Titan

by Stephen Baxter

  The pain in her feet dominated her mind. It was as if she was trapped in some tunnel, walled in by pain, receding ahead and behind her to infinity.

  She tried to objectify the pain itself.

  She imagined the pain as outside her, even as a living thing, a malevolent creature. It was a red-hot poker embedded in her bone, a crucifixion nail driven into her foot, a gigantic invisible snake-head with its jaws clamped over her foot…

  If only there was some way she could make it stop. If she was on some dumb stunt of a polar expedition, she’d call in the relief planes right now. If she was subject to some ghastly torture, she’d confess, give in, betray anybody or anything. Just to make this stop.

  But through all this the pain was still there, lurking beneath the distracting superstructures she erected inside her head. And every time she slipped or caught her boot on a ridge in the ice the pain would come bubbling up, overwhelming her conscious thought, raw and primeval.

  She kept getting ahead of Rosenberg. Each time she stopped, it seemed an increasing wait before his circle of helmet lamp light came weaving across the ice towards her.

  The journey just went on, without meaning save survival, day after day.

  After fifteen days out, they got back to Tartarus Base.

  In the light of her helmet lamp, the orbiter and Command Module, side by side, were just mounds in the gumbo, their surfaces streaked by bruised-purple tholin deposits. They were unrecognizable as man-made artifacts save for their symmetry of construction.

  Somehow, Benacerraf was disappointed. She’d been building this place up in her mind as her home, like a cliché of a family-Christmas fireside, somewhere warm and safe that would shelter her. But it was no such thing, of course; all there was here was a couple of downed spacecraft, a tiny, shivering farm, a cooling nuclear pile.

  She unbuckled her traces. She retraced her tracks, back towards Rosenberg. Her footsteps, in the dim yellow light of her helmet lamp, were shallow, infilling craters in the gumbo.

  She got them both into the airlock. She cracked their suit seals and took off their helmets, boots and gloves. Rosenberg’s helmet came away with strips of skin and tufts of hair and beard clinging to the lining.

  She led him through into the interior of the hab module. The air here was hot, thick and moist, hard to breathe, and so sterile it almost smelled antiseptic. Bizarrely, she found herself missing the warm, almost cozy suit-stink she’d been immersed in for two weeks.

  She helped Rosenberg to one of the Command Module couches. He sat there like a melting, gumbo-streaked snowman, his bony hands dumped in his lap, his head slumped forward.

  Benacerraf made her way to the far end of the hab module, her ruined socks leaving trails of sticky blood on the clean metal surfaces.

  She stripped off her own suit. She was stiff all over, particularly in her lower back, shoulders and hips; it was painful to put herself through the contortions required to shuck off the suit’s layers. The inner layers clung to her damaged flesh; she had to tease the cloth and plastic away from her skin, trying not actually to break her epidermis or pull away scabs. The suit was worn and badly damaged in places. They’d been lucky the suits had worked to carry them so far—the EVA had been well beyond the suits’ design limits.

  At last the suit lay as a heap of soiled Beta-cloth at her feet. She stood naked, shivering despite the cloying warmth of the hab module.

  She was skeletal, her ribs protruding under flat sacks she didn’t recognize as her breasts, her buttocks lumpy and flaccid, her knees and elbows hard knobs of bone. Her feet were a mass of lumpy, pus-filled growths and open frostbite wounds and scars. Crotch rot spread from the dark triangle of pubic hair, out over her thighs and belly, angry red. There were pressure sores where the harness had dug into her, and where her suit had chafed, over her hips, under her armpits and around her chest and waist. Her personal hygiene during the EVA hadn’t been too effective. Her upper legs and buttocks were flecked with yellow urine stains and smears of what looked like dried excrement, and there were patches of glaring red skin infections around her waist and legs, the parts of her body where she hadn’t been able, or willing, to reach.

  She allowed herself two minutes to shower. The hot, clean water felt like acid on her skin; it was actually painful to have the layers of filth lifted from her ghost-pale flesh.

