by Mike Ashley
“Damn dried-up stuffed-shirted bastard’s good at it,” she muttered as she wrapped herself around me that night. “It stinks in here, you know?” Then she fell asleep with tears in her eyes. She was desirable, cuddly, and beyond the stretch of my conscience.
That morning, when our eyes met and searched each other, I wondered if she had any expectations, and if, in the spirit of friendship, I should offer myself. But I decided not to risk being wrong, and she did nothing but smile. Except, possibly, for that brief look, we were simply friends.
Randi didn’t say anything about her night in Nikhil’s tent; I didn’t expect her to. She gave me a very warm and long hug after she talked to Cathy. We were all very kind to each other as we broke camp and began casting ourselves along a trail of great caverns with the strides of milligee giants.
Cathy passed out the last of our calcium retention pills that morning. In a week or so we would start to suffer some of the classic low-gravity symptoms of bone loss and weakness. It didn’t worry us greatly – that was reversible, if we survived.
At day’s end, I was not physically exhausted, but my mind was becoming numb with crystal wonders. Where are these crystals coming from? Or rather where had they come from; Sam and Nikhil concur that the existing gas flow, though surprising in its strength, is nowhere near enough to deposit these crystal forests in the few hundred million years since Miranda’s remaking.
We were 150 kilometres deep now and Nikhil says these rocks must withstand internal pressures of more than ninety atmospheres to hold the caverns open. Not surprisingly, the large caverns don’t come as often now, and when they do, the walls are silicate rather than clathrate; rock slabs instead of dirty ice. I thought I could hear them groan at a higher pitch last night.
“It’s after midnight, universal time,” Cathy announced. She seemed recovered from her near panic earlier, and ready to play her doctor role again. But there seemed something brittle in her voice. “I think we should get some sleep now.” She said this as we pushed our baggage through yet another narrow crack between the Rift galleries Sam kept finding with his sonar, so Randi and I had a chuckle at the impossibility of complying with the suggestion just then. But she has a point. We had come one-half of the way through Miranda in five of our twenty days – well ahead of schedule.
Nikhil on lead, missed her humour and said: “Yes, dear, that sounds like a very good idea to me. Next gallery, perhaps.”
“You humans will be more efficient if you’re not tired,” Sam pointed out in a jocular tone that did credit to its medical support programmers but, I thought, this feigned robot chauvinism probably did not sit well with Cathy.
“We,” I answered, “don’t have a milligram of antihydrogen in our hearts to feed us.”
“Your envy of my superior traits is itself an admirable trait, for it recognizes . . .”
“Shiva!” Nikhil shouted from the head of our column.
“What is it?” Three voices asked, almost in unison.
“Huge. A huge cavern. I . . . you’ll have to see it yourselves.”
As we joined him, we found he had emerged on another ledge looking over another cavern. It didn’t seem to be a particularly large one to start – our lights carried to the other side – just another crystal cathedral. Then I looked down – and saw stars. Fortunately, my experience in “Randi’s Room” kept my reaction in check. I did grab the nearest piton line rather quickly, though.
“Try turning off your strobes,” Nikhil suggested as we stuck our heads over the ledge again.
The stars vanished, we turned the strobes on again, and the stars came back. The human eye is not supposed to be able to detect time intervals so small, so perhaps it was my imagination. But it seemed as though the “stars” below came on just after the strobe flashed.
“Ninety kilometres,” Sam said.
“Ninety kilometres!?” Nikhil blustered in disbelief, his composure still shaken. “How is this possible? Clathrate should not withstand such pressure.”
Randi anchored herself, dug into the supply pallet I’d been towing, and came up with a geologists pick. She took a swing at the ledge to which the gentle three and a half centimetres per second local gravity had settled us and a sharp pink made its way to my ears, presumably through my boots.
“Nickel iron?” Nikhil asked.
“Uh-huh. Think so,” Randi answered. “Fractured, from here down.”
“Maybe this is what broke Miranda up in the first place,” Cathy offered.
