And now, in her side windows, the sun rose, a spot of light like a helicopter searchlight, rising up from the blurred haze, the multiple layers of atmosphere she would, today, traverse.

It was probably the last dawn she would ever witness.

“Hey there, Jitterbug.”

It was Benacerraf. Mott flicked the switch on her microphone wire. “I hear you, Bifrost.”

“I can see you, fat as a goose.”

She twisted in her couch. And there, framed by the small window to her right, was Bifrost. The familiar cone profile of the second Apollo, illuminated by Titan light, was unmistakable.

In space, the various upgrades were obvious. No attempt had been made to refurbish the Apollos’ old ablative heatshields. The base of Bifrost, which would take the brunt of the entry heating, was coated by black silica-based tiles, the same material used on the undersurface of the Shuttle orbiters, bonded to an aluminum honeycomb beneath. And the upper conical surface, which would reach much lower temperatures, was coated with white Nomex felt tiles. The black and white finish, punctured by windows and the gaping mouths of reaction control nozzles, gave Bifrost an oddly modern look, Mott thought, compared to the baroque silver hulls of the old Moon-mission designs.

Strapped to Bifrost’s base there was another novelty. The classic fat silver cylinder of the Apollo Service Module was replaced by a squat tube six feet long — about half the length of the Command Module — with a fat, flaring nozzle. This was a PAM-D-II, a payload assist module. It was a Thiokol solid rocket booster which had been used as an upper stage for launching satellites from Shuttle and Earth-orbit flights. It was strapped to the center of Bifrost’s heat-shield by metal straps, which would be severed by pyrotechnic bolts.

The PAM would be used to knock Bifrost out of orbit…

Discovery had already been flown down, under automatics, to the surface. So here were two Apollo Command Modules, flying in formation around a moon of Saturn.

“Okay, Niki,” Benacerraf called over now. “You ready for your preburn checklist?”

“I got it.” The checklist was Velcroed to the instrument panel in front of Mott.

“Thrust switches to normal.”

Mott closed her switches. “Thrust switches normal.”

“Inject prevalves on.”

“Okay. Prevalves on.”

“One minute to the burn, Niki. Arm the translational controller.”

“Armed…”

The crews had agreed that Mott, alone in Jitterbug, would be walked through her entry burn first, with the aid of Rosenberg and Benacerraf. Bifrost would descend an orbit later, two hours after Mott.

Thus, Mott would be the first human to land on Titan.

She had been given the mission’s remaining flag to set up, a plastic-coated Stars and Stripes, neatly wrapped in a little cellophane bundle. And on her chest was stitched a tiny Union Jack.

“Thirty seconds,” Benacerraf said. “Thrust-on enable, Niki.”

Mott unlocked the control and gave it a half-turn.

“Fifteen seconds. That’s it. You’ve done it, Niki. Sit tight, now.”

Sit tight.Sure. And what if the PAM-D doesn’t fire, after six years of space soak? The PAM-Ds were pretty reliable, but had been known to fail, even in Earth orbit, a couple of hours after leaving the KSC pad. And nobody was sure what would happen if those straps failed to sever, and a Command Module finished up carrying a PAM-D, partially expended, through the fires of entry.

She braced herself for the kick in the back.

“Two, one.”

There was a bang, a rattly thrust which pushed her into her couch. It had the crisp, crude sharpness characteristic of solid rocket burns. The push felt enormous, but she knew it was no more than a half-G.

There was a green light before her.

“Retrofire,” she said.

“Copy the retrofire, Niki. See you on the ground. Don’t mess up the place before we get there.”

“I won’t.”

The burn lasted thirty seconds, yellow rocket light flaring from the PAM-D nozzle ahead of Jitterbug.

The thrust died.

She heard a thump of pyrotechnics, a clatter against the hull, like birds hopping over a tin roof. It was the straps holding the PAM-D against the heatshield; they had burned through, and the PAM-D was discarded. After a few seconds she could see it through her window, a squat cylinder spinning away over the orange clouds, shiny straps dangling, abandoned after being hauled across two billion miles for its half-minute of service.

Jitterbug was still in orbit around Titan. But Mott’s orbit now would take her dipping deep into the outer layers of Titan’s thick atmosphere. And there, she would lose so much energy that she would not be able to climb out again.

She was, she knew, committed.

“Godspeed, Niki,” Benacerraf called distantly.

Six hundred miles above the surface of Titan, on the fringe of the deep, massive atmosphere, Mott felt the first brushes of deceleration. The couch frame dug into her microgravity-softened flesh.

In her window, she could still see Saturn, like a gigantic, gaudy toy.

There was a rattle of solenoids. Outside the windows, to her left and right, there were little flashes of light. That was the gas of the RCS clusters, flaring against the air of Titan. The onboard computer was trying to keep Jitterbug in its forty-mile-wide reentry corridor, before the air thickened so much that the reaction control system was disabled.

A light came on before her. It was the oh-five-G light, the measure of the first feeble tugs of deceleration.

Five hundred miles high, Mott passed through the first haze layer. It was a shell of faint rusty light, which seemed to coalesce above her, blurring Saturn’s image.

It ought to be a gentle entry. CM-115 was entering the atmosphere from low circular orbit around Titan. It would have to shed a mile per second against atmospheric friction. That compared to the Earth-orbital velocity of five miles per second survived by the Shuttle, Gemini and Mercury, and with the even greater seven miles per second survived by Apollo capsules returning from the Moon. The peak deceleration, in the next few minutes, ought to be no more than one and a half G. That was eminently survivable by an Apollo — even a Command Module that had been in storage for most of Mott’s lifetime…

The pressure mounted, climbing fast, impossibly quickly, slamming her into the couch. Titan’s thin, cold upper atmosphere was hauling at Jitterbug in earnest.

…Assuming, of course, the theoretical models of Titan’s atmosphere were right. And Mott, after six years in microgravity, for all her exercising, wasn’t as robust as she used to be.

A pale, grey-white glow began to gather at the base of the window. It was plasma, the atoms of Titan’s air smashed to pieces by the passage of this intruder from Earth, gathering in a thickening shock layer beneath the Command Module. The air of Earth produced a pinkish, almost welcoming glow on reentry. But the light of Titan’s plasma, a thin mix of ionized nitrogen, methane and argon, was a cold pearl-grey glow.

Even the plasma was alien here.

Benacerraf was still speaking to her, she realized belatedly. She tried to call back, to acknowledge; but Benacerraf’s voice was breaking up in static as the plasma shell engulfed Jitterbug.

A hundred and eighty miles above the surface, the deceleration peaked. Mott lay on her back, buffeted, compressed, while the cabin equipment rattled around her. She was deep in the atmosphere, moving at Mach twenty. The weight on her was huge, crushing, worse than anything she had imagined in six years of anticipation of this ordeal. The surges in deceleration seemed astonishingly abrupt, violent. She could feel her internal organs sliding over each other, flattening against her spinal column. Her limbs felt as brittle as twigs, her muscles as limp as wet string; she didn’t dare move a limb. She didn’t seem to have the strength to draw in a breath, and she felt panic creeping over her as the oxygen in her lungs grew depleted.