edges of the Marsmat—feeding? Or something else?
She couldn't quite dredge the murky idea from her subconscious. The arrangement with the mat was odd, handy for the shrimp. What was the relationship there? Some kind of symbiosis? And how did the swimming forms get to the pool?
They climbed down from the ledge. As they descended, the mist thickened and the walls got slick and they had to take more care. The cable was getting harder to manage, too. She could not stop her mind from spinning with ideas.
On Earth, hydrothermal vent organisms kilometers deep in the ocean photosynthesized using the dim reddish glow from hot magma. The glow becomes their energy source. Could some Martian organisms use the mat glow? Wait a minute—the "shrimp" had eyes! Or did they?
"Marc, did you notice anything peculiar about the shrimp?"
He paused before answering. "Well, I don't know what they should look like. They looked sorta like the shrimp I feed my fish at home."
"Did you notice their eyes?"
"Uh…"
"The knobby ends, those had lighter specks, remember?"
"Yeah, what about them?"
"So you saw them too."
"Why, what's the matter—Oh."
"Right!"
"I see, they shouldn't have eyes."
"Good for you. I'll make a biologist out of you yet. On Earth, cave-dwelling organisms have lost their eyes. Natural selection forces an organism to justify the cost of producing a complicated structure. You lose 'em if you don't use 'em."
"So if they have eyes—"
"On Earth, we'd say they were recent arrivals from a lighted place, hadn't had time to become blind."
"But that's impossible. The lighted parts of Mars have been cold and dry for billions of years. Where would they have come from?"
"I agree. So my next choice is that it's not dark enough here to lose the eyes. But the idea of some kind of transfer with the topside peroxide microbes is worth thinking about."
"That glow is pretty dim."
"To us, maybe. We're creatures from a light-saturated world. Our eyes aren't used to these skimpy intensities. Closest parallel on Earth to these light levels are the hydrothermal vents. There are light-sensitive animals down there, even microbes able to photosynthesize."
"Maybe they're not even eyes."
"They're light-sensitive. The critters clustered under the beam from my 'scope."
"Wow."
"I need more information, but at the very least it suggests that the glow is permanent, or at least frequent enough to give some advantage to being able to see. And that means there should be something that can use the glow as an energy source. Maybe the mat is symbiotic—a cooperation between glowing organisms and photosynthesizers?"
"Yeah…That suggests the glow is primary. What's it for?"
"Don't know, just guessing here."
"Curiouser and curiouser, as Alice said."
"I didn't know boys read Alice in Wonderland."
"It seems to fit what we're doing."
"Down the rabbit hole we go, then."

