There. A pale color of sky, a wide canyon of clear air between the polar storms.
“Hold on,” he said. “The ride is going to get humpy.” He banked to the right, following the edge of the storm north.
The polar cap revealed itself as a series of ice cliffs, each one rising above the last, the ice glistening blue. Fast the ice cliffs, the polar cap itself was smoking, the ice boiling away in the summer sun.
And then, suddenly, the ice below him dropped away. He was above an immense ice canyon. A hurricane wind drove down the canyon, a torrent of wind sweeping the airplane helplessly to the west. The wind from the entire evaporating polar cap was funneled into this channel, etching away the ice.
This was the immense Chasma Borealis. Over the eons, the swirling wind had carved away a kilometer’s thickness of ice, making a channel for the outflow of the evaporating atmosphere. The bottom of the chasm below him was jumble of dark rock, glacial moraine. He crabbed crosswind across the canyon, onward. To the left, an immense wall of blue ice rose a kilometer up from the jumbled rock of the base to the top.
He barely cleared the top, and abruptly it was calm.
At the top of the cliff was a rippled plain of snow-covered ice, stretching to the horizon. The pole, according to the inertial navigation system, was three hundred kilometers away.
It might have been a thousand.
Butterfly was out of fuel.
Ryan made another fifty kilometers before the rocket died completely. Engine out, in the thin atmosphere Butterfly could glide about as well as a brick. He stretched the glide as far as he could, eking out a few precious kilometers, and then flared it in to the lightest touchdown he could. It skidded across the snow like a sled, and Ryan struggled to hold the wings level as it fishtailed down the snow. It sledded, bumping against the irregular ice, and sledded—Ryan was beginning to wonder if it was ever going to stop. Until suddenly there was a boulder in the middle of the ice field.
There was no way to steer the aircraft. Ryan pulled back hard, but the airspeed was too low to hop the boulder. The rock ripped across the bottom of the fuselage. He did his best to keep the wings level, but the airplane slewed around and the right wing scraped on the ground. With a spray of snow, the wing buckled, and the ripped wing spar suddenly lost pressure. The wing bent back and tore off. The airplane rolled up, cartwheeled, and came apart.
13
North
Tana’s seat had come to rest upside down, completely detached from the fuselage, but remarkably intact otherwise. She unbuckled her harness and pushed the seat away. Debris from the airplane was scattered for a hundred meters down the ice. Estrela had been thrown clear and landed spreadeagled in a drift of snow a few feet away. Ryan, and the front half of the fuselage, protruded from a snowbank.
She could see Estrela moving, and then standing up. Her body was smoking. She brushed the smoke away, and with relief, Tana realized that it was just dry ice vaporizing away from the heat of her body.
In another moment, Ryan unfastened his harness and took a few steps onto the ice.
They were alive.
Ryan looked across at her. He seemed unhurt. The snow had apparently cushioned the landing.
She toggled her radio on to the common band. “Ryan, Estrela, are you okay? Any injuries to report?”
“Think I’m okay,” Ryan said. “Nothing broken, anyway.”
“Foda-se!” Estrela said. “Yes, I’m okay. I think.”
Tana wasn’t sure what she could have done if they had reported injuries anyway. The nearest emergency room was over a hundred million miles away. She looked across the ice. Liquid oxygen tanks, supplies, shards of aluminum-lithium alloy, the burned-out rocket engine, shreds of wing fabric; pieces of the Butterfly were spread on both sides of the skid mark the plane had made sliding along the snow. There was no way it was ever going to fly again. Jesus, that had been the most frightening moment of her life. She was amazed that Ryan had managed to hold it together for so long. “And what now?” she asked.
The question hung in the air for a moment, and then Ryan answered. “What choices do we have?”
A tremor shook the ice, and a moment later a sharp report. “What in the world—”
Tana pointed wordlessly.
A few hundred meters to the east, a geyser had sprung up from the snow, a brilliant white plume shooting a hundred meters into the air. Fragments of ice pattered down on the snow all around them. The ground below the geyser split open, and the glittering plume spread out, at first slowly, and then with increasing speed along the crack in both directions until it was a wall of glistening spray that raced toward the horizon in both directions.
Ryan reached down and touched the ground tentatively. The polar cap surface was dust mixed with ice, a rough, crusty surface. He tapped it gingerly. It seemed solid. “Ice,” he said. He rapped on it solidly and looked up at them. “The crust is ordinary water ice. But below the crust, it must be carbon dioxide—dry ice. It’s slowly sublimating away in the heat. When it gets trapped—wham. It all blows out at once.”
Already the sudden geyser was beginning to die away. In a few minutes, all that was left of it was a patch of broken snow.
“For certain we can’t stay here,” Ryan said. “We head north.”
“On foot?” Tana asked. Nobody said anything; the answer was obvious. “How far?”
“About two hundred and fifty kilometers,” Ryan said.
“You’ve got to be kidding.”
It took Tana ten minutes of searching to find the inertial navigation system. The laser gyros had no moving parts; it was a design that had been built to locate airplane crash sites on Earth. She checked it. “Still working. We ought to write the manufacturer.” It had been designed to be tough.
Ryan was ripping parts of skin off the Butterfly and examining their flexibility, but they didn’t seem to meet his needs. He moved over to salvage struts out of the wreckage of the seats, apparently a bit more to his liking. He looked up. “Do you know how to ski?”
“Now you really have to be kidding,” Tana said.
He held up one of the struts. It was a piece of aluminum-lithium alloy, strong and light. He had been able to flatten it down, and bent a crude curve at one end. He examined it critically, and then started to work on another. “Do you have another idea?”
Tana shook her head.
“North,” Ryan said.
14
To the Farthest North
The sun was circled by a luminous double halo, with mock suns on either side. It never set, but only circled constantly around them, dipping down almost to the horizon in front of them and then rising up at their backs.
The ground was a jumbled chaos of pressure ridges and fragmented ice-blocks half buried in snow. In regions the ground was solid ice, crisscrossed with cracks that hissed out jets of snow-laden vapor, and in other regions gleaming new snow lay flat and smooth and inviting. Ryan cheerfully steered into the middle of one of these, and as his makeshift skis touched the snow, it hissed and foamed around him. All friction vanished, and he skidded helplessly away on a cushion of foaming carbon dioxide vapor.
It took him an hour to painstakingly make his way out of the trap, warming each step down until he reached solid footing. After that, they learned to avoid the areas of new snow.
After six hours of skiing, Ryan called for a halt. They pulled off their skis and inflated the emergency habitat.
The emergency habitat was a cylinder, two meters long and a meter and a half in diameter, with translucent walls made of polyimide impregnated with netting of ripstop superfiber. An even, pinkish-orange light filtered through the habitat walls, making the inside look like the interior of a furnace. But the inside was cold. The only heat came from the radiators of the isotope power units on the Mars suits. It was so tightly crowded inside that it was hard for them to take their suits off; it had been designed to keep one person alive while waiting for rescue. But nobody was coming to rescue them. They silently stripped down to just the suit liners and piled together in the middle for warmth.