"We don't die."

She shrank away as if suddenly afraid of him. Pepe opened his mouth to ask something, and shut it without a word.

He chucked at our startlement. "We've engineered ourselves, you see, more than we've engineered the Earth."

Casey turned to look out across the shadowed craters at the huge globe of Earth, the green Americas blazing on the sunlit face, Europe and Africa only a shadow against the dark. He stood there a long time and came slowly back to stand in front of Uncle Pen.

"I'm going down to see the new Earth when I grow up." His face set stubbornly. "No matter what you say."

"Are you growing wings?" Uncle Pen laughed and reached a golden arm to pat him on the head. "If you didn't know, the impact smashed all your old rocket craft to junk."

He drew quickly back.

"Really, my boy, you do belong here." Seeing his hurt, Uncle Pen spoke more gently. "You were cloned for your work here at the station. A job that ought to make you proud."

Casey made an angry swipe across his eyes with the back of his hand and swallowed hard, but he kept his voice even.

"Maybe so. But where's any danger now?"

Uncle Pen had an odd look. He took a long moment to answer.

"We are not aware of any actual threat from another impacting bolide. All the asteroids that used to approach Earth's...o...b..t have been diverted, most of them steered into the Sun."

"So?" Casey's dark chin had a defiant jut. "Why did you want to dig us up?"

"For history." Uncle Pen looked away from us, up at the huge, far-off Earth. "I hope you try to understand what that means. The resurfaced Earth had lost nearly every trace of our beginning. Historians were trying to prove that we had evolved on some other planet and migrated here. Tycho Station is proof that Earth is the actual mother world. I've found our roots here under the rubble."

"I guess you can be proud of that," Casey said, "but who needs the station now?"

"n.o.body, really." He shrugged, with an odd little twist of his golden lips, and I thought he felt sorry for Casey. "If another disaster did strike the Earth, which isn't likely at all, it could be repeopled by the colonies.""So you dug us up for nothing?"

"If you knew what I have done," Pen leaned and reached as if to hug him, but he shrank farther away. "It wasn't easy! We've had to invent and improvise. We had to test the tissue cells still preserved in the cryostat, and build new equipment in the maternity lab. A complex system. It had to be tested." He smiled down into Tanya's beaming devotion. "The tests have turned out well."

"So we are just an experiment?"

"Aren't you glad to be alive?"

"Maybe," Casey muttered bitterly. "If I can get off the Moon. I don't want to sit here till I die, waiting for nothing at all."

Looking uncomfortable, Pen just reached down to lift Tanya up in his arms.

"We were meant for more than that," Casey told him. "I want a life."

"Please, my dear boy, you must try to understand." Patiently, Uncle Pen shook his furry head. "The station is a precious historic monument, our sole surviving relic of the early Earth and early man. You are part of it. I'm sorry if you take that for a misfortune, but there is certainly no place for you on Earth."

2.

Sandor Pen kept coming to the Moon as we grew up, though not so often. He brought tantalizing gifts.

Exotic fruits that had to be eaten before they spoiled. New games and difficult puzzles. Little holo cubes that had held living pictures of us, caught us year after year as we grew up from babies in the maternity lab. He was always genial and kind, though I thought he came to care less for us as we grew older.

His main concern was clearly the station itself. He cleared junk and debris out of the deepest tunnels, which had been used for workshops and storage, and stocked them again with new tools and spare parts that the robots could use to repair themselves and maintain the station.

Most of his time on the visits was spent in the library and museum with Dian and her holo mother. He studied the old books and holos and paintings and sculptures, carried them away to be restored, and brought identical copies back to replace them. For a time he had the digging machines busy again, removing rubble from around the station and grinding it up to make concrete for a ma.s.sive new retaining wall that they poured to reinforce the station foundation.

For our twenty-first birthday, he had the robots measure us for s.p.a.ce suits like his own. Sleek and mirror-bright, they fitted like our skins and let us feel at home outside the dome. We wore them down to see one of our old rocket s.p.a.ceplanes, standing on the field beside his little slipship. His robots had dug it out of a smashed hangar, and he now had them rebuilding it with new parts from Earth.

One of the great digging machines had extended a leverlike arm to hold it upright. A robot was replacing a broken landing strut, fusing it smoothly in place with some process that made no glow of heat. Casey spoke to the robot, but it ignored him. He climbed up to knock on the door. It responded with a brittle computer voice that was only a rattle in our helmets.

"Open up," he told it. "Let us in.""Admission denied." Its hard machine voice had Pen's accent.

"By what authority?"

"By the authority of Director Sandor Pen, Lunar Research Site."

"Ask the director to let us in."

"Admission denied."

"So you think." Casey shook his head, his words a sardonic whisper in my helmet. "If you know how to think."