* * * * *

Below the level of the pool ledge were twisty side channels to the vent. These ran more nearly horizontal, and they explored them hurriedly, clumping along until the ceiling got too low. No time to waste crawling back into dead ends, she figured. They headed back to the main channel and then found a broad passage that angled down. It was slick and they had to watch their footing.
The mats here were like curtains, hanging out into the steady stream of vapor from the main shaft of the vent. Some seemed hinged to spread before the billowing vapor gale. Ann was busy taking samples and had only moments to study the strange, slow sway of these thin membranes, flapping like slow-motion flags. "Must be maximizing their surface area exposed to the nutrient fog," she guessed.
"Eerie," Marc said. "And look how wide they get. There's a lot of biomass here—wonder if any of it's edible."
At turns in the channel the mats were the size of a man. She took a lot of shots with her microcam, hoping they would come out reasonably well in their lamp beams. The mats were gray and translucent. Under direct handbeam she could see her hand through one.
How did these fit in with the peroxide-processing microbes on the surface? Clearly these mats harvested vapor; did they somehow trade it with the peroxide bugs, water and methane for the racy stim of peroxide? She had a quick vision of an ecosystem specialized to use what it had: peroxides aplenty above, and ice below, awaiting a lava flow to melt it.
Did life negotiate between these resource beds? Oxides cooked by the searing sun, with microbes specialized to gather their energy. Those microbes must  have evolved after the great dryness came, when UV sizzled down and drove deeper all that could not adapt to it.
Yet below, where water still lurked, dwelled forms that owed their origin to the warm, moist eras of the Martian antiquity.
The mats—and what else, in such labyrinths as this, all around the globe?—transacted their own business with the peroxide eaters. They could harvest the moisture billowing from heat below, and perhaps melt the permafrost nearby. At the edges of Earth's glaciers lived plants that actually melted ice with their own slow chemistry.
The thermal vents and their side caverns could be extensive. With an exposed surface area as big as Earth's, there was plenty of room for evolution to experiment.
Nothing like this pale ivory cavern on Earth, ruled as it was by boisterous, efficient aerobic life. To escape the poisonous reach of oxygen, anaerobes retreated to inhospitable niches like hot springs and coal mines. In that infertile ground they survived, but remained as microbes, spawning no new forms. On Mars, any oxygen-loving forms would have died out when the planet lost its atmosphere. Here the anaerobes persisted, and evolved new forms; maybe the closest analogy was to the marsupials in Australia. Marsupials breed more slowly than true placental animals, and thus were eliminated all over the Earth except for the huge island of Australia. Free of competition, they populated an entire continent, evolving completely unique forms such as kangaroos, wombats and the duckbilled platypus. What were the equivalents on Mars?
Ann gently caressed a mat as it lazily flowed on the vapor breeze. Plants, flourishing in the near-vacuum. She could never have envisioned these…
Yet in the edges of her vision she sensed something more. She thought for a moment and said, "Turn off your lamps."
"Mine's getting pretty low," he remarked as they plunged into blackness.
The glow gradually built up in their eyes. "There's a lesion on the closest mat," said Marc.
She swung gently over, peered at it. "It's the same shape as the damage we did above." The mat around the wound shape glowed more brightly with pale phosphorescence. It seemed to be changing as she watched. "Look at it out of the corner of your eye," she said. "See?"
"It's spreading downwards."
The mats were growing ever larger as they went lower. She leaned over into the vent and peered around. "The glow increases below." They looked down the vent.
"It's definitely brighter down there."
"Let's go." They descended carefully, playing out line. Their lamps washed the mats in glare that seemed harsh now. Twenty meters down she said, "Lamps off again," as they rested on a shelf.
When her dark vision came back her eyes were drawn to a splotch of light. "Damn! How—?"
"It's the same shape again."
"A mimicking image. Parrots imitate sounds, this mat imitates patterns imposed on it, even destructive ones. Why?"
He drawled, "I'd say the question is, how the hell?"
"The mat here learned about the wound above."
"Okay, they're connected. But why the same shape?"
She sighed. "It's a biological pictograph. I have no idea why, but I am sure that any capability has to have some adaptive function."
"You mean it has to help these mats survive."
"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 up-welling 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 irretrievably 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 pre-positioned 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 lockstep 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 mat—those 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.
Somehow, she knew intuitively, the anaerobes had done it. They had evolved an intricate network. Peroxide eaters somehow traded with the harvesters of vapor. And they communicated—surely, for why else would they evolve light signaling?
The pearly lance, jutting up: A signal? A celebration? A mating dance? With so much energy expended, there must be some purpose.
It was natural to see it as a pointed message, but there are many behaviors in biology that defy easy logic. She knew what she would like to believe, but…Science is a systematic way to avoid fooling yourself, after all.
So much to guess…

* * * * *

They were three weeks out before Ground Control sent the liftoff pictures from the microcams she had positioned. One had pointed nearly north, along their trajectory. The rocket plume had blazed across the hard blackness and then vanished from the cam's fixed view. But the cam kept on recording because there was still something to see.
They had caught it. The ivory plume, towering kilometers into the sky, mingling with the gleaming stars.
What's this?—Earth wanted to know.
She smiled. Memory was always tricky, unreliable. That was why they trained you to observe and sample.
From the spectrum Earthside could tell that the gas was methane and hydrogen, with some sulfur. Useful stuff. But—what's this?
She knew then that she would return. Let Piotr sit in his estates, but she was a scientist. There was a whole vast world back there to fathom.
Not the seared surface, but the kilometers-deep labyrinth of ancient refuge.
In that last moment, she sensed, Mars had flashed au revoir, not adieu.

________________________________________
MNQ/2009.10.10
20,000 Words
From The Year's Best Science Fiction, Fifteenth Annual Collection
Gardner Dozois, Editor