At any rate, Markus had rolled the dice on the gambit that they were now executing. If it worked, and they could slow Ymir down enough to mate her with Izzy, then the Big Ride strategy became possible, and the arklets could climb to higher and safer altitudes behind the shelter of Amalthea’s metal and Ymir’s ice.

The one part of that plan that Markus apparently had not considered until now was that the atmosphere was too big.

In truth, it wouldn’t have made a difference if he had considered it. The crucial decision had been made and executed weeks ago by Sean Probst, when he had laid in a course at L1 and executed the burn that had placed Ymir on its current trajectory. This was an ellipse with a very low perigee. That was a sound idea from an orbital mechanics point of view in that the steam engine would have maximum leverage at that point—it was the natural place to make a burn and effect a transition to a low circular orbit matching Izzy’s. But, sick and exhausted from his two-year odyssey, isolated from the latest scientific discourse by radio failure, Sean might have overlooked the expansion of the atmosphere when making his calculations.

“Are we going in?” Vyacheslav asked. This being a polite euphemism for the scenario where Ymir got so deep, and slowed down so much, that it burned up and became just another streak of blue light against the lambent background of the pyrosphere.

“We are more likely to skip, I think,” Markus said. Meaning that Ymir might bounce off the atmosphere like a flat rock skimming across a pond. “With unpredictable results. But I cannot be sure. All I am saying is that this is not going to be the mission plan that Sean had in his mind. It is going to be something else. Something maybe a little more exciting.”

ANTICIPATING THAT CAMILA MIGHT BE ON HER TOES—SHE HAD ALREADY survived one attempt—the gunman had crouched behind the rear of her school bus, sawed-off shotgun at the ready, and waited for her to emerge. A narrow stretch of pavement separated the vehicle’s side door from the entrance of her school, so he didn’t have much margin for error. He jumped the gun, as it were, springing out into the open while Camila was still negotiating the descent to the street; the long hem of her burqa was apt to get caught on her foot as it probed for the running board, so she had to take it slowly. The delay saved her life. Alerted by a schoolteacher standing in the building’s doorway, Camila turned back into the bus. Rather than hitting her full in the face, the shotgun blast raked the left side of her jaw, removing eleven teeth, tearing away much of her cheek, and causing massive structural damage to her jaw. Surgeons in Karachi and, later, London had saved most of the functions of her tongue, rebuilt her mandible from pieces of bone carved from her pelvis, and fitted her with a set of artificial teeth. After a world tour raising money for girls’ education in Afghanistan and the tribal regions of Pakistan, Camila had been granted permanent asylum in Holland. Dutch plastic surgeons, funded by charitable donations from all over the world, had gotten to work repairing the cosmetic damage. This was a long-term project that had been interrupted by Camila’s selection as one of the Dutch candidates for the Cloud Ark. No one believed that this was a random outcome of the Casting of Lots. Clearly the Dutch authorities had placed their thumb on the scale and seen to it that she was chosen, as a rebuke to some conservative Muslim countries who had refused to nominate female Arkers unless given assurance that arrangements would be made for them to live in orbital purdah. Camila was well suited to serve that symbolic purpose, since she had not adopted Western ways. She dressed conservatively and wore the head scarf and the face veil. She was coy, however, as to whether the purpose of the face veil was submission to the demands of religion or to hide her disfigurement. She had pulled it down several times to display the scars to television cameras, and when she had dined at the White House she had gone uncovered in the dining room, by prearrangement with her hostess, the president of the United States.

Julia’s startling arrival in the Cloud Ark had therefore led to a reunion between the forty-four-year-old ex-president and the eighteen-year-old refugee. To call it joyous or even happy would have been wrong given the circumstances. It was a fact of human nature, though, that some people just got on well with each other. This had clearly been the case during that dinner at the White House and was no less true in Camila’s abode, Arklet 174, which was where Julia ended up lodging after she had recovered from her eventful flight up and gone through a bit of basic training in how to live in space.

Arklet 174 belonged to a heptad, or a cluster of seven arklets all connected to a hexagonal frame; it and five other arklets surrounded a seventh, which was positioned in the middle of the hexagon, where it served as a twenty-four-hour-a-day common room and working area for the people who lived in the others. Four to five people were assigned to each of those, and two more had been shoehorned into small private cabins at the boiler room end of the central arklet, so the total population of the heptad, including Julia, was twenty-nine. This increased to thirty when Spencer Grindstaff managed to hitch a ride on a Flivver that was bringing a spare part and a technician from Izzy to fix a problem in one of the arklets’ thrusters. The technician returned to Izzy when he was finished, but Spencer stayed, and talked his way into a berth on Arklet 215. There was a tendency for arklets within a group to become segregated by sex over time, as the populations sorted themselves out; 215, which was predominantly male, ran on the same shift as 174, which was all-female. They both ran on second shift, which, for reasons that were now purely historical, tended to be culturally American. They slept from dot 8 to dot 16. First shift was Asian and third shift was European. The cultural shadings were perpetuated by food: the warm odors that greeted one’s nostrils upon entering the common space first thing in the “morning,” the tastes one could expect to savor in the “evening.” Since space food was lacking in variety, this was largely a matter of spices. The second shifters had their little bottles of Tabasco, the first shifters had plastic packets of curry powder, and so on.

“Ganging” was the term used by the Arkitects to denote this clustering of arklets into formations of three or seven: triads and heptads. It helped simplify Parambulator’s job by reducing the total number of separate objects that needed to be tracked. It gave Arkies more living space to roam around in, and provided some redundancy in the case of a bolide strike. They didn’t like to form anything larger than a heptad, though.

“Spencer, I am fully aware that I am out of my depth here,” Julia said, “but I don’t understand the upper limit of seven. I was assured, during my early briefings, that any number of arklets could in principle be ganged. Limiting it to seven seems arbitrary. Which suggests that some deeper agenda might be behind it.”

“One moment please, Madam President,” Spencer said. He was doing rather a lot of typing.

“You really shouldn’t call me that,” Julia returned, though her tone of voice was indulgent.

Spencer smacked his laptop’s Enter key, then leaned back slightly and adjusted his glasses. His eyes jumped around to various parts of the screen. Then he looked up, and, in a clearer tone of voice, announced, “It’s all shut down.”

“The surveillance, you mean.”

“Situational Awareness Network,” he corrected her, and winked.

“Surveillance to you and me. It’s like living in the Nixon White House. Old reference. You wouldn’t understand. Now, where was I?”