  She padded to her quarters. She pulled on underwear, and an old Beta-cloth T-shirt and shorts. She tried to don her Beta-cloth slippers, but they wouldn’t fit over her swollen sores; so she wrapped old T-shirts loosely over her feet and bound them up with duct tape.

  She gave herself a moment to run her hands over her belongings, her books and photos, anchoring herself once more in these relics of her life, her personality.

  As an afterthought, she put on a facemask and a pair of surgical gloves. Then she made her way to Rosenberg.

  He was still in his suit. She stood him upright. He felt disturbingly light. His head was a mess, the hair matted with filth and patchily bald; there were cracks around his mouth, nose and eyes that had opened into fissures as deep as razor slices, dribbling thin blood.

  Slowly, she got him stripped. His undergarments were even more matted with waste and filth and blood than hers had been. It looked as if he had suffered some kind of dysentery attack and fouled his pants; when she pulled off the suit, hot stinking liquid flowed out over the clean floor of the hab module.

  Benacerraf got his longjohns away from his arms and lowered them around his legs. A shower of skin fragments and pubic hair fell onto the metal at Rosenberg’s feet. His legs and groin seemed to have been stripped clean of skin, left raw and compressed into folds. His kneecaps were just ripples of flesh, his genitals rubbed raw. She could see deep wounds dug by the edges of the harness straps, and within the patterns of straps she found eruptions like small, festering boils.

  The soles of Rosenberg’s feet had split, each of them, down the middle: almost neatly, like the soles of cheap shoes. The casts of dead skin came away like plastic molds in her hands, leaving roughened, raw tissue, from which a watery fluid leaked.

  “Dear God, Rosenberg.”

  He whispered, “It’s not as bad as it looks.”

  “What the hell is wrong with you?”

  His head lolled, and he sighed, his voice a rattle.

  “You know, don’t you?”

  His head rolled around until he was facing her. “Yes, I know what it is. I think, anyhow. You need to take a few blood samples to—”

  “Tell me.”

  “Vitamin A poisoning. Those damn baby carrots.” He opened his mouth to laugh, and spittle looped between his lips. “Remember, Paula? They were too bitter for you. Well, you were right. More vitamin A than dog liver. Another failure of this toy ecosystem we’re trying to maintain here. No buffering … the whole thing’s too small … levels of toxin all over the place. We just couldn’t control it well enough. We gave it a good try, but it was going to get us in the end…”

  There was a flap of skin, loose, beneath his ear. Like a ring-tab, she thought. With a sense of dread, she touched it. It was dry. She pulled at it.

  The epidermal covering of Rosenberg’s ear came away intact, a complete cast. It drooped between her finger and thumb. “Oh, Jesus Christ.” She shivered violently and tlung the thing away.

  He fell against her, clutching at her arm. “You have to get the samples in, Paula. Look for the kerogen. Do it while I can help you. Everything depends on that—everything—”

  His head lolled again, and he went limp.

  Gently, she tucked her arms under his body, and lifted him like a child.

  There had been no signal from the ground, of any kind. Benacerraf checked every day, and bounced test signals off Cassini, to ensure there was no fault with the satellite. And she sent transmissions home, regular updates, with their results, and some personal messages.

  In case anyone was listening.

  The choice was not to send at all, and th
at would have felt like giving up. Or as if, by her own loss of faith, by not acting as if there was someone left down there, she might actually somehow bring down the catastrophe they both feared.

  She could picture Seattle, almost as vividly as if she was there. She could picture the house where she’d grown up, the places she’d lived with Jackie as a child, her grandchildren… It was more real, to her, than this murky shit-hole.

  How could it be gone, ruined? How could there be nobody, walking the dog, watching the news, mowing the lawn?

  In the privacy of her room, though, she grieved, little by little, for her family. It was as if she was allowing herself to face the huge loss, piece by piece.

  What she feared most was the thought that she and Rosenberg might be all that was left. She hated the idea that her actions, the rest of her trivial life, had suddenly become so significant.

  She wished she had some way to climb up above the clouds, to lash up some kind of telescope and peer at the Earth, and see.

