one to rent. They’re of no help in fossil hunting, of course, and the standard uses for such things—beachcombing, searching for archeological artifacts, and so on—simply don’t apply here.”
He handed it to me.
I raised my eyebrows. “You want me to do the minesweeping?”
“I can’t,” Rory said. “I tried—but the metal in my body interferes too much with the detector. You, on the other hand . . .”
The guy was more clever than I’d given him credit for. He hadn’t brought me out here because I wanted to see the Alpha; he’d brought me out here because he needed the help of a biological.
He went back to the trunk and brought out another device: a tank of compressed gas with a flexible hose attached. “For blowing sand,” Rory said, evidently anticipating my question.
“Okay,” I said. “Show me where you found the first land mine.”
“This way. Follow in my footsteps precisely. I’ve used this path numerous times; it’s either free of land mines or they’ve all corroded like that one I brought to your office.”
He led, dust rising from his footfalls. I still found it bizarre to see a person in street clothes walking unprotected on Mars. Pickover was wearing what I imagined paleontologists wore back on Earth: brown work boots, heavy khaki pants, and a flannel work shirt. He’d also put on a baseball cap with the logo of the Toronto Blue Jays; I guess transfers needed something to keep the sun out of their eyes, too.
We headed out about fifty meters—I counted the paces—and came to an area that had been marked off into a grid of meter-wide squares by monofilament. The strands were almost exactly the same color as the red dust, and I mentioned that they were hard to see. “Not in the infrared,” Pickover replied. “I’m running a small current through them from that excimer pack, there. To me, they’re bright white, but the average prospector won’t notice them at all unless he trips over them.”
He stepped over one of the strands, and I gingerly did the same. We did this five more times and then stopped. “We’re still a ways from where the land mine went off,” he said crouching, “but let me show you this. It’s the spot where I found the counter slab for two-dash-thirteen-eighty-eight.”
“The fossils are lying right out on the surface?”
“Occasionally,” said Pickover, “but they’re usually a short distance down—but only a short distance. See, on Earth, sedimentary rocks have been forming for billions of years. But on Mars, sedimentation came to an end over three and a half billion years ago, when the open bodies of water dried up. So, instead of ancient sediments being deeply buried, they’re right on the surface—or just about. The water ice close to the surface here at the Alpha long ago either dissociated or sublimated, leaving eight or ten centimeters of loose, dry sand overtop of the ancient matrix. At the Alpha, that matrix is made out of areslithia—Mars stone. It’s really just sand and silt fused with water ice; the ground here is as much as sixty percent water ice by weight. Do you see what that means, Alex?”
I didn’t. “What?”
“Well, on Earth, most fossils are permineralized: the spaces in the original organic material have been filled in by minerals percolating through the ground; that new material replaces the original biological specimen, which ultimately disappears. But here at the Alpha, the fossils are the original material, simply embedded in the matrix. You can often get an Alpha fossil out of the matrix just by bringing the areslithia up to room temperature and letting the ice melt. That’s why the fossils from here at the Alpha are so good—they’re the actual ancient exoskeletons, unaltered, preserved in a dense slurry that’s been frozen solid for over three billion years.”
“Not completely, I bet. That land mine you brought in was corroded.”
Pickover nodded. “Yes, true. Something—maybe a micrometeoroid impact a couple of decades ago—heated a patch of the soil enough that there was a small pocket of running groundwater, and that’s what rusted out that mine. But most of the rest of this whole field”—he gestured expansively—“has been completely frozen since the Noachian.”
“But that counter slab you brought to my office was solid, even at room temperature.”
“Only because I’d infused it with a stabilizer, replacing the water content with thermoplastic.”
“Ah.”
He rose and continued walking. After about forty meters we came to a spot where there was a big divot out of the ground. “That’s where the mine that