The corvette he took was spartan compared to Nilis’s, and the crew, hardened Navy veterans irritated at being given such a chore, ignored Pirius for the whole trip. Pirius ate, slept, exercised. It wasn’t so bad; perhaps he was getting used to the strange experience of being alone.
In its final approach the corvette swept around the limb of the planet, approaching from the shadowed side, and the new world opened up into an immense crescent.
Pirius peered out of the transparent hull. The light was dazzling; he was actually inside the orbit of Earth here, and the sun seemed huge. Another new planet, he thought wearily, another slice of strangeness.
But this one really was extraordinary. Under a thick, slightly murky atmosphere, the ground was pure white from pole to equator, and from orbit it looked perfectly smooth, unblemished, like an immense toy. He had never seen a world that looked so clean, he thought, so pristine. The whole surface even seemed to sparkle, as if it were covered in grains of salt.
The corvette entered low orbit and the planet flattened out into a landscape. The air was tall, all but transparent, without cloud save for streaks of high, icy haze. But Pirius saw contrails and rocket exhausts, sparking through the air’s pale gray. Once he saw an immense craft duck down from orbit to skim through the upper atmosphere. It was a kind of trawler; air molecules were gathered into a huge electromagnetic scoop, its profile limned by crackling lightning.
This close, though, the geometric perfection of the world was marred by detail. Pirius made out the shapes of mountains, canyons, even craters. But everything was covered by white dust, every edge softened, every profile blurred. Pirius wondered if the white stuff could be water ice, or even carbon dioxide snow, but the sun’s heat was surely too intense for that.
Small settlements studded the land. Around these scattered holdings, quarries had been neatly cut into the creamy ground, their floors crisscrossed by the tracks of toiling insect-like vehicles. Tiny craft rose into space from small, orange-bright landing pads, carrying off the fruit of the quarries. Many of the buildings were themselves covered with white dust; evidently some of them were ancient.
Pirius asked the Navy crew what the white dust was. Their reply was blunt: “Chalk,” a word that meant nothing to Pirius. But they called this world “the carbon mine,” as Darc had. It was only later that Pirius learned that this “carbon mine” had once had a name of its own, an ancient name with nothing to do with the purposes to which the planet had been put. Once, it had been called Venus.
“So, another stop on your grand tour of Sol system, Ensign Pirius?”
“It’s not by choice, Commissary.”
“Of course. Well, come along, come along…” Nilis led the way along bare-walled corridors, padding over floors rutted by long usage.
Nilis was working in an orbital habitat; the corvette had cautiously docked at the heart of a sprawling tangle of modules, walkways, and ducts. The habitat was devoted to pure science, it seemed; to the planet’s secondary role as a “neutrino telescope.” And it was old: the modules’ protective blankets were cratered by micrometeorite impacts, and blackened by millennia of exposure to the hard light of the sun.
Within, the facility was a warren of corridors and small cylindrical chambers. Over a stale human stink, there was a lingering smell of ozone, of welding and failing electrical systems. The station had reasonably modern position-keeping boosters, inertial control, life support and other essential systems, but everywhere you looked maintenance bots toiled to keep the place going. The power nowadays came from a couple of GUT modules, but the habitat still sported an antique set of solar- cell wings, its glossy surfaces long since blackened and peeled away.
Nilis said that, as a pure science facility, without obvious military potential, this place had always been starved of resources. “You get used to it,” he said.
He brought Pirius to an observation module. They peered out at the gleaming face of the planet, and Pirius was dazzled. But he could make out the tracery of quarries and roads on the shining surface, and the steady streams of shuttles flowing through the atmosphere.
Nilis said conspiratorially, “I rather like it here. But it’s not a happy place to work. On Pluto, say, you’re truly isolated, out in the middle of nowhere. But here, Earth is close enough to show as a double planet to the naked eye — close enough to touch. Nobody wants to work in a place like this, when home is so temptingly close.”
Pirius ventured, “Venus is a carbon mine.”
“Yes. Though nobody calls it Venus anymore. Nobody but Luru Parz and her kind.”
Pirius knew enough basic planetology to understand that this planet must have been heavily transformed. It was a rocky world not much smaller than Earth, and this close to its parent sun it should have been cloaked with a thick layer of air, a crushing blanket of carbon dioxide and other compounds baked out of the rocks by the sun’s relentless heat.
Well, the atmosphere had once been over two hundred kilometers thick, Nilis said; it had massed about a hundred times as much as Earth’s, and had exerted a hundred times as much pressure at the surface. The bottom twenty kilometers or so had been like a sluggish ocean, and the rocks beneath had been so hot they had glowed red. That was the planet humans had first visited — and in those days the clouds were so thick that no human eye had ever seen the ground.
“Venus was infuriating. A world so close to Earth, and so similar in broad numbers, but so different. For instance there’s actually no more carbon dioxide on Venus than on Earth; but on Earth it is locked into the carbonate rocks, like limestone; here it was all hanging lethally in the air. So what do you do?
“In the early Michael Poole days, there were all sorts of schemes for terraforming Venus, for making it like Earth. Perhaps you could seed that thick air with nanobots or engineered life-forms, and use the sun’s energy to crack the useless carbon dioxide into useful carbon and oxygen. Fine! But there was so much air that you’d have finished up with a planet covered in a hundred-meter layer of graphite — and about sixty atmospheres worth of pure oxygen. Any human foolish enough to step out on the surface would have spontaneously combusted!
“So then there were mega-engineering proposals to blast that annoying blanket of air off the planet altogether, with bombs, or even asteroid strikes. Happily somebody had a brighter idea.”
It was realized that carbon was actually a vitally useful element — and the air of Venus contained the largest deposit of carbon in the inner system, larger than that of all the asteroids combined. It would be criminally wasteful to blast it away. So a new scheme was concocted, the planet seeded with a different sort of engineered organism.
“They drifted through the high clouds,” Nilis said, “little bugs living in acidic water droplets, fed by photosynthesis. And they made themselves shells of carbon dioxide — or rather, of carbon dioxide polymers, cee-oh-two molecules stuck together in complex lattices.” The nanotech that enabled these engineered bugs to make their shells was based on the technology of an alien species called the Khorte, long Assimilated. “It was one of the first applications of alien technology inside Sol system,” Nilis said. “And it worked. When each little critter died, its shell was heavy enough to drift down out of the clouds toward the ground, taking with it a gram or two of fixed carbon dioxide.”
Pirius saw the idea. “The carbon snowed out.”
“Yes. On the ground, as it compressed under its own weight, it melted and amalgamated, and even more complicated polymers were formed. Those who mine the stuff call it chalk; something similar forms at the bottoms of Earth’s seas.