Proxima

by Stephen Baxter

  The hundred days’ journey began.

  At first, as they travelled out through the Hub-centred disc of human colonisation, the going was easy. They followed the best roads, and, surrounded by habitation, used as little of their own supplies as they could while supplements could be acquired.

  And they got plenty of help. Even when they reached the sparser band of farming townships well beyond the central zone, Yuri was surprised by the attention they attracted. There had been much interest in the expedition in the embryonic Per Arduan media, and as Founders Yuri and Liu were both familiar figures anyhow. In some places they were even applauded as they went through, or a little caravan of trucks and kids on Arduan-made pushbikes would follow them out of town. Yuri was surprised, yes, and pleased.

  Stef seemed indifferent; she was intent on micro-managing the expedition hour by hour. People weren’t the point, it seemed, to her, in any of her endeavours. And Liu, wary of attention, shielded his face from the cameras that were thrust against the rover windows.

  In those first few days they easily exceeded their target of two hundred kilometres a day. Even so it took a full seven days before they had rolled past the last of the sparse new townships, and Yuri was impressed how far out from the centre people had already come, in search, he supposed, of a place of their own, and a little peace, and dignity. And he imagined how the face of Per Ardua must look from space now, with a great spiderweb of lurid Earth green spinning out from the Hub, along the riverbanks, the new roads, even along the inward trails carved out by the Founders as they had limped their way from the shuttle drop points in to the centre, scattering topsoil and seed potatoes and earthly bugs behind them as they went.

  By the eighth day, however, there were no more metalled roads, or even tracks. They crossed mostly untravelled ground, and their maps, even of the day side, were too coarse to be relied on without caution. Stef and the ColU between them kept a running record of the ground they crossed, the features they encountered, for the benefit of future generations. And they started to drop markers every fifty kilometres or so, lightweight darts they would fire into a suitable rock or bluff, with short-range radio transmitters. These would serve as beacons so they could find their way back – or to mark their trail for any prospective rescue party, should they need it. Their overnight stops were brief. They collected water when they could, but they had no need to find other provisions. They didn’t even pitch a tent; there was plenty of room for the three of them to sleep easily in the rover.

  As for the landscapes they crossed, water was the key to life, as ever in this arid continent. Wherever they came across a river or a lake of some kind there would be the usual menagerie of stem beds and lichen streaks on the rocks, and various species of kite working the water, and, often, the builders with their middens and their nurseries, at work around the margins. And always there were the stromatolites, like tremendous sculptures scattered across the planet’s face by some vanished race of artists.

  Sometimes the ColU or Stef would request a stop, if they came across an unusual rock formation, or volcanic feature, or even a novel life form. And the ColU would engage local builder groups in puppet-dance conversation. It was remarkable, the ColU said, that the languages of widely scattered groups was so consistent, even out here; there was little regional variation, little dialect. More evidence of the great antiquity of the species and their culture, the ColU argued. On the other hand, as Liu pointed out, builders rarely had anything interesting to say.

  As the days piled up, Yuri began to feel numbed. They just rolled on across the timeless, bowl-like face of this giant continent, kilometre after kilometre. Feeling his age, comfortable in his padded couch in this air-conditioned truck, he sometimes wondered how the hell he and Mardina had ever managed that epic trek across the wilderness, baby and all, with the jilla builders.

  Around day twenty they came across the remains of an Ad Astra shuttle drop.

  The signs were unmistakable. They crossed the scorched track of a shuttle landing, the long straight line of fused ground still visible after all these years. They cut off their route and followed the track to the remains of a shabby camp, and the smashed relic of a ColU’s bubble dome, wrecked beyond repair – and, the ColU said, mercifully without consciousness. They searched sparse debris for any evidence of identity, of who might have been dropped here. But the settlers seemed to have been efficient in the reuse of their meagre equipment, and little was left behind. The explorers couldn’t even find graves, which was unusual for such a site.

