Polar research had continued unabated, Lena recounted. The main efforts were to answer why, except for sporadic local anomalies, most rivers had stopped running and the water had frozen three billion years ago. There were efforts, both by drilling and by finding the oldest outcrops, to concentrate on the strata laid down around that time.
Results of a different sort had come about ten weeks back, when two successive drill bits shattered at a depth of five hundred meters. Initial speculations of the geology team centered around massive nickel-iron meteorite fragments, or some mysterious ore body. The splintering of two successively stronger drill bits capable of penetrating such materials ended that speculation. Eventually, imaging in the drill hole seemed to show a smooth, rounded surface, unmarred by the drill bits. Chemical probes showed a metalloid structure rich in titanium, silicon, and carbon, but failed to identify the precise composition or molecular structure. This is when Stafford had been called by Lena, and the secrecy lid had clamped down. Eventual enlargement of the drill hole allowed more complete imaging, and precarious human inspection revealed a horizontal-lying tube, a pipe about the thickness of a man's body. It ran east-west. In every test they could devise, the tubing proved impenetrable.
The next step had been to make another drill hole one hundred meters to the east. It uncovered what appeared to be an eastward extension of the same tubing. They couldn't keep drilling all over the pole to trace the extension of the thing. Geophysical measurements from the surface were attempted, in hopes of mapping the extent of the metal mass, but with no success.
By that time, still in early February, with the protocols in place, it was a crash program with unlimited budget, to learn as much as possible within ninety days. Sturgis and his security team had seized control of the operation and ordered the most sensitive geophysical equipment sent from Mars City and Phobos, piggybacked on other freight shipments so as not to attract attention. The science team had gone along with it, choosing to interpret the ninety days not as imposed secrecy but as the normal data development period before publication.
Renewed attempts to detect the buried tubing with the new geophysical equipment from Earth gave marginal results. But the drilling went quickly in the soft-rock polar sediments. New holes sunk one, two, ten, twenty, fifty kilometers to the east always hit the tubing. Where the tube crossed under the eroded valleys, it was shallower and easier to reach. When the drill holes had tracked a hundred kilometers of tubing, a curiosity was discovered as cartographers fit the positional data points onto ever-refined maps. The tubing, which at first had appeared to run straight as an arrow, did not follow a great circle on the globe, nor did it run truly east-west along a latitude line around the south pole. Instead, curve-fitting programs confirmed that the actual positions of the tube fit a spiral, and the center of the spiral lay close to the pole. The whole thing looked like a giant burner on an old-fashioned electric stove.
If the tube truly followed a spiral, it would wrap around the pole many times. Still more precise curve-fitting procedures were performed. Projection of the calculated spiral pattern indicated that the coils would be spaced roughly six hundred meters apart at this distance from the pole.
The geophysical probes were pressed back into service, surveying six hundred meters south of the line of the tube. A possible signal was buried in the noise, at 623 meters. A new drill hole probing the 3.2-billion-year stratum uncovered another tube segment running east-west. Or rather, it was not really another tube segment, but what came to be viewed as the next coil of the same tubing as it wrapped around the pole.
What would be found at the pole itself?
Geophysical probing around the true pole found nothing. Drilling found nothing.
Meanwhile, the cartographers refined their curves. The new solution put the center of the spiral not at the south pole, but offset about twenty-five kilometers from it, generally in the direction of Hellas basin.
They moved the geophysical probing efforts to that site and found evidence for a massive metal-rich complex beneath the surface. The polar sediments were deeper here. The complex was buried at the 3.2-billionyear stratum at a depth of thirty-two kilometers, out of reach of any excavations.
"At that point a different kind of information came into the picture," Elena was telling them. The bus had rolled to a stop in the valley mouth and they were suiting up. "In the late twenties they had begun mapping a paleomagnetic field of Mars. There's not much of a field now, of course, but three billion years ago the magnetic dipole field was pretty healthy around here. Way above the solar wind background. Of course, it showed a certain amount of wander. Fluctuated in strength and went through polarity reversals. The geophysicists developed some preliminary mapping of the pole positions as a function of time. Guess what? Our metallic complex was buried at the position where the magnetic pole was, 3.2 billion years ago. Near as they could tell anyway. This whole thing was somehow designed around the magnetic field of the planet at that time."
"Planetary engineering!"
"At least planetary-scale engineering."
"But what did it do? What was it for?"
"Nobody's got the foggiest." Lena was smiling and obviously enjoying herself for the first time in days.
Stafford explained, "That's how we can be so firm on the date, we've got two independent lines of evidence, like we mentioned yesterday. The pole position and the date of the strata both say this thing was emplaced 3.2 billion years ago. The error bars are pretty sloppy, maybe plus or minus 0.05 billion, but it's somewhere around 3.0, 3.2, 3.3."
"One thing bothers me," Philippe said. He had a very serious expression. "If this thing is less than a meter wide, and spaced six hundred meters apart, weren't you incredibly lucky to hit a piece of it with a drill? Do you expect us to believe that?"
