Phase Space

In that Houston sky outside, in the blizzard of possible worlds, there had been small Earths: wizened worlds that reminded her of Mars, with huge continents of glowering red rock. But some of them were huge, monster planets drowned in oceans that stretched from pole to pole. The Moons were different too. The smallest were just bare grey rock like Luna, but the largest were almost Earth-like, showing thick air and ice and the glint of ocean. There were even Earths with pairs of Moons, or triplets. One icebound Earth was surrounded by a glowing ring system, like Saturn's.

Kate had found it hard not to flinch; it was like being under a hail of gaudy cannonballs, as the alternate planets flickered in and out of existence in eerie, precise silence.

Sun-Drenched

Bado crawls backwards out of the Lunar Module.

When he gets to the ladder's top rung, Bado takes hold of the landrails and pulls himself upright. The pressurized suit seems to resist every movement; he even has trouble closing his gloved fingers around the rails, and his fingers are sore already.

He can see the small TV camera which Slade deployed to film his own egress. The camera sits on its stowage tray, on the side of the LM's descent stage. It peers at him silently.

He drops down the last three feet, and lands on the foil-covered footpad. A little grey dust splashes up around his feet.

Bado holds onto the ladder with his right hand and places his left boot on the regolith. Then he steps off with his right foot, and lets go of the LM.

And there he is, standing on the Moon.

He hears the hum of pumps and fans in the backpack, feels the soft breeze of oxygen across his face.

Slade is waiting with his camera. 'Okay, turn around and give me a big smile. Atta boy. You look great. Welcome to the Moon.' Bado sees how Slade's light blue soles and lower legs are already stained dark grey by lunar dust. Bado can't see Slade's face, behind his reflective golden sun-visor.

Bado takes a step. The dust seems to crunch under his weight, like a covering of snow. The LM is standing in a broad, shallow crater. There are craters everywhere, ranging from several yards to a thumbnail width, the low sunlight deepening their shadows.

Bado feels elated. In spite of everything, in spite of what is to come, he's walking on the Moon. 'Bado. Look up.'

'Huh?' Bado has to tip back on his heels to do it.

The sky above is black, empty of stars; his pupils are closed up by the dazzle of the sun, and the reflection of the pale-brown lunar surface. But he can see the Earth, a fat crescent.

And there, crossing the zenith, is a single, brilliant, unwinking star. It is Apollo, in lunar orbit.

A cloud of debris surrounds the craft, visible even from here, a disk as big as a dime held at arm's length.

Slade touches his shoulder. 'Come on, boy,' Slade says gently. 'We've got work to do.'

After the EVA, back in the LM, Bado has to ask Slade to help him take off his gloves. His exposed hands are revealed to be almost black, they are so bruised.

They get out of their suits. Bado climbs into a storage bag, to catch the rain of sooty Moondust, and strips down to his long Johns.

After a meal, they sling their Beta-cloth hammocks across the LM's cramped cabin. Bado climbs into his hammock. Without his suit, and in the Moon's weak gravity, he weighs only twenty-five pounds or so; the hammock is like a feather bed. Slade, above him, barely makes a dint in his hammock.

It is dark. They have pulled blinds down over the triangular windows. Bado is inside a cosy little tent on the Moon, with the warmth of Slade's body above him, and with the thumps and whirs of the LM's systems around him.

But he can't sleep.

In his mind's eye, Al Pond dies again.

It is before the landing. Just after separation, of LM and CSM, in lunar orbit.

Inside the Lunar Module, Bado and Slade stand side by side, strapped in their cable harnesses. In front of Bado's face is a small triangular window. It is marked with the spidery reticles that will guide them to landfall on the Moon. Through the window Bado can see the CSM: the cylindrical Service Module, with its big bell of a propulsion system nozzle stuck on the back, and the squat cone of the Command Module on the top.

Drenched in sunlight, Apollo is like a silvery toy, set against the Moon's soft tans.

Bado can picture Al Pond, who they have left alone in the Command Module.

