Space m-2

by Stephen Baxter

The ground was complex. The tractor’s lights showed how the ice was stained pink, as if by traces of blood, and there were streaks of darker material laid over the surface. But here and there the dirty water-ice rock was overlaid by splashes of white, brilliant in the lights; this was nitrogen snow, fresh-fallen.

  The land became more uneven. The tractor climbed a shallow ridge, and Madeleine found herself tipped precariously back in her seat. From the summit of the ridge she caught a glimpse of a landscape pocked by huge craters, each some thirty kilometers wide or more. But they weren’t like impact craters; many of them were oval in shape.

  The tractor plunged into the nearest crater. The ground broke up into pits and flows, like frozen mud, and the tractor bounced and floated in great leaps.

  “This is the oldest surface on Triton,” Lena said. “It covers perhaps a third of the surface. From orbit, the land looks like the surface of a cantaloupe melon, and that gave it its name. But this is difficult and dangerous terrain.” Her accent was odd, shaped by time, sounding strangulated to Madeleine. “These ‘craters’ are actually collapsed bubbles in the ice. They formed when the world froze… You know that Triton was once liquid?”

  “After its capture.”

  “Yes.”

  “Neptune raised great tides in Triton. There was an ocean hundreds of kilometers deep — crusted over by a thin ice layer at its contact with the vacuum — that stayed liquid and warm, for half a billion years, as the orbit became a circle.”

  Madeleine eyed her suspiciously. “Life. That’s what you’re getting at. Native life, here in the tidal melt of Triton.” Just as Ben had hinted. She wasn’t surprised, or much interested. Life emerged wherever it could; everybody knew that. Life was a commonplace.

  “You know,” Lena said, “when we first came here we spread out from Kasyapa, around this little world.”

  “You sang Triton.”

  “Yes.” Lena smiled. “We made our roads with orbiting lasers, and we named the cantaloupe hollows and the snow fields and the craters. We were exhilarated, on this empty world. We were the Ancestors! But we grew… discouraged. Nothing moves here, save bits of ice and snow and gas. Nothing lives, save us. There aren’t even bones in the ground. Soon we found we had to ration food, energy, air. We mapped from orbit, sent out robots.”

  “Robots don’t sing.”

  “No. But there is nothing to sing here…”

  Madeleine, with a sudden impulse, covered Lena’s hand with her own. “Perhaps one day. And perhaps there was life in the deep past.”

  “You don’t yet understand,” Lena said, frowning. She tapped a control pad and the motor gunned.

  The tractor followed complex ridge pathways, heading steadily away from Kasyapa.

  They talked desultorily, about planetary formation, Lena’s long life on Triton, Madeleine’s strange experiences among the stars. They were exploring each other, Madeleine thought; and perhaps that was the purpose of this jaunt.

  Lena knew, of course, about Ben’s relationship with Madeleine. At length they talked about that, tentatively.

  Lena had known about it long before Ben had left for the stars. She knew such things were inevitable, even necessary, in a separation that crossed generations. She herself had taken lovers, even an informal second husband with whom she’d raised children. The ties of galay and dhuwa were, she said, too strong to be broken by mere time and space.

  Madeleine found she liked Lena. She still wasn’t sure if she envied Lena the ties she shared with Ben. To be bound by such powerful bonds, for a lifetime of indefinite duration, seemed claustrophobic to her. Perhaps I’ve been isolated too long, she thought.

  After some hours they reached a polar cap. It turned out to be a region of cantaloupe terrain where every depression was filled with nitrogen snow. They camped here, near the pole, on the fringe of interstellar space. Overhead, Madeleine saw cirrus clouds of nitrogen ice crystals.

  The pole was a dangerous place to walk. She saw evidence of geysers — huge pits blasted clean of snow — and dark streaks across the land, tens of kilometers long, like the remnants of gigantic roads. All of this under Neptune’s smoky light, and a rich dazzle of stars.

  This was an enchanting world. Madeleine found herself, reluctantly, falling in love with Triton.

  Reluctantly, because, she was coming to realize, she would have to destroy this place.

  Lena brought her, on foot, to a small unmanned science station, painted bright yellow so it stood out from the pinkish snow.

