Titan - Stephen Baxter

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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 multicoloured 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.

      As the pilots prepared for the landing, Columbia’s flight deck took on the air of a little cave, Benacerraf thought, a cave glowing with the light of the crew’s fluorescent glareshields, and of Earth. Despite promises of upgrades, this wasn’t like a modern airliner, with its ‘glass’ cockpit of computer displays. The battleship-grey walls were encrusted with switches and instruments that shone white and yellow with internal light, though the surfaces in which they were embedded were battered and scuffed with age. There was even an eight-ball attitude indicator, right in front of Tom Lamb, like something out of World War Two; and he had controls the Wright brothers would have recognized: pedals at his feet, a joystick between his legs.

      There was a constant, high-pitched whir, of environment control pumps and fans.

      Lamb, sitting in Columbia’s left-hand commander’s seat, punched the deorbit coast mode program into the keyboard to his right. Benacerraf, sitting behind the pilots in the Flight Engineer’s jump seat, followed his keystrokes. OPS 301 PRO. Right. Now he began to check the burn target parameters.

      Bill Angel, Columbia’s pilot, was sitting on the right hand side of the flight deck. ‘I hate snapping switches,’ he said. ‘Here we are in a new millennium and we still have to snap switches.’ He grinned, a little tightly. It was his first flight, and now he was coming up to his first landing. And, she thought, it showed.

      Lamb smiled, without turning his head. ‘Give me a break,’ he said evenly. ‘I’m still trying to get used to fly by wire.’

      ‘Still missing that old prop wash, huh, Tom?’

      ‘You got it.’

      Amid the bull, the two of them began to prepare the OMS orbital manoeuvring engines for their deorbit thrusting. Lamb and Angel worked through their checklist competently and calmly: Lamb with his dark, almost Italian looks, flecked now with grey, and Angel the classic WASP military type, with a round, blond head, shaven at the neck, eyes as blue as windows.

      Benacerraf was kitted out for the landing, in her altitude protection suit with its oxygen equipment, parachutes, life-raft and survival equipment. She was strapped to her seat, a frame of metal and canvas. Her helmet visor was closed.

      She had felt safe on orbit, cocooned by the Shuttle’s humming systems and whirring fans. Even the energies of launch had become a remote memory. But now it was time to come home. Now, rocket engines had to burn to knock Columbia out of orbit, and then the orbiter would become a simple glider, shedding its huge orbital energy in a fall through the atmosphere thousands of miles long, relying on its power units to work its aerosurfaces.

      They would get one try only. Columbia had no fuel for a second

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