“If you can get them to grow. Lettuce is delicate.”

“We’ll have all the fertilizer we need.”

Coyote laughed. “I guess so. But it’s still out of whack. Tell you what, we’ll give you the coordinates for one of those trucks of uranium we sent off into Ceraunius.”

“Talk about potlatching!”

“No no, because there’s no guarantee that you’ll be able to recover the stuff. But you’ll know where it is, and if you do recover it, then you can just burn another picobar of nitrogen, and we’ll be even. How about that?”

“It still seems like too much to me.”

“You’re going to be feeling like that all the time with this caliche blanco you’ve found. There’s really that much of it?”

“Tons of it. Millions of tons of it. These badlands are layered through and through with it.”

“All right, maybe we can get some hydrogen peroxide from you too. We’re going to need the fuel for the trip south.”

Art leaned toward them as if pulled by a magnet. “What’s caliche blanco?”

“It’s nearly pure sodium nitrate,” the woman said. She described the areology of the region. Rhyolitic tuff— the light-colored rock surrounding them— had been overlaid by the dark andesite lava that roofed the tableland. Erosion had carved the tuff wherever cracks in the andesite exposed it, forming the tunnel-bottomed ravines, and also revealing great seams of caliche, trapped between the two layers. “The caliche is loose rock and dust, cemented together with salts and the sodium nitrates.”

“Microorganisms must have laid that layer down,” a man beyond the woman said, but she instantly disagreed:

“It could have been areothermal, or lightning attracted by the quartz in the tuff.”

They argued in the way people do when they are repeating a debate for the thousandth time. Art interrupted to ask again about the caliche blanco. The woman explained that blanco was a very pure caliche, up to eighty percent pure sodium nitrate, and thus, on this nitrogen-poor world, extremely valuable. A block of it sat on the table, and she passed it over to Art and went back to arguing with her friend, while Coyote bartered on with another man, talking about teeter-totters and pots, kilograms and calories, equivalence and overburden, cubic meters per second and picobars, haggling expertly and getting a lot of laughs from the people listening.

At one point the woman interrupted Coyote with a cry: “Look, we can’t just take an unknown pot of uranium that we can’t be sure we’ll get or not! That’s either gross potlatching or else ripping us off, depending on whether we can find the truck or not! What kind of a deal is that, I mean it’s a lousy deal either way!”