  “We are running a seismic survey,” she said. “There are stations like this all over Triton. Every time we shake the surface, by so much as a footstep, waves travel through this world’s frozen interior, and we can deduce what lies there.”

  “And?”

  “You understand that Triton is a ball of rock, overlaid by an ocean — a frozen ocean. But ice is not simple.” Lena picked up a loose fragment of ice and cupped it in her gloved hands. “This form is called ice one. It is the familiar form of ice, just as on Earth’s surface.” She squeezed tighter. “But if I were to crush it, eventually the crystal structure would collapse to an alternative, more closely packed, arrangement of molecules.”

  “Ice two.”

  “Yes. But that is not the end. There is a whole series of stable forms, reached with increasing pressure, the crystal structure more and more distorted from the pure tetrahedral form of ice one. And so, inside Triton, there are a series of layers: ice one at the surface, where we walk, all the way to a shell of ice eight, which overlays the rocky core…”

  Madeleine nodded, not very interested.

  The snows seemed to be layered. The deeper she dug with her booted toe, the richer the purple-brown colors of the sediment strata she uncovered. This hemisphere was entering its forty-year spring, and the polar cap was evaporating; thin winds of nitrogen would eventually carry all this cap material to the other pole, where it would snow out. And later, when it was autumn here, the flow was reversed. Triton’s atmosphere was not permanent: It was only the polar caps in transit, from one axis to another.

  But Lena was still talking. “…large scale rebuilding of the planet is the same as—”

  Madeleine held up her hands. “You left me behind. What are you telling me, Lena?”

  “That there is evidence of tampering, planetary tampering, from the deepest past, here on Triton.”

  Madeleine felt chilled. “Even here?”

  “Just like Venus. Just like Earth. Nothing is primordial. Everything has been shaped.”

  That inner layer of ice eight was no crude seam of compressed mush. It was very pure. And it seemed to have been sculpted.

  When they got back to the tractor Lena showed Madeleine diagrams, seismic maps. The core had facets — triangles, hexagons — each kilometers wide. “It’s as if somebody encased the core in a huge jewel,” she said. “And it must have been done before the general freezing.”

  “Somebody came here,” Madeleine said slowly, “and — somehow, manipulating temperature and pressure in that deep ocean — froze out this cage around the seabed.”

  “Yes.”

  “And the life-forms there—”

  “Immediately destroyed, of course, their nutrient supply blocked, their very cells broken open by the freezing. We can see them, their relics, in the deep samples we have taken.”

  Madeleine felt a deep, unreasoning anger well up in her. “Why would anybody do such a thing?”

  Lena shrugged. “Perhaps it was not malice. They may have had a mission — insane, but a mission. Perhaps they thought they were helping these primitive Triton bugs. Perhaps they wished to spare the bugs the pain of growth, change, evolution, death. This great crystal structure encodes very little information. You need only a few bits to characterize its composition — pure ice eight — and its regular, repeating structure. It is static, perfect — even incorruptible. Life, on the other hand, requires a deep complexity. It is this complexity that gives us our potential, and our
pain. Perhaps, you see, they felt pity…”

  Madeleine frowned. “Lena, did Ben encourage you to show me this? Are you trying to persuade me to back off the Nereid project?”

  “Ben and I have different experiences,” Lena said. “He traveled to the stars, and saw many things. I worked here, helping to uncover this strange, ancient tragedy.”

  Yes. There was no need to go to the stars, Madeleine saw now. It was here, all the time, on Venus and Triton and God-knows-where, and even Earth. The central paradoxical mystery of the universe. Everywhere, life emergent. Everywhere, life crushed. And no explanation why it had to be this way. Over and over.

  She felt her anger burn brighter. She had made her own decision. This wasn’t simply what Nemoto wanted. It had become what she wanted. And that burning desire felt good.

  Lena smiled, gnomic, wise.

  By the time they got back to Kasyapa, the flower-ships had grown in Triton’s sky, until at last their delicate filigree structure was visible, just, with the naked eye. The same fucking Gaijin who had watched as Earth had gone to hell.

  She sailed up to orbit, boarded Gurrutu, and headed for Nereid.

