Boom! She was thrown flat by the impact of the noise, picked up and dragged over the canyon floor, thrown and pummeled by rock. She was in a dark cloud, on her hands and knees, dust all around her, the roar of gnashing rock filling everything, the ground tossing underfoot like a wild thing. . . .

The jostling subsided. She was still on her hands and knees, feeling the cold rock through her gloves and kneepads. Gusts of wind slowly cleared the air. She was covered with dust, and small fragments of stone.

Shakily she stood. Her palms and knees hurt, and one kneecap was numb with cold. Her left wrist felt the stab of a sprain. She walked up to the low dike, looked over it. The landslide had stopped about thirty meters short of the dike. The ground in between was littered with rubble, but the edge of the slide proper was a black wall of pulverized basalt, sloping back at about a forty-five-degree angle, and twenty or twenty-five meters tall. If she had stayed standing on the low dike, the impact of the air would have thrown her down and killed her. “Goddamn you,” she said to Simon.

The northern border of the slide had run out onto the Melas glacier, melting the ice and mixing with it in a steaming trough of boulders and mud. The dustcloud made it hard to see much of that. Ann crossed the dike, walked up to the foot of the slide. The rocks at the bottom of it were still hot. They seemed no more fractured than the rock higher in the slide. Ann stared at the new black wall, her ears ringing. Not fair, she thought. Not fair.

She walked back to the Geneva Spur, feeling sick and dazed. The boulder car was still on the dead-end road, dusty but apparently unharmed. For the longest time she could not bear to touch it. She stared back over the long smoking mass of the slide— a black glacier, next to a white one. Finally she opened the lock door and ducked inside. There was no other choice.

2

Ann drove a little every day, then got out and walked over the planet, doing her work doggedly, like an automaton.

To each side of the Tharsis bulge there was a depression. On the west side was Amazonis Planitia, a low plain reaching deep into the southern highlands. On the east was the Chryse Trough, a depression that ran from the Argyre Basin through the Margaritifer Sinus and Chryse Planitia, the deepest point in the trough. The trough was an average of two kilometers lower than its surroundings, and all the chaotic terrain on Mars, and most of the ancient outbreak channels, were located in it.