Boundary 1: Boundary (14 page)

He checked the disposition of the Faeries. Ariel was very close to the surface of Phobos, no more than a mile off. The other probes had stopped about six or seven miles away and were bracketing the nearly fourteen-mile-long moon in a designed attempt to ensure that no point on Phobos' surface would go unmapped.

"Okay, let's get fancier."

A.J. considered the arsenal of sensors at his disposal. The Faeries were, in some ways, the most advanced instrumentation packages ever constructed, and they had an awful lot to offer. The primary modality on Earth was sight, so naturally the Faeries were well equipped with cameras. Visible light, ultraviolet and infrared—with their optics sealed between synthetic diamond windows for protection.

Unfortunately, the real detail he needed—down to a foot or less—he couldn't get at this distance. With a field of vision of only sixty degrees, he wasn't going to get much better than five feet or so, even with interpolation and super-resolution tricks. Narrower FOVs would have been better, but the tradeoffs involved had torpedoed that. He'd even had the engineers try a synthetic FOV approach, but that ran into problems with light-gathering capability which would take too long to solve.

"If only I could use something with decent resolution," he muttered, not for the first time.

The problem was an old one, dating back to the onset of space exploration. There was almost always a big lag between what technology could do on the surface and what you could get to work up there, with the radiation, vacuum, and other things to cope with. The gap had only gotten bigger in the last decade or so, because with most of the advances hinging on how much smaller and more efficient they could make the gadgets, they'd been getting progressively more sensitive to minor problems.

Tons of minor problems were pretty much what space handed you all the time. Cosmic rays, outgassing from vacuum, the list went on and on. And there was no corner store on the way to pick up a replacement. That meant that you couldn't afford to use something that wasn't fully space qualified on an interplanetary voyage. For a jump to orbit and back down, maybe, but not across a hundred million miles.

So, for the Faeries, A.J. was stuck with something not much better than he could've gotten on the street twenty years ago. Barely twenty-five megapixels in the visible, and worse in the IR and UV spectra.

But there was no point regretting the inevitable. A.J. had IR— near, mid, and far—along with visible and three UV bands. He had GPR, which would certainly be needed. Other frequencies of radio might prove useful, especially if he used the X-ray approach—have one transmitting and the other receiving. Measurement of heat signatures and any chemical emissions would be vital. If there were major caverns or differing composition beneath the surface—which did, as suspected, seem to be covered with about a meter of regolith—the heat absorption and radiation should show some differing patterns.

The other real bottleneck was data transmission. Even with all the advances made in other technology, the speed of data transmission from miniature sensor craft like the Faeries was only slightly better than that from old dial-up modems. That meant that most processing had to be done on the Faeries. Even one full-size image would take a significant time to send. And this was even though they were relaying through a separate satellite, put there by NASA a few years back, which had as its sole purpose being a communications facilitator.

The Faeries were advanced. Still, as they had to be space qualified, small, and mobile, their CPUs didn't have anything even vaguely like the power of current processors. With the transmission limitations, they couldn't send back too much data to be analyzed. That had to be reserved for truly unique work.

Both Tinkerbell and Rane's chemical sensing arrays were showing some water spikes. It was time to try mapping that out and see if he could get some idea as to where the outgassing was coming from.

It took another hour or so to figure out the optimal search pattern to cover with all sensors, and to ascertain the parameters of the low-power ion burns that each Faerie would have to perform in order to fly that pattern. Finally he was satisfied with the layout of search and sent out the directives. That, of course, triggered a slow-motion acknowledge-repeat-confirm cycle to ensure that all the directions had gotten through and were properly understood. Another hour later, he sent the final "go" confirmation.

He was tempted to go back to Elemental Flame, but there was business-related e-mail to answer and other work to do. And this part of the work would take a while.

A few hours later, the alert pinged in his ear, letting him know that he was receiving data from the completion of his survey pattern. He stretched and dropped the cubicle.

