Yet, there are reasons to go down beyond the simple thrill of it. Solar Astrographic’s expedition is half stunt, half science—and here is where the other half gets its due. There is a mystery here and the root of it lies in a contrary mysticism of celestial dynamics. Here, a mere sixty million kilometers from its fiery photosphere, are surfaces that have not seen the Sun since the Caloris impact defined Mercury’s final orientation.
This same counterintuitive magic then decrees that the ices of comets that orbit impossibly far—beyond even Pluto, Charon, and Persephone—are actually closer to the Sun, and Mercury, in the energy of their motion than anything in the inner Solar System. Something on Venus would have to be kicked at almost 11 km/s to reach Mercury, best case—but merely nudge a pair of Oort belt comets together and parts of them may fall into Mercury, decades hence. Sometimes these collisions give the planet a very temporary, tenuous atmosphere, which condenses in the deep freeze of Chao Meng Fu. Blame this on Kepler and Newton, not Ptolemy.
So near is far, and far is near, and the crevasse yawns from ’ere to ’ere. Does it have teeth? Do its open jaws reveal molecules from the beginning of time, such as measured in the Solar System? Lotati confers with his daughter, and Ed. Randi and Ed have a thing, I’ve found, and spend a fair amount of time touching helmets.
What great ideas I have! I despair of ever being able to itch again, let alone going to Miranda with its namesake. My rented vacuum gear fits like the skin of a hundred-year-old man; stretched taut digging into my flesh here, loose and bulging there. Randi says there’s an art to it and I should take more time getting in. Next time I will.
I edge closer to the brink, attracted to the danger perhaps, or perhaps wanting to demonstrate courage to Randi. I gaze down. Here and there the dust has fallen from the sheer ice walls, and the layered structure is clear. There are Mercury’s sediments. Each comet or meteor creates a temporary atmosphere for Mercury, and that which is not boiled away by the Sun condenses in the polar craters, mixed with ejecta dust. The bedrock lies perhaps a kilometer below us. After three days of the most physical labor I’ve done in decades, I now contemplate a rappel down to the bottom of a bottomless crevasse and the climb back up again.
I look away as though by not observing it, I can create the possibility that it does not exist.
But I have my journalist’s duty. At my command, my helmet camera plays back the view, and it floats, reflected off my face plate, against the stars. It doesn’t fit in the standard field of view, I realize, so I look over the edge again and slowly turn my head from horizon to horizon. An object of professional interest now, it begins to lose some of its scariness for me.
Bubka’s prescription for fear of something—study the hell out of it.
How long and wide! Then I turn off all my lights, let my eyes relax, and turn back to see the solar corona, a peacock’s tail of icy fire spreading from the Sun that sits just under those utterly black mountains that ring our horizon. If Chao Meng Fu did not flatten Mercury’s globe here, we would not be able to see those mountains this far into the trek, so close is Mercury’s horizon—but we have been heading ever so slightly inward, downhill, as well as south.
The furthest streamers of the corona glow far above that rim behind, looking almost like the aurora borealis back on Earth. Awed, I step back, and back again to catch my balance.
I happen to glance down—my boot is barely centimeters from the edge of the chasm.
“Bubka, freeze.” Randi’s voice echoes in my helmet.
I am already frozen.
“Now. Raise right hand,” she continues.
I am carrying a strobe lamp in my right hand so I automatically start to raise my left—
“Your other right!” she snaps, instantly.
This time I get it right, raising both my arm and the strobe lamp.
“Now lean that way. Walk slowly. Away from edge.”
I understand now: if I teeter, she wants me to teeter in the direction of safety. I walk away from the edge with as much dignity as I can muster, as if there were nothing at all wrong, knowing that anyone monitoring my heartbeat will know that I am anything but calm.
She detaches herself from the management group and strides toward me, ghostly dust glittering in my helmet light behind her footsteps. She halts in a cloud of fairy sparkles, grabs my hand, and leads me well away from the edge of the crevasse.
“Professor Bubka, near crevasses, tether. Always, always, tether.”
“Professor” hangs in my mind dripping with irony. On Mars, I taught her literature. Here, I am her student—and I had just come close to failing a test where failure is judged somewhat more harshly than at Jovis Tholis University.
Nodding ruefully, I pull a piton gun from my pack and harpoon the planet. A test pull shows that it’s secure, and I clip the line to my belt. Randi fires a piton in too, clips on, then clips another line between her belt and mine. “Ed, some baby-sitter you’d make! Going to take a look.”
“Sorry, mate. Watching, Randi.”
Baby-sitter?
“Now, Professor Bubka. Let’s go look.” Dark eyes, on a tanned face with a snub nose, twinkle at me behind the clear, non-reflecting visor.
We retrace my footprints together. We walk to the edge together. This time, I think to clip my strobe light to my belt as well.
One of the things I see is half a footprint at the edge of the crevasse. The toe half. Mine.
What I had done was, I realize, foolish, but I think I am forgiven. She pulls oh her line, then actually leans out over the cut, to inspect its near side.
“Light.” The word is a request and a command. Crystals from far down glitter in response.
Nervously, wrapping my line around my left hand and playing it out through a “smart slot” belay device, centimeter by centimeter, I lean out with her and shine my strobe on the wall under us. On a clean vertical, the layering resembles a diffraction grating—fine thin grooves, perfectly horizontal, broken occasionally by what must be the sections of ancient buried craters.
The strobe light looks continuous, but contains off-pulses for range—it times a journey of the absence of light. So. The crack goes down, a hundred meters, two hundred, three hundred. At five hundred, I can no longer see the light returning, but it can. I swing it slowly from side to side, as my helmet display paints a graph of angle and range. The walls seem to almost converge about twelve hundred meters below us here, with some flatness between them. I move the beam a bit to the left.
There is something across the chasm at eight hundred meters, just to our left. “Randi?”
“I see it. Bridge. Dad, channel seven.”
“I have it, Randi! I’ll think that is a billion years down if it’s a day! What do you say, Juanita, my Randi’s found a bridge!”
There seemed no point in immediately explaining that I’d found it.
“Eight hundred meters down and all the way across! Can we do it?” Juanita answers, thrill in her voice. “Do we have enough line?”
“Yes and yes,” Randi’s father answers after a moment of thought. Then he points to a slight dip almost above the bridge. “Probably half of an old crater, broken by the crack. That will get us a few meters closer. We could rappel down from there. Perhaps two billion years down, if the crevasse goes to the bottom of Chao Meng Fu. Do you want the bottom, Juanita?”
“God, yes, Emilio, if it isn’t too dangerous.”
Dr. Lotati shrugs. “It has been this way for millions of years of impacts; the walls should tolerate a few ants crawling on them. We’ll go ourselves, instead of waiting for some robots to do it.”
I look across the chasm for the other half of the ancient crater, but, like the other half of my footprint, there is no sign of it. Where did it go? I feel a curiosity as powerful as any hunger. What formed the bridge? What lies at the bottom? We shall find out, if the Laws of the Universe let us.