‘Use the support unit.’ The boxy machine rolled up to the wall and stood there, patient and silent. ‘You could stand on it—’

‘Reach the lip of the well, and pull myself out. OK. But I could never lift your unit out.’

‘No need. It contains grappling hooks, cables – it’s actually been specifically designed to negotiate Hatches, among other environments.’

She smiled. ‘I suppose that makes sense.’ She dug rope out of her pack anyhow and began to attach it to her pressure suit and her pack, so she could haul the stuff out after herself later.

Earthshine said, ‘Once we establish where we are the unit will adapt itself appropriately. It has extensive self-repair and self-modification facilities. Various kinds of fabricator, for instance.’

‘A regular Swiss Army knife.’

He looked at her. ‘That’s an old reference.’

‘Something my father used to say, some relic of his own past. His boyhood on Earth, before the freezer lid closed on him.’ As you know very well, she thought.

Earthshine just turned away.

She crossed to the machine, set her hands on its upper surface, and hoisted herself up. ‘I feel stiff. Stiff and heavy. That’s what a few hours on Mars will do for you. Getting too old for this.’

‘You’ll toughen up,’ Earthshine said dismissively. ‘Excuse me if I take a short cut.’ He flickered out of existence, and reappeared over her head, standing on the lip of the pit, hands on hips, surveying his domain.

‘I bet you can’t see a damn thing.’

‘Not with my eyes and ears still stuck down that shaft, no. Nothing but the crudest extrapolation from the available information. The star in the sky. A blank landscape, a horizon appropriately positioned for a rocky world of a size that can be extrapolated from the gravity we experience.’

On top of the support unit, Beth unsteadily stood upright and reached up to take hold of the rim of the cylindrical pit. The substance of the Hatch structure was smooth under the skin of her hands, and, as always, felt oddly elusive, as if her hands were slipping sideways. The Kalinskis had tried to explain to her that a Hatch, to the best of anybody’s knowledge, wasn’t a material artefact at all but a structure of distorted spacetime, and that the sideways forces she felt were something like a tide, a secondary gravitational effect … None of that made it any easier to climb out of this hole, however.

‘The gravity, yes.’ With a lunge she pulled herself up, straightening her arms under her and lifting one leg over the lip of the pit. ‘Ninety-eight per cent of Earth’s. Right?’ Of course that was the value; she’d grown up knowing it. She got to her feet, panting a little; she really did feel out of condition.

Now from the pit came a sound like small crossbows being fired. She glanced down and saw that two hooks, supported by suckers, had fixed themselves to the rim of the pit. Fine cables laced down to the support unit, and with a whir of hidden winches, the unit began to rise up from the pit floor. So that was how it got about.

Leaving the unit to its business, Beth turned and looked around.

She was in a forest, surrounded by trees with stout trunks and big, sprawling leaves that caught the light streaming down from above. But there was plenty of open ground – there was no continuous canopy, evidently no permanent cover. The Hatch structure itself sat in a broad clearing, with saplings sprouting beside trunks like fallen pillars, trunks infested with what looked like lichen, mosses, fungi. All of this was tinged in shades of green, some of it drab, some of it more vivid, brilliant in the wan light of the star overhead. In one direction, she saw, the view was more open, revealing water glimmering in the light. What looked like stubby reeds pushed out of the water. And, by the water’s edge, a cluster of glistening forms stood, almost like huge mushrooms. ‘Stromatolites.’ She said the word aloud, letting it roll on her tongue. She remembered how hard it had been for her to learn that word as a little kid, and how confused she had been when her mother had told her that the name was wrong, really, that it had been taken from an Earth organism that was like the structures she saw around her but not quite, structures that grew in the water, but not on land …

All this was familiar. And yet, she thought, it was not.

The support unit laboured to haul itself out of the hole in the ground. As it made the last perilous step, and extended stubby caterpillar tracks to claw at the ground, Beth stood by, trying to think of ways she could help if the hefty unit started to topple back into the pit.

Earthshine, meanwhile, paid no attention. He stalked back and forth, impatiently. ‘Nothing here,’ he growled.

Beth frowned. ‘Nothing? Nothing but the trees. The undergrowth. The water over there, a lake maybe. Life—’

‘Just this damn Hatch unit, sitting on the ground. Look at it …’

It was like every other Hatch she’d ever seen, a square of smooth, greyish material with the circular lid raised up over the cylindrical shaft beneath. ‘Just like the Hatch on Mercury, the first I came out of with my mother and father and the Peacekeeper. Just like the first I walked into, on Per Ardua.’

‘But there’s nothing here. No buildings, no structures, no community – no people …’

She raised her face, closed her eyes in the light.

‘I know what you’re thinking,’ he snapped.

‘It’s not what I think. It’s what I feel. I grew up on Per Ardua. I know its air, its scents, the way its gravity pulls on my bones.’

‘You think this is Per Ardua. That that star up there is Proxima.’

‘What else could it be? Look around, Earthshine. You’ve never been here before but you’ve seen the records, I’m sure of that. You’ve seen the analysis the scientists did once we came back to the solar system, the data the UN teams returned later. Look at these stems, pushing out of the ground. Stems, the basis of all complex Per Arduan life, all the way up to the builders.’

‘You really think that’s Proxima?’ He was squinting up into the light, his supporting software casting perfectly formed shadows across his face. ‘Kind of bland-looking, don’t you think? Where are the stellar flares? Where are the starspots?’

That was a point, and, oddly, she hadn’t noticed it before. The star’s surface, seen through scrunched-up eyes, was smooth, almost featureless, marked by only a few patches of greyish mottling – not the map of restless stellar energies she’d grown up beneath, not the uneasy god that had inflicted particle storms and starspot winters on its hapless planets.

Planets, yes. She walked a few steps and turned around, looking up at the sky, which was a featureless bronze wash. Proxima had had more than one planet. In the permanent daylight of its star-facing hemisphere, the stars and planets had been forever invisible – all save one, a brilliant beacon … ‘There,’ she said, pointing at a spark of light unwavering in the sky. ‘Proxima e, the fifth planet. We called it the Pearl.’ She laughed. ‘Just where I left it.’

He walked around, growing increasingly angry. ‘You seem to be seeing the similarities and screening out the differences. Such as the life forms. These tree-like structures, the “stromatolites” – they are like the samples shown in images retrieved from Proxima c, from Per Ardua. But they aren’t identical, are they? And what about this?’ He pointed dramatically at a small clump of plants at his feet, with sprawling bright green leaves. ‘How does this fit in?’

She crouched down to see. No, this didn’t fit in with her memories of a childhood on Per Ardua at all, at least not of the wild country away from the farms she and her parents and the ColU had laboured to create. These leaves bore the green, not of Arduan life, but of Earth life, a brighter and more vivid colour born under a more energetic star. You’d never have found such things growing in the wild. She dug her fingers into the soil – it was rust brown, quite dry – and found a mass of small tubers. ‘These look like potatoes, or a distant relative.’