Space

by Stephen Baxter

  She found a dent.

  It was maybe a half-metre across. There was a bar across the middle of it. The bar was held away from the lower surface, and was fixed by a kind of hinge mechanism at one end.

  Once more her heart hammered, and she felt a pulse in her forehead. Up to now, there had been nothing that could have proven, unambiguously, Nemoto’s assertion that the moonlet was an artefact. But there was surely no imaginable natural process by which a moon could grow a lever, complete with hinge.

  She wrapped both hands around the lever and pulled.

  Nothing happened. The lever felt immovable, as if it was welded tight to the rocky moon – as, of course, it might be, after all this time.

  She braced herself with a piton hammered into the ‘door’, and pushed. Nothing. She twisted the lever clockwise, without success.

  Then she twisted it anticlockwise.

  The lever turned smoothly. She felt the click of buried, heavy machinery – bolts withdrawing, perhaps. The floor fell away beneath her.

  Quickly she let go of the lever. She was left floating, surrounded by dust, suspended over a pit of darkness. Some kind of vapour sparkled out around her.

  Making sure her pitons were secure, she slid past walls of rock, and through the open door.

  Nemoto’s recruitment pitch had been simple. ‘The flight will make you rich,’ she’d promised.

  Carole had been sceptical. After all, she was only going as far as Venus, a walk around the block compared to the light-years-long journeys undergone by the handful of interstellar travellers who had followed Reid Malenfant through the great Saddle Point gateways – even if, twenty years after the departure of Madeleine Meacher, the first, none of them had yet returned.

  But still, Nemoto turned out to be right. Nemoto’s subtle defiance of the Gaijin’s unstated embargo on Venus had evidently struck a chord, and Carole’s shallow fame had indeed led to lucrative opportunities she hadn’t been ashamed to exploit.

  But it wasn’t the money that had persuaded Carole to commit three years of her life to this unlikely jaunt.

  ‘Think of your mother,’ Nemoto had whispered, her mask-like face twisted in a smile. ‘You know that I met her once, at a seminar in Washington. Reid Malenfant himself introduced us. She was fascinated by Venus. She would have loved to go there, to a new world.’

  Guilt, of course, the great motivator.

  But, of course, Nemoto was right. Her mother had grown to love Venus, this complex, flawed sister world of Earth. She used to tell her daughter fantastic bedtime tales of how it would be to sink to the base of those towering acid clouds, to stand on Venus itself, immersed in an ocean of air.

  But her mother’s studies had been based on scratchy data returned by a handful of automated probes, sent by human governments in the lost pre-Gaijin days of the last century. When the Gaijin had showed up, all of that had stopped, of course.

  Now humans rode Gaijin flower-ships to Mars, Mercury, even the moons of Jupiter. Where the Gaijin granted access, an explosion of data resulted, and human understanding advanced quickly. But the Gaijin were very obviously in control, and that caused a lot of frustration among the scientific community. The scientists wanted to see it all, not just what the Gaijin chose to present.

  And there were major gaps in the Gaijin’s gift. Notably, Venus. There hadn’t been a single Gaijin-hosted human visit to Venus – although it was obvious, from telescopic sightings of flower-ship activity, that this was a major observation site for the Gaijin.

  Not too many people cared about such things. To spend one’s entire life labouring in some obscure corner of science – when it was obvious that the Gaijin already had so much more knowledge – was dispiriting. Carole herself hadn’t followed her mother’s footsteps. She had gone instead into theology, one of the many broadly philosophical boom areas of academic discipline. And her mother had gone to her grave unfulfilled, leaving Carole with a burden of obscure guilt.

  The truth was, to Carole, these issues – the decline of science, the obscure activities and ambitions of the Gaijin – were dusty, the concerns of another century, of vanished generations. This was 2081: sixty years after Nemoto’s discovery of the Gaijin. To Carole, as she had grown up, the Gaijin were here, they had always been here, they always would be here. And so she had put aside her guilt, as much as any child can about her mother.

  Until Nemoto had come along.

