Titan n-2

by Stephen Baxter

The system had to cope with three kinds of ionizing radiation, high-energy particles and photons which could knock apart the atoms of the body as they sleeted through it. There was a steady drizzle of solar cosmic rays — the regular solar wind, a proton-electron gas streaming away from the sun, boiled off by the million-degree temperatures of the corona — and galactic cosmic radiation, GCR, a diffuse flood of heavy, high-energy particles from remote stars, even other galaxies, which soaked through the Solar System from all directions. And then, in addition to the steady stuff, there were SPEs — solar proton events, the kind of storm they were suffering now, intense doses of radiation which persisted for short periods, a few hours or days.

  Astronauts tended to think of solar and galactic radiation as career-limiting, and SPEs as life-threatening.

  Discovery’s aluminum shell would shield them from the worst of the effects of GCR, reducing their cumulative six-year dose, anyhow, to maybe three hundred rem. That was high — and significantly increased the risks they all faced of cancer and leukaemia later in life — but within the four hundred rem advisory career limit.

  Of course it meant they wouldn’t be able to sustain another six-year journey home again, without improved shielding.

  But to shelter from an SPE they had to retreat to their storm shelters, either the hab module or the farm, with their heavy plating of aluminum and water tanks clustered around the walls.

  If — just if — Siobhan was caught in the storm, she could expect a dose of a hundred rem. At least. That would give her nausea, vomiting for a day or so, fatigue. And some long-term damage to the more sensitive parts of her body — the gonads, lymphoid tissues.

  If Siobhan was unlucky her dose might rise five times as high.

  And anyhow, there was no safe lower limit, Benacerraf knew. However small the dose, you were at risk.

  To Benacerraf, huddled in her cabin and waiting out the storm from the sun, it felt as if the metal walls of the ship, the elaborate precautions and dosimeters they had taken, counted for nothing, as if Discovery was no more protection than a canvas-walled tent, in this storm generated by huge and remote and impossibly violent events. She had never felt so far from the protective embrace of Earth.

  The Discovery crew truly had stepped outside the farmhouse door.

  In the access tunnel, Libet started awake.

  She could see more flashes, within her eyeballs: little streaks and curves and spirals.

  She knew what that meant, of course: the flashes were caused by heavy particles, lacing into the matter of her eyes. She thought she could feel the radiation sleeting through her, warm and heavy. Those heavy nuclei would be ramming into the molecules of her body, smashing away electrons in little cascades.

  Hard rain, she thought.

  She really ought to open the hatch to the hab module, she thought. But, as she peered up through eyes that were laced with flashes and spirals, it seemed a long way away, and an awful lot of effort. Maybe soon.

  And anyhow she was starting to feel ill. Nauseous, a little giddy, tired. Maybe it was space adaptation syndrome back again.

  And she thought she could smell ozone, like a beach.

  She closed her eyes again, and drifted like a foetus in the air.

  Poor Niki, she thought.

  The flashes and spirals continued, as if a shoal of some tiny fish were swimming through her head.

  * * *

  Day 325

  The blood trickled sluggishly out of Angel’s arm.

  As he tended the donation bag, Rosenberg couldn’t tell what Angel was thinking.

  Bill just didn’t seem the same guy Rosenberg had got to know down on Earth. Floating around up here in the usual semi-foetal position, so many of his gestures and postures had changed: he would never sit with his legs crossed like he used to, or stand with his hands on his hips, or cross his arms… Microgravity had even messed up their body language. Rosenberg just couldn’t read Angel any more.

  It sure didn’t help them all get along, cooped up in here.

  Now Rosenberg watched, irritated, as the clear plastic bag suspended from Angel’s arm slowly filled up. “Clench, God damn it, Bill.”

  Angel’s fist closed harder around the little rubber grip, and the dripping flow of blood accelerated a little. “Fuck you, double-dome. You should be grateful. I got better things to do than bleed myself to death to preserve that shrivelled dyke in there.”

