They were plowing through the thin air at a speed and height calculated to put them into what aerodynamicists call transitional flow, a state halfway between free molecular flow and continuum flow. Free molecular flow would have been the preferred mode of travel, with the air that struck the heat shield shoved to the sides, and the resulting vacuum refilled mostly by molecular diffusion; but they were moving too fast for that, and they could only just barely avoid the tremendous heat of continuum flow, in which air would have moved over shield and ship as part of a wave action. The best they could do was to take the higest possible course that would slow them enough; and this put them into transitional flow, which vacillated between free molecular and continuum flow, making for a bumpy ride. And there lay the danger. If they were to hit a high pressure cell in the martian atmosphere, where heat or vibration or gee forces caused some senstive mechanism to break, then they could be cast into one of Arkady's nightmares at the very time they were crushed in their chairs, "weighing" four hundred pounds apiece, which was something Arkady had never been able to simulate very well. In the real world, Maya thought grimly, at the moment when they were most vulnerable to danger, they were also most helpless to deal with it.

But as fate would have it, Martian stratospheric weather was stable, and they remained on the Mantra Path. Which in actuality turned out to be a roaring, shuddering, breath-robbing eight minutes. No hour Maya could remember had lasted as long. Sensors showed that the main heat shield had risen to six hundred degrees Kelvin-

And then the vibration stopped. The roar ended. They had skipped out of the atmosphere, after skidding around a quarter of the planet. They had decelerated by some twenty thousand kilometers an hour, and the heat shield's temperature had risen to seven hundred and ten degrees Kelvin, very near its limit. But the method had worked. All was still. They floated, weightless again, held down by their chair straps. It felt as if they had stopped moving entirely, as if they were floating in pure silence.

Unsteadily they unstrapped themselves, floated like ghosts around the cool air of the rooms, an airy faint roaring sounding in their ears, emphasizing the silence. They were talking too loudly, shaking each others' hands. Maya felt dazed, and she couldn't understand what people were saying to her; not because she couldn't hear them, but because she wasn't paying attention.

# # #

Twelve weightless hours later their new course led them to a periapsis thirty-five thousand kilometers from Mars. There they fired the main rockets for a brief thrust, increasing their speed by about a hundred kilometers an hour; after that they were pulled toward Mars again, carving an ellipse that would bring them back to within five hundred kilometers of the surface. They were in martian orbit.