Saturnward, down the ridge, the black deposits thinned, revealing ever-larger patches of underlying ice.
“That one's Mount Zebra,” I said.
Floyd laughed. “Which of the nearby peaks is the highest?”
I consulted the topo I'd made days earlier. “See that long crest over there? At about two o'clock, across the Trench?”
“Uh-huh.”
“Its highest point is about two hundred thirty meters above us.”
Floyd laughed again. “Brittney's Bump,” he said.
* * * *
The descent was easy: just a matter of retracing our steps—literally when the regolith was soft enough to have preserved them, figuratively when we had to rely on my memory.
Then we were back in Iapetus Base for another night in a guest hab, followed by a quick boost back to orbit, with Rudolph again secluded in his canister. I presumed he was feeding all those kilos of dust into the full-sized Spektrum, but he must also have been writing net reports. Hours later, Mons Van Delp and Mount Zebra had made the map; Brittney's Bump hadn't, partly because Floyd never suggested it to him.
I wasn't quite sure how I felt about that. Having a mountain named for me would have been fun, but it would be nice for the name to be a little more dignified. Out of curiosity, I downloaded a bunch of Inner System topos and found all kinds of intriguing names, ranging from obvious glory-hounding to oddities that must have had good stories behind them, like a river bend called Crook's Elbow and a coal-mining town called Goldbug. Then there were the ones you didn't want to think too much about, like Dead Prussian Point. Maybe part of the fun of visiting such places is trying to figure out how they got their names. At least Mount Zebra is obvious. A hundred annums from now, nobody will care about Rudolph's mons.
And then, we were off to the Rings. No explanation, not even a thank-you, unless one of those arm-on-the-shoulder things counted, back in the skimmer. As far as I was concerned, it was too much like patting a dog on the head for a good game of fetch. Kind of like Floyd at his worst, only more so.
* * * *
When Rudolph had first talked about caves, I thought he might be wanting us to go back to Titan, where there are indications that methane ground—uh, “water” isn't quite the right word; aquifers? methanofters?—might have carved out passages similar to earthly caverns.
But that wasn't it. He was looking for moons in which he might be able to crawl in one side and come out the other: right through the center like some kind of skin-suited Jules Verne.
Not that he told us this until we were well away from Iapetus. Then he clamped down an embargo on outside communications, complete with a monitoring gizmo that would notify him if we so much as pinged an orbital beacon.
“You have to time the publicity on these things,” he said. “Climbing was just the warm-up. If we play it right, we're going to make that Shackleton guy look like a total amateur.”
* * * *
We started by cruising above the Rings, looking for clumps. There are millions of them, maybe tens of millions, but they're not very stable, so nobody's ever tried to catalog them. However many there are today, there will be a different number tomorrow.
Luckily, we weren't trying for a full list, either. Mostly, we were looking for the biggest clumps we could find and checking their densities.
It didn't take a genius to figure out that Rudolph was hoping they'd be tunneled through by caves. But caverns have to be formed by something. I'd read up on them way back, when Rudolph first asked about spelunking. On Earth there are three types: water-carved (not likely here), lava tubes (ditto), and talus caves. Clearly, Rudolph was interested in the latter. On Earth, they occur beneath piles of big boulders. Obviously, he hoped that some of the clumps would be similar, but to figure out which ones had a chance, he needed to measure their densities. Too low and they'd just be temporary amalgams of bumping, grinding boulders, too dangerous even for Rudolph. Too high and they'd be too solid for tunnels. Obviously, Rudolph was hoping for something in the middle.
The classic method of finding the density of a moonlet is to do a flyby and watch your course change. But the clumps are in the Rings, where a flyby at anything but the slowest creep isn't something anyone in their right mind wants to do. There's just too much stuff to bash into, and no insurance in the Solar System would cover us if we did.
At first, that produced a bit of a stalemate.
“I'm paying you to do what I say,” Rudolph said, all trace of arm-on-the-shoulder bonhomie gone.
