“What if we end up needing something they have and we don’t, or the other way round?” Sarah had not given up.

“Canyon or no canyon, we won’t be that far from them,” Bragg said. “If anybody needs anything that bad, he can holler for it.”

“What if we need a ride home?” Sarah asked softly.

Frank Marquard winced; Irv felt himself doing the same thing.

But Bragg said fatly, “Anybody who needs a ride home is dead, unless he can make it on Minerva until another expedition comes along. Athena’s life-support won’t take more than six people home, and neither will Tsiolkovsky’s. For that, folks, we are on our own. We’d all best remember it, too.”

The words hit home. Irv had lived on Athena long enough to have grown used to it, as he would have to, say, an apartment. Being reminded of how fragile a place it was hurt.

But Tsiolkovsky was just as fragile. “So the territory Viking saw was really on the east side of Jotun Canyon, then, not the west?” Irv asked. At Bragg’s nod, the anthropologist went on.

“What is the west side like, then? Are the Russians going to try to fly Tsiolkovsky down into badlands? If they are, I say we call them, and the hell with Houston. I wouldn’t do that to anybody.”

Bragg frowned, but then his face cleared as he thought it over. “That’s fair,” he said. “We’ll find out.” He folded the map and stuck it into a breast pocket of his coveralls. It was not nearly detailed enough to show him what he needed. He pulled the NASA Photographic Atlas of Minerva off a shelf; the Velcro that held the book in place let go with a scratchy sound of protest.

The mission commander riffled through the pages till he found the plate he needed. He held the book open. Five heads craned toward it. “Looks to be flatland and low hills, same as we’ll be landing in. None of the miles and miles of scree and boulders you see around the edges of the polar caps, and no big erosion features. They aren’t taking any worse chances than we are.”