Simak short story production this year was surprisingly small—but as is to be expected of this fine and sensitive writer, he came up with a concept that combines the infinite with the simple curiosities of ordinary Earthlings.

In that same year when men first walked on Mars the probe was launched from the moon for Pluto. Five years later the first pictures were transmitted as the orbiting probe trained its cameras on the planet's surface. The transmission quality was poor; but even so, certain features of the photographs were productive of great anguish as old theories fell to shards and were replaced by puzzlement, questions with no hint of answers. The pictures seemed to say that the planet had a smooth, almost polished surface, without a single geographic feature to break the smoothness of it. Except that at certain places, equidistant from one another along the equator, were tiny dots that would have been taken for transmission noise if they had not appeared consistently. Too, the dots still persisted when some of the noise was eliminated. So it seemed they must be small geographic features or shadows cast by geographic features, although at Pluto's distance from the sun shadows would be suspect. The other data did nothing to lessen the anguish. The planet was smaller than supposed, less than a thousand miles in diameter, and its density worked out to 3.5 grams per cubic centimeter rather than the unrealistic figure of 60 grams, previously supposed.

This meant several things. It meant that somewhere out there, perhaps something more than seven billion miles from the sun, a tenth planet of the solar system swung in orbit, for no planet the size and mass of Pluto could explain the eccentricities in the orbits of Uranus and Neptune. The calculation of Pluto's mass, now proved inaccurate, had been based on the measurement of those eccentricities and it must be admitted now that something else must account for them.

Beyond that, Pluto was most strange—a smooth planet, featureless except for the evenly spaced dots. The smoothness certainly could not be explained by a nonturbulent atmosphere, for surely Pluto had to be too small and cold to hold an atmosphere. A surface of ice, men wondered, the frozen remnants of a one-time, momentary atmosphere? But for a number of reasons that didn't seem right, either. Metal, perhaps; but if the planet were of solid metal the density should be far greater.

The men on Earth consoled themselves. In five more years the probe would come back to Earth, carrying with it the films that it had taken and from them, the actual films and not the low-quality transmissions, perhaps much that was hazy now might become understandable. The probe swung in its measured orbits and sent back more pictures, although they were little help, for the quality still was poor. Then it fired the automatic sequence that would head it back to Earth, and its beeping signals from far out in space said it was headed home on a true and steady course.

Something happened. The beeping stopped and there was a silence. Moon Base waited. It might start up again. The silence might indicate only a momentary malfunction and the signals might start again. But they never did. Somewhere, some three billion miles from the sun, some mishap had befallen the homing probe. It was never heard again—it was lost forever.

There was no sense in sending out another probe until a day when technical advances could assure better pictures. The technical advances would have to be significant—small refinements would do little good.

The second and third manned expeditions went to Mars and came home again, bringing back, among many other things, evidence that primitive forms of life existed there, which settled once for all the old, dark suspicion that life might be an aberration to be found only on the Earth. For with life on two planets in the same solar system there could no longer be any doubt that life was a common factor in the universe. The fourth expedition went out, landed, and did not come back again and now there was on Mars a piece of ground that was forever Earth. The fifth expedition was sent out even while the Earth still paid tribute to those four men who had died so far from home.

Now that life had been found on another world, now that it was apparent that another planet at one time had held seas and rivers and an atmosphere that had been an approximation of Earth's own atmosphere, now that we knew we no longer were alone in the universe, the public interest and support of space travel revived. Scientists, remembering (never having, in fact, forgotten, for it had gnawed steadily at their minds) the puzzlement of the Pluto probe, began to plan a manned Pluto expedition, as there was still no sense in sending an instrumented probe.

When the day came to lift from the Moon Base, I was a member of the expedition. I went along as a geologist —the last thing a Pluto expedition needed.

There were three of us and any psychologist will tell you that three is a number that is most unfortunate. Two gang up on one or ignore one and there is always competition to be one of the gang of two. No one wants to stand alone with the other two against him. But it didn't work that way with us. We got along all right, although there were times when it was rough going. The five years that the probe took to arrive at Pluto were cut by more than half, not only because of improved rocket capability, but because a manned craft could pile on velocity that couldn't be programmed—or at least safely programmed—into a probe. But a bit more than two years is a long time to be cooped up in a tin can rocketing along in emptiness. Maybe it wouldn't be so bad if you had some sense of speed, of really getting somewhere—but you haven't. You just hang there in space.

The three of us? Well, I am Robert Hunt and the other two were Orson Gates, a chemist, and Tyler Hampton, an engineer.

