“They’re not that valuable,” Coyote said in his plausible style. “You’re already giving us more nitrogen than we can burn.”

“Sure, but you have to get nitrogen before you can give it.”

“I know that.”

“Get before you give, and give before you burn. And here we’ve found this enormous vein of sodium nitrate, it’s pure caliche blanco, and these badlands are stuffed with it. It looks like there’s a band of it between the tuff and the lava, about three meters thick and extending, well, we don’t even know how far yet. It’s a huge amount of nitrogen, and we’ve got to get rid of it.”

“Fine, fine,” Coyote said, “but that’s no reason to start potlatch-ing on us.”

“We’re not potlatching. You’re going to bum eighty percent of what we give you—”

“Seventy.”

“Oh yeah, seventy, and then we’ll have these seeds, and we’ll finally be able to eat decent salads with our meals.”

“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 blancol”

“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 bracks 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!”

Coyote wagged his head mischievously. “I had to bring it in, or else otherwise you were going to bury me in caliche blanco, weren’t you. We’re out here on the road, we’ve got some seeds but not much else — certainly not millions of tons of new caliche deposits! And we actually need the hydrogen peroxide and the pasta too, it’s not just a luxury like lettuce seeds. Tell you what, if you find the truck you can burn its equivalent, and you’ll still have given us fair. If you don’t find it, then you’ll owe us one, I admit it, but in that case you can burn a gift, and then we’ll have given you fair!”

“It’ll take us a week’s work and a bunch of fuel to recover the truck.”

“All right, we’ll take another ten picobars, and burn six of it.”

“Done.” The woman shook her head, baffled. “You’re a hard bastard.”

Coyote nodded and got up to go refill their cups.

Art swung his head around and stared at Nirgal, his mouth hanging open. “Explain to me what just went on there.”

“Well,” said Nirgal, feeling the benevolence of the kava flowing through him, “they were trading. We need food and fuel, so we were at a disadvantage, but Coyote did pretty well.”

Art hefted the white block. “But what’s this get nitrogen, and give nitrogen, and burn nitrogen? What, do you torch your money when you get it?”

“Well, some of it, yeah.”

“So both of them were trying to lose?”

“To lose?”

“To come out short in the deal?”

“Short?”

“To give more than they got?”

“Well, sure. Of course.”

“Oh, of course!” Art rolled his eyes. “But you … you can’t give too much more than you get, did I understand that?”

“Right. That would be potlatching.”

Nirgal watched his new friend mull this over.

“But if you always give more than you get, how do you get anything to give, if you see what I mean?”

Nirgal shrugged, glanced at Vijjika, hugged her waist suggestively. “You have to find it, I guess. Or make it.”

“Ah.”

“It’s the gift economy,” Vijjika told him.

“The gift economy?”

“It’s part of how we run things out here. There’s a money economy for the old buy-and-pay system, using units of hydrogen peroxide as the money. But most people try to do as much as they can by the nitrogen standard, which is the gift economy. The Sufis started that, and the people in Nirgal’s home.”

“And Coyote,” Nirgal added. Although, as he glanced over at his father, he could see that Art might find it hard to envision Coyote as any sort of economic theorist. At the moment Coyote was tapping madly at a keyboard beside another man, and when he lost the game they were playing he shoved the man off his pillow, explaining to everyone that his hand had slipped. “I’ll arm wrestle you double or nothing,” he said, and he and the man plonked their elbows on the table and tensed their forearms, and went at it.

“Arm wrestling!” Art said. “Now that’s something I can understand.”

Coyote lost in seconds, and Art sat down to challenge the winner. He won in seconds, and it quickly became obvious that no one could resist him; the Bogdanovists even clustered across from him, and got three and then four hands clasping his hand and wrist, but he smacked every combination of them down onto the table. “Okay I win,” he said at last, and flopped back on his pillow. “How much do I owe you?”

To avoid the aureoles of shattered terrain clustered north of Olympus Mons, they had to circle far to the north. They drove by night, and slept by day.

Art and Nirgal spent many hours of these nights driving the car and talking. Art asked questions by the hundred, and Nirgal asked just as many back, as fascinated by Earth as Art was by Mars. They were a matched pair, each very interested in the other, which as always made a fertile ground for friendship.

Nirgal had been frightened by the idea of contacting Terrans on his own, when it first occurred to him in his student years. It was clearly a dangerous notion, which had come to him one night in Sabishii and never let go. He had spent many hours over many months thinking about the idea, and doing research to figure out who he should contact, if he decided to act on the thought. The more he learned, the stronger grew his sense that it was a good idea, that having an alliance with a Terran power was critical to their hopes. And yet he was sure that all the members of the First Hundred he knew would not want to risk contact. If he did it, he would have to do it on his own. The risk, the stakes…