‘And where’s that?’

He said simply: ‘The Long Mars.’

Sally Linsay was used to wonder. She had grown up stepping, as a child she had walked into uncounted alien worlds. But even so, as her father spoke those words, she felt the universe pivot around her.

They were met at the compound gate by a guy her father introduced as Al Raup. While his scalp was shaven, a thick black beard sprouted from his chin, giving Sally the odd impression that his head had been rotated around the axis of his stub nose and re attached upside down. He wore canvas shorts, grubby sneakers with no socks, and a black T-shirt too small for his belly with a faded slogan:

SMOKE ME A KIPPER

He might have been any age between about thirty and fifty.

He stuck out his hand. ‘Call me Mr Ttt.’ Tuh-tuh-tuh.

She ignored the hand. ‘Hello, Al Raup.’

Willis raised an eyebrow. ‘Now, Sal, play nice.’

‘Come, let me show you around my domain . . .’

Raup swiped them through the security barriers, and they walked into the compound. Sally heard the growl of heavy vehicles, smelled brick dust and wet concrete, and saw giant cranes loom over holes in the ground. Workers wandered around in yellow hardhats. In some cases she saw ‘danger: radioactivity’ signs, and that was new since she’d last visited. Nuclear rockets under develop ment maybe?

She did notice a party of trolls labouring at a concrete mixer, apparently happy enough. Sally cared little for technology, or people, compared with animals.

‘So,’ Raup said. ‘Welcome to Cape Nerdaveral, Marsonauts!’

‘You’re exactly the type I remember from my last visit here,’ Sally snapped at him.

‘Ah, yes. When you snatched those trolls.’

‘When I liberated them. Glad to see your kind hasn’t gone extinct with the corporatization of this place.’

Raup waved fat fingers. ‘Ah, well, we geeks were here first. We figured out the basic parameters of how to use the Gap, we started the construction of the Brick Moon and sent over a few test shots, all before anybody even noticed we were here.’ His accent might have been middle American, but he had a strangulated, showy way of speaking, with looping vowels and over-precise consonants. She had an odd sense that he had already rehearsed in his head almost everything he said, in case he ever had an audience to use it on. ‘We’re no innocents. We filed a few patents. But in the end the corporate guys had no interest in screwing us over. Easier to buy us out; we were relatively cheap, in their terms, and we had expertise they needed.’ He grinned. ‘We Founders are all dollar millionaires. How cool is that?’

Sally couldn’t have cared less, and dismissed his bragging.

In among the gargantuan industrial facilities she saw sprawling residential blocks, bars, a hotel, a cinema-cum-theatre, a lot of casinos and gaming houses, and shadier-looking establishments she guessed might be strip joints or brothels. And there was one modest chapel, she saw, built of what looked like native oak, with a small graveyard set out within a low stone wall: a reminder that space travel was a dangerous occupation even here.

‘I can see you have plenty of chances to spend all those dollars.’

‘Well, that’s true. It’s something like an Old West mining town,’ Raup said. ‘Or maybe an oil rig. Or even early Hollywood, if you want a more glamorous example. Actually you have to watch your step these days.’

‘He means, there’s organized crime,’ Willis murmured. ‘Always drawn to places like this. There have already been a few murders, over gambling debts and the like. One way to do it is to just drop you into the Gap without a pressure suit, and no Stepper box. Sleeping with the stars, they call it. That’s why there’s such a security presence now: policing the criminal element, and watching out for saboteurs.’

Raup said, ‘But it’s still a cool place to be.’

Sally just dismissed that remark.

At the heart of the complex they walked down a kind of central mall lined with office blocks, brand new, concrete gleaming white and unstained. Raup led them to a low, flashy building marked with a bronze plaque: ROBERT A. HEINLEIN AUDITORIUM. There was a crowd at the doors and Raup had to produce passes to enable them to jump the line. He said apologetically, ‘We built this for Walter Cronkite-type news conferences. Our corporate masters insisted. Normally it’s deserted. But you’re in luck, Ms Linsay; the scuttlebutt is that the Martian rainstorms have cleared enough for the Envoy mission controllers to attempt a landing this very day. So it’s a good chance to show off to you what we’re doing here.’

Sally glanced at her father. ‘Rainstorms? On Mars?’

‘It isn’t our Mars,’ he said. ‘You’ll see.’

Raup led them into a central auditorium, with rows of benches before a lectern, the walls coated with big display screens. The place was full of chattering technicians and scientist types. For now the wall screens were blank, but smaller screens and tablets around the room showed grainy colour images being put through various enhancement processes. Sally glimpsed fragments of landscapes, grey-blue sky, rust-red ground.

‘Wow,’ Raup said, seeing the screen images, for once not sounding like he was simulating the emotions he expressed. ‘Looks like they did it, they landed the Envoy. The first time we made it, to this copy of Mars.’

‘Envoy?’

‘A series of unmanned space probes.’ Raup drew her attention to hard-copy images on the wall: trophy pictures of chunks of a planet, taken from space. ‘The first couple of Envoys to Mars were flybys, and these are the pictures we got. Today’s was the first actual landing, a necessary precursor to the manned missions that will follow. The very latest pictures, live from the Mars of the Gap!’

Willis snorted. ‘Yeah, but they’re getting the mix wrong. The sky is nowhere near that colour.’

Sally stared at her father. If these were the first landings on this Mars, how could he know that? But she’d long ago learned not to try to interrogate him.

Raup said, ‘You understand that the probe itself is really only a test article. For now we’re just proving the propulsion technology. With the Gap, you can do a lot. We’re hauling over nuclear rocket stages – inertial confinement fusion, if you’re familiar with the technology – and with those babies we’re getting to Mars in weeks, where it used to take you seven, eight, nine months depending on the opposition. . .’

Sally knew or cared nothing about nuclear rocketry, but the pictures caught her attention. One showed a disc, presumably the full globe of Mars imaged from space – but it wasn’t the Mars she remembered from decades of NASA pictures back on the Datum. This Mars was washed-out pink, with streaks of lacy cloud, and patches of steel grey that glinted in the sun: lakes, oceans, rivers. Liquid water, on Mars, visible from space. And there was green, the green of life.

‘I told you,’ Willis said. ‘This Mars is different.’

‘You understand you’re seeing the Mars of the Gap universe, the universe one step over from here,’ Raup said, back to his over-rehearsed way. ‘The images are radioed back to the Brick Moon, our station in the Gap. We have a clever system of packet-feeding the data stepwise to our facilities here . . . Our Mars is a frozen desert. This Mars, the Gap Mars, is something like Arizona, though at a higher altitude. The Envoys confirmed the higher atmospheric pressure. On this Mars you could walk around on the surface with nothing more than a facemask and sun cream.

‘In this particular launch window, it was unlucky for us that our twin Envoy landers arrived in the middle of the worst storm season we’ve seen since we started watching Gap Mars, oh, a decade or more back. Not dust storms – here you get rain, snow, hail, lightning. The controllers didn’t want to risk that maelstrom, and for weeks the orbiters’ cameras have sent back nothing but images of lightning flashes. But now the storms have settled out, and evidently the mission planners agreed to go for a descent attempt. We’re just waiting for the images to stabilize . . .’