She walked back to her car in the twilight, moving clumsily. It was difficult to operate the locks, to get her helmet off. Inside she sat before the microwave without moving for more than an hour, images flitting through her mind. Ants burning under a magnifying glass, an anthill drowned behind a mud dam. . . . She had thought that nothing could reach her anymore in this preposthumous existence she was living— but her hands trembled, and she could not face the rice and salmon cooling in the microwave. Red Mars was gone. Her stomach was a small stone in her body. In the random flux of universal contingency, nothing mattered; and yet, and yet. . . .

She drove away. She couldn’t think of anything else to do. She returned south, driving up the low slopes, past Chryse and its little ice sea. It would be a bay of the larger ocean, eventually. She focused on her work, or tried. She fought to see nothing but rock, to think like a stone.

• • •

One day she drove over a plain of small black boulders. The plain was smoother than usual, the horizon its usual five kilometers away, familiar from Underhill and all the rest of the lowlands. A little world, and completely filled with small black boulders, like fossil balls from various sports, only all black, and all faceted to one extent or another. They were ventifacts.

She got out of the car to walk around and look. The rocks drew her on. She walked a long way west.

A front of low clouds rolled over the horizon, and she could feel the wind pushing at her in gusts. In the premature dark of the suddenly stormy afternoon, the boulder field took on a weird beauty; she stood in a slab of dim air, rushing between two planes of lumpy blackness.

The boulders were basalt rocks, which had been scoured by the winds on one exposed surface, until that surface had been scraped flat. Perhaps a million years for that first scraping. And then the underlying clays had been blown away, or a rare marsquake had shaken the region, and the rock had shifted to a new position, exposing a different surface. And the process had begun again. A new facet would be slowly scraped flat by the ceaseless brushing of micron-sized abrasives, until once again the rock’s equilibrium changed, or another rock bumped it, or something else shifted it from its position. And then it would start again. Every boulder in that field, shifting every million years or so, and then lying still under the wind for day after day, year after year. So that there were einkanters with single facets, and dreikanters with three facets—fierkanters, funfkanters— all the way up to nearly perfect hexahedrons, octahedrons, dodecahedrons. Ventifacts. Ann hefted one after another of them, thinking about how many years their planed sides represented, wondering whether her mind might not reveal similar scourings, big sections worn flat by time.