  After a day, Liu summed it up. ‘I think it’s clear enough what happened here.’ He pointed at a sketch map of the site Stef had made on her slate. ‘There’s the lake bed. Dried up.’ It was a hollow littered by dead stems, and what looked like the ruin of a builder nursery; only native lichen and mosses survived here now. ‘No fancy migrating jilla here, eh, Yuri? So they left, thataway.’ These people had set off south, for reasons of their own, heading away from the substellar, maybe hoping to make it to the rim forest. The tracks could still be seen; they had marked the way with a few cairns. ‘Who knows where they are now? Or what became of them.’

  ‘Somebody will find out, some day,’ said Yuri grimly. ‘And will tell their families back on Earth, or wherever. Look, we’ve made our records. We’ll leave one of our markers in case we don’t make it back to the Hub. So this won’t be lost again. OK? Come on, let’s pack up and move on.’

  On they travelled. Day after day passed, marked only by a human sleep cycle still slaved to light-years-distant Earth – that and the slow descent of Proxima in the sky, towards the north-west horizon, away from the zenith it occupied as seen from the substellar Hub. The shadows that preceded their two vehicles grew steadily longer, and as the dwarf star’s light struggled through thicker layers of air it frequently looked reddened, Proxima’s spitting flares and mottling of spots more easily visible to the naked eye. The air grew colder too; soon they couldn’t leave the rover’s heated interior without extra layers of clothing.

  After more than forty days they reached a belt of rim forest.

  Here they rested a day to stretch their legs and explore, while the ColU set out along the edge of the forest to seek a way through. Neither Liu nor Stef had seen such a forest before, and they wandered, wide-eyed, through its dimly lit, cathedral-like spaces, the slim stem trunks reaching up to those broad, patient triple leaves above. And they marvelled at the immense kites of the canopy, and the ferocious scavengers competing for the slightest fall of nutrient into the almost aquatic gloom of the forest floor. For Yuri, all this brought back memories of his earliest days on Per Ardua, when he had explored the forest of the northern reaches, so similar to this place, with the likes of John Synge and Harry Thorne and Pearl Hanks and Abbey Brandenstein, all long dead.

  The ColU returned with news of a break in the band of forest, at a broad valley not far south of here. They returned to the rover and set off that way. The valley proved to be the relic of a glaciation, with a wide floor and steep walls. A river running from distant hills, substantial in itself, was dwarfed by the ice-cut valley across whose floor it meandered.

  They followed the cut through the forest band, which proved to be quite narrow; soon it thinned out, leaving only isolated stands of trees.

  In the more open landscape beyond the forest the driving was easy, along the gravel beds that lined the banks of the glacial valley. There were stem beds here, and kites flying, big, slow, ungainly beasts of a kind Yuri hadn’t seen before, and builders, slowly working on their middens and nursery bowers. The scene was bathed in the dim light of a lowering Proxima, with the faces of hills up ahead washed with a pinkish glow. Life here seemed sparse, tentative, starved as it was of energy. Yuri remembered in contrast the tremendous vegetable vigour of the Hub jungle at the substellar point.

  The valley steadily narrowed as they worked their way upstream, towards a range of hills that were soon no longer so distant. The river’s source turned out to be a
corrie, a huge scoop high up in a glaciated hillside.

  Long before they reached that point Stef guided the rover away from the river and towards a pass through the hills, and beyond the pass they descended onto a plain. The shadows of the hills behind them now stretched far ahead, but they could see more ranges of hills marching off into the distance, with ice-coated peaks that gleamed in the dimming Proxima light and glaciers striping their flanks.

  As they crossed the plain the ColU requested more stops. It took samples of the life forms it found in pools of permanent shadow, mostly slow-growing lichens in frosty patches feeding off a trickle of reflected light, protected from any motile scavengers by the very darkness that cradled them.

  Once the ColU, digging, found what it called a rare, ancient fossil bed, saved from volcanic obliteration by some accident of uplift, which contained traces of creatures like builders but much taller, each with three long multi-jointed stem legs. These were creatures built for migration, for speed, the ColU argued. Perhaps these were relics of a transitional age, while the planet’s spin was slowing, but before it became fully locked in its synchronised day-orbit cycle. In such times, the ColU speculated, there must have been creatures that had migrated continually, keeping up with the slow passage of Proxima across the sky. Perhaps these ancestral builders had been among that throng. They discussed this, made some records, moved away.