“Pure supposition,” Nikhil demurred. “Friends, we must move on.”
“I know. Take samples, analyse later.” Randi said. “Got to move.”
“Across or down?” I asked. This wasn’t a trivial question. Our plan was to follow the main rift, which, presumably, continued on the other side. But down was an unobstructed ninety-kilometre run leading to the very core of the moon. I thought of Jules Verne.
“We need to get out of this moon in less than two weeks,” Nikhil reminded us. “We can always come back.”
“Central gas reservoir, chimneys, connected.” Randi grunted.
After a nonplussed minute, I understood. If we went down the chimney, our path would leave the chord for the centre. The Rift is along the chord; Sam could see it in his rangings. But, not being a gas vent, it wouldn’t be well enough connected to travel. We had to find another back door.
“Oh, of course,” Nikhil said. “All roads lead to Rome – which also means they all go from Rome. The outgassing, the wind from the core, is what connected these caverns and eroded the passages enough to let us pass through. She means our best chance is to find another chimney, and the best place to do that at the core, isn’t it.”
“Uh-huh,” Randi answered.
No one said anything, and, in the silence I swore I could hear dripping, and beneath that a sort of dull throbbing that was probably my pulse. At any rate, the pure dead silence of the upper caverns was gone. I risked another peak down over the edge. What was down there?
“We have a problem,” Cathy informed us. “Poison gas. The nitrogen pressure is up to a twentieth of a bar, and that’s more than there was on old Mars. It’s enough to carry dangerous amounts of aromatics – not just methane, but stuff like cyanogen. I don’t know if anyone else has noticed it, but this junk is starting to condense on some of our gear and stink up our tents. It might get worse near the core, and I can’t think of any good way to decontaminate.”
“Uh, rockets,” Randi broke the silence. “Sam’s rockets. Our reaction pistols. Try it first.”
So we did. We figured out how far to stand from the jets, how long to stand in them – enough to vaporize anything on the surface of our coveralls and equipment, but not long enough to damage it – and how many times we could do it. Sam had enough fuel for 120 full decontaminations – more than we’d ever live to use. Cathy volunteered to be the test article, got herself blasted, then entered a tent and emerged saying it smelled just fine.
We decided to go for the core.
This close to the centre of Miranda, gravitational acceleration was down to just over five centimetres per second squared, about one three-hundredth of earth normal. Five milligees. Release an object in front of you, look away while you count 1001, and look back again: it will have fallen maybe the width of a couple of fingers – just floating. So you ignore it, go about other things and look back after ten minutes. It’s gone. It has fallen ten kilometres and is moving three times as fast as a human can run; over thirty metres per second. That’s if it hasn’t hit anyone or anything yet. Low gravity, they drill you over and over again, can be dangerous.
That’s in a vacuum, but we weren’t in a vacuum any more. Even with the pallet gear apportioned, we each weighed less than ten newtons – about the weight of a litre of vodka back in Poland, I thought, longingly – and we each had the surface area of a small kite; we’d be lucky to maintain three metres per second in a fall at the start, and at the bottom, we’d end up drifting like snowflak
es.
For some reason, I thought of butterflies.
“Could we make wings for ourselves?” I asked.
“Really, wings?” Nikhil’s voice dripped with scepticism.
“Wings!” Cathy gushed, excited.
“Sheets, tent braces, tape, line. Could do,” Randi offered.
“We are going to be very, very, sorry about this,” Nikhil warned.
Four hours later, looking like something out of a Batman nightmare, we were ready.
Randi went first. She pushed herself away from the precipice with seeming unconcern and gradually began to drift downward. Biting my lip and shaking a bit, I followed. Then, came a stoic Nikhil and a quiet Cathy.
Ten minutes after jumping, I felt a tenuous slipstream and found I could glide after a fashion – or at least control my attitude. After some experimentation, Randi found that a motion something like the butterfly stroke in swimming seemed to propel her forward.
