“Right.” There were a thousand ways to evade the exercising, both Wojo and Paul knew.

Tinker joined them. “I’m all finished with my work. Can we go home now?”

Paul ignored him.

At first he wasn’t certain he actually saw it. Paul wanted to rub his eyes, but inside the spacesuit and helmet he couldn’t. Yet it looked as if a tiny pool of something shiny had formed on the bottom of the trench, right where the opened container was lying. A puddle that looked almost like glassy, shining liquid mercury.

“Am I seeing straight?” Wojo asked.

“Yeah,” said Paul. “Look! It’s spreading.”

A glassy smooth film of titanium was growing across the bottom of the trench. And its sides. Fascinated, Paul watched for hours as the titanium shell slowly arched above the surface of the regolith to form a complete cylinder. Then its ends began to close.

“The next set of bugs is the real test,” Cardenas said, looking much happier and more relaxed now.

“The airlock,” Paul said. If they can build a whole airlock by themselves, they can build just about anything, he thought.

Wojo carried the second cylinder to the open doorway of the titanium shelter with a good deal more confidence than he had borne the first.

They took turns going inside the pressurized bubble tent to grab a bite of dinner. Paul could hardly tear himself away from watching an, airlock assemble itself, as if by magic, literally from the ground up.

Now give them a few hours to fill the shelter with oxygen,” Cardenas said, positively glowing once the airlock was finished, “and you’ll have a complete prefabricated, ready-to-use shelter built entirely out of native materials by my nanomachines.”

The three men slept inside the pressurized tent, in their suits. It was uncomfortable. They could not lie down; the best they could do was to lean back against rests they had brought with them, reclining at roughly a forty-five degree angle. If the tent were suddenly ruptured they could snap down their visors and turn on their backpack life support systems in a second or two.

To make it worse, Tinker either would not or could not stop making puns. Paul groaned and Wojo threatened the astronomer’s life, but no matter what either of them said, Tink turned it into a maddening pun. They became very elaborate as the men prepared for sleep, climaxing with a pun based on the fact that making bowel movements in a spacesuit is a complex and miserable business.

“What we need is a special container, maybe two pints in capacity,” Tink merrily chattered away. “I think I’ll enter a class-action suit to force the corporation to supply us with special bottles for manure storage.”

“Tink…’ Wojo growled menacingly.

Undeterred, the astronomer concluded, “Yes, sir, that’s what I’ll do. Bring my request to a judge and see if he’ll demand ordure in the quart.”

Before Wojo could throw anything, Paul said, “Okay, Tink. That’s enough. Not another word out of you.”

Tinker looked from Paul to Wqjo and back again. The self-satisfied grin on his face faded a little. His eyes lit up as if he had thought of still another pun.

“No!” Paul said sharply, the way he would to a baby he was trying to train. Or a dog.

Tink nodded inside his helmet and pressed an upraised finger to his lips. Wojo, still looking grim, nodded his thanks to Paul.

Paul thought he would be unable to sleep, propped up inside the suit and excited about the nanomachines working away, silent and invisible out there. But he drifted off almost as soon as he closed his eyes, and if he dreamed at all he remembered none of it when he awoke a few hours later, long before his suit’s alarm was set to go off.

Wojo was snoring like an asthmatic ox and Tinker was muttering in his sleep. Paul quietly refilled his backpack oxygen supply from the tanks in the tent, then slid his visor down and stepped through the tent’s minimal airlock.

The shelter gleamed slightly in the Earthlight, its curved top uncovered as yet by protective dirt. Paul grappled one of the nitrogen tanks from the tractor’s back and hauled it to the shelter. He examined the airlock’s control panel. It was mechanical rather than electronic; rather crude but a good-enough test of the.nanomachines’ abilities. Cardenas had a team working on electronic assemblies, but Greg had wanted to go ahead with this test as quickly as possible and Paul had agreed with him.

He slid the outer hatch open, lugged the nitrogen cylinder inside and then stepped in himself and pulled the hatch closed. A set of four knobs projected from one side of the inner hatch. Paul turned the top one and soon heard the reassuring hiss of gas filling the airlock. Once the sound stopped he took a pressure gauge from his belt. Less than two psi, but holding steady. Oxygen pressure wasn’t as high as it should be, not yet, but at least the airlock didn’t seem to be leaking.

Is it really oxygen? Paul asked himself. The little portable mass spectrograph was still in the tractor. He’d have to assume the bugs were doing their work properly. For now.

Opening the inner airlock hatch, Paul stepped inside the shelter. In the light from his helmet lamp, the curving walls glistened almost as if they were wet. The pressure gauge held steady. The shelter was airtight. Paul dragged the nitrogen cylinder into the empty shelter and opened its valve. By noon tomorrow we’ll be able to sit in here in our shirtsleeves, he thought happily.

“We’ll eat lunch in here,” he promised himself aloud. Paul and Tink spent the morning hauling equipment into the new shelter, while Wojo worked the tractor, carefully piling up rubble over its curving roof.

At last, a few minutes after noon, the three of them entered the shelter.

For a long moment they simply stood inside the cylindrical space. The walls still glistened as if newborn. The bunks, table and equipment they had carried in looked shiny new, never; used. Tinker held the mass spectrometer in his gloved hands.

“Well?” Paul asked him.

Peering at the readout display, Tinker said, “Seventy-six percent oxygen, twenty-four nitrogen.”

“Good enough,” Paul said.

“Pressure’s just a tad over five psi,” Wojo said.

“Okay.” Paul slid his visor up and took a deep breath. “It’s not the Garden of Eden, but it’ll do.”

With great relief they peeled themselves out of their spacesuits, although the stench of bodies confined inside the suits for several days was less than pleasant.

“I won’t mention yours if you don’t mention mine,” Wojo said, pinching his nose with forefinger and thumb.

“Okay,” Tinker answered happily. “Let’s not make a stink about it.”

Paul understood how a man could be driven to murder.

They ate lunch in their coveralls at the small table they had carried in, after heating the prepackaged meals in the microwave cooker. Tinker seemed very impressed with the nanomachines’ achievement.

“We could build a radio telescope facility on the farside!” he said enthusiastically. “These bugs are going to change everything we do up here!”

Wojo chewed his soyburger thoughtfully, then replied, “Better make sure this shelter really works right before you go prancing off to the farside.”

“Oh, you want to work the bugs out of it?” Tinker asked, delightedly.

Wojo looked as if he wanted to spit.

After lunch Paul checked in with Kris Cardenas to assure her that all was going well. Then he patched through a call to Joanna. She was at home, in her sitting room.

“Are you okay?” were the first words out of Paul’s mouth when he saw her stretched out on the chintz-covered chaise longue.

It took three seconds for her to smile. “Of course I’m all right.”

“Oh, I thought maybe you didn’t feel well.”

Again the delay. Then, “Paul, it’s seven-thirty in the morning here. I’ve been trying to call you for more than an hour.”