“One set’s taking out the paint,” Cardenas explained. “Another is reducing the organic molecules in the tires to carbon dioxide, methane, and whatnot The third is working on the engine, separating out all the tungsten and platinum in the steel alloys.”

“Tungsten and platinum?”

“They’re valuable metals, y’know. We want to separate them out so we can recycle them.”

“I see,” said Paul.

“And the fourth set of nanos is gobbling the plastics in the dashboard, steering wheel, seat covers and such.”

Paul could see the sheer fervor of achievement radiating from her face. A muffled bang made him snap his attention back to the Cadillac. The one tire remaining had just blown out and now hung limply on its hub. Paul thought he could see it twitching like something alive being devoured by parasites.

“Why do you keep the car in a sealed chamber?” he asked.

“To keep the bugs from spreading, of course,” Cardenas answered. “We keep the chamber at ten below zero, Celsius. The bugs are programmed to stop at any temperature above zero.”

“But why—”

“To make sure they won’t start gobbling people!”

“Oh.” Paul hadn’t thought of that.

Cardenas didn’t seem the least bit condescending as she explained, “The bugs don’t see any difference between your molecules and the Cadillac’s, y’know. Except temperature. We design them to immobilize themselves way before they get to human body temperature.”

Paul nodded slowly. “Then how do you expect to use them in toxic waste dumps if you’re worried that they might attack people?”

Her smile faded slightly. “We’re working on that problem. We’ve got to make them much more specific than they are now.

Muchmore specific. Tailor them to distinctive molecules, so they’ll gobble those molecules and nothing else.”

“Can you do that?”

“In time,” she replied.

Time costs money, Paul knew. It was the old story: an exciting new possibility that could make fortunes of profit, but first you have to sink fortunes of investment into it and pray that it eventually succeeds.

“What else do you have?” he asked.

Cardenas went back to the control console, flicked her fingers across a different keyboard. Another section of shutters slid back, this time on Pauls left.

“Nanomachines can build things, too, y’know,” Cardenas said.

At first Paul thought he was looking at a child’s sand castle, the kind that kids build on the beach. The chamber he was looking into was hardly larger than a phone booth, dimly lit by a single bare bulb in the ceiling. Its floor was covered with sand or a grayish brown powder of some sort. In the middle of it stood a half-built tower.

“Here we’ve got assemblers at work,” Cardenas said, her voice low, almost a reverential whisper.

Paul studied the tower. It was about three feet tall. It wasn’t made of sand, he realized. It was gray, almost the same color as the stuff strewn over the floor, but it looked smoother, metallic.

“What is this?”

In the dim light from the display screens Cardenas’ expression was difficult to read. But her voice was vibrating with barely-suppressed excitement.

“Last week Mr. Masterson phoned me with a special request. This is the result.”

“What’d Greg want?”

“That sand is from the Moon,” Cardenas said. “We’ve put in a few simple assemblers and the tower is what they’re building.”

“Assemblers? You mean nanomachines?”

She nodded eagerly. “Actually, we put one hundred assemblers into the sand, five days ago.”

“And they’ve built the tower,” Paul said.

“They’re still building it. Watch real careful and you can see new features being added.”

Paul turned and stared at the tower rising out of the lunar sand. It rose perpendicularly from a wide, low base, its flanks smooth and featureless except for small setbacks every foot or so.

“Nothing seems to be happening,” he said.

Cardenas peered at the tower. “They stop every once in a while, like they’re taking a coffee break. Then they get busy again.”

“Don’t you know why they stop?”

“For sure.” She grinned. “Each time they reach a change in the blueprint we’ve programmed into them, they stop until the proper members of the team are in the right position to start the new phase of the building.”

Paul’s eyes widened. “You make them sound as if they’re intelligent.”

“About as intelligent as bacteria,” Cardenas replied.

Paul grunted.

“The assemblers spent the first four days building more of themselves out of the aluminum and silicon in the sand. Yesterday that tower wasn’t here.”

“No shit,” Paul breathed.

“The tower is mainly titanium, y’know. The assemblers are taking titanium atoms preferentially from the sand and using them to build the tower.”

“How do they know—”

“It’s all programmed into them,” Cardenas said. “We did this sort of thing last year, as a demonstration for Mr. Masterson and his father, when they visited here. We didn’t use lunar sand then; just beach sand. We built a really neat castle for them.”

Paul looked at her. “Could you build more complex stuff?”

Without an eyeblink’s hesitation, Cardenas said, “We could build a whole base on the Moon for you, if you give us the time to program the assemblers.”

Paul saw that there were a couple of little wheeled typist’s chairs by the consoles. He pulled one up and sank onto it Cardenas took the other one facihg him.

“Instead of sending tons and tons of heavy machinery to the Moon,” she said, leaning toward him, “all you’d have to do is send a sampling of the necessary assemblers. They’ll build more of themselves out of the raw materials in the Moon’s soil—”

“Regolith,” Paul corrected automatically.

“-and then they’ll construct your base out of the regolith, ” she stressed the word, “all by themselves.”

“One shipload of nanomachines,” Paul mused.

“Could build your whole base for you,” she said.

“How long would it take you to develop the nanomachines? Specifically for Moonbase, I mean.”

She waved her hands in the air. “Simple tasks, like building airtight shelter shells and other construction forms, that’s pretty easy. When you get down to complicated equipment, like air regenerators and pressure pumps, we’ll need a while to program the assemblers.”

“A while? How long?”

“Months. Maybe years. We’ve never tried to build anything very complicated. Not yet It’ll take some time.”

A new thought struck Paul. “Most of the compounds in the regolith are oxygen-bearing. And there’s hydrogen imbedded in the top layers of the regolith, blown in on the solar wind. Could your machines—”

“Produce water out of those atoms? For sure. That’s no problem!”

“Jesus H. Christ on a motorcycle.”

“You want a motorcycle, we’ll build you a motorcycle.” Cardenas laughed.

“Maybe we ought to be talking with Harley,” Paul kidded back.

“Or General Motors.” She was suddenly completely serious.