Pond calls over, 'You guys take it easy down there.'

'We will,' says Slade. 'And we'll clean up before we come back. We don't want to get Moondust all over your nice clean ship.' It is the kind of iffy thing Slade is prone to saying, Bado thinks.

'You better not,' calls Pond. '… Hey. I got an odd smell in here.'

Bado and Slade glance at each other, within their bubble helmets. Slade says, 'What kind of smell?'

'Not unpleasant. Sharp. Like autumn leaves after an early frost. You know?'

That could be smoke, Bado thinks.

T got a couple of lights on the ECU control panel,' Pond calls now. 'I'll go take a look.' His voice gets muffled. 'Okay. I got the ECU panel.' This is a small, sharp-edged metal panel, just underneath the commander's couch; lithium hydroxide air-scrub canisters are stored in there. 'I can't see nothing. But that smell is strong. Ow.'

'What?'

'The metal handle. I burned my hand. Okay. I got it open. About a foot length of the cabling in here is just a charred mess. Blackened. And there are bits of melted insulation floating around the compartment. Oh. I can see flames,' Pond calls distantly. 'But they're almost invisible. It's kind of like a blue ball, with yellow flashes at the edge, where the flame is eating away at the cabling. Man, it's beautiful.'

Fire in zero gravity, fed only by diffusion, is efficient; there is little soot, little smoke. Hard to detect, even to see or smell.

There are miles of wires and cables and pipes behind the walls of the Command Module's pressurized cabin. The fire could have got anywhere, Bado realizes.

Solenoids rattle. Slade is firing the LM's reaction thrusters.

Bado asks, 'What are you doing?'

'Backing off.'

The LM responds crisply.

T fetched an extinguisher,' Pond calls. 'Woah.'

'What?'

T got me a ball of flame. Maybe a foot across. It just came gushing out of the hatchway. It's a soft blue. It's floating there.' The two craft pass into the shadow of the Moon. Pond has fallen quiet.

Bado leans into his window. The silvery tent of the Command Module looks perfect, gleaming, as it recedes.

There is a small docking window, set in the nose of the CSM. Through this window Bado sees a bright light, like a star.

A human hand beats against the glass of the docking window.

The Command Module's hull bursts, abruptly, silently. There is a single sheet of flame, blossoming around the hull. Then black gas billows out, condensing to sparkling ice in an instant.

The silver hull is left crumpled, stained black.

Bado keeps doing mental sums, figuring their remaining consumables.

He looks at his watch. They are already half-way through their nine-hour sleep period.

He thinks about the mission. They have christened the landing site Fay Crater, after Bado's wife. And their main objective for the flight is another crater a few hundred yards to the west that they've named after Bado's daughter, Pam. Surveyor 8, an unmanned robot probe, set down in Pam Crater a couple of years ago; the astronauts are here to sample it.

Now they are here, Bado thinks bleakly, those names don't seem such a smart idea. Bado doesn't want to think about Fay and the kids.

Slade, of course, doesn't have a family, and offered no names at the mission planning sessions.

One of the LM's cooling pumps changes pitch with a bang.

Slade whispers from above. 'Bado. You awake, man?'

Bado snaps back, 'I am now.'

'That goddamn suit was killing me,' Slade says.

'How so?'

'I think the leg is too short. The left leg. Every time I walked it pulled down on my shoulder like a ton weight.'

Bado laughs. 'We'll have to fix it before the next EVA.'

'Yeah. Hey, Bado.'

'What?'

'You ever read any science fiction?' 'What science fiction?'

'Think about what we got here. A dead world. And two people, stranded on it.' 'So what?'

'Maybe we don't have to just die. Maybe we can populate the Moon.' He laughs. 'Adam and Eve on the Moon, that's us.' Bado feels anger and fear. Again it's the kind of iffy thing Slade

is always saying. He wants to lash out. 'Oh, fuck you, Slade.'

