The Ouroboros Wave (13 page)

2053CJ reappearing a century later as 2143SF was definitely interesting, but it wasn’t the key to our problem. Once again we’d come up empty-handed. This was turning out to be harder than we’d expected. For a while we just sat staring at each other.

“Aren’t we forgetting something in this analysis?” I said.

“We’ve looked at everything. The robot, the microwave relay array…” said Barbara.

“It just hit me—we’ve been ignoring the biggest factor of them all.”

“What, Seiya?”

“Rapushinupurukuru itself.”

“READY TO DISPLAY
results of analysis,” said the synthesized voice.

Barbara and I were still in the core block. I’d ordered a full workup on the asteroid, and
Dragonslayer
’s AI had just obliged.

“How’re we looking?”

“Nothing unexpected,” said Rebecca. “Except for one thing I’m surprised we didn’t notice. It looks like Rapu is a CAT.”

As their name implied, Comet-Asteroid Transition objects were comets that had exhausted most of their volatiles and were on the way to becoming plain old hunks of rock. Given Rapushinupurukuru’s highly inclined orbit, the possibility of it being a blown-out comet seemed at least plausible.

“The data suggest that Rapu carried a pretty light load of volatiles. Judging from the weathering profile, I’d guess the outer layer of volatiles boiled off quite a long time ago.” We were looking at a 3-D image of Rapushinupurukuru without its array, its reddish surface rotating slowly against a gray-white background. Regolith and weathered red rock. Even on the restricted scale of the solar system it was an insignificant heap of minerals, but I never got tired of staring at its surface.

After watching the image revolve ten times or so, it suddenly hit me. The asteroid was sheathed in its blanket of rock fragments. The mesh antenna had been covered with a fine dusting of regolith. Depending on mass and velocity, fragments kicked up through collisions either escaped and went into space or traced parabolic paths back to the surface. But there was no crater to explain the
regolith on the array.

“Barbara, can you change the view?”

“Depends. What do you want?”

“Regolith by size, color-coded. I want to see how the fragments
are distributed.”

“That’s easy. Wait for it.” Barbara was already sending the commands to her agent. After a few seconds the image was covered with a rainbow of colors. The distribution of regolith around craters formed hundreds of millions of years ago was as standard as anything you’d find in a textbook. The finest fragments had blown off into space while the heavier fragments had stayed on the surface. There was a gradation of material, from fine to coarse, near the craters.
Still, this wasn’t the answer to our riddle.

A completely different pattern showed up in several locations—small spots surrounded by tight concentric circles of surface fragments with completely different distributions from the craters. Each circle of regolith was composed of a different size of fragment, with the fragments becoming smaller with distance from the center. These formations were new—they were superimposed on the splash-out from the older craters. Maybe this was the source of the regolith on the array? It would explain why the weathering was different on different sides of the asteroid. The near-side array shielded the surface from falling regolith, but the far side was
exposed to the regolith.

“Captain, I think we have our answer.” Rebecca and Barbara looked at me in disbelief. “The asteroid
is
the problem. We just
need to prove it.”

“Can you do that?”

“
Dragonslayer
can transmit in microwave frequencies. That should tell us.”

IT TOOK A WHILE
to get the experiment set up. Some of the code for the microwave relay had to be tweaked so the emitters could be controlled independently instead of acting as a single array. Before the experiment we deployed laser spectrometers on the surface—especially around the concentric regolith deposits—throwing in some infrared sensors for good measure. These assets were more basic than their names suggested: light alloy poles a meter or so long, each topped with a simple sensor cluster about the size of a fist. Still, they were highly reliable. The surface of the asteroid was now dotted with these sensor packages, like giant pushpins. There were a few eyeballs too, cruising above the surface for backup observation.

“You think this is going to work, Seiya?”

“You never know till you try.” Barbara and I were on the surface, ready to respond if anything happened.
Dragonslayer
was already sending microwaves down to the surface. Nothing was happening so far, but that was expected.

We stood inside a support station, a kind of cage, monitoring the sensors. We’d been on the surface for hours now, so we were hooked up to an umbilicus that kept us supplied with oxygen and heating water.

The first sign that something was happening came from one of the infrared sensors. The microwaves were starting to heat up the surface. To the naked eye it was still nothing more than aluminum columns standing in the regolith-covered surface, but the columns and surface were already far above absolute zero.

