The force built up rapidly. The silence was eerie. She had her back to the direction of thrust, and she felt as if she was sitting up and being hurled forward, into some unknown future.

“Fifteen seconds in,” Stone said. “Point five G. Climbing.”

After a year of zero G, the pressure already felt enormous. So much for all those hours of exercises; didn’t do a damn bit of good.

There was a shudder, a vibration that set into the walls and equipment racks around her. Loose gear rattled. She heard a clatter somewhere behind her: some bit of equipment, inadequately stowed, falling the length of the Command Module.

“One G,” Stone called. “Two.”

The pressure built up further, compressing her chest.

“Jesus,” Gershon said. He had to shout over the rattling of the walls and equipment. “Eight minutes of this.”

“Can it,” Stone snapped. “Two point five Gs. We’re doing fine. Right down Route One. Three point six. Hang on, guys.”

She felt unable to breathe. It was as if the pressure suit was tightening around her, constricting her. It was a bizarre, terrifying, claustrophobic experience.

A fringe of bubbly darkness gathered at the edge of her vision.

They were utterly alone, inside a tiny artifact arcing above the surface of an empty planet, reliant on the smooth working of their machines to survive.

“Four point three Gs,” Stone called. She could hear the rattle of the thrust in his voice. “That’s it. That’s the peak. Coming up on pericenter.”

Stone and Gershon began to run through a readout of the status of the maneuver so far.

“Burn time four four five.” Four minutes, forty-five seconds. Halfway through. “Ten values on the angles: BGX minus point one, BGY minus point one, BGZ plus point one…” Velocity errors on the burn were amounting to only a foot per second, along each of the three axes of space. “No trim. Minus six point eight delta-vee-cee. Fuel thirty-eight point eight. Lox thirty-nine zip, plus fifty on balance. We ran an increase on the PUGS. Projected for a two nineteen point nine times twelve six eleven point three…”

York translated the numbers in her head. The burn was working. The cluster was heading for an elliptical orbit, two hundred by twelve thousand miles: almost perfect.

“Hey, Natalie.” It was Gershon.

“What?”

“Look up.”

With an effort, she tilted back her head. The helmet restricted her, and under the acceleration her skull felt as if it had been replaced by a ball of concrete, tearing at her neck muscles.

Through her small window she saw the battered southern plain of Mars.

And the bulging landscape above her was lit up, right at the center, by a soft, pink glow; it was like a highlight on a huge, ocher bowling ball.

It was the glow of the burn, the light of the MS-II.

For the first time in the planet’s four-billion-year history, artificial light had come to the Martian night.