As I say, we got along fine. We played chess tournaments—yeah, three men in a tournament and it was all right because none of us knew chess. If we had been any good I suppose we would have been at one another's throats. We dreamed up dirty ditties and were so pleased with our accomplishments that we'd spend hours singing them and none of us could sing. We did a lot of other futile things—by now you should be getting the idea. There were some rather serious scientific experiments and observations we were supposed to make, but all of us figured that our first and biggest job was to manage to stay sane.

When we neared Pluto we dropped the fooling around and spent much time peering through the scope, arguing and speculating about what we saw. Not that there was much to see. The planet resembled nothing quite as much as a billiard ball. It was smooth. There were no mountains, no valleys, no craters—nothing marred the smoothness of the surface. The dots were there, of course. We could make out seven groups of them, all positioned along the equatorial belt. And in close-up they were not simply dots. They were structures of some kind.

We landed finally, near a group of them. The landing was a little harder than we had figured it would be. The planetary surface was hard—there was no give to it. But we stayed right-side up and we didn't break a thing.

People at times ask me to describe Pluto and it's a hard thing to put into words. You can say that it is smooth and that it's dark—it's dark even in broad daylight. The sun, at that distance, is not much more than a slightly brighter star. You don't have daylight on Pluto— you have starlight and it doesn't make much difference whether you're facing the sun or not. The planet is airless, of course, and waterless and cold. But cold, as far as human sensation is concerned, is a relative thing. Once the temperature gets down to a hundred Kelvin it doesn't much matter how much colder it becomes. Especially when you're wearing life support. Without a suit containing life support you'd last only a few seconds, if that long, on a place like Pluto. I've never figured out which would kill you first—cold or internal pressure. Would you freeze—or explode before you froze?

So Pluto is dark, airless, cold, and smooth. Those are the externals only. You stand there and look at the sun and realize how far away you are. You know you are standing at the edge of the solar system, that just out there, a little way beyond, you'd be clear outside the system. Which doesn't really have to be true, of course. You know about the tenth planet. Even if it's theory, it's supposed to be out there. You know about the millions of circling comets that technically are a part of the solar system, although they're so far out no one ever thinks of them. YOU could say to yourself this really is not the edge—the hypothetical tenth planet and the comets still are out there. But this is intellectualization; you're telling yourself something that your mind says may be true, but your gut denies. For hundreds of years Pluto has been the last outpost and this, by God, is Pluto and you're farther away from home than man has ever been before and you feel it. You don't belong to anything anymore. You're in the back alley, and the bright and happy streets are so far away that you know you'll never find them.

It isn't homesickness that you feel. It's more like never having had a home. Of never having belonged anywhere. You get over it, of course—or come to live with it. So we came down out of the ship after we had landed and stood upon the surface. The first thing that struck us —other than the sense of lostness that at once grabbed all of us—was that the horizon was too near, much nearer than on the moon. We felt at once that we stood on a small world. We noticed that horizon's nearness even before we noticed the buildings that the probe had photographed as dots and that we had dropped down to investigate. Perhaps buildings is not the right word—structures probably would be better. Buildings are enclosures and these were not enclosures. They were domes someone had set out to build and hadn't had time to finish. The basic underlying framework had been erected and then the work had stopped. Riblike arcs curved up from the surface and met overhead. Struts and braces held the frames solid, but that was as far as the construction had gone. There were three of them, one larger than the other two. The frames were not quite as simple as I may have made them seem. Tied into the ribs and struts and braces were a number of other structural units that seemed to have no purpose and made no sense at all. We tried to make sense out of them and out of the scooped-out hollows that had been gouged out of the planetary surface within the confines of each construct— they had no floors and seemed fastened to the surface of the planet. The hollows were circular, some six feet across and three feet deep, and to me they looked like nothing quite as much as indentations made in a container of ice cream by a scoop.

About this time Tyler began to have some thoughts about the surface. Tyler is an engineer and should have had his thoughts immediately—and so should the rest of us—but the first hour or so outside the ship had been considerably confusing. We had worn our suits in training, of course, and had done some walking around in them, but Pluto seemed to have even less gravity than had been calculated and we had had to get used to it before we could be reasonably comfortable. Nor had anything else been exactly as we had anticipated.

"This surface," Tyler said to me. "There is something wrong with it."

"We knew it was smooth," said Orson. "The pictures showed that. Coming in, we could see it for ourselves."

"This smooth?" Tyler asked. "This even?" He turned to me. "It isn't geologically possible. Would you say it is?"

"I would think not," I said. "If there had been any upheaval at all this floor would be rugged. There can't have been any erosion—anything to level it down. Micrometeorite impacts, maybe, but not too many of them. We're too far out for meteorites of any size. And while micro-meteorites might pit the surface there would be no leveling process."