  Rosenberg sat on a Command Module couch. He was wrapped up, pupa-like, in layers of clothing and thick blankets of Beta-cloth, but he still complained about feeling cold. He wore heavy sunglasses—they’d belonged to Bill Angel—to protect his eyes from the glare of the hab module floods. He’d lost most of his hair, and much of the skin from his scalp and face; swathes of raw tissue showed where his flesh was exposed, riddled by crimson crevasses.

  Benacerraf made herself a meal: rice, boiled in Titan melt, with lettuce and some beef jerky from the stores. She sat opposite Rosenberg as she ate. She’d already fed him tonight, spooning the contents of one of their last soup sachets into his mouth, trying not to react to the blood and hunks of loose skin that followed the spoon back out of his lips.

  Rosenberg had become the defining feature in her mental landscape now, as so much of her time was given over to caring for him: medical attention, tending to his basic needs—wiping my ass, as Rosenberg put it—and covering his work for him.

  He told her what he’d found in the samples from El Dorado. His voice was a thin, robotic rasp.

  “I found a lot of interesting products. Beyond the usual organic sediments that come from the stratospheric chemistry, there are traces of urea, organic acids, diacids, some amino acids. Products of tholin hydrolysis. Other amino acids resulting from cyanogen addition to nitriles. Results of cyanogen and nitrile polymerization, including imidazole, purines, pyrimidines. I got aldehydes, ketones, acetaldehyde—the results of alkyne hydrolysis. Some Strecker synthesis—aldehyde-nitrile condensation. Aldehyde polymers, including sugars, glycerol, some other species of—”

  “Christ, Rosenberg. Did we find kerogen or not?”

  “… No,” he said. “I’m sorry, Paula. I guess I was wrong; El Dorado can’t have been a carbonaceous chondrite crater after all. My best guess now is that it was formed by a fragment, a calving of a much bigger bolide, which was probably water ice… There is a large water ice crater system a little further to the west.” His head rolled back and forth. “And that’s recent. Maybe the impact was in historic times. Maybe it could have been visible from Earth through a telescope, if anyone had been looking that way, a giant ice comet smashing into Titan… A hell of a thing.”

  “So we’re fucked. The EVA was a wild goose chase.”

  “All the products I found were the result of reacting Titan materials with water from the bolide. I’m sorry, Paula.”

  She grunted. “It was a good shot. Anyhow, I didn’t have any smarter ideas.”

  He seemed to be trying to lean forward; he struggled, feebly, within his Beta-cloth layers. “Look, Paula. We have to face facts. We’re beyond rescue from Earth. We’re on our own here. We ought to look at the worst case.”

  “The worst case?” She laughed, around a mouthful of rice. “Look at us, Rosenberg. What could be worse than this?”

  “We are the last humans.”

  He fell silent, his breathing a noisy rasp.

  She felt the motion of her jaw slow, without conscious volition. Saliva pooled in her mouth, flooding the rice grains and lettuce there, swamping her sense of taste.

  Rosenberg said, “The great unspoken truth, huh.”

  Deliberately she started to chew again; she swallowed a mouthful of saliva.

  “But what difference does it make?” she said. “We’re fucked anyhow.”

  “True. Without the kerogen supplement, our ecosystem isn’t going to last long. A couple more system crashes and we won’t be able to recover. We just aren’t viable here. We tried hard to make it so, but in the long term we were always going to lose. And the whole thing will die with the two of us anyhow.”

  “Right,” she said brutally. “So what does it matter? Rosenberg, Earth is a billion miles away. We could try to eke out our lives up here for years, or we could blow up the damn Topaz today. So what? It makes no difference, except to ourselves.”

  “You’re wrong, Paula,” he whispered, his ruined mouth gaping open. “I’ll tell you what difference it makes. We’re still part of Earth’s biosphere, even if we are a little seed pod transplanted across a billion miles. Even here, we’re still connected; in fact, we have a greater responsibility. We might be all that’s left. You and I as individuals are going to die here. But what we do before then might determine the future of Earthlike life in the Solar System. We have a responsibility, Paula.”

  She stared at him. “You’re crazy, Rosenberg,” she said bluntly. “You’re such a pompous asshole. Everybody’s dead, except us, and we have no resources at all, and here you are talking about the destiny of life.”

