Jamie started to reply, then realized he was indulging in wishful thinking. "Good question, Mikhail. We’ll make a scientist out of you yet."

He heard the Russian’s deep chuckling. "Not likely."

Jamie squinted up at the sun. "Let’s set up the winch. I want to…"

"Not down there!"

"Just the first three layers," Jamie said. "I know we can’t get down to the bottom or anywhere near it. But I can reach that layer with the yellowish intrusions, at least. Come on, the sun’s starting to hit this side."

"No lunch?"

"You can eat lunch after the winch is up. I’m too excited to eat."

In his stolid, immovable fashion Vosnesensky insisted that they both eat before breaking out the winch and climbing harness.

"Nutrition is important," the Russian insisted. "Many mistakes are made because of hunger."

Despite himself Jamie grinned. "You sound like a commercial for bran flakes, Mikhail."

Neither man bothered to take off more than his helmet and gloves once inside the rover. They each ate a hot meal perched on the edge of their facing half-folded bunks in their cumbersome hard suits. Vosnesensky brought the bottle of vitamin supplement pills from their little pharmaceutical cabinet.

"We forgot at breakfast," he said, handing the bottle to Jamie.

"Right." Jamie shook one of the orange-colored pills loose. "Wouldn’t want to miss the Flintstones."

Vosnesensky scowled, puzzled. "It is no joke. Our diet lacks vitamins; we get no sunshine on our skins. The supplement is necessary."

"Besides," Jamie kidded, "it’s written into the mission rules."

Jamie popped the pill into his mouth and washed it down with the last of the coffee in his mug. God, what I’d give for a cup of real coffee instead of this instant crap!

Then he saw that the sunlight was slanting into the rover through the canopy up in the cockpit.

"Come on, Mikhail, we’re wasting time."

It took all four of their hands to work the harness over Jamie’s backpack and crotch, then fasten it across his chest. With the Russian standing guard at the winch, Jamie lowered himself gingerly down the steep face of the cliff. Far, far below some tenuous threads of mist still clung to the rocks, gray and ghostly, slowly rising and sinking like long ocean swells or the breath of a sleeping giant.

There was no opposite wall of the canyon in sight, it was too far away beyond the horizon. Instead of the trapped feeling that had frightened him at Noctis Labyrinthus, Jamie felt as if he were working his way down the face of a mesa back home. Biggest goddammed mesa anybody ever saw, he said to himself as he peered down between his dangling feet toward the bottom, miles below. If this were New Mexico, the other end of this canyon would be in Newfoundland.

Jamie had to consciously force himself to turn his attention to chipping out rock samples. Still, as he started his work, dangling in the harness, he wondered about the world at the bottom of the solar system’s largest canyon. We didn’t expect mists in the summertime, didn’t think there’d be enough moisture in the air for that. Down in the Hellas Basin, yes. But we didn’t expect it here. Wish we could have taken samples of the stuff. Maybe it’s ice crystals. But it doesn’t look like an ice fog. How can you tell, though? The rules are different here; at least the conditions are. Down toward the bottom of the canyon there must be a completely different ecosystem from what we see up on the surface. Maybe the air’s denser down there. Wetter. Warmer. Maybe there’s life down there, hiding out in warm little niches the way our ancestors used to live in caves.

We should have set up base camp here, not out on that dumb plain. Then we could have spent our time exploring the canyon. This old rut in the ground has more to tell us than anyplace else on Mars.

Dangling in the harness, suspended a few meters from the lip of the canyon and many kilometers from its mist-shrouded bottom, Jamie thrilled that the cliffs here were completely different from those at the Noctis Labyrinthus badlands. There the cliff walls were a uniform slab of iron-red stone. Here the cliffs were layered, tier upon tier, as weathered and seamed as the mesas back home, rich pages of a petrified book that told the entire history of this world to those with the skill and patience to read it.

The topmost layer of the cliff, just under the caprock, had been almost soft; the rock there, crumbly, easily broken loose. On Earth it would have been weathered away by wind and rain in a geological twinkling. But here on dry, calm, gentle Mars it could remain for eons, undisturbed except for the slow erosion from the sun’s warmth and the night’s cold that eventually cracked it. Even so, there was no water in this layer, Jamie was willing to bet. Not even permafrost. If there had been, the water’s expansion and contraction during the day-night cycle would easily have crumbled such friable stone.

The next tier was much tougher rock, its color a deeper red. More iron, Jamie guessed. Shergottite, like the meteor I found in Antarctica.

Jamie whacked away with his hand pick until he had several loose bits of the rock in his free hand. Chips and flakes fell clattering down, down beyond sight and hearing toward the canyon bottom so far below. As he slipped the rock samples into a collecting bag Jamie realized he was soaked with sweat from the exertion. The suit’s fans were buzzing, sounding angry at him for pushing them so hard. He pulled in a deep breath of canned air as he carefully tucked the pick into its loop on his belt and then pulled out the ballpoint pen (guaranteed to work even in zero gravity) and labeled the sample bag precisely: date, time, exact distance from the rim. He got his depth, measured from the canyon’s edge, by having Vosnesensky read off the tick marks on the winch’s tether.

"Not much daylight remaining." Vosnesensky’s voice sounded as remote and unemotional as a computer.

Jamie glanced up, then leaned a booted foot against the rock wall to turn himself around in the harness.

His leg flared into a million pinpricks. Hanging in the harness, both legs had gone asleep. Jamie muttered and cursed to himself as he flailed his legs and wiggled his toes to get some circulation going again. He felt as if a whole colony of ants were gnawing at his legs.

"What is it?" Vosnesensky’s voice was suddenly urgent. "Are you all right?"

"My goddam legs are asleep," Jamie answered.

"I will pull you up."

"No… it’ll be okay in a minute or so. I want to get down to that third tier, where the yellow stuff is."

"Time is getting short."

"Isn’t it always?" Jamie looked out across the vast chasm, saw the shadows creeping toward him. "We’ve got another hour, at least."

"One hour," said Vosnesensky, with implacable finality.

"Yeah. Okay."

Jamie pushed the sample bag into the pouch strapped to his right thigh, next to his fetish, then started to reach up to the keypad on his chest that controlled the winch. And froze.

His eyes caught a dark rift in the cliff wall a kilometer or more off to his left, a horizontal cleft with a flat floor and a slightly bulging overhang of rock above it. Like the cleft at Mesa Verde where the ancient ones had built their village of dried mud bricks.

And there were buildings in the cleft.

Jamie felt the breath rush out of him, felt his insides go hollow, drop away as if he had been suddenly pushed off the edge of the tallest mountain in the universe.

They can’t be buildings, a part of his mind insisted. Yet as he stared he could make out square shapes, walls, towers. There was no haze to obscure his vision; the air was as clear as a polished mirror at this level.

Fumbling at his belt without taking his eyes from the vision, Jamie found the video camera clipped there and yanked it free. He banged it against his visor, his head jolting back in surprise, then held it steady and adjusted its telescopic lens.