  They drove on, and on.

  Close to the fiftieth-day halfway mark, Proxima touched the horizon at last. Now, Yuri knew, they would descend into the shadow of the planet itself.

  In the days that followed Proxima descended with agonising slowness, its light ever more twilight red, its apparent shape distorted to obliquity by layers of the cool air, its lower rim sliced off by the horizon. Still there were a few stands of trees, an occasional kite flapping. But life here was dominated by the stromatolites. Some of them, huge, were oddly cup-shaped, their surfaces shaped like bowls to collect the drizzle of photons from the setting sun. Liu said they looked like natural radio antennae.

  They didn’t get to see Proxima set fully. Before that point they drove into weather, seemingly unending storms, rain showers, fog banks, even snow blizzards. Stef argued that as the warm air of the starlit side spilled over into the cool of the dark side, it must dump all its water vapour as clouds and precipitation. The whole terminator, right around the planet, must be a band of semi-permanent snow and rain and fog, and they saw no more of the sky for a while. But they did see streams, rivers, some ice-flecked, flowing down the cloud-shrouded flanks of hills and uplands: the water delivered by the air from the day side, flowing back the way it had come. Thus, Stef observed, cycles of energy and mass would be closed, all around the terminator, the dividing line between night and day.

  When they passed through the weather band and the sky cleared at last, the view was spectacular. Now they rolled through a sea of shadow that pooled at the feet of hills whose upper slopes were still in the light, shining above. Trees clung to these islands of illumination in the sky, with huge kites flapping lazily. Even further down the slopes life prospered, a secondary kind, pale, starved-looking creatures a little like crabs or segmented worms, all stem-based, which seemed to feed solely on the fall of dead leaves and other detritus from the higher ground.

  Yuri felt stiff from the travelling, eyes rheumy, perpetually tired. Yet he was discovering wonders. ‘This stuff is wasted on three old fogies like us.’

  The ColU asked for an extended halt. ‘Those summits are effectively islands. There could be unique biota up there, at least among the non-flyers, even the tree species. A whole array of unique ecosystems, in starlight islands all around the terminator.’

  ‘To be explored by somebody else,’ said Yuri gently. ‘We’ve got our own goals to achieve. Come on, ColU. I hoped you tested out your floodlights . . .’

  So they went on, rushing past marvel after marvel.

  They lost Proxima’s direct light at last. Now, under the cloudy skies that persisted near this terminator line, the only glow came from the pools of light cast by their own floods, and the rover’s brightly lit interior was a refuge from the dark.

  Stef and the ColU both kept a careful watch on the temperature outside; it was dropping, of course, but not dramatically quickly. Under thicker cloud it could even rise above freezing. ‘Thus proving the theory,’ said Stef, ‘that a thick atmosphere on a world like this is enough of a thermal blanket to transport sufficient heat around to the dark side to keep everything from freezing up.’

  ‘That and the fact that all the air didn’t freeze up in great bergs of solid oxygen and nitrogen on the far side a billon years ago,’ Liu said drily. ‘That and the fact that we are still breathing.’

  ‘But it’s always good to have observational confirmation.’

  As they pushed on the cloud cover broke up, quite abruptly, to reveal a star-crowded sky. The temperature plummeted, and frost gathered.

  During one rest stop Yuri bundled himself up in thermal underwear and padded coat and over-trousers, and went out with the others to look at the sky.

  ‘Funny thing,’ he said. ‘I’ve never seen much of the stars, one way or another. When I was a kid, before the cryo, the night sky of Earth was a wash-out. Full of space mirrors and other orbital clutter, even away from the glow of city lights and the smog. You could see the stars from Mars, but we weren’t let out of the domes. And then, here on Per Ardua, the sun never set at all.’