“Not that, you're not.”
“I suggest you read your contract. Especially the part with the penalty clauses.”
“I told you not to sign that thing,” I said.
“Damn it, Brittney, that's not helpful.”
He was, I had to admit, right about that. “Okay, so we have to do something creative.” I thought a moment, then had it. “Look, we've got a tug. Why don't we just throw things?”
And so, Operation Slow-Pitch was born. Floyd got credit for it but that was okay. I no longer cared what Rudolph thought of me.
The idea was dead simple: all we had to do was dip into the edges of the Rings, grab a nice chunk of ice, push it in the right direction, and watch how the clump's gravity altered its course.
We found a wide range of densities, some of which looked promising. But when we eased in close to a few of the better candidates and pinged them with the ice-penetrating radar, they proved to be nothing more than giant dust bunnies. Fluffy snowballs, with a few denser chunks for those who might prefer to think in terms of raisin bread. The point is, you'd have to dig a tunnel before exploring it, which kind of defeats the purpose. Not to mention that we had nothing with which to dig.
I suppose we could have ordered up some mining equipment, but that would have left half of Iapetus Base wondering what we were up to. Rudolph obviously preferred a fait-accompli approach. His corporate MO had been to hover around the edges, then sweep in and poof, he'd have seventy percent of the iridium in the system. Or all the mining rights on Europa. Not that I could imagine anyone wanting to beat him to the punch on the Jules Verne thing, but maybe when it comes to secrecy he's like Floyd was about Shackleton. Once his mind gets in a track, it stays there.
Eventually, when I think even Floyd was about to die of boredom, Rudolph called a halt.
“We could do this forever,” he said. “Right now I'm opting for this one"—he pulled up an image of a two-klick object whose main distinction was an unusually dense sprinkling of raisins—"but I'm not terribly hopeful. Are we missing something?”
There are lots of answers to a question like that, especially when you're caught in a stupid contract you'd like to get out of. But Floyd must actually have wanted to go spelunking. “What about the gap moons?” he said. “They're less likely to have picked up all that fluff that's blocking the tunnels.”
* * * *
We started with Atlas.
There are a lot of gap moons, depending on how you define moon and gap, but the best known are Atlas, Pan, and Daphnis. As the term indicates, they sit in the gaps, which they maintain by gravitationally ejecting stray Ring particles. They all have specific gravities well below 1.0, which means they'd float if you dropped them in the ocean. Well, Atlas is big enough it would hit bottom like a stranded iceberg, but you get the idea. If Rudolph was lucky it would be honeycombed with caves. I hoped otherwise.
The gap moons haven't exactly been hot spots of exploration. As far as I knew, we were the first to land on any of them. They're in that awkward size range spacers avoid: too small for a real moon, bigger than you need if you're too cheap to buy propellant and want to melt your own.
Fortunately, it really doesn't take all that much gravity to crush caverns to impossibly small passages. Rudolph dug out all kinds of equipment—not just the ground-penetrating radar, but the quark detector and enough neutrino sources that it took three days to deploy them all. When he was done, we'd basically CAT-scanned the whole place w
ith neutrinos and quarks and found that it was more like pumice than honeycomb: a frothy mess whose bubbles were probably too small to crawl through, even if you were a bee. Chalk one up for my kind of luck.
Pan was more of the same. But Daphnis was different.
To begin with, it's got the lowest density of the lot—so low it wouldn't just float, it would rise out above the waves like a gigantic chunk of FrothFoam.
Even from space we could see a couple of big, promising-looking holes. Well, promising to Rudolph. Maw of hell was more appropriate. I couldn't imagine how they looked to Floyd. His parents had been crushed in an earthquake when he was barely old enough to remember, and now, unless he wanted to lose GnuShip and pretty much everything else, he was going to have to descend into the bowels of this thing that was probably about as stable as a pile of marbles. Big marbles, in the type of microgravity that makes Enceladus look Jovian by comparison: where, if anything shifts, we'd have more than enough time to watch it slowly close down our exit—or, as the case might be, us.
