Dragging the MET, Stone began to walk, more or less north of Bleeker.
“Okay, Natalie. I’m coming off this layer of loess, now. I’m arriving on what looks like a gravel bed, loosely compacted. I can see striations. Kind of streamlined, like scour marks. It looks as if water has flowed here…”
York called, “Why don’t you make a sample stop?”
“Rog.”
He picked a spot, reasonably level, and set up the calibrating gnomon. He walked around the gnomon, carefully photographing it from every side. Next he worked the mechanical tests. He pressed a spring-loaded metal plate against the soil, and thrust a cylindrical probe into the ground. Then he put a lump of aggregate into a crusher, a handheld nutcracker affair. He called out readings to Natalie York as he worked.
When he’d fully documented his site he took samples from the surface. He picked up loose material with tongs, rakes, and scoops, and tried breaking a piece off a larger rock with a hammer.
Actually, the landscape baffled Stone. He’d been taking a geology field trip each month for the last year, and he’d gotten familiar with the subject to some extent. But he’d never seen an area like this.
Most EVA training was taking place out in the high deserts in the western USA. At one site, in Nevada, half a square mile of desert had been faked up to simulate the Martian surface as observed by the Soviets, with fine sand raked in, large boulders set deliberately on the surface. There was even a fake MEM descent stage set up there, a mock-up of wood and paint. The MEM had a compartment for a full-scale Mars Rover, which you could pull down and unfold, just like the real thing. That was a sim exercise Stone could appreciate: bouncing across a fake, but recognizably Martian desert, in a four-wheel-drive Rover…
But he really did not know what the hell was going on today. How was this piece of shit in Washington State, across which they were dragging this fucking Apollo-class golf cart, supposed to relate to whatever the hell was waiting for them on Mars?
After maybe half an hour, he’d piled the MET with carefully selected — and uniformly worthless — samples of Washington State. “Okay, Natalie, I figure I’m done here.”
“Well done, Phil. We’ll make a rock hound out of you yet. But I still haven’t heard much about the morphology of your site.”
He growled, and wiped sweat from his brow with a dusty hand. “Give me a break.”
“Come on now, Phil. Taking samples isn’t enough — you ought to know that by now — what’s crucial for the geologists is the context. Tell me what you see.”
Stone began to walk forward again. His pack chafed at his shoulders, but looking around more systematically, he began to see some pattern, some logic underlying the landscape formations; and as he did so, he began to forget his discomfort.
“I see a mix of landscape here. I see what looks like bare bedrock, and sedimentary stuff that’s been scoured out, and depositional material. As if left behind by running water.”
“Good.”
“The land here can’t be of much value. Light pasture, maybe; there isn’t much growing, certainly not in the bare rock faces. I think the rock is basalt. Volcanic, anyhow. The macroforms in the bedrock are mostly channels. The channels are pretty straight: not much sinuosity. They look as if they are basically river valleys, but widened and deepened. Maybe by glaciation?” Great tongues of ice, flattening and deepening valleys, scouring down to the bedrock -
“Don’t speculate, Phil. The goddamn Apollo astronauts speculated all the time, and they confused the hell out of everybody. Just observe.”
“Sure.” Speculating test pilots on Mars. Natalie’s number one nightmare. “I see evidence of channel anastomosis. And uplands left isolated between the channels.”
Back at the CELSS, Bleeker looked up skeptically. He called, “Anasto-who?”
Stone imagined York’s chagrin at that remark. Bleeker’s comparative backwardness at the geology wasn’t surprising. The guy was under real pressure; as well as field trips like this in support of the eventual landing mission, Bleeker was also working toward the D-prime Earth-orbit mission next month.
But then, Stone reflected, Bleeker was supposed to be the landing mission surface specialist.
“Anastomosis, asshole. It’s all in your Boy’s Coloring Book of Geology. Where a channel has been breached, and cut a branch through into another channel. Look. See the way the channels over there seem to diverge, then join up again. And you can see over there, where that bit of plateau has been left isolated. Cut off by the new channels.”
The isolated upland was like a tabletop of rock, stuck in the middle of the plain.
“Yeah. Okay, I see it. So what caused the breach?”
“Phil—”
“Okay, okay, Natalie. Don’t ask me questions like that, Adam. I won’t speculate.” It could be glaciation, though. Must be. What the hell else could have caused so much damage to the landscape? A lava flow, maybe?
“What other macroforms?” York asked.
Stone climbed on top of a rock, the heavy pack banging against his back, and peered around. “More uplands, carved out of the sedimentary stuff. They look—”
“What?”
“Smooth. Streamlined.” Like islands, their flanks smoothed out, left stranded by the drying out of a parent river. “And I can see what look like bars of gravel, some maybe twenty, thirty feet high. Kind of like sandbanks. They seem to have formed behind outcroppings, maybe of loess, or bedrock. Like tails. The rock has grooves scoured in it. Longitudinal. The grooves flow past the islands, and the gravel bars.”
He came to a bed of loose clay and sand. “This is more loess, I think. I see—”
“What?”
“Ripples. Kind of frozen here, in the loess. Like small dunes, I guess. The dunes are stratified. It looks as if a river has dried out here.” He stalked on over the rock. “I have pits in the rock surface. Circular, a few inches deep, width from a foot wide upward. Scallop pits, I think.” Gouged out by pebbles, carried by turbulence… “The whole place is kind of like a river bottom,” he said. “Yeah. You basically have the topography of a dried-out river bottom — but magnified. Channels and bars and islands. All shaped by flowing water on a massive scale…”
He looked around with a new excitement, seeing the geology with new eyes, with Natalie York’s eyes: the deep-carved, breached channels, the huge deposits of loess, the carved-out islands. “Christ. Is that it, Natalie? Is that what you’ve brought us out here to see? Was all of this region formed by a flood?”
“You’re speculating again, Stone.”
“Oh, come on, York.”
“Okay. You’re right, Phil. At least, that’s the favored hypothesis.”
Bleeker gave up on the half-assembled CELSS, and came to stand close to Stone. “What is?”
York said, “In the Late Pleistocene — maybe twenty thousand years ago — much of Idaho and west Montana was covered by an immense lake. Called Missoula. Thousands of square miles of it. The lake was contained by an ice dam. The dam eventually burst, and released a catastrophic flood that swept over this area. Tens of millions of cubic yards per second, maybe a thousand times as much as the Amazon’s discharge rate—”
“Jesus,” Stone said.
“Yeah. The existing streamways couldn’t cope with the sudden volume, so they burst; the valleys were widened and deepened, and interconnecting channels were cut — all the way into the bedrock — in hundreds of places. Thousands of square miles were swept clean of the superficial structures, right down to the basalt bedrock, and another thousand square miles were buried in river-bottom debris.