Spinneret by Timothy Zahn Page B

happened several times in the past hundred thousand years.”
    Meredith and Perez both looked at him, Perez as if seeing him for the first time. “What’s that supposed to mean?” the Hispanic demanded.
    â€œJust what it sounded like,” Hafner replied. “Something’s been leeching metals out of Astra’s crust since at least before the Kaf Mountains were formed. “
    Meredith shifted his attention to Carmen, cocked an eyebrow questioningly. “I thought you should hear Dr. Hafner’s theory as soon as possible,” she said. “It makes a lot of sense, and I was afraid it would be bounced by someone if he sent it through channels.”
    Meredith nodded and leaned back in his chair. Listening to all this would at the very least buy him some time to figure out what to do with Perez. “All right, Doctor, let’s hear it. For starters, how do the Kaf Mountains figure in?”
    â€œIf you examine the rocks there, you find out two interesting things: the mountains were formed recently, geologically speaking; and they were formed after the metals were removed from the crust.”
    â€œWho said there ever were metals on Astra?” Perez interrupted. “You’re arguing your conclusion.”
    Hafner gave him an irritated look. “This isn’t a freshman logic class. I’m describing what turns out to be a self-consistent scenario.”
    â€œYou’re welcome to leave if you’re not interested,” Meredith offered. The Hispanic sent him an angry glare; Meredith ignored it and looked back at the geologist. “Why couldn’t they have formed earlier?”
    â€œBecause most of the rocks in Terran mountains involve reasonably high percentages of metals—aluminum, iron, and sodium in particular—and if you suddenly pulled all those atoms out you’d completely destroy the structural strength. I haven’t had a chance yet to study the satellite photos, but I’d bet we’ll find evidence of collapsed mountains ranges now that we know to look for them. The Kafs, on the other hand, are composed almost entirely of christobalite—silicon dioxide—and moissanite, a silicon-carbon mineral. In other words, they’re made of the strongest rocks available after the metal was gone.”
    â€œI see.” This was starting to make altogether too much sense, and Meredith didn’t like that at all. “You said it had happened several times … ?”
    Hafner nodded. “Some of the meteor craters have been formed more recently than that, and they almost certainly brought metals in with them. The fact that those metals were gone before the Rooshrike surveyed Astra means this happened at least one more time.”
    â€œYou keep saying the metal is ‘gone,’” Perez said. “Gone where? The center of the planet? And more importantly, how? I don’t know much chemistry, but I do know yanking iron atoms out of a solid hammer ought to be impossible.”
    â€œAgreed,” Hafner shrugged. “So should getting those atoms to slide through the soil. I don’t know how it was done, either; but I might know where to look for the answers.”
    Meredith straightened up in his seat, belatedly touching his terminal’s audio record button. “The Rooshrike base?”
    â€œNo, I’m pretty sure they aren’t involved in any of this. The source of the effect is on Astra … and I think it’s a localized source, as well.” He hesitated. “I suppose I should explain my reasoning on that one. Basically, I’m assuming this leeching effect singles out metals because of their electrical conductivity, which probably implies the mechanism is electromagnetic in origin. Anyway, it occurred to me that ions dissolved in water also act somewhat like conductors, and that whatever force draws the metal atoms might draw those ions, too.”
    Meredith had a sudden flash of