It was later than he'd thought. There was hardly anyone left around, except Bernie Hsiung over at the
Nike
construction section, overseeing some of the remote construction work in orbit. NASA had been assembling the material for
Nike
slowly but surely over the past year, and the work would continue for some time. Like him, Bernie often spent much of his time just keeping an eye on otherwise automatic processes, but it was still necessary to have someone around who had the capability to respond in an emergency.

"Let's see what we got. Hmm . . . the internals are still weird, I'm going to have to let the experts argue over this stuff. Water emissions as plotted over time . . . heating patterns correlations . . . There's water in there, no doubt, and possibly quite a bit of it. That'll make it a lot more attractive as a base. Transporting water is such a pain. Emissions and internal mapping plus heat signatures . . . Ah-ha! Two possible emission sources. Ariel, my sprite, come to me! Time for you to earn your living."

As Ariel was already closer to Phobos, A.J. would use her as his "point man." Ariel would examine the surface up close near the areas where water vapor was apparently escaping. If he got lucky, there would be a crack or cave in the area.

After another hour and a half, with Ariel now conducting its survey of the Phobian surface, A.J. headed off for a bathroom break. He stopped off for a candy bar and soda and then headed back. By then, Ariel's transmitters were showing the gray, soft-edged surface covered with fluffy regolith—powdered stone the consistency of flour—up close as it drifted along with a carefully defined path of examination.

The first emission site was a bust. There were some cracks, which clearly were the source of some of the outgassing. But they wouldn't have admitted a mouse, let alone a sensor drone the size of a large breadbox. Ariel continued along her way, approaching the locale of the second outgassing.

As it cleared a small crater ridge, A.J. couldn't quite restrain a triumphal "Yes!"

Even to eyes still accustoming themselves to the sharp-edged perceptions needed in the airless setting, there was a clearly darker streak that couldn't be anything other than a crack in the surface of Phobos. It seemed to be a crack yawning wide about two meters above the surface in one of the many little cliff ridges that meandered across the moon's surface.

"
That's
why it's not buried in regolith," A.J. muttered to himself. "Horizontal entryway instead of vertical. Hope that doesn't mean it's to some shallow deposit in the cliff."

As Ariel approached the crack, the automated sensor platform slowed according to prior instructions and directed illuminators into the chasm. It was wider than Ariel by a good half meter in any dimension. Ariel hovered, waiting for instructions. It wasn't permitted to proceed into the interior unless A.J. directly ordered it to.

There was considerable risk here, of course. The width of the crack was sufficient, but there was no way of knowing how far that ran, and even so the margin of safety was very thin. Piloting would be purely in the hands of the automatics, as there was no way A.J. could react in time to change anything that happened. And an accident could easily destroy Ariel.

On the other hand, looking at Ariel's sensor data, there was clearly water outgassing from below. Ice had to be present, possibly in significant quantities. And all of his other Faeries were running perfectly. Speaking cold-bloodedly, he could afford to lose one of them.

The call was entirely A.J.'s to make, since this was his project and no one else could make the judgments necessary. That fact didn't make it all that much easier. In some ways it made it harder, because if something went wrong he could hardly shove the blame away to someone else. But the way A.J. looked at it, finding out as much as possible about Phobos was his mission. He didn't see any reasonable alternative.

He went through the back and forth of order and confirmation once more. This time, once the acknowledgement came through, he stayed glued to his screen. It was true that he couldn't really do anything for Ariel if something went wrong, or at least not immediately, but he still wanted to know right away if something damaged her.

Slowly, turning on both ion and low-powered chem thrusters, Ariel drifted into the darkness, illuminating it with LED strobes timed with her frame captures to minimize power drain. Tinkerbell positioned itself above the chasm as a telemetry relay, since the farther into rock the drone descended the less signal would penetrate.

Twenty-two meters in, the dark lateral chasm intersected with another going almost straight downward. A.J., enhancing the view ahead slightly, could see that the lateral one narrowed and eventually ended a few dozen meters farther in.