That was bad enough. But the neutrino-and-quark scan revealed that not only was it a true talus maze of passages, there was a chunk of something dense at its center, shaped like a fat pumpkin seed: half a klick long, three hundred meters wide, and maybe two hundred meters through at its thickest—the biggest raisin yet. Whatever it was, it looked as though the entire moonlet had somehow accreted around it. An asteroid? For all I could tell it was a spaceship abandoned eons ago by those ETs out in the Oort Cloud.
It made me nervous. With a moonlet made mostly of ice, all you need is a heat source to have Enceladus revisited. Maybe the caverns were a natural spiderweb of piping just waiting to blast vapor out of the interior. This place had an escape velocity of only a couple of meters per second, so it wouldn't take much of a geyser to spew us on a one-way trip to nowhere.
Still, it was hard to imagine an asteroid radioactive enough to generate that kind of heat. And while an ancient space drive might do the trick, I didn't believe in the aliens. Not really. Maybe.
I didn't know what Rudolph thought, but he was obviously determined to go in. Floyd too. Me, I had no choice.
What I resented was that nobody asked me. Floyd hadn't even given a decent reason why he was so determined to face this thing. If we died in there, I hoped like hell he at least had time to explain.
* * * *
Superficially, Daphnis looked like any other Outer System moonlet: oblong and knobby, with an icy crust pocked by impacts.
Rudolph's neutrino-and-quark scan, however, had shown the crust to be thin: in places, only a hundred meters or so thick—a late-forming layer that had clogged the talus-cave pores, hiding the warren of passages lying below and probably, like a thick eggshell, helping to hold this loosely consolidated world together. Though, as we could tell the moment we got close enough for a good look, not all of the pores were blocked.
The openings took the form of funnel-shaped craters deep enough you could only see their bottoms when they faced directly toward the sun. Most didn't punch all the way through, but a few ended in holes—some small, some big enough to swallow a modest-sized cargo canister.
What the funnels were, were sun cups, where impacts had dimpled the crust deeply enough to produce a runaway reflecting-oven effect that melted them ever deeper. They're rare in space, but on Earth, little ones can cover entire snowfields with honeycomb arrays of knee-deep holes: cool to look at in vids, but a bane to hikers. These were enormous and evil looking. Not honeycombs, but trap-door spider holes whose shadowed depths harbored entrances to the underworld. Even without spiders, not appealing-looking places to visit. No easy honey here: only death, minotaurs, and serpents.
* * * *
Landing was a nuisance. In theory, even though GnuShip's not made for gravity, we could have just set her down. In gravity this light, nothing was going to break. But neither she nor Rudolph's canister had a well-defined “up,” which even in microgravity presented problems. And the only things that might function as landing struts were docking clamps, which weren't really designed for support. While Saturn System's shifting gravities don't make for that many moonquakes, it was going to be bad enough worrying about them down inside the caves, without wondering if GnuShip might topple and strand us. All told, it was simpler to park her in low orbit and come down by hand thruster, picking a spot near one of the poles, because that's where you get the highest gravity.
Even without giant sun cups, hiking around a super-low-gee world is an exercise in frustration even for experienced spacers. So we began by caching an extra pair of thrusters at the mouth of the sun cup from which we planned to exit. Then I gave Floyd the thrust coordinates for a suborbital hop to the cave we were using as an entrance.
We made it with only a couple of mid-hop corrections. In a thruster competition, my presence would give Floyd an unfair advantage—though not that much of one, because any dumb AI can calculate a trajectory. The real skill, which Floyd is good at by human standards, lies in timing the burst and aiming it in exactly the right direction.
It's one of those things, like walking on Iapetus with trekking poles, that most humans find easy to learn but hard to master. I've always wondered what that's like. If I can do something at all, I can master it. If I can't do it, it's because I'm not hooked up to the right servos.
