“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 Earth-like 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 spectrum 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… Clostridiunt, 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?”
“I still don’t get it. Even if I find the ponds, even if I seed them, they’re just going to freeze over, in a few hundred or a thousand years.”
“Sure.”
“So what’s the point?”
He shuddered. “Things will change. In time — billions of years, Paula — the sun will reach the end of its life. It will become a red giant… And then, for a time, Titan will be as warm as the Earth. Titan summer. Maybe our bacterial spores will give rise to a new evolutionary sequence. You see?”
She pulled back from him. Suddenly she felt chilled. “You think big, Rosenberg.”
“Little packets of bacteria… Seed the planets, the comets. If you’re serious about spreading life to other worlds, that’s how you’d do it. Cheap, too. It’s absurd to carry humans around… all that plumbing…” His eyes closed, the big broken lids sweeping down like curtains.
She picked him up, and carried him to the hygiene station.
* * *
Sitting on the floor of the hab module, a Beta-cloth blanket thrown over them both, she cradled him. His head felt huge in her lap, the massive skull with its paper-thin covering of flesh and skin, but his body was feather-light.
He whispered: “How can I die? How can the world keep turning without me? I’m unique, Paula. The center of the universe. The one true sentient individual in an ocean of shapes and noises and faces. How can I die? It’s a cruel joke.”
Dear Rosenberg. Analytical to the end.
“They’ll remember you for coming to Titan. A member of the first expedition. That’s one hell of a memorial.”
“If there is anyone left to remember. Anyhow, even so, I’ll just be a freak in a circus show.”
She said gently, “No god waiting for you, Rosenberg?”
He tried to laugh. He whispered, “What do you think? God died in 1609, when Galileo raised his telescope to the Moon, and saw seas and mountains. We flew to Titan. But with that one act Galileo discovered the universe. God can’t share the same cosmos as a Moon like that.”
“No,” Benacerraf said sadly. “No, I don’t suppose He can. But where does that leave us, Rosenberg?”
“Fucked,” he said brutally. “Science is a system of knowledge, Paula. Not a comfort.”
“I know,” she said. She stroked his forehead, and crooned her words, as if to a sick child. “I know.”
He gripped her arm with a claw-like hand. “Paula. You have to put me through the SCWO.”
“Sure, Rosenberg.”
“I mean it. You can’t afford to waste the biomass. B
ut freeze yourself, Paula. Go out on the ice, when… It’s important.”
He coughed, but even that had lost its vigor. The color seemed to be draining from his face, even from the exposed tissue there, as if his blood was drawing back to the core of his body.
His head rolled on its spindle of neck across her lap. “You know, I’m not afraid. I thought I would be. I’m not.”
She squeezed his hand; it felt as if his bones were grinding together. “You don’t need to be afraid, Rosenberg. I’m here.”
He said, with a spark of sour energy, “It isn’t that. The human stuff, monkeys holding hands against the dark. I never thought that would make any difference. And I was right. But you and I—”
He coughed, and shuddered; his ruined eyes fluttered closed.
She leaned over, closer to his bleeding mouth.
“You and I, with what we’re doing here, are the most important humans who ever lived. We will cast a shadow across five billion years. And that’s a hell of a thing,” he whispered. “A hell of a thing.”
He relaxed, with a rattling sigh, and lay still, collapsing into her arms with a slow-motion, low-gravity calmness. “You know, I learned a lot,” he whispered. “More than I expected.”
“You did good, Rosenberg.”
“But you know, I never figured out why…”
“What?”
“Why did it feel like this?”
She could feel his body settle, the internal organs relaxing and losing their tension; the last gases escaped from his stomach in a long, low fart.
She got him into the frigid ground only an hour later.
The grave was just a shallow ditch, scraped out of the gumbo, already infilling. His naked body lay at its base, thin, skeletal, glistening with the frozen water ice of his body.
Once again she had to find words to say over a corpse.
She checked her transmission link to Cassini. She wanted this moment to be sent to Earth. Maybe there was somebody there to listen; maybe not. If there was, maybe this would somehow help them.
“I’m sorry I didn’t have a flag to wrap you in, Rosenberg,” she said. “Anyhow, I know this was what you wanted, in spite of what you said. And if you think I was going to have your sorry ass circulating around my ecosystem, you got another think coming.
“Casting a shadow across five aeons.Maybe you will at that. You did good, Rosenberg.”
I guess that will do, she thought.
She threw a handful of Othrys ice crystals into the grave, and began to drag her snowshovel over the gumbo, filling in the shallow pit.
* * *
In the last days she spent a lot of time in the CELSS farm, trying to stabilize it as much as she could. She kept power supplied to the farm, and left it seeded with a new crop, of wheat, barley and lettuce.
She felt a great responsibility for the drawn, etiolated little plants here. They were, after all, the only living things other than herself on this whole moon, and she felt loyal to them, and regretted she was abandoning them to die.
But there wasn’t much she could do for them. She figured the CELSS farm might last without human intervention a few weeks, before a pump broke down, or a nutrient pipe clogged, or a short burned out half the lamps, or some runaway feedback biocycle caused the miniature ecology to crash.
Even if by some miracle that didn’t happen, eventually the power from the Topaz reactors in Discovery’s cargo bay would fail. The lights would dim, and the last, spindly plants would finally die, as Titan’s cold broke in.
She took spare seeds and wrapped them in airtight bags. She buried them, under a marker, in the gumbo outside Bifrost. That way, perhaps they would survive, deep-frozen, until Discovery’s next visitors came this way, whatever became of her.
