Titan n-2

by Stephen Baxter

  Now Rosenberg wrapped the end of the boat’s steel mooring cable around his waist, and stepped back a few yards from the ethane’s edge. He kicked off his snowshoes and let himself sink into the gumbo, anchoring himself there. “Okay, Paula. I’ll pull you back at the first sign of trouble. The shallows should be okay, but that boat won’t be able to withstand any problems in deeper water. I mean, ethane. And, Paula. Whatever you do, don’t fall in. Don’t even sit down. That ethane lake has a much bigger heat capacity than your ass, it will give you one cosmic case of hemorrhoids…”

  “I’ll bear it in mind, Rosenberg.”

  She took off her snowshoes, and lifted them carefully back up the beach. Then she hauled on the cable to pull the boat a little closer to the shoreline, to minimize the ethane wading she would have to do.

  She stumbled through the shallow ethane to the boat. As fast as she walked, the stabbing cold of the liquid pierced the multiple layers of her heated boots.

  She stepped over the boat’s foot-high wall, and moved to the center of the boat. The little vessel rocked back and forth with slow grandeur, and she could hear a slow, sombre sloshing from the liquid around its hull.

  She looked down at her feet. Droplets of ethane fizzed as they boiled away from her boots. The rocking steadied, slowly.

  Rosenberg was climbing further back up the beach, stepping backwards, making sure his footing in the slush was secure. He sent waves rippling up and down the steel cable. The cable moved with languorous, snakelike grace in the low gravity; but it sliced through the low-density ethane liquid as if it wasn’t there. And where the cable penetrated the liquid Benacerraf could see a puncture in the heavy meniscus, surface tension hauling ethane up the steel Rosenberg pressed a stud on his chest panel to take photographs with the digital Hasselblad mounted there. “The boat is riding well. You’ve dipped into the liquid by no more than a few inches, under the combined weight of the boat itself, you, and the equipment…”

  “Just as you calculated.”

  “Just as I calculated. The density of the ethane—”

  “Archimedes’ principle applies, even on Titan. I do understand, Rosenberg.”

  “Sorry. Good luck, Paula.”

  “Yeah.”

  Benacerraf stepped to the rear of the boat and picked up the paddle. This was just another piece of Jitterbug hull, a curved shovel shape, fixed to a bar which had once been a couch strut. Feeling self-conscious, she leaned over to dip the paddle blade in the liquid.

  She waved the paddle to and fro, in the ethane. There was little resistance to her motion, and the blade cut smoothly through the fluid without turbulence, but she could feel how the ethane was being cupped by the paddle.

  With painful slowness, the boat inched away from the shore.

  She was soon panting with the effort of waving the paddle. As she couldn’t sit down she had to lean over the side of the boat to reach the liquid, and that was making her back and arms ache. Her suit was too stiff for rowing, a task for which it had never been designed. And besides, she knew her muscles still hadn’t recovered from their extensive space soak. She made a mental note that they would need a longer handle the next time they tried this stunt.

  Despite all this, the boat was gliding forward across the oily surface, fat ripples spreading away from its circular bow, the only sound a glutinous gurgle of ethane against the sides.

  “That’s it,” Rosenberg said. “A back and forth motion; that’s fine. Remember the viscosity of the ethane is very low. Once you build up some momentum you should just sail on. Just like the air-bearing facility back in Building 9 at JSC, right? Don’t forget you have a back-up paddle in case you drop that one. Don’t try to reach in after it. And—”

  “Let me row the damn boat, Rosenberg.”

  He fell silent.

  The shoreline receded, the ethane surface between her and solid land, growing into a thick black band.

  Behind her, the lake’s far shore began to protrude over the horizon. It was a shallow, dome-shaped hill, blackened by gumbo streaks.

  When she had judged she had got to a hundred yards out, she lifted her paddle out of the liquid and dropped it at her feet; her back and shoulders were aching, and she moved her arms around, trying to ease the muscles.

  The boat continued to sail on over the surface of the oleaginous fluid. It was as smooth a ride, she thought, as if she was a beetle riding a hockey puck over damp ice.

