Bleeker shrugged and said, willingly enough, “North and south are different. The top half of your map is pink, the bottom yellow. More or less.”

“Right. The logical basis of geology is that no solid planet is either a homogeneous blob, or a disorganized jumble. They’re all made up of pieces — called geologic units. Each unit was formed in a certain way at a certain time; each has depth as well as breadth and width, and when we do geology we’re always trying to look beneath the surface, to reconstruct the three-dimensional structure that is hidden from direct view. The relations between the units show their age relations, something about the processes that formed them, and something about how far beneath the surface they extend…”

Stone, surreptitiously, was checking his watch.

“Do I have your full attention, gentlemen?”

Stone and Bleeker glanced at each other like guilty children.

“I’m sure you’re just doing your job, Natalie,” Bleeker said languidly, “and we’re glad you’re running the site selection committee—”

“I’m not running it. I’m just on it.”

“Whatever. But we’d have a year en route to Mars with nothing much else to do but study this stuff. Can’t this wait until then?” As usual, Bleeker sounded calm, rational, reasonable, colorless.

A year? Yes, but I won’t be there to hold your hands, or make you think. I’ll be light-minutes away…

And this guy was likely to be designated the Ares mission specialist. My God.

Phil Stone waved Bleeker quiet. “Go on, Natalie. We’re committed to the science. You’ve got us.”

“All right. Now,” she plowed on, “the probes have shown us that in the case of Mars we have two main types of landscape. The yellow stuff in the south is heavily cratered, and looks ancient. And this pink stuff, to the north, is made up of smooth, young plains. The planet bulges out below the equator; most of the south is above the mean altitude, and most of the north is below.”

“You say ‘ancient’ and ‘young,’ ” Stone said. “Meaning?”

“ ‘Young’ is maybe half a billion years old. The plains are volcanic — frozen lava fields. And the ancient cratered stuff is three to four billion years old. That’s almost as old as the planet itself…”

Bleeker said, “So let’s get back to the flags. I guess those seven Hammer and Sickles are the sites the Soviets have identified as prime interest.”

“Yes. You can see—”

“So screw that,” Stone said easily. “Let’s look at the good old American selections. Those two white stripes at the top and bottom of your chart — I guess we’re looking at the polar caps.”

“Yeah.”

“I see no flags up there.”