She spent a last night in the hab module. She took a long, hot, luxurious shower, extravagantly spending, the reactors’ reserves of energy.
She tried to read a book on her softscreen, but could barely concentrate. She kept on thinking that this would likely be the last book she ever read. The words seemed just a foolish dancing, against dark emptiness.
She put the softscreen aside.
She looked at her images of Jackie and her grandchildren. She stared into the sunny photos, trying to will herself into the pictures with her family.
She slept well, in her quarters, with the lights off and the door closed, shut in against the shells of emptiness around her: the deserted hab module, the empty moon, the billion miles separating her from Earth.
When she woke she ate a gigantic breakfast, using up a lot of stores: dried apricots, an irradiated breakfast roll, rehydrated granola with blueberries, ground beef with pickle sauce, noodles and chicken, stewed tomato, pears, almonds, drinks of grapefruit and strawberry.
She went to the hygiene station and took a long, slow, luxurious dump. She cleaned herself with antiseptic wet-wipes.
She stripped naked. She folded up her Beta-cloth clothes neatly and put them away in a drawer. She washed one last time, then put plasters and bandages over the places where she knew to expect problems from cold and pressure sores: her toes and ankles and the sides of her feet, her hips, stomach, chest and shoulders. She put cream — all that was left was the hemorrhoid ointment — over her groin, in anticipation of crotch rot.
She pulled on her suit. She took great care over each layer; she wouldn’t get another chance to fix it, and she would hate to go to her destiny with a fold in her underwear rucked up her ass.
Inside the suit layers, duct-taped to the fabric, she stored Rosenberg’s canister of bacteria samples — protected there against the cold — and a little packet of photographs, old-fashioned hard-copy images, of Jackie and the kids.
She sealed up her helmet, gloves and boots, and ran methodically through the suit checklist fixed in its ring binder to her arm. She went through the list twice. In a way her biggest dread, now she was alone, was that without anyone to check her she would miss out some crucial step, kill herself through carelessness.
She looked around the hab module one last time before leaving it. It was clean, tidy, everything stowed away, as if ready for reoccupation. She felt obscurely proud; she’d remained civilized to the end.
Just like Captain Scott.
She slipped on her Apollo hull-metal snowshoes and stepped out into the gumbo. The tholin slush sucked at her feet with its familiar stickiness, and she felt Titan cold immediately seeping through the layers of her suit.
She looked over Tartarus Base.
She could make out the delta shape of the grounded orbiter, with the cone of the Command Module alongside. The cover they had erected over the open cargo bay of the orbiter was still in place, the parachute fabric stiff and streaked with gumbo. In a final extravagant gesture she’d left the flood lights of Discovery’s flight deck burning; the yellow Earth-like light now glared out through tholin-streaked windows, shining over glimmering slush.
There was little geologic activity here; the ground was stable. Even the tholin deposition rate was slow. It might take a billion years, Benacerraf thought. But at last Titan would claim Tartarus, its patient tholin drizzle ultimately covering over the pyramidal peak of Apollo, Discovery’s big boattail. The spacecraft hulls would ultimately crumple and shatter, until nothing remained of this, the first human outpost on another planet, save a thin, isolated layer of metallic crystals, and a few anomalous deposits of organic residue.
She looked up, towards the marginally lighter horizon. She cut in her IR visor and made out the spark of light, pixel-blurred, that was the sun. From here, the entire orbit of Earth was a circle the size of a small plate held at arm’s length, with the planet itself — with all its freight of humanity, and hope and love and war and history — a dull-glowing bead on the rim of that circle, impossible to make out. She could hold up her bulky gloved hand and obscure the entirety of the orbit, the whole span of human experience before the Discovery expedition.
She buckled the Command Module couch harnesses a
round her. She dug her snowshoes into the gumbo and shoved. Immediately she felt twinges from the sites of the pressure sores she’d suffered last time, at her hips and chest and shoulders.
The sled came free of the clinging gumbo with a sucking noise. She staggered forward.
The sled was heavier, this time, than when she’d set out for her previous extended EVA with Rosenberg. This time, all the essentials — the tent, the recharged skimmer power cells, all her food and water — were stacked high on this one sled.
On the other hand, her food load was lessened. Just enough for a one way trip.
Soon, she managed to settle into a steady rhythm, with each step jerking the sled free of the gumbo which clutched at it.
Every instinct told her that Rosenberg’s billion-year scheme couldn’t work.
It was, of course, a typically arrogant technocratic fantasy — in a way an extension of the gigantic, ludicrous journey they had undertaken to come here — to suppose that it would be possible, with a handful of micro-organisms thrown into a lake of ejecta melt, to reach out across billions of years and shape the evolution of a world.
For instance, Rosenberg had made a lot of assumptions about the viability of bacterial spores over such huge deserts of time. And who could really say what the future evolution of the sun would be hike? Nobody had actually watched a star follow through its ten-billion-year evolutionary cycle, from birth to death; every theory was inferred from humankind’s mayfly-like snapshot perception of the stars that happened to be scattered through the universe today. Maybe the red giant sun would grow so huge it overwhelmed Titan, boiling away its atmosphere in moments. Or maybe the sun would just go nova, blasting Saturn and its ancient moons to fragments…
It was, she thought, a pretty dumb plan.
But, in the end, it gave her a goal.
Thus her life would end, she thought: struggling to fulfil another project, one more technological dream, because she had nothing better to do.
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