  Madeleine first sighted Nereid ten days out. It grew rapidly, day by day, finally hour by hour, until its battered gray hide filled the viewing windows.

  Rendezvous with the hurtling rock was difficult. The Gurrutu couldn’t muster the velocity change required to match Nereid’s crashing orbit. So Madeleine had to burn her engines and use tethers, harpooning this great rock whale as it hurtled past, letting her ship be dragged along with it. Gurrutu suffered considerable damage, but nothing significant enough to make Madeleine abort.

  She entered a loose, slow orbit, inspecting the moon’s surface. Nereid was uninteresting: just a misshapen ball of dirty ice, pocked by craters; it was so small it had never melted, never differentiated into layers of rock and ice like Triton, never had any genuine geology. Nereid was a relic of the past, a ruin of the more orderly moon system that had been wrecked when Triton was captured.

  But, despite its small size, it massed as much as 5 percent of Triton’s own bulk. And where Triton’s orbit, though retrograde, was neatly circular, Nereid followed a wide, swooping ellipse, taking almost an Earth year to complete a single one of its “months” around Neptune.

  Nereid could be driven head-on into Triton. It would be a useful bullet.

  She navigated with automatic star trackers, with radio Doppler fixes on Kasyapa, and by eye, using a sextant. Her purpose was to check the trajectory of the little moon, backing up the automated systems with this on-the-spot eyeballing, which, even now, was one of the most precise navigation systems known.

  Nereid was right on the button. But this game of interplanetary pool was played on a gigantic table, and Triton was a small target. Even now, even so close, Nereid could be deflected from its impact.

  At times the cold magnitude of the project — sending one world to impact another — awed her. This is too big for us. This is a project for the arrogant ones: the Gaijin, the others who strangled Venus and Triton.

  But when she was close enough, she could see the glow of engines on Nereid’s far side: engines built by humans, placed by humans. Placed by her. She clung to her anger, seeking confidence.

  Even now Ben debated the ethics of the situation with his people. Most people here had been born long after the emigration: born in the caverns of Kasyapa, now with children of their own. To them, Madeleine and Ben Roach were intruders from the muddy pool at the heart of the Solar System, invaders from another time who proposed to smash their world. The shortness of human lives, she thought. Our curse. Every generation thinks it is immortal, that it has been born into a world that has never changed, and will never change.

  She dozed in her sleeping compartment, a box little larger than she was. Inside, however, tucked into her sleeping bag with the folding door drawn to, she felt comfortable and secure. She would track Nereid as long as she could, guiding it to its destination, unless she was ordered to stand down.

  She got a number of direct calls from Nemoto that she did not accept. Nemoto was irrelevant now.

  At the very last minute Ben came through.

  Somewhat to her surprise, the colonists had agreed to let the project go ahead. Ben would arrange for the temporary evacuation of the colonists from Kasyapa, to the hulks of the old transport ships still in orbit, now drifting without their engines.

  “Lena is pleased,” he told her.

  “Pleased?”

  “By your reaction to the crystal shell around the core. The ice eight. She wanted to make you angry. If the project succeeds then the crystal shell will be destroyed. And the last trace of the native life will surely be destroyed with it.”

  Madeleine growled. “I know, Ben. I always knew. The Triton bugs lost their war a long time ago, before they even had a chance to voice an opinion. Their memory should motivate us, not stop us. The crystal builders have gone, but the Gaijin are on their way, here, now. Well, the hell with them. This is the trench we’ve dug, and we aren’t going to quit it.”

  “If,” he said, “the Gaijin are the true enemy.”

  “They will do for now.”

  He smiled sadly. “You sound like Nemoto.”

  “None of us age gracefully. Why didn’t you tell me about the native life, Ben?”

  His virtual image shrugged. “Not everybody who’s grown up here knows about it. Life is hard enough here without people learning that there is an alien artifact of unknown antiquity buried at the heart of the world.”

  She nodded. And yet he hadn’t answered her question. Despite all we’ve been through — even though we’re both refugees from another age, and we traveled to the stars together — I’m not close enough for you to share your secrets.

  At that moment, she felt the ties between them stretch, break. Now, she thought, I am truly alone; I have lost my only companion from the past. It was surprising how little it hurt.