“Keep an eye on the spectrometers. It’ll take a while for the heat to penetrate the surface.”

“Will do. Looks like you were right.”

“It’s too early to tell. But we’ll know soon enough.”

The spectrometers started returning solid indications sooner than I’d expected. The first reading came from an area near one of
the hottest parts of the surface.

“Seiya, look! We’ve got gas. Steam… cyanide… hydrocarbons.
Typical comet constituents.”

“I knew it. This is why Rapu started revolving.”

“You found it!” Rebecca was jubilant. She probably hadn’t expected such a clear-cut outcome. With the data we were getting, the answer was straightforward. Rapushinupurukuru was a CAT object. Although it was stripped of nearly all its volatiles, thousands of tons remained in subsurface fissures and spaces. The microwave system was designed to relay huge amounts of power transmitted from Kali’s accretion disk. That generated heat. Dissipating this heat down through the columns and into the asteroid shouldn’t have caused any problems, but a simple sensor malfunction on the construction robot had led to the columns being much shorter than planned. This had massively increased the amount of heat
reaching the surface.

As the asteroid warmed, gas streaming from cracks in the surface had blown regolith particles upward, essentially acting on the asteroid as a rocket engine—and causing it to rotate. Its rotational force had shredded the greater part of the array, which hadn’t been anchored to the surface but extended for kilometers into space, held together with flimsy joints never intended to withstand more than
a tiny amount of external stress.

All that was left of the array was the central section. That had held some of its heat a bit longer, and now finer particles of regolith blown upward from the surface could reach and settle on what was left of the array. Rotation had then gradually brought the asteroid
back to its original frigid temperature.

“See? It wasn’t little green men after all.” I basked in my moment of glory. Rebecca shook her head.

“Not so fast. There’s still that anomalous transmission.”

Frankly, I’d forgotten about that, but Rebecca had orders to run down anything unexplained. “Maybe the signal came from the volatiles? Induced current flow from the power supply?”

“A pulsed signal at regular intervals? Come on, Seiya.”

“Well, how should I know?”

“I can hear it,” Barbara murmured. Rebecca and I glanced at each other. For a moment we wondered if Barbara was losing her mind.

“One of the eyeballs picked up a signal. It’s weak, but it’s definitely there.”

Rebecca peered at the monitors. “It’s two hundred meters from here, right under the center of the array.”

We walked to the array, where we ducked underneath the mesh and crouched close to the surface. Our semi-rigid suits made it difficult to crawl; instead, we advanced toward the eyeball on our hands—actually the tips of our fingers—stirring up coarse regolith in the low gravity. It felt like we were moving very fast, though it was probably only about walking speed.

Barbara pointed ahead. We dug our fingers into the surface to stop our forward motion. Our fingertips scored patterns in regolith that had lain undisturbed for millions of years.

“Look, Seiya. Do you see what I see?” Barbara was pointing to a slender spar of metal, about thirty centimeters long, emerging from the regolith directly below the floating sphere. A transmitter.

I carefully began to clear regolith from around the transmitter. The regolith was deeper here than elsewhere. A few seconds later we could see a metal tube about twenty centimeters in diameter. Protected by the regolith, the tube and its nameplate looked as new as the day they’d been built.

“What is this?” said Rebecca.

“A penetrator. From an unmanned probe, launched from Callisto.”

“YOU WERE RIGHT,
Seiya. But how did you figure it out?”

“Partly intuition. The database had no record of data from a probe sent to 2053CJ. But then again, we only checked for data from successful missions.”

“Then they did send a probe. And it carried a penetrator to send
back information about surface composition.”

“Penetrators were part of the standard instrument suite.”

We looked at the piece of space hardware built a century ago. We could hear its faint signal on our suit receivers; it was probably transmitting a range of telemetry data about this far-flung rock.

I asked Barbara to run another database query—not for observational data from unmanned probes, but for launch information on all known probes, successful or not. It turned out that Callisto’s
colonists had been busily studying 2053CJ after all.

The probe used an ion propulsion system. To rendezvous with the asteroid as it passed its ascending node on the ecliptic, the probe had to reach a speed of at least twenty-two kilometers per second to match the complex velocity vectors of the asteroid, respective to orbital speed as well as speed relative to the ecliptic. On paper, the probe’s engine had enough power to reach the required velocity.