Tyler let himself down on his knees rather awkwardly. He brushed a hand across the surface. The seeing was not too good, but you could see that there was dust, a thin layer of dust, a powdering.

"Shine a light down here," said Tyler.

Orson aimed his light at the spot. Some of the gray dust still clung where Tyler had wiped his hand, but there were streaks where the darker surface showed through.

"Space dust," said Tyler.

Orson said, "There should be damn little of it."

"True," said Tyler. "But over four billion years or more, it would accumulate. It couldn't be erosion dust, could it?"

"Nothing to cause erosion," I said. "This must be as close to a dead planet as you ever get. Not enough gravity to hold any of the gases—if there ever were gases. At one time there must have been, but they've all gone—they went early. No atmosphere, no water. I doubt there ever was any accumulation. A molecule wouldn't hang around for long."

"But space dust would?"

"Maybe. Some sort of electrostatic attraction, maybe."

Tyler scrubbed the little patch of surface again with his gloved hand, removing more of the dust, with more of the darker surface showing through.

"Have we got a drill?" he asked. "A specimen drill."

"I have one in my kit," said Orson. He took it out and handed it to Tyler. Tyler positioned the bit against the surface, pressed the button. In the light of the torch you could see the bit spinning. Tyler put more weight on the drill.

"It's harder than a bitch," he said.

The bit began to bite. A small pile of fragments built up around the hole. The surface was hard, no doubt of that. The bit didn't go too deep and the pile of fragments was small.

Tyler gave up. He lifted out the bit and snubbed off the motor.

"Enough for analysis?" he asked.

"Should be," said Orson. He took the bit from Tyler and handed him a small specimen bag. Tyler laid the open mouth of the bag on the surface and brushed the fragments into it.

"Now we'll know," he said. "Now we will know something."

A couple of hours later, back in the ship, we knew.

"I have it," Orson said, "but I don't believe it."

"Metal?" asked Tyler.

"Sure, metal. But not the kind you have in mind. It's steel."

"Steel?" I said, horrified. "It can't be. Steel's no natural metal. It's manufactured."

"Iron," said Orson. "Nickel. Molybdenum, vanadium, chromium. That works out to steel. I don't know as much about steel as I should. But it's steel—a good steel. Corrosion resistant, tough, strong."

"Maybe just the platform for the structures," I said. "Maybe a pad of steel to support them. We took the specimen close to one of them."

"Let's find out," said Tyler.

We opened up the garage and ran down the ramp and got out the buggy. Before we left we turned off the television camera. By this time Moon Base would have seen all they needed to see and if they wanted more they could ask for it. We had given them a report on everything we had found—all except the steel surface and the three of us agreed that until we knew more about that we would not say anything. It would be a while in any case until we got an answer from them. The time lag to Earth was about sixty hours each way.

We went out ten miles and took a boring sample and came back, following the thin tracks the buggy made in the dust, taking samples every mile. We got the answer that I think all of us expected we would get, but couldn't bring ourselves to talk about. The samples all were steel.

It didn't seem possible, of course, and it took us a while to digest the fact, but finally we admitted that on the basis of best evidence Pluto was no planet, but a fabricated metal ball, small-planet size. But godawful big for anyone to build.


That was the question that now haunted us. Who had built it? Perhaps more important—why had they built it? For some purpose, surely, but why, once that purpose had been fulfilled (if, in fact, it had been fulfilled) had Pluto been left out here at the solar system's rim?

"No one from the system," Tyler said. "There's no one but us. Mars has life, of course, but primitive life. It got a start there and hung on and that was all. Venus is too hot. Mercury is too close to the sun. The big gas planets? Maybe, but not the kind of life that would build a thing like this. If had to be something from outside."

"How about the fifth planet?" suggested Orson.

"There probably never was a fifth planet," I said. "The material for it may have been there, but the planet never formed. By all the rules of celestial mechanics there should have been a planet between Mars and Jupiter, but something went haywire."

"The tenth planet, then," said Orson.

"No one is really positive there is a tenth," said Tyler.

"Yeah, you're right," said Orson. "Even if there were it would be a poor bet for life, let alone intelligence."

"So that leaves us with outsiders," said Tyler.

"And a long time ago," said Orson.

"Why do you say that?"

"The dust. There isn't much dust in the universe."

"And no one knows what it is. There is the dirty ice theory."

"I see what you're getting at. But it needn't be ice. Nor graphite nor any of the other things that have been—"

"You mean it's that stuff out there."