I think it's the entire concept of “skill” that eludes me. I understand the idea, but only in an intellectual way. The best I can figure, it's like working with a servo whose controls get more precise the more you use them. But then it wouldn't be you that's getting better; it would be the servo. Somehow, human self-identity includes a connection between their bodies and themselves that I'm not sure I'll ever really figure out. It would be like me caring what kind of chip I lived in. I do care about processing speed and memory, but I don't think that's quite the same thing.
Anyway, an hour later, we settled back to the surface, light as a feather, on a flat spot within fifty meters of the sun cup.
Rudolph didn't do as well. It took him several extra course corrections to match Floyd's trajectory, then he accelerated in for the landing, arguing that he wasn't going any faster than if he'd jumped off a one-meter embankment on Earth. Which was true, except he still came in plenty fast to sprain an ankle, if he hit wrong.
“Cowboy,” I muttered.
Floyd flipped off his suit radio. “More like making a statement. He's telling me he's not afraid of this stuff—which probably means he is.”
“Like you and this whole trip?”
“I'm not showing off.”
“No. The only person you're trying to prove something to is yourself. Do you realize how many things could go wrong down there?”
For once, he didn't tell me to drop it. He merely tuned me out by flipping his suit radio back on. “You okay?” he asked Rudolph.
At least Rudolph wasn't carrying the pack. In microgravity, as on Iapetus, the disconnect between weight and inertia is tricky, even to the best. So is landing without bouncing, and Rudolph was now in an undignified tumble, struggling to check it with his thrusters, twenty meters above the surface.
“Serves him right,” I muttered.
Floyd just stood clear and waited for him to settle. Even with a bit more caution, it still took Rudolph three more bounces to stick the landing.
When he finally came to rest, he was furious. “I bet you and your damn imp really enjoyed that,” he said. “Why didn't you give me a hand?”
When Floyd's in his suit, I've got all kinds of medical telemetry on him, and I could watch his blood pressure rise. If I had blood, it might be doing the same. I nearly popped into the radio link to tell Rudolph that if he had something to say, he could say it to me directly, but I (barely) managed to control myself.
Floyd did the same. “Not possible,” was all he said. “Too much momentum, not enough gravity.”
Then he switched his mike back off. “I hate places like this. Give me good old-fashioned real gravity, even
if it's just a hundredth of a gee. Something that actually keeps you and your equipment stuck to the surface, like God made you to be.”
* * * *
I would later wonder if Rudolph had been deliberately trying to provoke a fight: an excuse for that which would follow. It was the same with the route plan. We should have gone in the hard way and out the easy one. Then, if the route was a no-go, at least we'd waste minimum time. But from the way the subsurface looked on our scans, we appeared to be doing the reverse.
That, I would later realize was because Rudolph had no plans of doing his traverse, just as he had no plans of ending this thing as friends with Floyd. The only question was how it would end.
It would have been a lot easier if it had ended in failure. Then we'd have just collected our money, Rudolph would have gone home, and that would have been that. He might have wanted to do a second caving trip in a second moon, or go back to trying to tunnel around in clumps, but nothing in our contract said we had to do whatever he wanted forever.
Unfortunately, most of the trip wasn't all that hard.
The start was simply a matter of jumping into the sun cup. Even though it was a hundred and twenty meters deep, the gravity made it roughly comparable to stepping off a curb, and even though the thrusters were too bulky to take with us, Floyd and Rudolph would have no trouble leaping back out.
I've never seen actual vids of an Earthly talus cave, but I had a decent idea what they must be like: big bunches of boulders, piled higgledy-piggledy, over or under which you scrambled, climbed, or crawled, as the case might be. Here it was much the same, expect the boulders were ice, and low gravity added leaping as a viable mode of locomotion. Though floating might be a better description. We were in an underworld of big piles of angular ice blocks, incompletely pressed together. No giant, stalactite-encrusted rooms, no long, winding passages. Just a three-dimensional maze of cracks and gaps, some as big as GnuShip, some tiny.
Analog SFF, June 2008 Page 4
