At last, though, she seemed to be getting up a little momentum. The mass of her backpack tugged at her, its inertia constantly dragging her off her line; whenever she wanted to change direction she had to think four or five steps ahead.

The MEM drifted before her, remote and all but unattainable, bathed in movie-set floodlights. The mock-up’s hatch gaped open, the fluorescent light within revealing the hardwood-and-ply nature of its construction.

Not far from the MEM was a mocked-up Mars Rover, the TV camera mounted on its prow swiveling to stare at her with its dark lens. The camera was live. York, under its gaze, felt like some gorilla loping around its cage.

Ralph, of course, had taken to Mars-walking as if he’d been born to it.

What they were doing was actually a simulation of their second walk on Mars, the first time they would get to do any serious work. The first walk would be an hour-long solo by Phil Stone, as commander. The purpose of the first walk — according to the mission plan — was for him to test out the systems of his suit and his general mobility, to check out the status of the MEM after landing, and to resolve any glitches with the comms systems. Stone would do little science, that first time out, except to pick up a small contingency surface sample.

Of course there was a hidden agenda.

The attention of the Earth — and all of NASA’s sponsors in the White House and on the Hill — would be on that first walk, the first small steps by a man on Mars. So all the ceremony — putting up the Stars and Stripes, the footprints-and-flags stuff, the speech by President Reagan (who was basking in his recent landslide win against Teddy Kennedy) — could be gotten out of the way in that first hour. And on Joe Muldoon’s advice, learning from his Apollo experiences, everything in that first walk was being checklisted and time-lined, including Reagan’s call.

After that, hopefully, the rest of the program would be free for some serious work.

It made some sense to York. She knew how such things had to be accommodated. But it still seemed odd to her, sometimes, that NASA should be planning the exploration of Mars around TV ratings.

At last, she reached the MEM. She skidded a little as she came to a halt, at the foot of the ladder down from the hatch.

The simulation supervisor spoke to her over her headset. “Natalie, this time we’d like you to try extracting a SNAP from its cask.”

“Rog.” She tried to keep the weary irritation out of her voice. That meant she had to trudge farther, across to the plywood Mars Rover. She swiveled on her heel like a puppet, until her body was pointing at the Rover, and then lumbered across the crunching surface.