He showed her a Packard Bell softscreen, stuck to one wall, which was cycling through displays of what turned out to be a thermal profile through Titan’s atmosphere, as sampled by the descending Huygens lander. Grabbing a mouse, he cleared down the screen and pulled up data from a fresh database.

She’d met him a few days before at a party at her old fraternity at Caltech, where he was getting steadily drunk on ice beer and talking too much, loud and fast and humorlessly, about his work here at JPL on the Cassini/Huygens mission. He’d attracted a rotating audience of student types, some intrigued, some argumentative; as the group cycled, Rosenberg would happily launch into his obsessive monologue again, as far as Jackie could tell pretty much from the beginning.

He was talking about biochemistry — the chemistry of life — on Saturn’s moon, Titan.

Jackie was intrigued. Here was a classic loser magnet, but with a story of such compelling intensity that it was attracting a crowd, if a transient one. And she got even more interested, when the sensational claims about life on Titan had started appearing in the press and the net.

She was in the middle of a new effort to revive her once-promising career in journalism, which had been pretty much dormant since her second kid was born. If she was going to progress, she knew, she was going to have to develop a nose for a story, her own story, something dramatic and compelling — but out of the way, far from the attention span of the big boys.

And maybe — she’d thought, listening to this skinny monomaniac mouthing off to a bunch of strangers about weird chemistry results from Titan, and with his eyes shining — maybe, she’d found it.

Before the end of that party she’d buttonholed Rosenberg and arranged to meet him here, at JPL. She’d figured it was a better than evens chance that he would have forgotten all about her, in which case she would have driven all this way out here to the arroyo for nothing. But when she’d arrived at the security gate, she found he’d left a media pass for her to collect.

Soon the softscreen was covered by chemical notation and complex molecular structure charts.

He said, “How much biochemistry do you know?”

Actually, she’d picked up a little in her graduate days. But she said, “Nothing.”

“All right. I’m working in the group responsible for the GCMS results.”

“GCMS?”

“Gas chromatograph and mass spectrometer. In-situ measurements of the chemical composition of gases and aerosols in Titan’s atmosphere, and at the end of Huygens’s descent, a direct sample of the surface. The lead scientist is a guy at Goddard. On the lander, a slug sample was drawn in through filters and into an oven furnace, which—”

“Enough. Tell me what you do.”

“I’m working on high atomic number results. Complex molecules. Look — what do you know about conditions on the surface of Titan?”

“Only what I’ve seen in the pop press the last few weeks.”

“All right. Titan is an ice moon, with a thick layer of atmosphere. The only moon with a significant layer of air, anywhere. In a lot of ways, Titan right now is like primeval Earth — say, four and a half billion years ago. Its chemistry is mostly based around carbon, hydrogen and nitrogen. And chemistry like that produces a lot of the key molecules of prebiotic chemistry.”

“Prebiotic?”

“The components of life. But there’s a crucial difference. Titan has no liquid water. It’s too cold for that. The importance of water on primitive Earth is that it was a solvent. It allowed the polymerization of volatile reactive organics and the hydrolysis of prebiotic oligomers into biomolecules… I’m sorry. Look, you need water as a solution medium, so that the components, the building blocks, can assemble themselves into proteins and nucleic acids, the main macromolecules of our form of life.”

Our form of life.That phrase made her shiver. “But maybe there are other solvents.”

“Correct. Maybe there are other solvents. In particular, ammonia. And we knew before Huygens that there is ammonia on Titan. Now. Look here. Look what the Huygens GCMS found.” He pointed to a diagram of a molecule shaped like a figure eight on its side, with some of its edges highlighted in blue for double covalent bonds.

“What is it?”

“Ammono-guanine. That is, guanine with the water chemistry systematically replaced by ammonia.” He looked up at her, the multicolored diagram reflected in his glasses. “Do you get it? Exactly what we’d have expected to have found, if some ammonia-based analogue of terrestrial life processes was going on down there. Look at these ratios.” He pulled up another image. “See that? Here, close to the surface, you have a depletion of methane and gaseous nitrogen, and a surplus of ammonia and cyanogen, compared to the atmosphere’s average. The analogy is clear. Methane and nitrogen are being used in place of monose sugars and oxygen, and you have ammonia and cyanogen instead of water and carbon dioxide—”

“What are you saying, Rosenberg?”

“Respiration,” he said. “Don’t you get it? Something down there has been breathing nitrogen, and exhaling ammonia.”

“So, could it mean life?”

He looked puzzled by the question. “Yes. That’s the point. Of course it could.”

She frowned, staring at the molecular imagery. It was exciting, yes, but it was hardly the electric thrill she’d been hoping for. Even those blurred images of the microfossils in that meteorite from Mars had had more sex appeal than this obscure stuff.

“What do you think we should do about this?”

“Send another probe, of course,” he said, staring into the screen. “It ought to be a sample-return. We’ve just got to follow this up. Look at this.”

He studied his results, and Jackie studied him.

Right now, her own mother was on orbit, in Columbia.

In the long months of her mother’s work absences, Jackie had often wondered why it was always people with no life of their own on this planet — Rosenberg, her own mother after her lawyer husband walked out with his secretary — who became obsessive about finding life on others.

Anyhow it was academic. The funding just wasn’t there. Maybe not for the rest of your working life, Rosenberg, she thought sadly. This data, here, might be all you’ll ever see.

Rosenberg flexed his fingers, as if itching to thrust them into the ammonia-soaked slush of Titan.

“Lei Feng Number One, there are five minutes to go. Please close the mask of your helmet.”

Jiang obeyed, locking the heavy visor in place with a click of aluminum. “My helmet is shut. I am in the preparation regime.”

“Four minutes and thirty seconds to go.”

As her helmet enclosed her she was aware of a change in the ambient sound; she was shut in with the sound of her own voice, the soft words of the launch controllers in the firing room, the hiss of oxygen and the scratch of her own breathing.

Impatience overwhelmed her. Let the count proceed, let her fly to orbit, or die in the attempt!

Still the holds kept off: still she waited for the final, devastating malfunction which might abort the flight completely.

But the holds did not come; the counting continued.

The voices of the firing room controllers fell silent. There was a moment of stillness.

Jiang lay in the warm, ticking comfort of her xiaohao, the little Mao bell motionless above her, the couch a comfortable pressure beneath her, no sound but the soft hiss of static in the speakers pressed against her ear.

She closed her eyes.

And so the countdown reached its climax, as it had for Gagarin, Glenn and Armstrong before her.