Slade sighs. Bado can see him shifting in his hammock. 'You know, you fit right in with this job, Bado. We're not supposed to be humans, are we? And I truly believe that you're more afraid that I'm going to grab your ass than of what happens when the Goddamn oh-two runs out, in a couple of days from now. Listen, Bado. I'm cold, man.'

'Fuck you.'

Slade's voice rises, brittle. 'We're two human beings, Bado, stuck here in this goddamn tin-foil box on the Moon, and we're going to die. I'm cold and I'm scared. Al Pond had to die alone -'

'Fuck you, Slade.'

Slade laughs. 'Ah, the hell with you,' he says eventually. He turns over in his hammock, swings his legs over, and floats to the floor. He sits on the ascent engine cover. His face is in shadow as he looks in at Bado. 'So. You going to help me with this leg, or what?'

Bado gets out of his own hammock and folds it away. Slade hauls on the layers of his pressure suit. Bado kneels down in front of Slade and starts unpicking the cords laced around Slade's calf. To adjust the suit's fitting, he will have to unknot every cord, loosen it a little, and retie it.

It takes about an hour. They don't say anything to each other.

They prepare for their second, final EVA. Their traverse is a misshapen circle which will take them around several craters. They will follow the timeline in the spiral-bound checklists on their cuffs.

They climb easily out of Fay Crater. They both carry tool pallets, containing their TV camera, rock hammers and core tubes, Baggies for Moon rocks.

Bado has worked out an effective way to move. It is more of a giraffe-lope than a run. It is like bounding across a stream; he is suspended at the peak of each step. And every time he lands a little spray of dust particles sails off in perfect arcs, like tiny golf balls.

On the hoof, Bado tries to give the guys on the ground a little field geology. 'Everything's covered in dust. It's all kind of reduced, you can see only the faintest of shadings. But here I can see a bigger rock, the size of a football maybe and about that shape. Zap pits on every side, and I can see green and white crystals sticking out of it. Feldspar, maybe, or olivine…'

Nobody is going to come up here to collect the samples they are carefully assembling. Not in a hundred years. But the geology back-room guys will get something out of his descriptions.

Slade is whistling as he runs. He says, 'Up one crater and over another. I feel like a kid again. Like I'm ten years old. All that weight - it's just gone. What do you think, huh, Bado? Now we're out and moving again, maybe this isn't such a bad deal. Maybe a day on the Moon is worth a hundred on Earth.'

They take a break.

Bado looks back east, the way they have come. He can see the big, shallow dip in the land that is Fay Crater, with the LM resting at its centre like a toy in the palm of some huge hand. Two sets of footsteps come climbing up out of Fay towards them, like footsteps on a beach after a tide.

His mouth is dry as sand; he'd give an awful lot for an ice-cool glass of water, right here and now.

'Adam and Eve, huh,' Slade says now.

'What?'

'Maybe it will work out that way after all. We're changing the Moon, just by being here. We're three hundred pounds of organic stuff, dropped on the Moon, and crawling with life: gut bacteria, and cold viruses, and -'

'What are you saying?'

'Maybe there will be enough raw material to let life get some kind of a grip here. When we've gone. Life survives in a lot of inhospitable places, back home. Volcano mouths, and the ocean deeps.'

'Adam and Eve,' Bado says. 'I choose Adam.' Slade laughs. 'You got it, man.'

They lope on, to the west. Bado can hear Slade's breath, loud in his ears.

Bado thinks about Slade.

Everyone in the astronaut office knows about Slade. And Bado came in for some joshing when the crew roster for this flight was announced. Three days on the Moon? Better make sure you take your K-Y jelly, man.

Bado defended Slade. None of that stuff mattered a damn to his piloting abilities.

Anyhow, outside the Agency Slade is painted as the bachelor boy. He has even put up with getting his photograph taken with girls on his arm.

Noone knows, the Agency assured Bado. Noone will think anything questionable concerning you.

Slade stops. He says, 'Hey. We're here.' He points. Bado looks up.

