The marines exchanged an uncomprehending glance. "Aerogels are ninety-nine percent air," said Herat. "We use them as insulation. They weigh almost nothing, but they're pretty strong. Our hosts, here," he waved around at the tunnel, "found they could make a kind of substitute for water, at a thousandth the weight. The grains don't crush easily, but they'll deform and move past each other. They behave mechanically almost exactly like a liquid."

Katz nodded vigorously. "Cheaper to accelerate," he said.

"I kind of thought that was what it was," said Evan. "But I didn't want to say so in case I was wrong."

"So now what?" asked Rue. "Can we go in it?"

"Oh, sure! It's not going to have any effect on our suits. And the sonar penetrates it. Perfect."

"In that case, we'd better set up camp. Corinna?"

She and Evan began unpacking and pasting down a pressure tent. "Just like old times, huh?" said Evan with a grin.

Herat shot a significant glance at Michael; that was his cue to butt in and make sure the halo-worlders followed proper quarantine procedure. He went over and politely asked to help. Meanwhile Herat, Rue, and the others crouched at the edge of the lake and ran their hands through it, discussing how best to proceed.

They erected two pressure tents and stuck them to the floor using a degradable glue. After several more hours spent surveying the axis, they retreated to the tents. Michael was in the larger tent, with Herat, Salas, Katz— and Rue Cassels. They stripped out of their suits, but left the black skintight underlayer on, as per regulations. In the event of a depressurization, the underlayer would protect them for several minutes.

There was almost no gravity here, so they pitched their sleeping bags standing up. That left plenty of floor space, where Salas and Herat hunkered down to play with samples of the aerogel. Katz fussed with the air mix for a while, then put on blinkers and earplugs and climbed into his sleeping bag. "See you in the morning, if that concept still has value around here," he said.

Michael sat down next to Herat. His employer had an uncharacteristically dreamy expression on his face. "Look at this place," said Herat, peering out of the tent's small window.

Michael called over his shoulder. "We've seen alien technology before."

"Yes… but this is different."

Michael nodded.

"How?"

They both turned their heads. Rue Cassels stood behind them. "How is this different?" she asked.

Herat scratched his ear. "Hmm… pretty fundamental question." Herat and Michael turned, offering a place in their circle. Rue drifted down to sit with them.

"Well," said Herat, "you know the R.E.'s been expanding through what used to be the cycler civilization for sixty years now. We actually had the FTL drive twenty years before that, but Earth hushed it up and started slowly, with exploratory vehicles that deliberately avoided the suns colonized by the cyclers. Even then the plan was to arrive at the cycler worlds with overwhelming force and complete knowledge about the stellar neighborhood.

"We sent exploration ships out to search for Earthlike worlds. The program concentrated almost exclusively on single, G-class stars like the sun. We did find life, everywhere, in fact. The universe is overflowing with it, it appears in unthinkable environments. It thrives brainless and without senses on nearly every world that could sustain liquid water. But intelligent life? That's another story. We didn't find any during that period— not currently existing intelligence, that is. But everywhere we went, we found the ruins of great ancient civilizations… cities and shattered fleets; burnt-off continents still radioactive after a million years… and everywhere, we found Earthlike planets that had been bombarded by meteors all at the same time, sixty-five million years ago.

"I spent a summer on the Yucatan peninsula, in Mexico, studying the Chicxulub crater. It's sixty-five million years old; the meteor that made it caused the extinction of the dinosaurs. I'm partly responsible for naming the particular aliens who made that crater and thousands like it throughout the galaxy. The Chicxulub, you see, were the last pangalactic civilization. They wiped out every other sentient species in the galaxy by sending out self-reproducing planet killers— von Neumann machines— that bombarded every world that had animal life bigger than a fly. Then they died out in turn.

"The Chicxulub left the galaxy empty of technological species. Our studies showed that it took at least thirty million years for new toolmaking species to develop from the Chicxulub extinction event.

"The Chicxulub partly explain why the galaxy is so empty of intelligent life— but not completely. In the early years of the exploration the Panspermia Institute was formed and I was one of the first graduates. They filled our heads with idiotic notions; I was starry-eyed and intent on uncovering a galactic pyramid of consciousness, with microbes at the bottom, ancient wise species at the top, and us somewhere in the middle— A vision inherited from the mystical writings of Teilhard de Chardin, though I had never even heard his name at that point. But the stupid ideas we got from him resulted in the fiasco the Institute's in now.

"Our goal was to find our counterparts— conscious, toolmaking aliens whose civilizations might help us understand our own. We would find or help establish a galactic government, integrate our culture with those alien ones and follow the path to species-maturity. It was a fine vision and heavily funded by the R.E. We even built a giant orbital station, called Olympus, which was to be the home for our ambassadorial counterparts."

Rue nodded. "And you sponged our wealth off relentlessly to pay for it, until places like Chandaka can no longer survive on their own."

"Yes, but we thought it was for a good cause! We genuinely believed that the outcome would be a galactic civilization with a future history of millions, maybe billions of years, with humanity as the founders and chief patrons. Think of it! What greater dream could there be?"

Rue shook her head. "But the halo worlds could never be a part of it. We can't travel at faster than light. We could never visit Olympus."

"Well." Herat looked uncomfortable. "Nobody on Earth ever really believed anyone would live in the halo by choice. How could people live their whole lives without seeing the light of a sun? No— anybody born on a lit world would wither and die in the halos and we thought— they thought— that over time, the halo worlds would be abandoned. That's still the prevailing opinion in the R.E.

"So the Rights Economy went from being a completely local, Earthbound incestuous loop into a kind of panhuman taxation empire. It expanded like a swarm of locusts, devouring the inhabited lit worlds of the cycler civilization, bypassing the halo worlds and leaving them stranded and alone." Herat sighed. "I know it's a tragedy. I saw it happen. But at the time… it made so much sense. The R.E. was the only way to maintain control over the far-flung colonies, to prevent them from developing into political rivals, or from going transhuman on us.

"Anyway, thousands of ships were fanning out across the galaxy, searching for intelligent species. There was life everywhere, after all— why not life like ourselves?"

"Hang on," said Rue. "It sounds like you're saying you never found aliens. But I've heard about them— they do exist."

"Ah, well." Herat smiled sadly. "For political reasons, we have found it necessary to label certain species and… things… as aliens. Don't get me wrong— there are starfaring species out there, like the hinge foxes, or the autotrophs. We have found intelligent entities. Just… not what we expected. Not what we were looking for.

"Take the autotrophs. Because their planet had a more active carbon cycle than Earth, oxygen from photosynthesis took a billion years longer to concentrate in their atmosphere. Animals never developed, because autotrophic life— life that produces its own nutrients from ambient energy and minerals— had a billion extra years to evolve.