  At last she came to rest. The air seemed a little clearer here, in the middle of the lake, perhaps because of the constant dissolving and exsolving of gases from the ethane. It was as if she was embedded in some clear orange resin, with the dark grey methane clouds scattered over her head in their well-defined layer, like shadows on a ceiling.

  From this far out she could make out more of the shape of the lake. It was obviously a horseshoe shape, curving around that central mountain — although from here, if she was honest, it was hard to tell if the lake was a true open horseshoe or if it closed over, around the far side of the mountain, into an annulus.

  Looking back to shore was like looking across a sheet of blackened glass, to an encrustation of purple ice and foam at the lake’s rim. She could see Rosenberg standing patiently, stained with gumbo up to his waist, where the cable termination glittered. Seen from here, Rosenberg was very obviously alone on that primeval beach. His figure was the only vertical in a landscape of horizontals, starkly isolated. There was nobody else standing with him: no houses or buildings or cars behind him on that landscape of soft undulations, no trees, no birds in the sky. And in the frigid, mushy depths below her there was no life she could recognize, perhaps no life at all.

  The boat rocked with a slow, soothing gentleness, with a period of maybe five or six seconds. The lake surface was almost a perfect black, its ripples heavy and shallow, free of breakers. Most organic solids, raining down from the atmosphere, would simply sink to the bottom of the lake. But here and there Benacerraf could see scatterings of foam, grey and purple. Some of that was spindrift, aerosols caused by bubbles bursting on the surface.

  She felt her sense of place and time shift around her. It was as if the landscape of Titan was reaching her, through the isolating layers of her suit; she started to get a sense that she was truly here, alive and sentient, on this ethane lake, a billion miles from her birthplace. It took moments of stillness like this to understand this, she thought. Moments that the Apollo guys, Marcus White and the rest, were never given, in their hectic, task-crammed timelines. Moments that had come only, perhaps, in the quiet of their sleep periods, as those fragile Lunar Modules ticked and creaked around them. Moments, little fragments of true humanity, they were never encouraged to report. What a pity.

  She wondered how long she’d been out here.

  She felt as if her sense of time was dissolving, stretching like melted candle-wax. Pendulums would swing more slowly here, like the rocking of her boat, in the gentler gravity. Perhaps some pendulum hidden deep in her own being was slowing, too, in response to this small world.

  But now Rosenberg waved. He had set up the small TV camera on its stand, looking out at her. And the portable antenna pointed straight up, to where Cassini hovered far above the clouds and haze in its fifty-thousand-mile Clarke orbit.

  The comms gear was a reminder that this wasn’t some dumb jaunt on a lake. She was out here to look for amino acids and other good stuff. And this was a NASA extravehicular activity, on the surface of an alien world; they had a duty to return data on what they were doing, whether anybody was listening or not.

  Anyhow, she thought, this is the first time in all of human history that a grandmother has gone boating on the surface of a low gravity moon. It ought to be on TV. Jackie should see this. And the boys, she thought wistfully.

  She began the series of experiments Rosenberg had set out for her. The first was a series of sample collections; she gathered up droplets from the lake into plexiglass test tubes, and bottom sediment that she trawled up u
sing tubes fixed to a line.

  She started up the tilt meter. This little gadget was something like an electronic spirit level. It contained two vials of a conductor fluid; as the boat tipped back and forth under the influence of the lake’s slow waves, the electrical resistance of the fluids in the tubes changed, and could be measured. Next she dipped a refractometer into the liquid to measure its speed of light. The refractometer was a cute thing, a little transparent box with prisms inside it, which she filled up with Clear Lake fluid. She measured the fluid’s ability to conduct heat; by filling up a tube with fluid she immersed a platinum wire, and watched how its resistance changed as she passed current through it. She deployed a simple gadget which measured the speed of a sound wave travelling between two piezoelectric transducers. The sound speed would tell a lot about the ocean, and when she reconfigured the gadget, Benacerraf might be able to make a sonar estimate of the depth of the lake, if the grunge-coated bottom proved reflective enough. She measured the ethane’s dielectric constant — its ability to hold an electric charge — by filling up a plate condenser with fluid, and measuring its capacitance. And so on.

