“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?”