lilting tone I imagined he normally reserved for talking to students. “And why do we call it permafrost, Alex?”
“Because it’s permanently frozen.”
“What’s permanently frozen?”
“The soil.”
“You can’t freeze something that’s already a solid.”
“Oh, right, okay. Well, the water in the soil, then.”
“Exactly. Isidis Planitia is a giant, shallow impact basin. Billions of years ago, it was filled with water. That water didn’t disappear; most of it is now locked into the soil. As I told you, core samples show the ground around the Alpha is as much as sixty percent water.”
“So they melted it?
“I think so, yes. Weingarten and O’Reilly had to have had a plan to hide their descent stage. I think they had the onboard computer fire its big landing engine until the frozen water melted, turning the soil into mud. The down blast would have blown the mud aside, creating a pit. The descent stage would have settled down into that, and, after the engine was cut, the mud would have flowed back in, burying it.”
“Neat. But what would that look like from orbit?”
“Well, any surface rocks would have sunk into the mud. So, what you’d see is a circular area free of such things, maybe forty or fifty meters across. To the untrained eye, it’d look pretty much like a crater. Even at a one-meter orbital survey, it would be hard to tell from one; you’d have to look at multiple lighting angles to notice that it was a circle that didn’t have any concavity.”
“And you’ve found such a thing?”
“Yes.”
“Because you had the Alpha as a starting point,” I said. But then I shook my head. “No, no—it’s the other way around, isn’t it? You found this circular thingamajig first—and that led you to the Alpha.”
“You are a good detective, Alex. That’s right. I knew there was no way to just stumble upon the Alpha, not in all the vastness of Isidis Planitia. And I knew that the prospectors here mostly lacked the geological training to interpret orbital-survey images. I’d suspected they’d buried the descent stage—the one they took on the third mission would have made a great part of a permanent habitat. And so I started looking at satellite photos. There aren’t that many that have been made in the last forty years; most of the Mars photo-survey maps are much older than that, and nobody has bothered to update them, because, after all, Mars is a dead world. But there was a Croatian satellite survey about fifteen years ago, and I accessed those images. Took me months of poring over photographs, but I finally found it.”
“Nice work,” I said.
“Beats hiking around endlessly, looking for the Alpha.”
“Did you ever meet Dougal McCrae?” I asked. The bootleg Pickover had, of course, but I didn’t recall this one ever having the pleasure.
“No.”
“You’d like him. Chief detective at the NKPD. He doesn’t like to have to get up from his desk to investigate, either.”
“I’ve logged over five thousand field hours on Earth and Mars,” Pickover said, sounding slightly miffed with me.
“Sorry.” I turned to look through the canopy at the darkness. On long car trips, I sometimes felt a duty to help keep the driver alert. But Pickover was in no danger of falling asleep, although I supposed he might get bored with no one to talk to. “Do you mind if I nod off?”
“It’s fine,” he replied. “I’m listening to music.”
* * *
When I woke, the sun was coming up and we were pulling in near where we’d been before: the ruins of Lakshmi’s buggy and the one we’d rented were about thirty meters to our right. I got into the surface suit I’d rented—it was brown this time—and Pickover swung the blockish canopy back. We headed outside.
“First things first,” Rory said. “Let’s see if we can find that map.” He paused. “How meta! Looking for a map without a map!”
“Where do we start?” I asked.
Pickover pointed past the crater he’d tussled with Lakshmi in. “About five hundred meters that way. I don’t want to drive in again—tire tracks take too long to disappear.”
We started walking. It felt good to stretch my legs. “Oh, say,” I said, “there’s something I’ve been meaning to ask you about. You said something odd to that guy, Darren Cheung—something about flirty girls?”
Rory rattled it off: “‘The girls can flirt and other queer things can do.’”
“Yeah. What’s that mean?”
“It’s an old mnemonic for Mohs scale of mineral hardness. If he’d really been with the US Geological Survey, he’d have known it.”