  Nemoto: herself a weird historic relic, riven by barely comprehensible obsessions, huddled on the Moon, nursing her fragile body with a suite of ever more exotic anti-ageing technologies. Nemoto continually railed against the complacency of governments and other bodies regarding the Gaijin and their activities. ‘We have no sense of history,’ she would say. ‘We have outlived our shock at the discovery of the Gaijin. We do not see trends. Perhaps the Gaijin rely on our mayfly lifespan to wear away our scepticism. But those of us who remember a time before the Gaijin know that this is not right …’

  And Nemoto was worried about Venus.

  One thing that was well known about the Gaijin was that their favoured theatre of operations was out in the dark, among the asteroids, or the stately orbits of the giant planets, or in the deeper cold of the comet clouds even further out. They didn’t appear to relish the solar system inward of Earth’s orbit, crammed with dust and looping rogue asteroids, drenched by the heat and light of a too-close sun, a place where the gravity well was so deep that a ship had to expend huge amounts of energy on even the simplest manoeuvre.

  So why were the Gaijin so drawn to Venus?

  Nemoto had begun to acquire funding, from a range of shadowy sources, to initiate a variety of projects: all more or less anti-Gaijin – including this one.

  And that was why the first human astronaut to Venus was under Nemoto’s control: not attached to a Gaijin flower-ship, but riding in a clunky and crude human-built spacecraft, little advanced from Apollo 13 as far as Carole could tell, a ship that had been fired into space from a great electromagnetic cargo launcher on the Moon.

  The Gaijin could have stopped her, Carole supposed. But, though they had shadowed her all the way here, they had shown no inclination to oppose her directly. Perhaps that would come later.

  Or perhaps, to the Gaijin, Carole and her fragile ship simply didn’t matter.

  She was surrounded by blackness, the only lights the telltales in her helmet and on her chest panel. The aperture above her was a star field framed by the open doorway.

  Nemoto, time-delayed, began to speculate about the vapours that had been trapped by the translucent sheet. ‘A good deal of sulphuric acid,’ she said. ‘Other compounds … some clay particles … a little free oxygen! How strange …’

  On her belt Carole carried a couple of miniaturized floods. She lit them now. Elliptical patches of light splashed on the walls of the chamber, which curved around her. She glimpsed an uneven, smoothly textured inner surface, some kind of structure spanning the interior.

  She reported to Nemoto. ‘The moonlet is hollowed out. The chamber is roughly spherical, though the walls are not smooth. This single chamber must take up most of the volume of the moonlet. The walls can’t be much more than a few metres thick anywhere …’ She aimed her beams at the centre of the cavern. There was a dark mass there, about the size of a small car. It was fixed in place by a series of poles that jutted out radially, like the spokes of a wheel, to the wall of the chamber, fixing themselves to the moonlet’s equator. The spokes looked as if they were made from rock too. Perhaps they had just been left in place when the chamber had been carved out.

  She described all this, without speculating about the purpose of the structures. Then she blipped her thruster pack and drifted to the wall.

  The wall looked carved. She saw basins, valleys, little mountains and ridges, all on the scale of metres. It was like flying over a miniaturized landscape at some theme park.

  ‘… The central structure is obviously a power source,’ Nemoto was saying. ‘There
is deuterium in there. Fusion, perhaps. A miniature sun, suspended at the centre of this hollow world. And from the topography of that inner surface it seems that the moonlet’s basins and valleys have been carved to take a liquid. Water? A miniature sun, model rivers and seas – or at least, lakes. Perhaps the moonlet was spun up to provide artificial gravity … This is a bubble world, Carole, designed to support some form of life, independent of the outside universe.’

  ‘But that makes no sense,’ Carole replied. ‘We’re orbiting Venus. There’s a gigantic sun just the other side of that wall, pumping out all the energy anybody could require. Why would anybody hide away in this – cave?’

  But Nemoto, time-delayed, kept talking, of course, oblivious of her questions.

  Carole stopped a metre or so short of the wall. She deployed her portable lab, letting its laser shine on the wall.

  She stroked the wall’s surface. The texture was nothing like the lunar-surface rock and regolith of the moonlet’s exterior. Instead there seemed to be an underlay of crystalline substances that glinted and sparkled – quartz perhaps. Here and there, clinging to the crystalline substrate, she found a muddy clay. Though the ‘mud’ was dried out in the vacuum, she saw swirls of colour, complex compounds mixed in with the basic material. It reminded her of the gloopy mud of a volcanic hot spring.

