What were we to make of it? Could our own lineage mater have somehow been connected with the Atlantis disaster? Worse—if she was—what did it mean for us now that we knew?
We did what any prudent firm of bankers would do, upon being presented with circumstantial evidence from dusty archives that implicated a senior director in an embarrassing incident that had possibly enriched the institution but which, in any case, had long since been rendered irrelevant by the passage of time: We agreed to bury it deep and not breathe a word about it to anyone. Least of all to mother dearest.
Except . . .
I swam on, for hours and then days.
There were three more platform stops. I had no clear sense of time passing: But by my best guess, I was descending perhaps six or seven kilometers and traveling twenty kilometers horizontally between each resting place. I didn’t sleep for the full eight hours at all of them, but I made sure to recharge and acclimatize and to eat all the feedstock provided.
There were no more worm-mats, after that first near-disastrous encounter. Twice I came close enough to see ghostly pisciform hunters, feral mechanocyte colonies that had accreted around a dream of fishy form. Eyeless, they had circular, tentacle-rimmed maws, the tentacles branching into a fuzz of—well, I was at pains not to get close enough to examine them in any detail. My guide capsules could emit a searing flash of light, and a shrieking band-saw rasp of noise that drove them off if they tried to approach me. And I am not inclined to go looking for trouble.
After the third platform, I saw no more living things. The water was acrid and unpleasant, and I felt that I ought to be choking in it. I was swimming through the anoxic depths, far below the level at which photosynthetic organisms could oxygenate the waters: What life existed here was forced to subsist on the anaerobic decomposition of the steady thin rain of disrupted cellular debris that fell from the world-roof high above. Not much of anything that was big enough to see with the naked eye survived down here.
But once, in the distance, my eyes registered a faint blue glow, pulsating. I thought I was hallucinating at first, before my guide capsule chirped up: “Attention, Krina! Danger! Radiation hazard below!”
“Wait, what?”
“Danger! Avoid radiation hazard below!”
“What is it?” I turned, triangulated. Heard hissing, sizzling—felt the first distant touch of heat against my skin. The blue glow was becoming more intense.
“Danger! Avoid rad—” The guide capsule’s warning tempo became urgent, and suddenly I realized what I was seeing. Half-panicking, I turned and shoved myself away from it as fast as I could, until the glow faded from sight.
“Am I clear yet?” I demanded, my motor groups painfully aflame with excessive exertion.
“Stand by. Clear. Krina, wait here for half an hour. Avoid radiation hazard.”
“Was that a blue smoker?”
“Krina: Blue smokers are radiation hazards.”
So yes, it was a blue smoker. I shuddered, half-disbelieving. I’d been lucky enough to see one of the wonders of the known universe with my own eyes—and I’d survived.
Shin-Tethys is a young planet, and this is reflected in its isotope balance. Among other corollaries of this is the fact that much of the uranium 235 that was present when it formed has not had time to decay; uranium found locally is around 1 percent U-235. When volcanoes erupt on the surface of the mantle, down in the mixed rock-and-ice-VII crust below the bottom of the sea, the magma they eject is rich in uranium. And when the magma bubbles up through the rock and the ice and encounters seawater, well . . .
On Old Earth, the Fragiles’ birth world, the floor of the oceanic abyssal plains were punctuated by black smokers—volcanic vents from which issued streams of superheated, mineral-rich water, under too much pressure to boil but hot enough to melt lead. The black smokers in turn supported complex ecosystems, as rich minerals precipitated out of the hot solution rising from their chimneys and provided warmth and nutrients in the chilly depths.
Blue smokers are not so friendly to life.
Rising magma meets rock and dissolves it, then boils up into a layer of heavy water ice. This is not ice as we know it, under Fragile-friendly temperature and pressure conditions. Ice under such immense pressure transitions to a different, denser crystalline structure: one that is denser than water, so that it sinks to the bottom of the sea. When magma meets heavy ice, the ice melts, forming a mineral-rich liquor at very high temperature. The bolus of molten minerals rises, melting its way through the ice progressively, until it reaches open water, still hundreds of kilometers below the surface.
As to why it remains liquid . . .
Neutrons from naturally fissioning U-235 meet the hydrogen nuclei in the ice and water. Hydrogen is a moderator, slowing fast neutrons, making them easier for heavy nuclei to capture. The rate of fission shoots up, achieving criticality. The bolus of molten minerals gets hotter, roiling and glowing blue with Cerenkov radiation—photons emitted by particles traveling faster than the speed of light in water. If it gets too hot, the water molecules break apart into gaseous hydrogen and oxygen, and the nuclear chain reaction slows—but then the water molecules re-form under immense pressure, and things pick up again. The only constant is the radiation. And the bubble of dissolved uranium salts, of course, fissioning merrily away like a deadly kettle.
Blue smokers—feral uncontained fission reactors—periodically wander up from the depths. It can take weeks or months for them to reach the surface thermocline, driven by the pressure gradient: Finally they pop, exploding in a gout of viciously radioactive steam while still below the surface of the sea, sending a dome of whitewater and finally a mushroom cloud boiling up from below. Along the way, as they rise, they wreak havoc. A blue smoker will kill anything and anyone too slow and stupid to get out of the way—it will kill them just as dead as any other uncontained nuclear reaction, cooking them thermally, then with slow neutrons and gamma radiation. If you want to dispose of a corpse, a blue smoker is the ultimate in waste-disposal tools.
They have other uses.
If you can break a blue smoking bolus of fissile uranium-laden water apart with water jets, you can cool it down. And then you’re left with a mineral strike of incredible value: thousands of tons of saturated uranium solution, rich in U-235 and plutonium isotopes. Blue smokers tend to repeat in the same crustal area, time and again, bursting out like geysers. Frequently they erupt on a schedule regular enough to set a clock from. The farther down you capture your radioactive nightmare, the less of its fissile material will have decayed. And so the maniacs who mine the blue smokers of Shin-Tethys do so as deep in the abyssal depths as they can venture.
I watched, from a borderline-safe distance, as the faint blue glow of a lethal treasure strike wobbled and shimmered up from beneath the path I had been following. Finally, my guide capsule chirped up: “Krina, resume descent. Calculating detour.”
“Okay, I’m moving.” The guide beam snapped on again, pointing prudently away from the smoker, and I stroked into motion again, following it into the gelid darkness.