Titan. Stephen Baxter

      Melted slush frosted over the buried portals of the inert, cooling lander. And a thin rain of light brown organic material began to settle on the upper casing.

      The chatter of telemetry to Cassini fell silent. The orbiter passed beneath the horizon, and then turned its high gain antenna away from Titan, to Earth. Patiently, Cassini began to download everything the lander had observed.

      Some of the results were unexpected.

      

      Paula Benacerraf worked through her EVA suit checklist.

      She connected her Snoopy hat comms carrier to the suit’s umbilical. She set the sliding oxygen control on her chest pack to PRESS. She put on her gloves and snapped home the connecting rings. Then she lifted her helmet over her head. The suit built up to an overpressure, and she tested it for leaks.

      The ritual of checks was oddly comforting. It took her mind off what she was about to do.

      Tom Lamb rapped on her backpack.

      Paula Benacerraf turned, awkwardly. Foot restraints held them both in standing positions, packed in head-to-toe. In her EMU – her suit, her EVA mobility unit – she felt ludicrously bulky, awkward in the confines of Columbia’s airlock, which was just a cramped, cylindrical chamber in the orbiter’s mid deck.

      ‘That’s it, Paula. I think we’re go.’

      She said, ‘Already?’

      ‘Already.’ Lamb grinned out of his helmet at her, and she could see silvery stubble in the creases of his leathery cheeks. ‘You’re an independent spacecraft now.’

      Her heart was hammering under the tough surface of her HUT, her hard upper torso unit. ‘Spaceship Paula. It feels good.’

      Tom Lamb had once been the youngest Moonwalker. Now, at sixty-two, he was one of the oldest humans to have flown in space.

      And Benacerraf, forty-five, a grandmother, was one of the oldest rookies.

      Benacerraf disconnected her suit from the wall mount.

      Lamb said, ‘Houston, we’ve got the hatch closed and we’re waiting for a go for depress on time.’ His native Iowan twang was overlaid with a Texan drawl acquired over long years at Houston.

      ‘Affirmative, EV1; you have a go for depress.’

      Lamb turned to the control panel and turned the depress switch to position 5. Then, with the pressure down to five psi, Lamb turned the switch to its second position. ‘Depress valve to zero.’

      Benacerraf heard a distant hiss. She moved the oxygen control on her chest pack to its EVA position.

      ‘Pressure down to point two,’ Lamb said now. ‘Let’s motor.’ He kicked his feet out of their restraints. With a confident motion he twisted the handle of the outer airlock hatch. Benacerraf thought the hinges and handle looked old, like bits of a school bus, with the polish of long use.

      Lamb pushed the hatch outward, and Paula Benacerraf gazed into space.

      She was looking along the length of the orbiter’s payload bay. The big bay doors were gaping open, the silvered Teflon surfaces of their radiator panels gleaming, and the bay itself was a complex trench, crammed with equipment, stretching sixty feet ahead of her. There was no direct sunlight; the bay was in the shadow of a wing, and the light in the bay was like a diffuse daylight.

      Tom Lamb moved out through the airlock’s round hatchway, and drifted over to the left payload bay door hinge. There was a handrail and two slide wires that ran the length of the big hinge, and Lamb tethered himself to the wires. She could see his bright EV1 armbands.

      He turned and waited for her.

      ‘Houston, the hatch is open and EV1 is out.’

      ‘We see you, Tom.’

      ‘EV2 is halfway out, getting ready.’

      Benacerraf, with her hands on the doorway, felt as if she was frozen in place, as if she really couldn’t step out there.

      Lamb lifted up his big gold visor, so she could see his face. ‘Just stay with it, kid. One step at a time.’

      She grunted. ‘Some kid,’ she said.

      Somehow, though, Lamb’s gravelly words punctured her tension.

      She kept her eyes down on the floor of the payload bay and drifted through the hatch, just as she had done a hundred times in training, in the big swimming pool in the Sonny Carter Facility at Ellington Field. She fixed her own tether in place. Now, at least, she wouldn’t go drifting off into space.

      For the first time she looked up.

      Columbia was flying with her instrument-laden payload bay pointing at Earth, so that the planet was a ceiling of light above Benacerraf, a belly of ocean strewn with white, shadowed clouds.

      Earth flooded the orbiter with light.

      When he saw she was tethered, Lamb pulled himself along the length of the payload bay with practised ease. He reached the far end, and, diminished, he performed a simple pirouette, his tether flailing around him slowly.

      ‘Hey, Paula,’ Lamb said now. ‘Look at your hands.’

      She lifted up a gloved hand before her face. There was grease on the glove, from the payload bay door hinge.

      

      When she’d first joined the astronaut corps six years ago Benacerraf had been in complete awe of Tom Lamb.

      He was the last Apollo veteran still working in the program, all of thirty-two years since the last Lunar Module had lifted off that remote surface. Tom Lamb still called himself an aviator, Navy style. She knew he had some kind of antique aeronautics degree from some technology institute in Georgia. But as far as he was concerned, Lamb was primarily a graduate of the Naval Pilot Test School at Patuxent River, in Maryland. She knew he had been known as a superb stick-and-rudder man, and his specialism had been night carrier landings, the hairiest flying in the Navy.

      And as a young teenager Paula Benacerraf had watched Lamb and his commander Marcus White bounce like sun-drenched beach balls over the rubble-strewn floor of Copernicus.

      How could you meet, how could you work with, a man like that?

      But the awe had soon worn off, for Benacerraf.

      Benacerraf was an engineering specialist – her discipline was orbital construction techniques – and she’d come into NASA with a hatful of qualifications, awards and degrees. She’d worked as a ground-based contractor on a number of Space Station construction missions. It was only when, because of Shuttle launch wave-offs and Russian construction delays, the Station assembly sequence had started to fall drastically behind its timeline that the need had been identified to draft the right experience directly into the program.

      So – against the advice of her daughter Jackie, against the resistance of her employers – Benacerraf had given up her fancy consultant’s salary and her nice apartment in Seattle, and moved down to the humid stink of Houston, on Government pay.

      At first she’d worked as a specialist in the backrooms behind the Mission Control rooms, in Building 30 of JSC, the Johnson Space Center. Then she’d been promoted to work as a Mission Controller, in the FCR – the Flight Control Room – itself.

      But it still wasn’t enough. It was pretty obvious that this construction project – if it was ever going to get back on schedule – needed foremen in space.

      Benacerraf had been a space nut since watching Lamb and his buddies on the Moon, all those years ago. But the thought of actually going up there herself, in a dinged-up old Space Shuttle, pretty much appalled her.

      Tom Lamb himself had been deputed to talk her round. He’d used all the grizzled charm at his disposal.

      … But I’ve got two grandchildren, Tom.

      Hell, so have