Stafford: "We musta had two hundred drill holes out there by the time we hit it. If you figure the tube is nearly a meter across and lines of tube are six hundred meters apart, we were getting a fair chance of hitting it. Woulda hit it sooner or later."
"C'mon," Elena called to them from the front of the bus. "Get your helmets on. We're going out there."
After they were out on the surface, Carter discovered he had been so excited that he put on his helmet too fast. The inner fitting that held the microphone had slipped and was scratching his neck. He had to speak loudly to be heard.
The bus was parked near a cluster of instrument boxes and vehicles in the center of the broad valley mouth. Carter and the others walked across the frosty soil to a fencelike barrier, erected from pipe lengths that were diagonally striped with yellow and black. The barrier surrounded a pit that had been widened and reinforced to form a broad shaft, as much as ten meters across, which disappeared vertically into the valley floor. Out of the shaft came an array of cables and tubes, like a mass of giant black worms slithering out of a hole. The cables ran to various instrumented wagons parked around the hole. A brilliant yellow bulldozer brooded nearby.
Peering as far as they could over the barrier, they could see that the inside of the shaft was lined and illuminated, and that it descended about forty meters.
"This is one of the shallowest exposures," Lena was intoning over the intercom. "We're in a pretty deeply cut valley."
An elevator cage ran down one side of the hole. There were two suited figures working in the claustrophobic space at the bottom of the hole.
"Look. At the bottom," Lena prompted.
Peering downward, Carter could dimly see a strangely innocent tube crossing the bottom of the hole. It was smooth and had a greenish metallic luster. Here, at last, was what humanity had awaited since the days of Herschel and Welles and Bradbury and Clarke, the fantastic discovery of an artifact from another civilization. In that dully gleaming curved surface, the four-century attempt to confirm "the plurality of worlds" had become reality. Here was the first stop on humanity's long road of search for companionship, or at least non-uniqueness, in the cosmos. No matter that it was three bil
lion years old and that its builders were not only nowhere to be seen, but perhaps long vanished. Whatever the caveats, this little tube proved that humanity was neither some unique mistake of Nature, nor necessarily had dominion over field and fowl.
"Shouldn't we have music swelling up in the background?" Philippe said.
The tube might as well have been a deep sewer line attended by city engineers. The patchy greenish patina reminded Carter of aged bronze. They stood around the railing, Annie panning downward with a minicam. Eventually, there was nothing new to see. The city engineers bustled around the surface, in the spotlights, as if repairing a broken water main.
Carter tried to fix the moment in his mind for the rest of his life. Gusts of wind off the polar hills blew the bus-and-tractor-disturbed dust into little eddies around the mouth of the drill hole. Even the wind was special: it blew across the polar wastes where They had been.
"There's one more thing." Lena's voice jarred Carter out of his reverie. "Remember how I told you about the big buried complex at the far end of the tube? Well, this is the other end." She gestured toward the cavelike aperture in the hill.
Led by Elena, the group started walking toward the foot of the hill on one side of the valley, where the dark maw of the tunnel loomed, surrounded by the flashing turquoise lights that designated an emergency shelter. It looked like the entrance to a carnival ride.
Suddenly Sturgis's voice on the radio broke Carter's reverie. "Give it up, Annie Pohaku. All the satellite communications channels on your suits are closed. Did you really think we'd leave you a comsat channel open to the outside world?"
Annie's voice came on, angrily. "Shit."
"We wanted to see if you'd try that." Sturgis again. "Suspicion confirmed." Carter could almost imagine a smirk on his face. "But you see, we hold no grudges here. Come on; there're things to see."
Annie made no reply.
Carter immediately realized what had happened. With the distraction of the drill hole, and with its alien contents finally confirmed by their own eyes, Annie had attempted to raise one of the Marsnet satellites on an emergency channel. And failed, thanks to Sturgis.
So they were truly cut off.
"It's important that we stick close together," Sturgis was saying, "since you have no outside links if you wander off and get into trouble." He sounded sincere now that he was speaking to the group as a whole. His sarcasm always seemed reserved for Annie. "I apologize to you.... It's crazy to cut off the emergency channels, I know, but this whole situation is an emergency of a unique sort. Really, we can't afford to have anyone wandering off. Anyway, we won't be outside very long."
They approached the cavern. Carter caught up to Annie and touched her puffy arm, catching her by surprise. She swung her shoulders toward him aggressively, to see who it was. Her arms fluttered upward, an ineffectual gesture of defeat, and then she touched his shoulder in return.
It was not truly a cave, but a long tunnel, cut into the hill by Trevina's crew. The tunnel slanted down. A long catwalk led down its center, flunked on either side by rails for carts that had hauled equipment in and dirt out.
Partway down the tunnel, in a zone constricted by massive dark rock, was a tripartite airlock. They squeezed into its narrow central chamber, flanked on either side by larger chambers for the rail cars and machinery.
As the airlock door opened, Sturgis took his helmet off and gestured for them to do the same. It took an effort of will, breaking the seal, with the bare Martian rock around them. But Carter was relieved to get his helmet off. With the back of his hand he soothed his chin where the misplaced mike had rubbed his skin raw. The humid air was bitterly cold and their breath hung in front of them in ragged clouds of gray vapor.