  One of Benacerraf’s favorite instruments was a pair of thin metal vanes mounted on a piezoelectric crystal. The crystal drove the vanes, and their resonance depended on the density of the fluid in which they were immersed.

  The results of the experiments ought to help determine more about the lake’s nature. The lake wasn’t a simple pool of ethane. There were fractions of other paraffins — methane, propane, butane, others — as well as dissolved nitrogen, and a slew of higher organics. For instance, the refractive index of the lake fluid was very sensitive to the percentage of dissolved methane.

  She had to bend over the side of the boat to work, and soon her back was aching once more. She tried to keep her hands clear of the cryogenic fluid of the lake itself. She worked with tongs and pipettes, as if dealing with some acid. She fumbled a little with her gloved hands.

  Her last experiment was a plumb line, pleasingly crude and intuitive, just dropped over the side. The line was loaded with a scrap of Command Module aluminum, and the depth was marked out by simple knots in the steel cable. It was a little hard to tell when the string was fully paid out, so soft and muddy was the bottom. When she estimated the weight had reached a reasonably firm surface, she read off the depth. Ten feet.

  She described the result, and what she could see, to Rosenberg.

  “That’s good, Paula,” he said. “The ethane is deposited at a rate of three feet every ten million years. So that makes your lake maybe thirty million years old, which is pretty young for a crater of such size. When it formed, the crater would have had the kind of shape we recognize on the Moon — a shallow saucer, with maybe a central peak. After that, the ethane lake gathered. But the bedrock ice on Titan flows, on the timescale of a few million years. Viscous relaxation. That pushed up the center of the crater into that ice dome you see. So the ethane was shoved into an annulus, a ring around the domed mountain…”

  “And the horseshoe shape?”

  “Saturn’s tides. If Titan was covered by an ocean, the surface would be drawn into an egg shape by Saturn’s gravity, with the sharp ends pointing towards and away from Saturn. Our isolated lake is a fragment of that egg-shaped surface. It’s as if the crater is tipped up a little bit; all the fluid is pushed to one end of the annulus channel by the tidal acceleration.”

  Benacerraf felt awed. She looked around at the horseshoe shape of the lake once more. Saturn was invisible, but its gigantic influence was everywhere, its gravity field shaping the very nature of the landscape over which she moved. Benacerraf felt tiny, irrelevant, as if cupped in the palm of huge, invisible forces.

  On impulse, she bent, stiffly. She got hold of the lip of the boat’s wall, and got down to one knee. Immediately she could feel the cold of the hull, and of the mass of ethane below: it was as if the heat was being drained out of her body through the bone of her knee, the layers of her suit, and she could feel the hot, ineffectual triangles of her laboring suit heater.

  She leaned out of the boat, and looked into the ethane. Fat ripples, concentric with the circumference of the boat, oozed across the surface of the lake, suffused with the slow time of Titan. The ethane was utterly black, returning no reflection of her helmet, her face. It was unnerving, as if this wasn’t a liquid at all; it was as if she was poised over a hole in the world, a pit of black space that stretched down to infinity.

  She reached out with a gloved hand. She passed her fingers through the ethane. In her peripheral vision she could see that a warning light flashed on her chest panel.

  She pulled her hand out of the lake.

  She lifted up her glove. The residual ethane gathered into fat little globules on her fingers and palm; its high surface tension had pulled it into these light, mercury-like balls. Set against the blue of her glove, this sample of the lake was a kind of dull brown, but not completely opaque, like dirty petrol. She thought she could see particles, swirling about in the interior of the globules, but the light was poor.

  Even as she studied the globules they were shrinking. The boiling point of pure ethane was around ninety below — which was about ninety degrees above the ambient temperature. It was a big temperature jump, but even so, so quickly, the ethane droplets were absorbing the heat which was leaking out of her suit. The rapid evaporation was disturbing, a tough reminder of the fragility of her situation here. And every molecule of ethane that left her hand would carry away a little more of the heat her body needed.