  The first results of her lab’s analysis began to chatter across its surface. Quartz, yes, and corundum – aluminium oxide. And everywhere, especially in those clay traces, she found traces of sulphuric acid.

  Nemoto understood immediately.

  ‘… Sulphuric acid. Of course. That is the key. What if these artificial lakes and rivers were once filled with acid? An acid biosphere is not as unlikely as it sounds. Sulphuric acid stays liquid over a temperature range three times that of water. Of course the acids dissolve most organic compounds – have you ever seen a sugar cube dropped in acid? But alkanes – simple straight-chain hydrocarbons – can survive. Or perhaps there is a biochemistry based on silicones, long-chain molecules based on silicon-oxygen pairs … Only a few common minerals can resist an acidic environment: quartz, corundum, a few sulphates. These walls have been weathered. Your mother would have understood … Venus is full of acid, you see. The clouds are filled with floating droplets of it. This is a good place to be, if what you need is acid …’

  Carole gazed into the empty lake basins, and tried to imagine creatures whose veins ran with acid. But this toy world, Nemoto had said, was hundreds of millions of years old. If any of their descendants survived they must be utterly transformed by time, she thought, as different from those who built this moonlet as I am from my mindless Mesozoic ancestors.

  And if we found them – if we ever touched – we would destroy each other.

  ‘… This bubble world is surely not meant to stay here, drifting around Venus, forever. We may presume that this was merely the construction site, Venus a resource mine. The bubble is already on a near-escape orbit; a little more energy and it could have escaped Venus altogether – perhaps even departed the sun’s gravity field. You see?’

  ‘I think so –’

  ‘This rogue moonlet could travel to the nearer stars in a few centuries, perhaps, with its occupants warmed against the interstellar chill by their miniature interior sun …’

  They had been migrants to the solar system, born in some remote, acidic sea. Perhaps they had come in a single, ancient moonlet, a single spore landing here as part of a wider migration. They had found raw materials in Venus’s orbit – perhaps a moon or captured asteroids – to be dismantled and worked. They had made more bubble worlds, filled them with oceans of sulphuric acid mined from Venus’s clouds, and sent them on their way – thousands, even millions of moon-ships, the next wave of colonization, continuing the steady diffusion of their kind.

  ‘It’s a neat method,’ Nemoto said. ‘Efficient, reliable. A low-technology way to conquer the stars …’

  ‘Could it have been the Gaijin?’ Carole asked.

  ‘… But how convenient,’ Nemoto was saying, ‘that these sulphur-eaters should arrive in the solar system and find precisely what they needed: a planet like Venus whose clouds they could mine for their acid oceans, a convenient moon to dismantle. And where did the energy come from for all this? … Oh, no, Carole, these weren’t Gaijin. Whatever the secrets of this sulphuric-acid biology, it is nothing like the nature of the Gaijin. And this is all so much older than the Gaijin.’

  Not the Gaijin, Carole thought, chilled. An earlier wave of immigrants, hundreds of millions of years in the past. The Gaijin weren’t even the first.

  ‘We can’t know why they stopped before they had completed their project,’ Nemoto said softly. ‘War. Cataclysm. Who knows? Perhaps we will find out on Venus. Perhaps that is what the Gaijin are here to discover.’

  My mother’s generation grew up thinking the solar system was primordial – basically unmodified by intelligence, before we crawled out of the pond. And now, though we barely started looking, we found this: the ruin of a gigantic colonization and emigration project, ancient long, long before there were humans on Earth.

  ‘You expected to find this,’ she said slowly. ‘Didn’t you, Nemoto?’

  ‘… Of course,’ Nemoto said at last. ‘It was logically inevitable that we would find something like this – not the details, but the essence of it, somewhere in the solar system. The violation. And the secretive activities of the Gaijin drew me here, to find it.

  ‘One more thing,’ Nemoto whispered. ‘Your data has enabled me to make a better estimate of the artefact’s age. It is eight hundred million years old.’ Nemoto laughed softly. ‘Yes. Of course it is.’