  Paula Benacerraf came out of her quarters and joined them in the common area of the hab module. She looked as if she had been sleeping; her face was slack and baggy, and she was struggling into a grubby T-shirt. They were all wearing stinking, dirty clothes right now, because the laundry was malfunctioning again — clogging and leaking water — and none of them had had the will to fix it. “I think we’ve all heard what you have to say, Bill, a dozen times.”

  “Oh, you have. Then screw you.” Angel pulled the loose bandage off his arm, and began to tug at the needle protruding from his skin.

  Rosenberg said, “Hey, leave that alone. You’re not done.”

  “Yes, I am.” The needle came loose, and Rosenberg hastily swabbed at the puncture wound in Angel’s flesh. Angel glared at him, his eyes wild above his tangle of floating, greyed beard. “This isn’t a goddamn nursing home. We don’t have the resources for this. I say we cut our losses.”

  Rosenberg held up the half-full bag. “Paula, he didn’t complete the donation.”

  Benacerraf looked at him from eyes sunk in pads of puffy flesh. “Make it up from stores, Rosenberg.”

  Rosenberg kicked off the wall and caromed in front of Benacerraf, thrusting the bag in her face. “Don’t you get it? We don’t have any stores. This is all there is.”

  “Make it up,” she said wearily. Without waiting to see if he complied, she pulled herself along the hab module to the waste management facility.

  Angel snorted contempt, and went into his own quarters, slamming the door closed behind him.

  Rosenberg was left alone in the common area, his own anger surging. He threw the bag of blood against a wall. It bounced off, soggily, and began drifting away from him, the viscous blood undergoing complex, slow-motion oscillations.

  After a couple of minutes, his heart still rattling with anger, he scooted along the module to retrieve the blood.

  Rosenberg’s personal theory of Angel was that he was the kind of bad-mouthing asshole who would always bitch at any leadership shown by anybody else, but would always be unwilling to take any real responsibility for himself. He reacted, not acted, and in the meantime made life a living hell for the rest of them stuck here with him.

  But strictly speaking, of course, he was right about Libet.

  Rosenberg was a biochemist, but he was also doubling up as the nearest thing Discovery had to a doctor. He’d done a crash basic medical training program. At the time he hadn’t taken it all that seriously: as the only crew member with any real grounding in the life sciences, he was the logical choice, but somehow he’d never thought he’d have to put any of this into practice.

  But here they were — still inside the orbit of Earth, with a deep space maneuver and their second Venus flyby still to come — and not even one of the six years of the mission elapsed. Yet already one of the crew was basically hospitalized.

  The purpose of the crew’s med training had been to enable them to prevent biological death. They had all rehearsed in resuscitation procedures: mouth-to-mouth, sternum compression to get the heart pumping, electroshock paddles, endotracheal intubation, cricothyroidotomy, tracheostomy. They had even — back in the remote early days of the mission when they had all still been talking to each other — tried to rehearse such procedures under microgravity conditions. It had soon become comically obvious that grappling with a limp crewmate in microgravity was physically awkward, distasteful, almost grotesque. And many of the steps in their manuals — tip the victim’s head back at forty-five degrees — no longer made any sense…

  Anyhow, the theory of th
eir training was that if they could just stabilize whatever situation came up, there would be time to wait for radio waves to crawl across the Solar System and bring advice from the medics on the ground.

  But they simply weren’t geared up to nursing anyone — even one person, twenty percent of their crew — long term. This was a marginally capable interplanetary craft, not a convalescent home.

  The blood had been the first, and most visible, stock to be diminished; the almost daily routine of drawing blood from the crew — who were already weakened by their own reactions to microgravity — had jammed the cost of maintaining Libel’s life in the faces of everybody on board.