  She shook her hand free of the remaining droplets; they scattered from her glove in slow-motion parabolic arcs.

  When she looked at her hand again, she found that the evaporating ethane had left a purplish scum on the fabric, in little discrete spots. Complex, prebiotic hydrocarbons: once more, she was immersed in the stuff of life.

  “Paula,” Rosenberg called now, urgency in his voice.

  “What?”

  “Take a look up there. The clouds.” Benacerraf had to tilt back on her heels to see. The methane clouds were still more broken now, and were streaming, across the orange haze ceiling beyond.

  “Wind coming up,” she murmured. “That was sudden. What do you think, Rosenberg? Fifteen knots?”

  “More like twenty, I’d say. And that means waves. Paula, get out of there.”

  It was probably good advice. Waves on Titan were not like Earth’s.

  She looked around, towards the center of the lake.

  The waves were already coming, radiating out from the domed ice mountain at the heart of the horseshoe, fired by Titan’s low gravity, they were like slow-motion tsunamis: walls of black ethane, each of them at least a hundred and fifty feet tall. It was hard to tell, but Benacerraf estimated the waves were a half-mile apart. They were moving across the surface of the lake at maybe thirty miles an hour — a glacial pace by Earth standards, where waves of such size would have moved seven times as fast.

  Maybe the boat could ride this out, just float over the back of those huge, stretching beasts.

  Maybe not.

  She began to drag her paddle through the paraffin lake once more, and she could see Rosenberg hauling clumsily on his cable, his feet scrabbling at the gumbo for footing.

  Within a couple of minutes, with a heavy bump, the boat had grounded against the shore of Clear Lake.

  Benacerraf looked back. The waves were heaping up still, glistening black walls sweeping grandly towards the shore. But they would break when they reached the shallows.

  With Rosenberg’s help, she began to haul the boat up the beach, far enough that the breaking waves couldn’t reach.

  * * *

  “Get moving, you old bastard.” Bart went around the room, his white jacket stained by some yellow fluid, and he de-opaqued the windows with brisk slaps.

  It took Marcus White a while to figure out where he was. It often did nowadays. So he just lay there. He’d been in the same position all night, and h
e could feel how his body had worn a groove in the mattress. He wondered if Bart had ever seen Psycho. “I thought—” His mouth was dry, and he ran his tongue over his wrinkled gums. “You know, for a minute I thought I was back there. Like before.”

  Bart was just clattering around at the bedside cabinet, pulling out clothes, and looking for his stuff: a hand towel, soap, medication, swabs. Bart never met your eyes, and he never watched for the creases on your pants.

  “My father was there.” Actually he didn’t know what in hell his father was doing up there. “The sunlight was real strong. And the ground was a kind of gentle brown, depending on which way you looked. It looked like a beach, come to think of it.” He smiled. “Yeah, a beach.” That was it. His dream had muddled up the memories, and he’d been simultaneously thirty-nine years old, and a little kid on a beach, running towards his father.

  “Ah, Jesus.” Bart was poking at the sheet between White’s legs. His hand came up dripping. Bart pulled apart the top of White’s pajama pants. White crossed his arms over his crotch, but he didn’t have the strength to resist. “You old bastard,” Bart shouted. “You’ve done it again. You’ve pulled out your fucking catheter again. You filthy old bastard.” Bart got a towel and began to swab away the piss.

  White saw there was blood in the thick golden fluid. Goddamn surgeons. Always sticking a tube into one orifice or another. “I saw my buddy — Tom, you know — jumping around, and I thought he looked like a human-shaped beach ball, all white, bouncing across the sand…”

  Bart slapped at his shoulder, hard enough to sting. “When are you going to get it into your head that nobody gives a flying fuck about that stuff? Huh?” He swabbed at the mess in the bed, his shoulders knotted up. “Jesus. I ought to take you down to the happy booth right now. Old bastard.”

  Like a beach. Funny how I never thought of that before. It had taken him forty years, but he was finally making sense of those three days. More sense than he could make of where he was now, anyhow. Not that he gave a damn.