Half an hour down, and we found we could manage the airspeed of a walk with about the same amount of effort. Soon we were really gliding, and could actually gain altitude if we wanted.
After drifting down for another hour we came to the source of the dripping sound I had heard the night before. Some liquid had condensed on the sides of the chimney and formed drops the size of bowling balls. These eventually separated to fall a kilometre or so into a pool that had filled in a crack in the side of the chimney. The Mirandan equivalent of a waterfall looked like a time-lapse splash video full of crowns and blobs, but it was at macroscale and in real time.
“Mostly ethane,” Sam told us. Denser and more streamlined than we were, the robot maintained pace and travelled from side to side with an occasional blast from a posterior rocket: a “roam fart” it called it. If I ever get out of this, I will have to speak to its software engineers.
“Wojciech, come look at this!” Cathy called from the far side of the chimney. I sculled over, as did Randi and Nikhil.
“This had better be important,” Nikhil remarked, reminding us of time. I needed one, having been mesmerized by drops that took minutes to fall and ponds that seemed to oscillate perpetually.
Cathy floated just off the wall, her position maintained with a sweep of her wings every three or four seconds. As we joined her, she pointed to a bare spot on the wall with her foot. Sticking out near the middle of it was a dirty white “T” with loopholes in each wing.
“It’s a piton. It must be.”
What she left unsaid was the fact that it certainly wasn’t one of ours.
“Sam, can you tell how old it is?”
“It is younger than the wall. But that, however, looks to be part of the original surface of one of Miranda’s parent objects. Do you see the craters?”
Now that he pointed it out, I did. There were several, very normal minicraters of the sort you find tiling the fractal surface of any airless moon, except 200 kilometres of rock and clathrate lay between these craters and space. I had the same displaced, eerie feeling I had when, as a child, I had explored the top of the crags on the north rim of the Grand Canyon of the Colorado on Earth, over 2,000 metres above sea level – and found seashells frozen in the rock.
“The piton,” Sam added, “is younger than the hoar crystals, because the area was first cleared.”
Something clicked in for me then. The crystals surrounding the bare spot were all about a metre long. “Look at the length of the nearby crystals,” I said, excited with my discovery. “Whatever cleared the immediate area must have cleared away any nearby crystal seeds, too. But just next to the cleared area it must have just pushed them down and left a base from which the crystals could regenerate. So the height of the crystals just outside the cleared area is the growth since then.”
“But what do you think that growth rate is?” Nikhil asked. “We can’t tell, except that it is clearly slow now. I regret to say this, because I am as interested as anyone else, but we must move on. Sam has recorded everything. If we regain the surface, other expeditions can study this. If we do not – then it does not matter. So, shall we?”
Without waiting for assent from the others, Nikhil rotated his head down and started taking purposeful wingstrokes towards the centre of Miranda.
“Damn him,” Cathy hissed and flew to the piton and, abandoning one wing sleeve, grabbed the alien artifact. So anchored, she put her feet against the wall it protruded from, grasped it with both hands and pulled. Not surprisingly, the piton refused to move.
“Other expeditions. We’ll come back,” Randi told her.
Cathy gasped as she gave up the effort, and let herself drift down and away from the wall. We drifted with her until she started flying again. We made no effort to catch up to Nikhil, who was by this time a kilometre ahead of us.
The air, we could call it that now, was becoming mistier, foggier. Nikhil, though he still registered in my helmet display, was hidden from view. Sam’s radar, sonar, filters and greater spectral range made this a minor inconvenience for him, and he continued to flit from side to side of this great vertical cavern, gathering samples. When we could no longer see the walls, we gathered in the centre. Incredibly, despite the pressure of the core on either side, the chimney widened.
“This stuff is lethal,” Cathy remarked. “Everyone make sure to maintain positive pressure, but not too much to spring a leak; oxygen might burn in this. If this chimney were on Earth, the environmental patrol would demolish it.”