"Excellent. Down we go!"

Ariel could also see the same thing, and despite being orders of magnitude less intelligent than her master, quickly reached the same conclusion. The little probe paused, rotated, and descended into the abyss.

Fifty meters down.

With a slow and steady precision, Ariel passed by gray-black rock with occasional tinges of other colors like reddish-brown. The crack descended at a slant, and its irregular walls showed that some sort of violence had caused its opening. That wasn't much of a surprise, of course.

One hundred meters down.

Ariel slowed and rotated, seeing a large rock blocking part of the crack dead ahead. It was clear to either side, however, so the automated sensing drone continued its descent, having chosen the left-hand side of the rock to pass by.

Two hundred thirteen meters down.

Dark shadows showed on either side of the crack, indicating another cavity or cavern. As Ariel drew level with this new intersection, it was clear that whatever cataclysm had caused this crevice to open had also caused it to cut straight across another long, slender cavern. Ariel hovered at the three-way intersection, consulting its own data to decide its course—further down, or into one of the two tunnellike cavern segments. A.J. did the same, in case he had to transmit to Ariel to abort and take a different route.

But Ariel made the same decision he would have. The flow of water vapor outgassing was stronger from one branch of the bisected cavern.

Here, Ariel had a bit more room to maneuver. The tunnellike cavern, oval in cross-section, was ten feet wide and eight feet high. Strange rippled formations were visible along the walls at regular intervals. A.J. was reminded of the scalloping he had seen in several caves, but clearly these odd shapes could not have resulted from running water over millennia. He wondered if cometary outgassing could have a similar effect.

Two hundred meters farther along, the tunnel reached a branching. One side turned deeper into Phobos, while the other stayed roughly level beneath the surface.

Tinkerbell was starting to show a clear drop in signal strength from its sister drone, but both A.J. and Ariel calculated that at least another three hundred meters would be possible before it would be time to decide on whether Ariel would have to go totally solo or not. Once more Ariel selected the path with the strongest H2O concentration—this time continuing along the original passageway.

Two hundred meters more, and the signal was starting to show some signs of interference. Suddenly the walls fell away on three sides, leaving only one—the side towards the surface—relatively level with respect to the prior tunnel. On Earth, this would be the equivalent of entering a large room in a cavern, with the relatively level side being the "floor." Ariel began a surveying drift around the dim, airless space, which seemed to be huge, something like a football field across. Its light began picking up other cavern exits along the "floor" area.

A.J. realized how stiff his neck was. He'd been leaning forward, watching tensely, despite the fact that on a VRD leaning forward was just useless. Amazing what instinctive reactions will do. For what must have been . . .

Two hours? It was heading for six in the morning! He got up, stretched hugely, and slugged down the rest of his now-warm soda.

Something nagged at the corner of his vision, which had been concentrated on the mundane for the past couple of minutes. He refocused on his VRD screen and sat down. It had seemed that there'd been a flicker of slightly different color . . .

Ariel had noticed it too, apparently. The probe had many subroutines for analyzing images, noticing anomalies, and returning to them. It was slowing and turning around now. Using gyros, it spun in place. Something flicked across the field of view, then stopped and was centered. Slowly it began to grow, with slight flickers of interference across it, as Ariel approached.

A.J. was barely aware of himself standing slowly, his mouth half-open, hand stretching towards the virtual screen, his hindbrain trying to reach out and touch the image glowing before him.

Inset into the wall, perhaps a meter from the nominal "floor," was a massive...

Something. It shone with a brownish-gold luster, undeniably metallic. It was symmetrical, a generally triangular shape with rounded sides and smaller, round-sided triangles at each corner. Across its surface, in curved sequences like waves, mysterious black and silver symbols marched in organized ranks.

Ariel had stopped with the object just filling its field of view. This target lay entirely out of its search parameters, and it was now waiting to be told what to do.