"It could be. What do you think, Robert?"

"I can't be sure," I said. "The only thing I know is that it couldn't be erosive."

Before we went to sleep we tried to fix up a report to beam back to Moon Base, but anything we put together sounded too silly and unbelievable. So we gave up. We'd have to tell them some time, but we could wait.

When we awoke we had a bite to eat, then got into our suits and went out to look over the structures. They still didn't make much sense, especially all the crazy contraptions that were fastened on the ribs and struts and braces. Nor did the scooped-out hollows.

"If they were only up on legs," said Orson, "they could be used as chairs."

"But not very comfortable," said Tyler.

"If you tilted them a bit," said Orson. But that didn't figure either. They would still be uncomfortable. I wondered why he thought of them as chairs. They didn't look like any chairs to me..

We pottered around a lot, not getting anywhere. We looked the structures over inch by inch, wondering all the while if there was something we had missed. But there didn't seem to be.

Now comes the funny part of it. I don't know why we did it—out of sheer desperation, maybe. But failing to find any clues, we got down on our hands and knees, dusting at the surface with our hands. What we hoped to find, I don't know. It was slow going and it was a dirty business, with the dust tending to stick to us.

"If we'd only brought some brooms along," said Orson.

But we had no brooms. Who in his right mind would have thought we would want to sweep a planet?

So there we were. We had what appeared to be a manufactured planet and we had some stupid structures for which we could deduce not a single reason. We had come a long ways and we had been expected to make some tremendous discovery once we landed. We had made a discovery, all right, but it didn't mean a thing.

We finally gave up with the sweeping business and stood there, scuffing our feet and wondering what to do next when Tyler suddenly let out a yell and pointed at a place on the surface where his boots had kicked away the dust.

We all bent to look at what he had found. We saw three holes in the surface, each an inch or so across and some three inches deep, placed in a triangle and close together. Tyler got down on his hands and knees and shone his light down into the holes, each one of them in turn.

Finally he stood up. "I don't know," he said. "They could maybe be a lock of some sort. Like a combination. There are little notches on the sides, down at the bottom of them. If you moved those notches just right something might happen."

"Might blow ourselves up, maybe," said Orson. "Do it wrong and bang!"

"I don't think so," said Tyler. "I don't think it's anything like that. I don't say it's a lock, either. But I don't think it's a bomb. Why should they booby-trap a thing like this?"

"You can't tell what they might have done," I said. "We don't know what kind of things they were or why they were here."

Tyler didn't answer. He got down again and began carefully dusting the surface, shining his light on it while he dusted. We didn't have anything else to do, so helped him.

It was Orson who found it this time—a hairline crack you had to hold your face down close to the surface to see. Having found it, we did some more dusting and worried it out. The hairline described a circle and the three holes were set inside and to one edge of it. The circle was three feet or so in diameter.

"Either of you guys good at picking locks?" asked Tyler.

Neither of us were.

"It's got to be a hatch of some sort," Orson said. "This metal ball we're standing on has to be a hollow ball. If it weren't its mass would be greater than it is."

"And no one," I said, "would be insane enough to build a solid ball. It would take too much metal and too much energy to move."

"You're sure that it was moved?" asked Orson.

"It had to be," I told him. "It wasn't built in this system. No one here could have built it."

Tyler had pulled a screwdriver out of his tool kit and was poking into the hole with it.

"Wait a minute," said Orson. "I just thought of something."

He nudged Tyler to one side, reached down, and inserted three fingers into the holes and pulled. The circular section rose smoothly on its hinges.

Wedged into the area beneath the door were objects that looked like the rolls of paper you buy to wrap up Christmas presents. Bigger than rolls of paper, though. Six inches or so across.

I got hold of one of them and that first one was not easy to grip, for they were packed in tightly. But I managed with much puffing and grunting to pull it out. It was heavy and a good four feet in length.

Once we got one out, the other rolls were easier to lift. We pulled out three more and headed for the ship.

But before we left I held the remaining rolls over to one side, to keep them from tilting, while Orson shone his light down into the hole. We had half expected to find a screen or something under the rolls, with the hole extending on down into a cavity that might have been used as living quarters or a workroom. But the hole ended in machined metal. We could see the grooves left by the drill or die that had bored the hole. That hole had just one purpose, to store the rolls we had found inside it.

Back in the ship we had to wait a while for the rolls to pick up some heat before we could handle them. Even so we had to wear gloves when we began to unroll them. Now, seeing them in good light, we realized that they were made up of many sheets rolled up together. The sheets seemed to be made of some sort of extremely thin metal or tough plastic. They were stiff from the cold and we spread them out on our lone table and weighed them down to hold them flat.