  ‘Drink it in, my friend,’ Liu said. ‘Drink it in. You can’t beat the Alpha suns, can you?’ A dazzling pair of diamonds, their light bright enough to cast shadows – bright enough, the ColU thought, to power some feeble photosynthesis.

  Stef, meanwhile, was staring east. ‘Look. Can you see that?’ It was a brilliant star, hanging low on the horizon.

  ‘I see it,’ murmured the ColU. ‘But a star of that magnitude does not feature in the constellation maps I have stored in my memory. A nova, perhaps?’

  ‘We’d have heard of that,’ Stef said. ‘I guess we’ll find out . . .’

  CHAPTER 76

  They drove on, over ground that was permanently frozen now. The ice was gritty and old, Stef pointed out; away from the terminator region, where the warm air spilled over into the dark and quickly dumped its vapour, fresh precipitation must be rare.

  Ten days past the terminator zone the ColU called a halt, on an otherwise unremarkable plain of ice. ‘We are no longer over dry land,’ it announced simply.

  ‘I can confirm that,’ Stef said quickly, inspecting ghostly radar images of a crumpled hidden surface beneath them. ‘This is the ocean, about where the Ad Astra maps indicated the shore should be. Just here it’s solid ice all the way to the ocean floor, which is no more than a dozen metres or so beneath us. Further out where the ocean is deeper we’re expecting liquid water under a crust of ice. The next landmass, and the antistellar, are thataway,’ she said, pointing. ‘The driving should be easy, but let’s take it carefully.’

  They drove on into the silent dark, the light of their floods splashing ahead. They adopted a new driving strategy now, out on the ice, for safety in these different conditions. The ColU and the rover drove not in a convoy but in parallel, with maybe a quarter of a kilometre between them. That way neither of them would fall into the same crevasse, at least, and they could better triangulate the position of any obstacles. The landscapes they had crossed, with all their intricate detail, had been replaced now by a smooth plain of ice. Cloud and mist were rare, and the brilliant, unwavering starlight hung over them. It was an eerie, featureless, timeless phase of the journey, Yuri thought. With barely a vibration from the rover’s smooth-running engine, with no sense of the ground transmitted through the vehicle’s sturdy suspension, for long periods it felt as if they weren’t moving at all.

  But then they began to see icebergs, like tremendous ships, bound fast in the frozen sea. ‘Evidently,’ the ColU said, ‘there are times when the ice melts enough for bergs to float
across the open surface. During exceptional volcanic warming pulses, perhaps. But then the sea refreezes, trapping the bergs . . .’

  Stef and the ColU seemed exhilarated by the confirmation of liquid water persisting under the ice. ‘It had to be there,’ Stef said. ‘There is probably a global system of deep ocean currents, transporting heat right around the planet. Part of the water cycle too, probably, restoring some of the mass lost to the unending rain at the terminator. Had to be there. But it’s ground truth; you don’t know for sure until you see it.’

  The workings of an invisible ocean were less than captivating for Yuri and Liu. In these changeless hours they dozed, watched the stars, and for the first time in his life Yuri learned to play chess.

  Stef, meanwhile, spent a lot of time watching that strange eastern star rise in the sky, tracking its motion using images captured by her slate. More brilliant than any star save the Alpha twins, it was rising too quickly, she said. ‘So not a star at all,’ she murmured. ‘Then what?’

  On the seventy-first day the ColU called for a cautious slowdown. ‘We are approaching landfall . . .’

  This was the single landmass they would encounter before the antistellar point, an Australia-size island continent that, according to the Ad Astra maps, lay between their terminator crossing point and the antistellar. They crept forward over the last of the sea pack ice, wary of its thinning, and then rolled up a shallow beach onto the land. Their floods picked out grimy ice beneath their treads, and low, eroded-looking hills, icebound, were shadows against the starry sky. They swung north and east, travelling in convoy once more.

  Stef said, ‘There has to be an ice cap in the middle of this continent, even if it doesn’t show up in the Ad Astra data set. So we’re going to keep to the coastal fringe. If we get stuck we can always duck out onto the sea ice again.’

  ‘Actually the air temperature is rising,’ reported the ColU blandly.