Back inside the air lock, Pen had waited to help us shuck off the mirror suits. Casey thanked him for the gift and asked if the old s.p.a.ceplane would be left here on the Moon.

"Forget what you're thinking." He gave Casey a penetrating glance. "We're taking it down to Earth."

"I wish I could come."

"I'm sorry you can't." His face was firmly set, but a flush of pleasure turned it a richer gold. "It's to stand at the center of our new historic memorial, located on the Australian subcontinent. It presents our reconstruction of the prehistoric past. The whole story of the pre-impact planet and pre-impact man."

He paused to smile at Tanya. Flushed pink, she smiled back at him.

"It's really magnificent! Finding the lunar site was my great good fortune, and working it has been my life for many years. It has filled a gap in human history. Answered questions that scholars had fought over for ages. You yourselves have a place there, with a holographic diorama of your childhood."

Casey asked again why we couldn't see it. "Because you belong here." Impatience edged his voice.

"And because of the charter that allowed us to work the site. We agreed to restore the station to its original state, and to import no genetic materials from it that might contaminate the Earth. We are to leave the site exactly as it was before the impact, protected and secured from any future trespa.s.s."

We all felt sick with loss on the day he told us his work at the site was done. As a farewell gift, he took us two by two to orbit the Moon. Casey and I went up together, sitting behind him in his tiny slipship. We had seen s.p.a.ce and Earth from the dome all our lives, but the flight was still an exciting adventure.

The mirror hull was invisible from inside, so that our seats seemed to float free in open s.p.a.ce. The Moon's gray desolation spread wider beneath us, and dwindled again to a bright bubble floating in a gulf of darkness. Though Pen touched nothing I saw, the stars blazed suddenly brighter, the Milky Way a broad belt of gem-strewn splendor all around us. The Sun was dimmed and hugely magnified to let us see the dark spots across its face.

Still he touched nothing and I felt no new motion, but now Australia expanded. The deserts were gone. A long new sea lay across the center of the continent, crescent-shaped and vividly blue.

"The memorial." He pointed to a broad tongue of green land thrust into the crescent. "If you ever get to Earth-which I don't expect-you could meet your doubles there in the Tycho exhibit."Casey asked, "Is Mona there?"

Mona Lisa Live was the professional name of the woman Casey's father brought with him when he forced his way aboard the escape plane just ahead of the first impact. We knew them only from their holo images, he with the name "El Chino" and the crossed flags of Mexico and China tattooed across his black chest, she with the Leonardo painting on her belly.

Those ancient images had been enough to let us all catch the daring spirit and desperate devotion that had brought them finally to the Moon from the Medellin nightclub where he found her. From his first glimpse of her holo, Casey had loved her and dreamed of a day when they might be together again. I'd heard him ask my holo father why she had not been cloned with us.

"Ask the computer." He shrugged in the fatalistic way he had when his voice had its dry computer undertone. "It could have been done. Her tissue specimens are still preserved in the cryostat."

"Do you know why she wasn't cloned?"

"The computer seldom explains." He shrugged again. "If you want my own guess, she and Kell reached the Moon as unexpected intruders. The maternity lab was not prepared to care for them or their clones."

"Intruders?" Casey's dark face turned darker. "At least DeFort thought their genes were worth preserving. If I'm worth cloning, Mona ought to be. Someday she will be."

Back in the station dome, Pen made his final farewell. We thanked him for that exciting glimpse of the far-off Earth, for the s.p.a.ce suits and all his gifts, for restoring us to life. A trifling repayment, he said, for all he had found at the station. He shook our hands, kissed Tanya and Dian, and got into his silvery suit.

We followed him down to the air lock. Tanya must have loved him more than I knew. She broke into tears and ran off to her room as the rest of us watched his bright little teardrop float away toward Earth.

"We put them down there," Casey muttered. "We have a right to see what we have done."

When the robots left the restored s.p.a.ceplane standing on its own landing gear, the digging machine crept away to join the others. Busy again, they were digging a row of deep pits. We watched them bury themselves under the rubble, leaving only a row of new craters that might become a puzzle, I thought, to later astronomers. Casey called us back to the dome to watch a tank truck crawling out of the underground hangar dug into the crater rim.

"We're off to Earth!" He slid his arm around Pepe. "Who's with us?"

Arne scowled at him. "Didn't you hear Sandor?"

"Sandor's gone." He grinned at Pepe. "We have a plan of our own."

They hadn't talked about it, but I had heard their whispers and seen them busy in the shops. Though the s.p.a.cebending science of the slipship was still a mystery to us, I knew the robots had taught them astronautics and electronics. I knew they had made holos of Pen, begging him to say more about the new Earth than he ever would.

