Scarborough nodded. Scout’s cleated titanium wheels would have left just such imprints. And their close spacing suggested the vehicle was too small to be anything but an unmanned drone. Also, his earlier remark to Bradley hadn’t been a colorful exaggeration. There truly weren’t any other mechanical ponies on the range. To reduce the environmental impact of their activities and preserve the dry valleys as a scientific resource, field workers refrained from operating wheeled or tractor-belted vehicles on ice-free ground, making the snowmobiles that towed their supplies and equipment across lake crusts the only motorized conveyances in use. This self-imposed restriction had been observed for three decades before it was formalized in a multinational code of conduct to which the United States was a signatory. In their negotiations to secure approval for the rover’s trials, UpLink and NASA had been firm about guaranteeing participant states that they would avoid leaving behind a mess—or in the language of their written application, would “minimize and remedy any disturbances caused to the natural landscape.”

Ultimately, though, the good name of Roger Gordian, UpLink’s founder and standard bearer, had carried more weight than diplomatic niceties or signed promises. As a practical matter, implementation of any treaty in this freezing, desolate wilderness relied on the honor system. Somebody broke the rules, who was going to catch on?

The story was in the math, and Scarborough had done his calculations long ago. Antarctica’s total land area was five and a half million square miles, double the size of Australia, triple that of Europe. With a winter population of about two thousand cocooned in the research stations, and maybe four times that many summer residents, it averaged between fifty and a hundred fifty thousand miles of open space per person, depending on the season. A tough chunk of real estate to police and patrol. Almost impossible, in fact, because the same agreement that regulated experimentation in the dry valleys imposed a continent-wide ban on military bases, effectively forbidding armed enforcement of its protocols.

But none of this presently concerned Scarborough. He rose from his squat, took his binoculars from the case strapped around his neck, and raised them to his eyes. What he saw of the rover’s trail encouraged him. Yes, the wind had scrambled the trail. Completely erased entire segments of it. And was dissipating it into spindling little wisps of sand even as he watched. However, it remained plain enough for several hundred yards before cutting around a sharp eastward bend in the pass.

“All right,” he said. “Looks like we’re in business—”