On the first sheet were diagrams of some sort, drawings, and what might have been specifications written into the diagrams and along the margins. The specifications, of course, meant nothing to us (although later some were puzzled out and mathematicians and chemists were able to figure out some of the formulas and equations).

"Blueprints," said Tyler. "This whole business was an engineering job."

"If that's the case," said Orson, "those strange things fastened to the structural frames could be mounts to hold engineering instruments."

"Could be," said Tyler.

"Maybe the instruments are stored in some other holes like the one where we found the blueprints," I suggested.

"I don't think so," said Tyler. "They would have taken the instruments with them when they left."

"Why didn't they take the blueprints, too?"

"The instruments would have been worthwhile to take. They could be used on another job. But the blueprints couldn't. And there may have been many sets of prints and spec sheets. These we have may be only one of many sets of duplicates. There would have been a set of master prints and those they might have taken with them when they left"

"What I don't understand," I said, "is what they could have been building out here. What kind of construction? And why here? I suppose we could think of Pluto as a massive construction shack; but why exactly here? With all the galaxy to pick from, why this particular spot?"

"You ask too many questions all at once," Orson told me.

"Let's look," said Tyler. "Maybe well find out."

He peeled the first sheet off the top and let it drop to the floor. It snapped back to the rolled-up position.

The second sheet told us nothing, nor did the third or fourth. Then came the fifth sheet.

"Now, here is something," said Tyler.

We leaned closer to look.

"It's the solar system," Orson said.

I counted rapidly. "Nine planets."

"Where's the tenth?" asked Orson. "There should be a tenth."

"Something's wrong," said Tyler. "I don't know what it is."

I spotted it, "There's a planet between Mars and Jupiter."

"That means there is no Pluto shown," said Orson.

"Of course not," said Tyler. "Pluto never was a planet."

"Then this means there once actually was a planet between Mars and Jupiter," said Orson.

"Not necessarily," Tyler told him. "It may only mean there was supposed to be."

"What do you mean?"

"They bungled the job," said Tyler. "They did a sloppy piece of engineering."

"You're insane!" I shouted at him.

"Your blind spot is showing, Robert. According to what we think, perhaps it is insane. According to the theories our physicists have worked out. There is a cloud of dust and gas and the cloud contracts to form a proto-star. Our scientists have invoked a pretty set of physical laws to calculate what happens. Physical laws that were automatic-since no one would be mad enough to postulate a gang of cosmic engineers who went about the universe building solar systems."

"But the tenth planet," persisted Orson. "There has to be a tenth planet. A big, massive—"

"They messed up the projected fifth planet," Tyler said. "God knows what else they messed up. Venus, maybe. Venus shouldn't be the kind of planet it is. It should be another Earth, perhaps a slightly warmer Earth, but not the hellhole it is. And Mars. They loused that up, too. Life started there, but it never had a chance. It hung on and that was all. And Jupiter, Jupiter is a monstrosity—"

"You think the only reason for a planet's existence is its capability of supporting life?"

"I don't know, of course. But it should be in the specs. Three planets that could have been life-bearing and of these only one was successful."

"Then," said Orson, "there could be a tenth planet. One that wasn't even planned."

Tyler rapped his fist against the sheet. "With a gang of clowns like this anything could happen."

He jerked away the sheet and tossed it to the floor.

"There!" he cried. "Look here."

We crowded in and looked.

It was a cross section, or appeared to be a cross section, of a planet.

"A central core," said Tyler. "An atmosphere—"


"Could be. Could be Mars or Venus."

The sheet was covered with what could have been spec notations.

"It doesn't look quite right," I protested.

"It wouldn't if it were Mars or Venus. And how sure are you of Earth?"

"Not sure at all," I said.

He jerked away the sheet to reveal another one.

We puzzled over it.

"Atmospheric profile," I guessed halfheartedly.

"These are just general specs," said Tyler. "The details will be in some of the other rolls. We have a lot of them out there."

I tried to envision it. A construction shack set down in a cloud of dust and gas. Engineers who may have worked for millennia to put together star and planets, to key into them certain factors that still would be at work, billions of years later.

Tyler said they had bungled and perhaps they had. But maybe not with Venus. Maybe Venus had been built to different specifications. Maybe it had been designed to be the way it was. Perhaps, a billion years from now, when humanity might well be gone from Earth, a new life and a new intelligence would rise on Venus.

Maybe not with Venus, maybe with none of the others, either. We could not pretend to know.

Tyler was still going through the sheets.

"Look here," he was yelling. "Look here, the bunglers—"