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.
“It was a very long-term proposition, one of humanity’s first mega-projects. But the cost was modest; you only had to pay for the first generation of engineered bugs. The project has now been going on for twenty thousand years — at least that long; it was founded by the ancients, it’s believed, in the days even before the Qax Occupation.”
Once Venus’s carbon had been locked up in the convenient form of the chalk, it was easily mined, and had a myriad possible uses. But, said Nilis, it was only after the first few thousand years of the project that an unexpectedly useful application of Venus’s new crust of carbon dioxide polymers was discovered. “It turned out that some of the structures formed, in the hot, compressed layers of Venus chalk, had very interesting properties indeed.”
Pirius took a guess. “You’re talking about neutrinos.”
“Yes.”
Neutrinos were exotic subatomic particles. Like ghosts, they passed through matter, through Pirius’s own body, or even the bulk of a world like Venus, barely noticing that anything was in the way. “And that makes them rather hard to observe,” said Nilis.
Which was where Venus’s chalk came in. It was found that some of the more exotic polymers formed at high temperature and pressure in Venus’s gathering chalk layers were good at trapping neutrinos — or rather, traces of their passage.
Neutrinos took part in nuclear reactions: when atomic nuclei fissioned or fused, releasing floods of energy in the process. Nilis said, “There are two places in nature where such reactions are commonplace. One was in the first few minutes of the formation of the universe itself — the moments of nucleosynthesis, when primordial baryonic particles, protons and neutrons, combined to form the first complex nuclei. The other is in the center of the stars, which run on fusion power. So, you see, a neutrino telescope can see into the fusing heart of the sun.”
So Venus was given a new role: as a watchtower.
“The ancients believed a deep monitoring of the sun was important — but not for the sun itself. Stars are pretty simple machines, really, much simpler than bacteria, say, and were thoroughly understood long before the first extrasolar planet was visited. No, it wasn’t the sun they were interested in but what lay within the sun. Dark matter,” Nilis said. “That’s what Michael Poole’s generation were watching. Dark matter, in the center of the sun…”
As the sun swept through its orbit around the center of the Galaxy, it encountered dark matter. Almost as ghostlike as neutrinos, much of it simply passed through the sun’s bulk. But some interacted with the dense, hot stuff at the center of the sun, and losing energy, was trapped. Nilis said, “It orbits, lumps of dark matter orbiting the sun, even within the fusing heart of the star. Remarkable when you think about it.”
It was this strange inner solar system of dark matter, entirely contained within the bulk of the sun, that the Venus facility had been designed to study. The dark-matter particles would annihilate each other, and in doing so released more neutrinos, to be trapped at Venus and analyzed.
“I’ve glanced at the data streams,” Nilis said. “You can see structure in there: clumps, aggregates — even what looks like purposeful motion. There are some who speculate there is life in there, life- forms of dark matter. Why not, I say?”