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 causes for the irregularities…