Space

there must be a backup mechanism. And I’ll wager that is still working.”

So Carole got to her hands and knees, trying to keep from pushing herself away from the ground, and she scrabbled in the dirt, her gloved hands soon filthy.

She found a dent.

It was maybe half a meter 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 artifact. 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 counterclockwise.

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 vapor 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 skeptical. 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 masklike 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, the great motivator.

But 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 tothe 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 laboring 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 in 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 antiaging 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 life span to wear away our skepticism. 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 favored theater 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 farther 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 maneuver.

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 vapors 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 meters thick anywhere…” She aimed her beams at the center 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. 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 meters. 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 center 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 to her questions.

Carole stopped a meter 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 color, 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 — aluminum 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.”