Elena waved them on. "You should see the pumps we've got for keeping up the air pressure in here. Course, we lose some through the rock porosity, but we manage to keep ahead of that."
Stafford nudged Carter and pointed clumsily ahead of them, where the tunnel seemed to open into a larger room. "Wait'll you see this."
They had been saying that to him since yesterday.
Lights blazed from scaffolding, making a latticework of starlike beacons around them. A vast room the size of a stadium had been hollowed out of the strata. The cavern looked as if it should have been dank and dripping, but it was as dry as chalk and bright as day. The solid rock walls had been neatly pared away, to expose surfaces banded in red and brown like stacks of old books. Some of the horizontal strata were delicately thin; another was ten meters thick, a single band the color of mahogany.
The vast underground room was dominated by a single, unprecedented structure looming in the center. Elena waved toward it in a cheerful, sweeping gesture. "Well, there it is."
Towering above them, in the cleared space at the end of the cavern, was a huge, organ-pipe mass of vertical cylinders, with the same greenish metallic sheen that they had seen outside, but this time rising vertically.
The cylinders had different diameters, tiny ones clustered among the big ones. The whole complex had a fractal quality. There were large tubes, smaller tubes touching them, still smaller tubes of shorter or longer length nestled among those. The outer surface was an impenetrable complex of small tubes studded with still smaller tubes. The diameter of the complex was perhaps forty meters. On the left side of the room they could see the only horizontal tube in the room, the same as the one in the pit outside, entering the cavern from the left at eye level and piercing the cluster of tubes in a baroque collar of fittings that gleamed faintly of gold.
Surreal organ pipes gone mad, erected in some deserted cathedral. Organ pipes left by ... whom? Giants? Dwarfs? Strangely, nothing in the installation gave a clue as to the size or shape of the unknown beings who had left this ... thing.
A deep, broad shaft had been excavated around the vertical tubes to a depth of thirty meters. Down, down the tubes plunged, and disappeared into the soil at the bottom of this excavation.
"We think that all the horizontal tubing was laid on the surface that existed 3.2 billion years ago, and then covered during later centuries by younger sediments." Lena patted the horizontal tube, as if it were the most normal thing in the world. "What you see here is the end of the horizontal spiral, where it joins this"—she looked toward the towering complex—"we call it a node. The interesting thing is that the pipes in the node run vertically down with no sign of disturbance, as if they were sunk in carefully bored drill holes or magically pushed directly through the soil. We don't understand that."
Carter was developing an odd feeling about the room. The upward and downward thrusting of the strange tubes was clean and direct, and yet something was uncanny about it—about the very air in the room. Carter was surprised to feel the hair rise on the back of his neck. It was as if there were some presence, some unseen purpose, hidden in the room with them. It was the feeling you have when you waken at midnight and sense that something unseen and unfamiliar is in the dark bedroom with you. Yet the presence did not seem evil. The more he examined the feeling, the more it seemed neutral. Or was it positive?
Stafford, holding his helmet under his arm, beamed proudly. "As Lena said, the horizontal tube is an extension of the same tube we saw outside, in the drill hole. But it doesn't extend any farther west. This is the end of the line. It's the outermost end of the spiral around the old magnetic pole. The vertical node was big enough for us to locate with geophysical detectors on the surface, and the goal of our tunneling was to get in to where we could see it. You see, we've exposed the top of it. We don't know how far down it goes." He pointed toward the top of the cold room, where the ceiling was shored with carbonal cross beams.
The tubes ended at different levels, each terminating in a rounded, solid cap. Not quite hemispherical, Carter noticed, more like ellipses or egg-shaped curves. There were no seams; it was as if the rounded caps were turned out smoothly from solid masses of metal. The caps gleamed uniformly with the now familiar, subtle greenish hue.
> "The interesting thing," Lena added, "is that we think there's another node at the other end, at the site of the old magnetic pole. From the surface measurements we made before we started excavating, this node and the one at the magnetic pole have the same signature in the mag/grav surveys. So the whole artifact, it's a long spiral with one of these at each end. We don't know what they are. Look. It goes down and down."
They were still standing where they had entered, on a wide ledge inside the airlock door, dwarfed by the scale of the cavern. In front of them was another railing, the edge of the excavation, which was even wider and deeper than the one outside. Workers in the bottom looked like small beetles. They walked forward to the edge. The tubes disappeared into the flat soil at the bottom of the excavation.
"We tried to get as much vertical exposure as we could, but finally we gave up. Nothing seems to change as you go downward. The geophysical measurements say it probably goes down for kilometers. God knows how far. Hard to get a reading on it. May go all the way into the core for all we know."
They had gazed for many minutes in silence, as if the unseen presence had robbed them of the power of speech. Finally, Philippe reached for a sketch pad, which seemed to bring all of them back to reality, and the questions poured forth.
"But what does it do?"
"Did you take any readings on the soil they cleaned out of there?"
"Of course."
"Did they strain the soil? Don't archaeologists strain the soil with filters? I mean, there might have been artifacts."
MARS UNDERGROUND Page 33