A quick check revealed my suit was doing okay – but the pressure makeup flow was enough that I would think twice about being near anything resembling a flame. Our suits were designed, and programmed, for vacuum, not chemical warfare; we were taking them well beyond their envelope.
“Chimney needs a name,” Randi said. “Uh-huh. Job for a poet, I think.”
That was my cue. But the best thing I could come up with on the spot was “Nikhil’s Smokestack.” This was partly to honour the discoverer and partly a gentle dig at his grumpiness about exploring it. Cathy laughed, at least.
Having nothing else to look at, I asked Sam for a three-dimensional model of the chimney, which it obligingly displayed on my helmet optics. A three-dimensional cut-away model of Miranda reflected off my transparent face plate, appearing to float several metres in front of me. Our cavern was almost precisely aligned with Miranda’s north pole, and seemed to be where two great, curved, 100-kilometre chunks had come together. Imagine two thick wooden spoons, open ends facing.
These slabs were hard stuff, like nickel-iron and silicate asteroids. Theories abound as to how that could be; radioactivity and tidal stress might have heated even small bodies enough to become differentiated; gravitational chaos in the young solar system must have ejected many main belt asteroids and some might well have made it to the Uranian gravitational well; or perhaps the impact that had set Uranus to spinning on its side had released a little planetesimal core material into its moon system.
My body was on autopilot, stroking my wings every ten seconds or so to keep pace with Randi while I daydreamed and played astrogeologist, so I didn’t notice the air start to clear. The mist-cloud seemed to have divided itself to cover two sides of the chimney, leaving the centre relatively free. Then, they thinned – and through gaps, I could see what looked to be a river running . . . beside? above? below?
“Randi, I think I can see a river.”
“Roger, Wojciech.”
“But how can that be? How does it stay there?”
“Tides.”
“Yes,” Nikhil added. “The chimney is almost three kilometres wide now. One side is closer to Uranus than Miranda’s centre of mass and moving at less than circular orbital velocity for its distance from Uranus. Things there try to fall inward as if from the apoapsis, the greatest distance, of a smaller orbit. The other side is further away than the centre and moving at greater than orbital velocity. Things there try to move outward.
“The mass of Miranda now surrounds us like a gravitational equipotential she
ll, essentially cancelling itself out, so all that is left is this tidal force. It isn’t much – a few milligees, but enough to define up and down for fluids. In some ways, this is beginning to resemble the surface of Titan, though it’s a bit warmer and the air pressure is nowhere near as high.”
“Is that water below us?” Cathy asked
“No,” Sam answered. “The temperature is only 200 Kelvins, some seventy degrees below the freezing point of water. Water ice is still a hard rock here.”
At the bottom, or end, of Nikhil’s smokestack was a three-kilometre rock, which had its own microscopic gravity field. The centre of Miranda, we figured, was some 230 metres below us. Close enough; we were effectively weightless. We let Sam strobe the scene for us, then set up our tents. Decontamination was a bit nervy, but most of the bad stuff was settled on either side of the tidal divide, and the air here was almost all cold dry nitrogen.
Nonetheless, set up took until midnight, and we all turned in immediately.
It has been a very long day.
Nikhil and Cathy forgot last night that, while they were in a vacuum tent, the tent was no longer in a hard vacuum. Much of what we heard was thankfully faint and muffled but what came through in the wee small hours of the morning of day eight clearly included things like:
“. . . ungrateful, arrogant, pig . . .”
“. . . have the self discipline of a chimp in heat . . .”
“. . . so cold and unfeeling that . . .”
“. . . brainless diversions while our lives are in the balance . . .”
Randi opened her eyes and looked at me, almost in terror, then threw herself around me and clung. It might seem a wonder that this steely woman who could spit in the face of nature’s worst would go into convulsions at the sound of someone else’s marriage falling apart, but Randi’s early childhood had been filled with parental bickering. There had been a divorce, and I gathered a messy one from a six-year-old’s point of view, but she had never told me much more than that.
I coughed, loud as I could, and soon the sound of angry voices was replaced by the roar of distant ethane rapids.