  Carole frowned. ‘I don’t understand. What’s the significance of that?’

  ‘Your mother would have known,’ said Nemoto.

  Chapter 12

  SISTER PLANET

  Four hundred kilometres high, Carole was falling towards Venus. The lander had no windows; the conditions it had to survive were much too ferocious for that. But the inner walls were plastered with softscreens, to show Carole what lay beyond the honeycombed metal that cushioned her. Thus, the capsule was a fragile windowed cage, full of light and her universe was divided into two: stars above, glowing planet below.

  Her descent would be a thing of skips and hops and long glides as she shed her orbital energy. The sensation was so gentle, the panorama so elemental, that it was almost like a virtual simulation back on Earth. But this was no game, no simulation; she was really here, alone in this flimsy capsule, like a stone thrown into the immense air ocean of Venus, a hundred million kilometres from any helping hand.

  Still she fell. The cloud decks below her remained featureless, but they were flattening to a perfect plain, like some geometric demonstration. Looking up, she could see a great cone of shining plasma trailing after her lander as it cut into the high air. She imagined seeing herself from space, a fake meteorite shining against the smooth face of Venus.

  As her altitude unravelled the air thickened, and the bites of deceleration came hard and heavy, the buffeting more severe. Now the noise began, a thin screaming of tortured air, molecules broken apart by the heat of her descent, and there were flashes of plasma light at her virtual windows, like flashbulb pops. The temperature of the thin air outside rose to Earth-like levels, twenty or thirty centigrade.

  But the air was not Earth-like. Sulphuric acid was already congealing around her, tiny droplets of it, acid formed by the action of sunlight on sulphur products and traces of oxygen that leaked up from the pool of air below.

  At seventy kilometres she fell into the first clouds.

  The stars winked out, and thick yellow mist closed around her. Soon even the sun was perceptibly dimming, becoming washed-out, as if seen through high winter clouds on Earth. Still the bulk of Venus’s air ocean lay beneath her. But she was already in the main cloud deck, twenty kilometres thick, the opaque blanket which had, until the age of space probes, hidden Venus’s surfac
e from human eyes.

  The buffeting became still more severe. But her capsule punched its way through this thin, angry air, and soon the battering of the high superstorms ceased.

  Her main parachute blossomed open; she was briefly pushed back hard in her seat, and her descent slowed further. There was a rattle as small unmanned probes burst from the skin of her craft and arced away, seeking their own destiny.

  The visibility was better than she had expected: perhaps she could see as far as one, even two kilometres. And she could make out layers in the cloud, sheets of stratum-like mist through which she fell, one by one.

  Now came a patter against the hull: gentle, almost like hail, just audible under the moaning wind noise. She glimpsed particles slapping against the window: long crystals, like splinters of quartz. Were they crystals of solid sulphuric acid? Was that possible?

  The hail soon disappeared. And, still fifty kilometres high, she dropped out of the cloud layer into clear air.

  She looked up at rigging, giant orange parachutes. The capsule was swaying, very slowly, suspended from the big parachute system. The clouds above were thick and solid, dense, with complex cumulus structures bulging below like misty chandeliers, almost like the clouds of Earth. The sun was invisible, and the light was deeply tinged with yellow, fading to orange at the blurred horizon, as if she was falling into night. But there was still no sign of land below, only a dense, glowing haze.

  With a clatter of explosive bolts her parachutes cut away, rippling like jellyfish, lost. She dropped further, descending into thickening haze. The lower air here was so dense it was more like falling into an ocean: Venus was not a place for parachutes.

  The light was dimming, becoming increasingly more red.

  Telltales lit up as her capsule’s protective systems came online. The temperature outside was rising ferociously, already far higher than the boiling point of water – though she was still twice as high as Earth’s highest cirrus clouds. The lander’s walls were a honeycomb, strong enough to withstand external pressures that could approach a hundred atmospheres. And the lander contained sinks, stores of chemicals like hydrates of lithium nitrate, which, evaporating, could absorb much of the ferocious incoming heat energy. But the real heat dump was a refrigeration laser; every few minutes it fired horizontally, creating temperatures far higher even than those of Venus’s air.