It was the first time she’d seen the craft from the outside since the rendezvous in Earth orbit. The fat, faithful MS-II injection engine was still evidently the stack’s center of gravity — though the two External Tanks were long discarded — and ahead of it was fixed the slim MS-IVB stage which would brake them back into Earth orbit. The whole of Endeavor, their cylindrical Mission Module with its solar array wings, had been separated from the MS-IVB, turned around and redocked nose first; the idea was to free up the MEM from its shroud at the Mission Module’s base. Meanwhile Discovery, their Apollo, was docked to a lateral port, so it dangled sideways from the Mission Module, like a berry from the line of fuel-tank cylinders.

When Challenger returned to Martian orbit, the MEM would be discarded, and the remaining modules — booster stages, Mission Module, and Apollo — would be reassembled, once more, in a straight line, for the burn home.

The cluster was a collection of cylinders and boxes and panels, crudely assembled — and clumsily repositioned since their entry into Martian orbit. To York, all the orbital construction work — sliding modules through space like kids’ construction blocks — was unnerving. When they separated the Mission Module from the boosters, they were cutting themselves loose from their only ride home, for God’s sake! But she understood that there were backup strategies at every stage, ways they could reassemble some kind of configuration that could tolerate a ride home, even if they lost the landing.

It’s all a symptom of the clumsy way we’re constrained to do this, the lousy technology. One day, maybe we’ll have the power and energy to do this journey in something resembling comfort, without having to take the damn spacecraft apart all the time.

The assembled craft had none of the detailed, toylike brilliance she had observed about ships in Earth orbit. After a year in space, the brilliant white paint of prelaunch had faded to a pale yellow; and the shadowed areas of the hull were picking up brown shading from the battered skin of Mars. The cluster looked aged, soaked in space.

When Ares had receded from view she could see nothing through the little window but darkness.

Darkness, and, occasionally, a sliver of ocher landscape.

Challenger flew over the shadowed limb of Mars.

“Thirty seconds to DOI,” Stone said. “Everything’s go.”

“I confirm a go,” Gershon said.

DOI: insertion into descent orbit — a new, low, elliptical orbit, an orbit that would intercept the surface of the planet.

York could see Gershon’s hand, hovering over the manual fire button. Challenger was Gershon’s baby, of course; the landing — the next few minutes — were the culmination of a decade of work for him. He looked keyed up to York, tense, expectant.