When you have the oxygen you want, and the dry ice all flat on the lowlands, cover the dry ice with foamed rock, so that the CO ₂is a completely sequestered feature of the lithosphere.

Now take the chunks of Dione you have been saving and crack them against each other in the oxygen-and-buffer atmosphere at the correct height to create steam and rain. This will add back to the planet some heat, which at this point has been taken below the human-friendly range. Possibly some light can be let through the sunshield if needed to help heating. It will only take two years for the greater part of the impact water to rain and snow onto the surface, so be ready to work fast.

The water on the surface after this Dione infusion will be equal to about 10 percent of Earth’s water. It will be freshwater; salt to taste. The water will cover 80 percent of Venus, which is much flatter than Earth, to an average depth of 120 meters. If deeper seas are preferred, but also a maximum amount of land, consider digging an oceanic trench with some of the Dione impactors. Remember this will complicate the CO ₂sequestration if you choose to do it, so make adjustments accordingly. If it is done carefully, however, Venus could ultimately end up with about twice the land surface that Earth has.

At this point (140 years freezing and preparation, 50 years scraping and poaching, so be patient!) you might think that the planet is ready for biological occupation. But remember, combining the Venusian year of 224 days with its daily rotation period of 243 days, you get a screwball curve (retrograde motion, sun rising in the west) in which the solar day for any particular point on the planet is 116.75 days. Tests have long since determined that that’s too long for most Terran life-forms to survive, tweaked or not. So at this point, two main options have been identified. First is to program the sunshield so that it lets through sunlight to the surface and then blocks it off again, flexing like a circular venetian blind to make a more Terran rhythm of night and day. This would make it easy on the new biosphere, but would require that the sunshield work without fail.

The second option would call for another round of impactor bombardments, this time striking the surface of the planet such that their angular momentum spins the planet up to something like a fifty-hour day, which is considered within the tolerance limit for most Terran life-forms. The problem with this option is the way it would delay occupation of the planet’s surface, by its release of a considerable amount of the sequestered dry ice under the foamed rock layer. Biosphere establishment would have to be put off for another two hundred years, effectively doubling the time of terraformation. But there would be no further reliance on a sunshield. And a properly constituted and maintained Venusian atmosphere could handle full sunlight without greenhousing or other spoilage.

Which option you choose is your preference. Think about what you want in the end, or, if you don’t believe in endings, which process you prefer.

KIRAN AND SHUKRA

A few days later they were approaching Venus. Kiran was pleased to see Swan joining him on the ferry ride down. She wanted to talk to a friend; she would introduce Kiran to him, then be on her way.

There were no space elevators on Venus, because the planet rotated too slowly for such a system to work. So their ferry sprouted wings, and as they tore down through the atmosphere the windows torched yellow-white. They landed on a huge runway next to a domed city, then got into a subway car, and came up from that short ride into the city. There they found what seemed like the entire population in the streets. Kiran followed Swan through the crowds, and in a side street they went up some stairs into a little Mercury House, set over a fish shop. They dropped off their bags, then went back out to join the crowd.

The faces of the city were mostly Asian. People shouted, and in the din no one could hear well, so they shouted even louder. Swan looked at Kiran and grinned at his expression. “It isn’t always like this!” she shouted.

“Too bad!” Kiran shouted back.

Two big ice asteroids were apparently headed for a collision at the upper edge of the new Venusian atmosphere, roughly above the equator. This city, Colette, was three hundred kilometers north of the collision, and would therefore be quickly enveloped in a downpour. The rain would not stop for a couple of years, Swan said, after which they would let a little light through their sunscreen and have more ordinary weather.

But first the big rain. Crowds stood around them waiting for it, singing and cheering and shouting. And right at midnight the southern sky lit up white, then incandescent yellow, then all the reds ever seen. The inside of the city looked briefly like they were seeing it in the infrared. The noise of the cheering was stupendous. Somewhere a brass band was playing—Kiran spotted the musicians, on risers across the square—several hundred trumpets, French horns, baritones, trombones, tubas, all the euphoniums, everything from miniature cornets to alphorns, playing immense dissonant chords that blatted in the air and shifted ceaselessly toward harmonies that never came. Kiran didn’t know whether to call it music; it sounded like they played without a plan. The effect was to make people shout and howl, leap and dance. They were making their sky.

Within the hour a wild rain had erased the stars and was drumming onto the dome as if trying to wash it away. They might as well have been at the bottom of a waterfall. The city’s lights bounced off the dome glass and came back somehow liquefied, so that shadows ran over people’s faces.

At some point Swan squeezed Kiran’s upper arm in a manner very like the way he had hers the night they had met. He felt the pressure, he knew what she meant; his blood burned up and down from the spot she held. “All right already!” he shouted to her. “Thank you!”

With a little smile she let him go. They stood in the streaming light, the dome a dim milky white over them. The roar of voices was like waves breaking on a beach of cobbles. “You’ll be all right?” she said.

“I’ll be fine!”

“So now you owe me.”

“Yes. But I don’t know what I can give you in return.”

“I’ll think of something,” she said. “For now, I’ll introduce you to Shukra. I worked for him a long time ago, and now he’s moved into some very high circles here. So if you work for him and do your best, and he likes you, then you’ll have your chance. I’ll give you a translator to help you.”

Back in Colette’s Mercury House they ate a breakfast, then Swan took Kiran across town to meet her friend Shukra. He proved to be a middle-aged man with a round cheerful face under a shock of white hair.

“Sorry about Alex,” he said to Swan. “I enjoyed working with her.”

“Yes,” Swan said. “Seems like everyone did.”

She introduced Kiran: “I met this young man when I went out to Jersey, and he got me out of a mess. He wanted a job, and I thought he might be someone you could use.”

Shukra heard this impassively, but Kiran could see from the bunching of his eyebrows that he was interested. “What can you do?” he said to Kiran.

“Construction, retail, janitorial, bookkeeping,” Kiran said. “And I can learn fast.”

“You’ll need to,” Shukra said. “I’ve got jobs that need doing, so we’ll get you into something.”

“Oh,” Swan said, “and he needs papers.”

“Ah,” Shukra said. Swan met his gaze without flinching. Now she was going to owe him, Kiran saw. “If you say so,” he said at last. “You are my black swan. I’ll see what I can do.”

“Thanks,” Swan said.

After that she needed to get out to the spaceport to catch her flight. She took Kiran aside and briefly hugged him. “I’ll see you again.”