  Then there were the drugs. There was a pretty wide range of products in long-term storage. They had intravenous fluids, whole blood, crystalloid solutions: both saline and normal serum albumin, morphine sulphate, lidocaine, digitalis preparations… But the difficulty they faced now was that Libet had already absorbed a lot of the resources they’d started out with. And that had caused growing resentment among everybody else. Including, Rosenberg admitted, himself. Why the hell do we pour this stuff into Libet? This is all we have to keep us alive for the next decade or more… Anyway, getting caught by the flare was her own damn fault.

  He tried not to think about it. There were other problems to face.

  He dug out his softscreen, with his copy of today’s checklist. He was scheduled to put in a little time in the centrifuge himself right now. But he could feel the steady whir of the arm as it rocked the spacecraft. That was Nicola Mott; even as Libet declined, Mott seemed to be taking an obsessive interest in her own health, and was putting in extraordinary hours up there.

  He listened for a moment to Mott wheeling overhead, grimly fighting back the tide of microgravity changes. Whump, whump.

  According to the checklist, Mott should have been putting in some time in the farm. Rosenberg decided he might as well cover for her.

  He pulled himself through the hab module hatchway, along the little flexible access tube, where Siobhan had gotten her close, and into the CELSS farm. He pulled on the protective gear — now, after months, rank with the sweat of others — and began to work around the racks of plants.

  He didn’t like it in here.

  Most of Rosenberg’s work, though on living systems, had been at the microbiological or biochemical level. The fact was, he hadn’t had much contact with living creatures, human or otherwise, and he found these ranks of straining plants a little sinister.

  Overall the hydroponic system was working as it should, and he could see that many of the plants had the large leaves and small roots characteristic of such a facility. But he could also see, at a glance, there were the usual mechanical problems with the facility: clogged irrigation nozzles, a couple of failed fans, a suspiciously dark hue to the solution in one tank, indicating maybe a problem with the nutrient mix. And here was one place where the solution looked aerated, full of fat, sluggish bubbles which clung to the roots of the plants. Aeration was bad. The roots had to stay in contact with the solution to prevent dehydration and nutrient starvation, and to Rosenberg those plants looked, even to his naked, inexpert eye, undernourished.

  There were more fundamental problems. Within the muddy hydroponic nutrient he could see roots growing — not downwards — but in straight lines away from the seed plate, and at bizarre angles to the shoots. And in these late-generation growths, healthy plants were dotted among many unhealthy and abnormal growths.

  It wasn’t a surprise to Rosenberg that after billions of years of adaptation to a gravity well the plants were having trouble with microgravity. There were gravity-related mechanisms that controlled branch angles and leaf orientation, and gravity dominated plant cell growth, elongation and development. Without gravity, the physical stresses and loading on cells disappeared. In fluids buoyancy was lost, and gas-filled volumes and vesicles would not move as they should…

  He could see that some of the wheat crop would need reseeding. Several generations since leaving Earth, the yield of the crops was reducing, and although he could see no gross morphological defects there was some evidence of discoloration and perhaps malformation of the stem growth. He reached into the trays and took out a couple of stems as samples. He was sure he would find problems in cell division, nuclear and chromosomal behavior, metabolism, reproductive development and viability.

  He understood, deep down, that it had always been a gamble that they could make this little farm work, and they were just going to have to work their way through the problems as they came up. The truth was, nobody knew what the long-term effects of microgravity and GCR would be. The handful of experiments on biological systems in space — in Salyut, Mir and a few unmanned satellites — had not shown up enough data to provide much insight. Still, he thought, it was a shame to see the farm degrade from the triumph of the earliest months of the mission, when it had returned satisfying yields.

  Libet had been the most assiduous farmer; her absence, here, among these fragile green things, was keenly felt.

  In his softscreen he made a brief list of the main problems he found, to raise at a crew meeting later, and he began to strip off the protective gear.

  Back in the hab module he had to climb past the wreckage of the laundry, which, it appeared, Benacerraf had been disassembling. The front cover was drifting loose, and he had to shove it aside to get by. It took a little experimentation; if he pushed away from the line of its center of mass the cover just spun, or oscillated in space. There was also other debris from the half-finished job, mops and small tools and a little clear plastic bag of nuts and washers, cluttering up the air.

