The canyon wall was a nearly vertical drop. The thought of climbing down that rock wall thrilled him and frightened him at the same time. The bottom was so far down! Yet he could see it with absolute clarity. The thin air had not the faintest hint of haze in it.
To his geologist’s eye it seemed clear that this labyrinth of canyons had been caused by a splintering of the ground, a gridwork of faults in the underlying rock that had weakened the crust, cracked it. When water had flowed here, however long ago it was, it had followed along those cracks, widening and deepening them. Or more likely the permafrost beneath the crust melts from time to time and undermines the ground until it collapses.
“Is that the way it happened?” Jamie asked the silent arroyos in a barely vocalized whisper. “How long ago was it?”
The twisted gullies remained mute.
The more Jamie stared into the deep ravines the more he realized that there had been no great rushing flood here. Mars is a gentle world, he told himself. The ground doesn’t quake. There are no storms. If there ever was a flood on this planet it didn’t happen here.
He straightened up and looked across the huge gulf toward the other side of the canyon. Our ignorance is even wider, he knew. Every geologist on Earth could spend a lifetime here and still it wouldn’t be enough to get all the information these tired old canyons have to yield. All I’ve got is the rest of today and tomorrow. Unless I can get Mikhail to change the excursion plan.
He turned to the Russian, who was standing between him and the rover, looking down into the canyon. The rover’s bright aluminum finish was coated with reddish dust now, especially around the wheels and fenders. It made the vehicle look as if it were rusting.
Fighting down a tiny irrational fear that nagged at the back of his mind, Jamie called, “Mikhail, I’ve got to climb down to the bottom. I’ll need your help.”
The Russian, in his red hard suit, started walking toward Jamie. “That is an unnecessary risk.”
Jamie made himself laugh. “I’ve done a lot of rock climbing. And in full gravity, too.”
“It is an unnecessary risk,” Vosnesensky repeated.
“Then why did the mission planners allow us to stow climbing gear in the rover? Come on, Mikhail, with the winch and all it won’t be much of a risk at all. If you think I’m in danger you can haul me up whether I like it or not.”
“The sun is setting. It will be too cold to work. Tomorrow you can have the whole day.”
“I’m okay in the suit. We’ve got three-four hours before sunset,” Jamie said. “Besides, the sun’s hitting this side of the canyon now. Tomorrow morning this side’ll be in shadow.”
It was impossible to see the Russian’s face behind the gold-tinted visor of his helmet. He was silent for a long time, obviously thinking, weighing the options. Finally he said, “Very well. But when I say to come up, you do not argue.”
“Deal,” said Jamie.
Jamie spent the next hour inching slowly down the sheer rock face of the canyon wall, stopping every ten meters or so to chip out samples. He wore a climber’s harness over his hard suit, attached to the electrical winch at the canyon rim by a thin cable of composites stronger than steel. Jamie himself controlled the winch with a set of buttons built into the harness, although Vosnesensky could override him by using the controls on the winch itself or even hauling him up manually, if necessary.
The rock’s not stratified, Jamie saw. Seems to be all the same, all the way down to the bottom. That puzzled him. One thick slab of undifferentiated stone? How can that be? He remembered a novel he had read years ago, a scene where an infantry division had been assembled on a parade ground that was described as solid iron one mile thick. Had that scene been set on Mars? Jamie could not remember.
This is different from the area around the dome. There’s never been an ocean here to lay down silt deposits and have them turn into rock layers over the years. I’m looking at the actual mantle of the planet, the original material that made up the planet from its very beginning. One enormous slab of rock that must go down not just one lousy mile, it must be a hundred miles deep! Or even more!