  “Here is another possibility,” Ben said. “Beyond ethics, beyond this perceived conflict with the Gaijin. You like to meddle, to smash things, Madeleine. You are like Nereid yourself, a rogue body, come to smash our little community. Perhaps this is why the plan is so appealing to you.”

  “Perhaps it is,” she said, irritated. “You’ll have to judge my psychology for yourself.”

  And with an angry stab, she shut down the comms link.

  Alone in Gurrutu, she assembled a complete virtual projection of Triton, a three-dimensional globe a meter across. She looked for the last time at the ice surface of Triton, the subtle shadings of pink and white and brown.

  She switched to a viewpoint at Triton’s evacuated equator. It was as if she were standing on Triton’s surface.

  Nereid was supposed to do two things: to spin up Triton, and to melt its ancient oceans. Therefore she had steered the moon to come in at a steep angle, to deliver a sideways slap along Triton’s equator. And so, when she turned her virtual head, Nereid was looming low on the horizon: a lumpy, battered moon, visibly three-dimensional, rotating, growing minute by minute.

  An icon in the corner of her view recorded a steady countdown. She deleted it. She’d always hated countdowns.

  Her imaging systems picked out Gaijin flower-ships in low orbit around the moon, golden sparks arcing this way and that. She smiled. So the Gaijin were curious too. Let them watch. It would be, after all, the greatest impact in the Solar System since the end of the primordial bombardment.

  Quite a show. And for once it would be humans lighting up the sky.

  The end, when it came, seemed brutally fast. Nereid grew from a spot of darkness, to a pebble, to a patch of rock the size of her hand, to, Jesus, a roof of rock over the world, and then—

  Blinding light. She gasped.

  The image snapped back to an overview of the moon. She felt as if she had died and come back to life.

  A plume of fragments was rising vertically from Triton’s surface, like one last mighty ge
yser: bits of red-hot rock, steam, glittering ice, some larger fragments that soared like cannonballs.

  Nereid was gone.

  Much of the little moon’s substance must already have been lost, rock and ice and rich organic volatiles blasted to vapor in that first second of impact: lost forever, lost to space. Perhaps it would form a new, temporary ring around Neptune; perhaps eventually, centuries from now, some of it would rain back on Triton, or some other moon.

  This was an astoundingly inefficient process, she knew, and that had been a key objection of some of the Kasyapa factions. To burn up a moon, a whole four-billion-year-old moon, for such a poor gain is a crime. Madeleine couldn’t argue with that.

  Except to say that this was war.

  And now something emerged from the base of the plume. It was a circular shock wave, a wall of shattering ice like the rim of a crater, plowing its way across the ground. The terrain it left behind was shattered, chaotic, and she could see the glint of liquid water there, steaming furiously in the vacuum and cold. Ice formed quickly, in sheets and floes, struggling to plate over the exposed water. But echoes of that great shock still tore at this transient sea, and immense plates, diamond white, arced far above the water before falling back in a flurry of fragments.

  Now, in that smashed region — from cryovolcanoes kilometers wide — volatiles began to boil out of Triton’s interior: nitrogen, carbon dioxide, methane, ammonia, water vapor. Nereid’s heat was doing its work; what was left of the sister moon must be settling toward Triton’s core, burning, melting, flashing to vapor. Soon a mushroom of thickening cloud began to obscure the broken, churning surface. Some of the larger fragments thrown up by that initial plume began to hurtle back from their high orbits and burn streaks through Triton’s temporary atmosphere. And when they hit the churning water-ice beneath, they created new secondary plumes, new founts of destruction.

  The shock wall, kilometers high, plowed on, overwhelming the ancient lands of ice, places where nitrogen frost still lingered. It was not going to stop, she realized now. The shock would scorch its way around the world. It would destroy all Triton’s subtlety, churning up the nitrogen snows of the north, the ancient organic deposits of the south, disrupting the slow nitrogen weather, destroying forever the ancient, poorly understood cantaloupe terrain. The shock wall would be a great eraser, she thought, eliminating all of Triton’s unsolved puzzles, four billion years of icy geology, in a few hours.