  He looked absently inside the laundry. Benacerraf had opened up the exit vents, and he could see there was some kind of growth in there, what looked like a black algae, coating the walls and vent grilles. He’d found some of the same growth himself on the shower curtain. Micro-organisms tended to flourish in the habitable compartments, surviving on free-floating water droplets in the air.

  But the problem was deeper than that. Their miniature biosphere had fundamental problems of scale. It was poorly buffered; the biota were connected with a much smaller reservoir of biogenic materials than on Earth. Carbon dioxide, for instance, was recycled through the Discovery system in a few hours or days, compared to several years on Earth. So minor imbalances could significantly affect the composition of the buffer in a short time, and imbalances could run away rapidly.

  This algal growth was a typical, relatively harmless, example. The others bitched about scraping this stuff out of the shower, but things could get a lot worse: if, for instance, the levels of cee-oh-two rose or fell away from nominal too dramatically, the whole life support system could crash altogether.

  Nobody knew what was really going on in here, and they just had to cope with it as best they could. Rosenberg felt he understood this, that he’d understood it before he got on board Discovery. It was part of the life he’d chosen.

  As he waited for his mail to open on the softscreen he listened to the continuing slow rattle of Mott in the arm. He wondered if he ought to get her down out of there. These long periods in the arm wouldn’t do Mott any harm, but if she started giving them all an excuse not to do their hours in there she could damage them all…

  One of his messages, from the surgeons on the ground at JSC, was a little worrying.

  They had been monitoring the routine electrocardiogram readings Rosenberg had been sending down the loop. All five of them had suffered minor heart irregularities over the last twenty-four hours. Rosenberg himself had suffered a so-called bigeminy rhythm, in which both sides of the heart contracted at once. Rosenberg thought he could feel his own heart thumping now inside his chest, huge and vulnerable, as he tried to digest this piece of information. He checked the time of his bigeminy. He didn’t remember anything wrong, except maybe feeling tired. He frowned. He’d have to look into this later; the surgeons wanted more EKGs taken of all the crew, and they had a number of suggested cau
ses for the irregularities…

  He moved his analysis of the farm plant samples up his mental priority list. He was becoming convinced many of the problems with the biosphere could be related to deficiencies or surpluses of trace elements. The plants, on analysis, would be a good check of such problems.

  He looked again at his checklist.

  He couldn’t find any excuse to avoid his patient any longer.

  Siobhan Libet was slung in her sleeping bag, and her cramped little quarters had been made over as a kind of miniature hospital ward. The place was cluttered, but it was clean and smelled fresh, if a little antiseptic. That was thanks to Mott, Rosenberg knew. As far as he was aware neither Benacerraf nor Angel ever ventured in here.

  Libet was unconscious. She’d been that way for three days now.

  He pulled the door closed behind him, and started his examination.

  Siobhan’s problems were multiple, and linked.

  The effects of microgravity were marked in Libet, who, after all, hadn’t been able to get to the centrifuge for a hundred and sixty days. Her skeletal muscles were deeply atrophied. The wasting of her cardiac muscles seemed to have stabilized at about eight percent. That was higher than the crew’s average, and Rosenberg worried about eventual cardiac arrest. Libet’s hemoglobin was down by fifteen percent, enough to mark her out for treatment, on Earth, as an anemic. That hemoglobin count meant less oxygen being carried to the debilitated heart and skeletal muscles.

  Her white cell count was down too, so her ability to fight off infection was reduced. Rosenberg was administering interferon to her, a protein involved in the immune system — production of which was also suppressed.

  A couple of simple tests showed him that Libet’s flexor muscles had lost around twenty percent of their strength, the extensors twenty-five percent. Even the cell structure of her muscle fibers was changing, he knew; microgravity was working on her right down to a micro-anatomical level.