Dry Dock

TThe object had a name for eight months before anyone looked at it, and the name was a number.

UCT-40-0217. Uncorrelated target, year forty, the two hundred and seventeenth thing Mars Traffic Control's radar had found that year in orbit and could not match to anything in the catalogue. It had turned up in February, a faint return far out in high Mars orbit, and gone into the backlog with three thousand others: dead boosters, lost tool bags, shed insulation, the slow litter of a century of people working in the sky. Twice a year, Traffic paid somebody to go and look at the biggest ones. This quarter it was Voltaire Yard on Deimos, and this morning, the twenty-third object on the list, it was Mara.

It was not glamorous work. Voltaire was a repair and breaking yard: two hangars and a tug apron dug into the side of a crater on a moon so small you could throw a wrench into orbit if you threw it hard enough, and an open steel dock called the Gantry where dead ships came to be taken apart. Mara was its salvage engineer, which meant structures, recoveries, surveys, the long arithmetic of whether a thing was worth saving and what it would cost to move. Most of the objects on Traffic's list turned out to be junk. A fuel tank. A solar panel the size of a door. Last quarter, memorably, a frozen sack of laundry from a Phobos dormitory. Traffic paid by the object, junk or not, and Teodor Ilunga, who ran the yard and owed the bank for the Gantry, had taken the contract the way a man in a cold room takes a blanket.

"Range forty kilometres," Mirela Dancu said. "Closing at nine metres a second. You can stop staring at the screen. It isn't going to get bigger faster because you want it to."

The tug Kittiwake was a brick with an engine on one end and a cockpit on the other, and the cockpit had two seats and a window the size of a dinner table. Out of the window, so big it filled half the glass, was Mars. At periapsis the object came down to twenty-three and a half thousand kilometres, just outside Deimos's own orbit, and for a few hours it moved fast, swinging low past the planet before climbing away again for twelve days towards the far end of its orbit. Catching it here had cost Kittiwake half a kilometre a second of velocity. Mirela had complained about every metre.

Below them, rust and butterscotch and dust-grey, the Tharsis volcanoes stood up out of the morning terminator in a row, their shadows hundreds of kilometres long. Mara had lived at Voltaire for six years and still looked.

"Radar cross-section's big," Mara said. "Bigger than anything else on the list. Nine hundred square metres, maybe more. And it's flickering on a four-minute cycle. Something long, turning end over end."

"A booster stage."

"Too big for a booster."

"A habitat module somebody lost and was too embarrassed to report." Mirela adjusted their closing rate with two short taps of the thrusters, which went through the hull as a pair of thumps. She was a small woman with a shaved head and a tattoo of a swallow behind one ear, and she flew the tug the way some people played the piano, without looking at her hands. "Whatever it is, it's dark. No transponder, no beacon, no lights. Traffic hails it every week and it never answers. Thirty kilometres."

Mara checked the suit locker behind the seats out of habit, and the tether reels, and the cutting kit, none of which anyone would need today. Survey runs were look-and-leave: images, a radar profile, a spectrum of whatever the surface was made of, and a line in Traffic's catalogue changed from a question to an answer. Then home to the yard for a hot meal in three hundredths of a percent of a gravity, and the next number on the list.

Mara ran the long-range camera out to full zoom. At this range the object was still only a smudge against the black, a sliver of something that caught the sunlight and lost it again as it turned. Four minutes, and the glint again. Four minutes. As patient as a clock.

Mara pulled up Traffic's file while Mirela flew. It was short. First detection, 4 February. Twenty-two radar observations since, all from Phobos, none closer than a hundred thousand kilometres. An orbit fitted to them and refitted every month: periapsis twenty-three and a half thousand kilometres, apoapsis three hundred and ten thousand, period twenty-four days. Status: uncorrelated, non-cooperative, low priority. Somebody at Traffic had typed a note into the comments field in March, large, possibly derelict hull, recommend survey, and nobody had answered it.

"Eight months," Mara said. "It's been going round and round for eight months and nobody came."

"Nobody comes for anything unless somebody pays." Mirela tapped the thrusters. "Five kilometres. Floods."

At two kilometres, in the floodlight, it was a ship.

There was no mistaking it now. It was perhaps a hundred and forty metres long, a squared-off spine with four fat cylindrical tanks clustered along its middle like cans in a crate. At one end, behind a thick conical shield, sat the reactor housing, and just forward of it, caged in a truss, a blunt cluster of plasma thrusters, dark and cold. The radiators, folded half open, were each the size of a sports field. Its hull was coated in the matte grey-black that freighters wore against the sun, and in places the coating had been scoured by eight months of dust and was the colour of old pewter.

It was turning end over end about an axis a little off its middle, once every four minutes, and every four minutes its forward end came swinging through the floodlight, and the light caught a band of white paint around the hull, and letters.

Mara did not breathe. Mara sat in the cockpit of Kittiwake with her left-handed hand flat on the console and watched the letters come round, and go, and come round again.

The first time Mara read only a word: HALCYON.

The second time, the whole of it. HALCYON REACH. And under it, smaller, a hull number and a port of registry: 4472, SHACKLETON.

"That's a Calloway hull," Mirela said quietly. Her hands had stopped on the controls. "Halcyon class. Calloway Lines. Water carriers, Ceres to Mars, when they aren't running freight from Luna." She looked across at Mara, and for once there was nothing dry in her face at all. "Mara, there are only two of those ships, and that is not where either of them is supposed to be."

Mara made her hands work. Transponder: silent on every band. Distress beacon: silent. No running lights, no heat bloom on the infrared except the faint, even warmth of a hull in sunlight. The reactor housing read cold. The tumble was steady at four minutes and two seconds a turn, about an axis nine degrees off the long one, the kind of slow, stable spin a ship could keep for years once something had set it going. Halfway along the spine, just forward of the tanks, there was a small pressurised module with a docking collar and a single dark port, the maintenance module that uncrewed freighters carried for the crews who came out to service them. It was dark too.

"Voltaire, Kittiwake," Mirela said into the radio, and then had to say it again, because her voice had come out wrong the first time. "Survey object twenty-three is a vessel. Repeat, a vessel. Large, intact, non-responsive, tumbling. Request you wake Teodor."

The answer came a few seconds later, a sleepy voice from the yard: "He's awake. He's always awake. What vessel?"

Mirela looked at Mara.

"Tell them to look up Halcyon Reach," Mara said. "Tell them to look her up before they say anything else to anybody."

The hull turned. The name went out of the light, and came back, and went out again, as patient as a clock. Below them the sun came up over Tharsis, and the shadows of the volcanoes began to shorten, and Voltaire Yard, on its small grey moon, was still an hour and a half behind them, coming round the curve of the world.