Gershon and his wingman climbed back to altitude, and Gershon turned his nose for home. Mission Elapsed Time [Day/Hr:Min:Sec] Plus 000/00:12:22

Earth was a wall of blue light, as bright as a slice of tropical sky; it dazzled her, dilating her eyes, making the sky pitch-black when she looked away. The Command Module’s windows were tiny, already scuffed, but even so they let in shafts of startling blue, and the cabin was bright, cheerful, light-filled.

“Houston, we have a hot cabin.” Stone tapped a gloved forefinger against a temperature gauge. “Running at seventy-seven.”

“Copy, Ares” Young said. “We recommend you put coolant fluid through the secondary coolant loop.”

“Roger,” said Gershon. “Ah, okay, Houston, now I’m seeing a fluctuation of my water quantity gauge. It’s oscillating between, I’d say, 60 and 80 percent.”

“Copy, Ralph, working on that one…”

And Stone said he suspected there was a helium bubble in an attitude thruster propellant tank. Young recommended that he perform a couple of purge burns of the attitude thrusters to burn out the bubble. So Stone began to work that out. Meanwhile, Young came back with an answer to the water gauge problem; it looked as if it was traced to a faulty transducer…

And on, and on, a hail of small checks and detailed, trivial problems.

York had her own checklist to follow. She worked her way through the pale pages quickly, opening and closing circuit breakers, throwing switches, calling out instructions for Stone and Gershon. She was immersed in the hiss of the air in her closed helmet, the humming of the Command Module’s instruments and pumps, the rustle of paper, the crackle of Young’s voice calling up from the ground, the soft voices of Gershon and Stone as they worked through their post-orbit checklists.

It was a mundane procedure they’d followed together dozens of times in the sims.

But, she realized, it was a profound shock to go through this routine — not in some stuffy ground-based trainer — but here.

If she looked ahead of the craft, she could see the planet’s curve. It was a blue-and-white arc with black space above it. But when she looked straight down, the skin of the Earth filled her window, scrolling steadily past as if she were viewing some colorful map on a computer screen.