Sax leaned over to shout again in Ann’s ear. “I believe this is one of those situations in which we are meant to use the lifeboat function!”

“… lifeboat?” Ann said.

Sax nodded. “The boat is its own lifeboat!” he shouted. “It flies!”

“What do you mean?”

“It flies!”

“You’re kidding!”

“No! It becomes a — a blimp!” He leaned over and put his mouth right to her ear. “The hulls and the keels and the bottom of the cockpit empty their ballast. They fill with helium from tanks in the bow. And balloons deploy. They told me about it back in Da Vinci, but I’ve never seen it! I didn’t think we’d be using it!” The boat could also become a submarine, they had said in Da Vinci, quite pleased with themselves at the new craft’s versatility. But the ice packing against the lee shore made that option unavailable to them, something that Sax did not regret; for no particular reason, the idea of going down in the boat didn’t appeal to him.

Ann pulled back to look at him, amazed at this news. “Do you know how to fly it!” she shouted.

“No!”

Presumably the AI would take care of that. If they could get it into the air. Just a matter of finding the emergency release, of flicking the right toggles. He pointed at the control panel to mime this thought, then leaned forward to shout in her ear; her head swung in and banged his nose and mouth hard, and then he was blinking with bright pain, the blood running out of his nose like water from a faucet. Impact, just like the two planetesimals, he grinned and split his lip even wider, a painful mistake. He licked and licked, tasting his blood. “I love you!” he shouted. She didn’t hear him.

“How do we launch it?” Ann cried.

He indicated the control panel again, there beside the AI, the emergency board under a protective bar.

If they chose to try an escape by air, however, it would bring about a dangerous moment. Once they were moving at the wind’s speed, of course, there would be very little force brought to bear on the boat, they would simply blimp along. But at the moment of liftoff, while they were still nearly stationary, the howler would tear hard at them. They would tumble, probably, and this might disable the balloons enough to cast the boat back into the ice-choked breakers, or onto the lee shore. He could see Ann thinking this through herself. Still — whatever happened, it was likely to be preferable to the bone-jarring impacts that continued to rack them. It would be a temporary thing, one way or the other.

Ann looked at him, scowled at the sight of him; presumably he was a bloody mess. “Worth a try!” she shouted.

So Sax detached the protection bar from the emergency panel, and with a final look at Ann — their eyes meeting, a gaze with some content he could not articulate, but which warmed him — he put his fingers on the switches. Hopefully the altitude control would be obvious when the time came. He wished he had spent more time flying.

As the boat rose up the foamy face of each wave, there came a nearly weightless moment at the top, just before the falldown into the next icy trough. In one of these moments Sax flicked the switches on the panel. The boat fell down the waveback anyway, hit the growlers with its usual jar — then bounced right up and away, lifted, and tilted right over on its lee hull, so that they were hanging in their restraints. Balloons entangled no doubt, the next wave would capsize them and that would be that; but then the boat was dragging away over ice and water and foam, almost free of contact, rolling them head over heels in their restraints. A wild tumbling interval, and then the boat righted itself, and began to swing back and forth like a big pendulum, side to side, front to back — oops then all the way over again, topsyturvy — then righted, and swinging again. Up up up, thrown this way and that, hold on — his shoulder harness came free and his shoulder slammed against Ann’s, even though he had been pressed against her. The tiller was bashing his knee. He held on to it. Another crash together and he held on to Ann, twisted in his seat and clutched her, and after that they were like Siamese twins, arms around each other’s shoulders, in danger at every slam of breaking each other’s bones. They looked at each other for a second, faces centimeters apart, blood on both of them from some cut or other, or no it was probably just from his nose. She looked impassive. Up they shot into the sky.

His collarbone hurt, where Ann’s forehead or elbow had struck it. But they were flying, up and up in an awkward embrace. And as the boat was accelerated to something nearer the wind’s speed, the turbulence lessened greatly. The balloons seemed to be connected by rigging to the top of the mast. Then just when Sax was beginning to hope for some kind of zeppelinlike stability, even to expect it, the boat shot straight up and began its horrible tumbling again. Updraft no doubt. They were probably over land by now, and it was all too possible they were being sucked up into a thunderhead, like a hail ball. On Mars there were thun-derheads ten kilometers tall, often powered by howlers from far to the south, and balls of hail flew up and down in these thunderheads for a long time. Sometimes hail the size of cannonballs had come crashing down, devastating crops and even killing people. And if they were pulled up too high they might die of altitude, like those early balloonists in France, was it the Montgolfiers themselves it had happened to? Sax couldn’t remember. Up and up, tearing through wind and red haze, no chance to see very far —

BOOM! He jumped and hurt himself against his seat belt, came down hard. Thunder. Thunder banging around them, at what had to be well over 130 decibels. Ann seemed limp against him, and he shifted sideways, reached up awkwardly and twisted her ear, trying to turn her head so he could see her face. “Hey!” she cried, though it sounded to him like a whisper in the roar of the wind. “Sorry,” he said, though he was sure she couldn’t hear him. It was too loud to talk. They were spinning again, but without much centrifugal force. The boat was shrieking as the wind pushed it up; then they dove, and his eardrums hurt to bursting, he wiggled his jaw back and forth, back and forth. Then up again and they popped, painfully. He wondered how high they would go; very possible they would die of thin air. Though maybe the Da Vinci techs had thought to pressurize the cockpit, who knew. It behooved him to try to understand the boat as blimp, or at least master the altitude adjustment system. Not that there was much to be done against the force of such updrafts and downdrafts. Sudden rattle of hail against the cockpit shell. There were small toggles on the emergency panel; in a moment of less violent tumbling he was able to put his face down near the bar and read the display terminal embedded in it. Altitude … not obvious. He tried to calculate how high the boat would go before its weight caused it to level off. Hard when he wasn’t actually sure of the boat’s weight, or the amount of helium deployed.

Then some kind of turbulence in the storm tossed them again. Up, down, up; then down, for many seconds in a row. Sax’s stomach was in his throat, or so it felt. His collarbone was an agony. Nose running or bleeding continuously. Then up. Gasping for air, too. He wondered again how high they were, and whether they were still ascending; but there was nothing to be seen outside the shell of the cockpit, nothing but dust and cloud. He seemed in no danger of fainting. Ann was motionless beside him, and he wanted to tug her ear again to see if she was conscious, but couldn’t move his arm. He elbowed her side. She elbowed back; if he had elbowed her as hard as that, he would have to remember to go lighter next time. He tried a very gentle elbowing, and felt a less violent prod in return. Perhaps they could resort to Morse code, he had learned it as a boy for no reason at all, and now in his reborn memory he could hear it all, every dit and dot. But perhaps Ann had not learned it, and this was no time for lessons.