  His cracked lips spread in a grin. “I have a plan.”

  “You and your plans, Rosenberg.”

  “I think I know a place where we can find liquid water…”

  The surfaces of all Saturn’s moons had been shaped by impacts. Titan’s surface had been shielded by its thick blanket of atmosphere, but its huge mass had acted to focus impacting objects onto itself.

  Thus, there were impact craters all over Titan.

  “Paula, think about a pool of impact melt at the bottom of a crater, dug into Titan ice, heated by the kinetic energy of the impact. It cools down to the freezing point, and stays there at constant temperature—zero degrees—as it freezes and shrinks. It can only lose heat by thermal conductivity. It’s a slow process. The conduction equations are well understood. And water is good at retaining heat…”

  “It will stay liquid.”

  “A crater a hundred miles across might have an impact melt pool ten miles wide. And it would take ten thousand years to freeze.”

  She frowned. “So if the crater beyond El Dorado, the primary that spawned the smaller crater we found, is only a few hundred years old—”

  “It should contain a pool of liquid water. With a concentration of organics of a few parts in a thousand…”

  “Holy shit, Rosenberg.”

  “Yeah. That’s not all. What about impact ejecta?” Ejecta was material thrown out after an impact, through the explosive decompression of the shocked solid surface. “On the Moon, ejecta is thrown out into a near-vacuum, and it’s a mixture of vapor and solid. But on Titan, with its thick atmosphere, you’ll have something more like the cratering process on Venus. Ejecta will flow in blankets over the surface, to three or four times the crater width, and maybe a hundred yards deep. And there will be a lot of organic-containing sediments mixed in with the surface ejecta flow. You can calculate the cooling lifetime using heat conduction partial differential equations which—”

  “Cut to the chase, Rosenberg.”

  “Yeah. There will be ponds of liquid water, maybe a hundred yards deep, scattered over the surface around the primary crater. Even they should last for centuries, maybe longer. They’ll freeze over, of course; so will the impact melt pool at the heart. It will have a thin crust of ice, but will be liquid beneath. With time, as the layer of liquid water shrinks, it will become more concentrated in organics, and you’ll get a whole spect
rum of reactions: amino acids, aldehydes and ketones, nucleotide bases… In those pools, we should find an emulation of nearly all the prebiotic chemical pathways on the early Earth, except for the steps involving phosphates… Damn, damn.”

  “What?”

  “If only we’d gone a little further. I might have found it all, just waiting under the surface, a thin crust of ice. Just waiting for a seed.”

  “Waiting for a… Oh.” Suddenly, she saw his plan. “You’re kidding.”

  “No.” His sunglasses slipped down over his bony nose. His eyes were blue rocks in the crusty red mass of his face. “Paula, I’ll show you what to do. I made notes in my softscreen. You have to go back to Cronos again. Go further than we did before. Find the primary crater beyond El Dorado, and the impact melt pool at its center. Or maybe you’ll find ejecta ponds. Liquid water, Paula. I’ll prepare a package—”

  “What kind of package?”

  “Earth-origin microbes that can metabolize tholin.”

  “We don’t have the facilities for genetic engineering.”

  “We don’t need to engineer them,” he snapped. “Don’t tell me my job, Paula.”

  “I’m sorry.”

  “I’m talking about common soil bacteria. Aerobic and anaerobic… Clostridium, Pseudomonas, Bacillus, Micrococcus… They are present in our nutrient solutions in the farm. They can extract their carbon and nitrogen requirements from tholin…” He started coughing, big spasms that racked his body inside its Beta-cloth shroud. “Drop them in that liquid-water soup of prebiotic organics and they’ll thrive… Earth life, surviving on Titan…” He coughed again.

  She stood before him. “Rosenberg, maybe you ought to rest. I’ll clean you up.”

  “No.” His eyes were still steady, despite the shuddering of his body “I have to be sure you understand. The responsibility.”

  “I know” She knelt before him and put her hand on his bony arm. “Responsibility for the future of Earth’s biosphere. All on your shoulders. I understand, Rosenberg,” she said gently. “But—” “But what?”