“About a mile to the east of the Union Pacific. I just heard a whistle.”

Natalie York’s radio voice crackled in Stone’s headset. “Say again please, EV2; I do not copy.” York was playing capcom in the comparative comfort of her tent.

Bleeker straightened up. He caught Stone’s eye and mouthed an obscenity.

Stone said, “Roger, Natalie. We’re both a little weary here, on the surface of Mars. I guess we’re using up our consumables at a heavy rate.”

“Then take a drink, you babies.”

Bleeker mouthed more obscenities, but Stone waved him silent. “She’s right, goddamn it. Come on.” He reached behind his head, to where two short plastic tubes dangled from his backpack. He pulled one of them to his mouth and sucked; tepid Tang squirted over his tongue.

Bleeker took a mouthful of water from his own plastic spigot, swilled it around, and spit it onto the black rock underfoot, where it sizzled, running away and drying quickly.

“Try some Tang,” Stone said.

“Tang gives me the farts.”

“Yeah, but you need to replace the potassium you sweat out. Good for the heart…”

“You two heroes ready to carry on?”

“Oh, up yours, York,” Stone said.

They straightened up and walked on.

They came to a bed of gravel and clay, broad and sweeping; the bedrock thrust through it like blackened, exposed bone. “We’ve found what looks like loess, Natalie,” Stone said. “River valley deposit.” He found he was breathing hard, and he was aware that Bleeker, struggling with the heavy MET, was sweating so heavily he had soaked right through his thin T-shirt. “I think we should go for a SEP setup.”

“Roger, EV1.”

Damn right it’s “Roger.” Staying in one place and playing at scientists for a while was going to be a hell of a lot easier than footslogging across this goddamn volcanic battleground. After all, this was worse than the real thing; his Mars suit would be air-conditioned, for God’s sake.

“Adam, why don’t you scout on ahead. Go that way, up across the loess.”

“Okay.” Bleeker set down the MET’s handle, hitched his pack on his shoulders, and set off along the loess, his blue Mars boots stained and muddy.

Stone dug out a set of gloves from the MET. The gloves were thick and stiffened with wire, to simulate the pressurized gloves he’d have to wear on Mars. With the gloves on he picked the SEP out of the buggy. The SEP — the Surface Experimental Package, a suite of scientific instruments — was folded up into a heavy dumbbell shape, weighted to mirror how the real thing would feel under Martian gravity.

Bleeker had walked maybe a hundred feet down the loess. “Over here,” he called. “This is good and flat.”

Stone began to walk toward him. “Okay, Natalie, I’m deploying the SEP now.”

“Rog.”