Desmond closed on the sight, then banked their plane sharply and headed north. “The beam from the aerial lens is moving south, so up the line we should be able to fly closer.”

For many kilometers the channel of melted rock ran northeast without changing. Then as they got farther away from the current burn zone, the orange of the lava darkened and began to cake over from the sides with a black surface, broken by more orange cracks. Beyond that the channel surface was black, as were the banks on each side of it; a straight swath of pure black, running over the rust-colored highlands of Hesperia.

Desmond banked and turned south again, and flew closer to the channel. He was a rough pilot, shoving the light plane around ruthlessly. When the orange cracks reappeared, a thermal updraft bucked the plane hard, and he slid to the west a little. The light of the molten rock itself illuminated the banks of the channel, which appeared to be smoking lines of hills, very black. “I thought they were supposed to be glass,” Sax said.

“Obsidian. Actually I’ve seen some different colors. Swirls of various minerals in the glass.”

“How far does this burn extend?”

“They’re cutting from Cerberus to Hellas, running just west of Tyrrhena and Hadriaca volcanoes.”

Sax whistled.

“They say it will be a canal between the Hellas Sea and the northern ocean.”

“Yes, yes. But they’re volatilizing carbonates much too fast.”

“Thickens the atmosphere, right?”

“Yes, but with CO2! They’re wrecking the plan! We won’t be able to breathe the atmosphere for years! We’ll be stuck in the cities.”

“Maybe they think they’ll be able to scrub the CO2 out when things are warmed up.” Desmond glanced at him. “Have you seen enough?”

“More than enough.”

Desmond laughed his unsettling laugh, and banked the plane sharply. They began to chase the terminator to the west, flying low over the long shadows of the dawn terrain.

“Think about it, Sax. For a while people are forced to stay in the cities, which is convenient if you want to keep control of things. You burn cuts with this flying magnifying glass, and fairly quickly you have your one-bar atmosphere, and your warm wet planet. Then you have some method for scrubbing the air of carbon dioxide— they must have something in mind, industrial or biological or both. Something they can sell, no doubt. And presto, you have another Earth, and very quickly. It might be expensive—”

“It’s definitely expensive! All these big projects must be setting the transnationals back by huge amounts, and they’re doing it even though we’re a good step on the way to two-seventy-three K. I don’t get it.”