"I don't know your plan." Arne made a guttural grunt. "But I have seen the reports of people who went down to evaluate our terraforming. They've never found anything they liked, and never got back to theMoon."

"Que importa?"Pepe shrugged. "Better that than wasting our lives waitingpor nada ."

"We belong here." Stubbornly, Arne echoed what Pen had said. "Our mission is just to keep the station alive. Certainly not to throw ourselves away on insane adventures. I'm staying here."

Dian chose to stay with him, though I don't think they were in love. Her love was the station itself, with all its relics of the old Earth. Even as a little child, she had always wanted to work with her holo mother, recording everything that Pen took away to be copied and returned.

Tanya had set her heart on Sandor Pen. I think she had always dreamed that someday he would take her with him back to Earth. She was desolate and bitter when he left without her, her pride in herself deeply hurt.

"He did love us when we were little," she sobbed when Pepe begged her to join him and Casey. "But just because we were children. Or just interesting pets. Interesting because we aren't his kind of human, and people that live forever don't have children."

Pepe begged again, I think because he loved her. Whatever they found on Earth, it would be bigger than our tunnels, and surely more exciting. She cried and kissed him and chose to stay. The new Earth had no place for her. Sandor wouldn't want her, even if she found him. She promised to listen for their radio and pray they came back safe.

I had always been the station historian. Earth was where history was happening. I shook hands with Pepe and Casey and agreed to go with them.

"You won't belong," Tanya warned us. "You'll have to look out for yourselves."

She found water canteens and ration packs for us, and reminded us to pack safari garments to wear when we got out of our s.p.a.ce gear. We took turns in the dome, watching the tank truck till it reached the plane and the robots began pumping fuel.

"Time." Casey wore a grin of eager expectation. "Time to say good-bye."

Dian and Arne shook our hands, wearing very solemn faces. Tanya clung a long time to Pepe and kissed me and Casey, her face so tearstained and drawn that I ached with pity for her. We got into our shining suits, went out to the plane, climbed the landing stair. Again the door refused to open.

Casey stepped back to speak on his helmet radio.

"Priority message from Director Sandor Pen." His crackling voice was almost Pen's. "Special orders for restored s.p.a.ceplane SP2469."

The door responded with a clatter of speech that was alien to me.

"Orders effective now," Casey snapped. "Tycho Station personnel K. C. Kell, Pedro Navarro, and Duncan Yare are authorized to board for immediate pa.s.sage to Earth."

Silently, the door swung open.

I had expected to find a robot at the controls, but we found ourselves alone in the nose cone, the pilot seat empty. Awed by whatever the plane had become, we watched it operate itself. The door swung shut. Air seals hissed. The engines snorted and roared. The ship trembled, and we lifted off the Moon.Looking back for the station, all I found was the dome, a bright little eye peering into s.p.a.ce from the rugged gray peaks of the crater rim. It shrank till I lost it in the great lake of black shadow and the bright black peak at the center of the Tycho crater. The Moon dwindled till we saw it whole, gray and impact-battered, dropping behind us into a black and bottomless pit.

Pen's flight in the slipship may have taken an hour or an instant. In the old rocket ship, we had time to watch three full rotations of the slowly swelling planet ahead. The jets were silent through most of the flight, with only an occasional whisper to correct our course. We floated in free fall, careful not to blunder against the controls. Taking turns belted in the seats, we tried to sleep but seldom did. Most of the time we spent searching Earth with binoculars, searching for signs of civilization.

"Nothing," Casey muttered again and again. "Nothing that looks like a city, a railway, a ca.n.a.l, a dam.

Nothing but green. Only forest, jungle, gra.s.sland. Have they let the planet return to nature?"

"Tal vez." Pepe always shrugged. "Pero o no. We are still too high to tell."

At last the jets came back to life, steering us down into air-breaking orbit. Twice around the puzzling planet, and Australia exploded ahead. The jets thundered. We fell again, toward the wide tongue of green land between the narrow cusps of that long crescent lake.

3.

Looking from the windows, we found the s.p.a.ceplane standing on an elevated pad at the center of a long quadrangle covered with tended lawns, shrubs and banks of brilliant flowers. Wide avenues all around it were walled with buildings that awed and amazed me.

"Sandor's Tycho Memorial!" Pepe jogged my ribs. "There's the old monument at the American capital! I know it from Dian's videos."

"Ancient history." Casey shrugged as if it hardly mattered. "I want to see Earth today."

Pepe opened the door. In our safari suits, we went out on the landing for a better view. The door shut. I heard it hiss behind us, sealing itself. He turned to stare again. The monument stood at the end of the quadrangle, towering above its image in a long reflecting pool, flanked on one side by a Stonehenge in gleaming silver, on the other by a sandbanked Sphinx with the nose restored.