He has, he realizes, reached the rim of Pam Crater. In fact he is standing on top of its dune-like, eroded wall. And there, planted in the crater's centre, is the Surveyor. It is less than a hundred yards from him. It is a squat, three-legged frame, bristling with fuel tanks, batteries, antennae and sensors, and its white paint has turned tan.

Bado sets the TV camera on its stand. Slade hops down into Pam Crater, spraying lunar dust ahead of him.

Slade takes a pair of cutting shears from his tool carrier, gets hold of the Surveyor's TV camera, and starts to chop through the camera's support struts and cables. 'Just a couple of tubes,' he says. 'Then that baby's mine.'

The camera comes loose, and Slade grips it in his gloves. He whoops.

'Outstanding,' Bado says. He knows that for Slade, getting to the Surveyor, grabbing a few pieces of it, is the finish line for the mission.

Slade lopes out of the crater. Bado watches his partner. Slade looks like a human-shaped beach ball, his suit brilliant white, bouncing happily over the beach-like surface of the Moon.

Bado thinks of a human hand, pressing silently against the window of a burning capsule.

He is experiencing emotions he doesn't want to label.

'Hey, Slade,' Bado says.

'What?'

'Come here, man.'

Slade obediently floats over to him, and waits. He has one glove up over his chest, obscuring the tubes which connect his backpack to his oxygen and water inlets. His white oversuit is covered in dust splashes.

Carefully, clumsily, Bado pushes up Slade's gold sun visor. Inside he can see Slade's face, with its four-day growth of beard. He touches Slade's suit, brushing dust off the umbilical tubes. Patiently, Slade submits to this grooming.

Then Bado gets hold of Slade's shoulders with his pressurized gloves. He pulls Slade against his chest. Slade hops forward, into his embrace. Bado puts his arm over the Stars and Stripes on

Slade's left shoulder, but he can't get his arms all the way around his partner.

Their faceplates touch. Slade grins, and when he speaks Bado can hear his voice, like an echo of the radio, transmitted directly through their bubble helmets. 'Get you,' Slade says softly. 'Aren't you afraid I'm going to make a grab for your dick?'

'I figure I'm safe locked up in this suit.'

Slade laughs.

For a while they stay together, like two embracing balloons, on the surface of the Moon. They break.

The TV camera sits on its tripod, its black lens fixed on them. Bado takes a geology hammer and smashes the camera off its stand.

Bado stands harnessed in his place beside Slade. In his grimy pressure suit he feels bulky, awkward.

Slade says, 'Ascent propulsion system propellant tanks pressurized.'

'Roger.'

'Ascent feeds are open, shut-offs are closed.'

The capcom calls up. 'Everything looks good. We want the rendezvous radar mode switch in LGC just as it is on surface fifty-nine… We assume the steerable is in track mode auto.'

Bado replies, 'Stop, push-button reset, abort to abort stage reset.'

Slade pushes his buttons. 'Reset.' He grins at Bado.

The guys on the ground are playing their part well, Bado thinks. So far it is all being played straight-faced, as they work together through the comforting rituals of the checklists.

The Agency must have decided that the crew has finally gone crazy. Bado wonders how much of this will ever become public.

Looking at the small, square instrument panel in front of him, Bado can see that the ascent stage is powered up now, no longer drawing any juice from the lower-stage's batteries. The ascent stage is preparing to become an independent spacecraft for the first time. He feels obscurely sorry for it. It isn't going to fly any more than he is.

'One minute,' the capcom says.

'Got the steering in the abort guidance,' Slade says.

Bado arms the ignition. 'Okay, master arm on.'

'Rog.'

'You're go, Apollo,' says the capcom.

'Clear the runway.' Slade turns to Bado. 'You sure you want to do this?'

I Actually, Bado is scared as hell. He really, really doesn't want to die.

'Adam and Eve?' he asks.

'Adam and Eve. This is the best way, man. A chance to leave something behind.'

Bado makes himself grin. 'Then do it, you fairy.'

Slade nods, inside his bubble helmet. 'Okay. At five seconds I'm going to hit ABORT STAGE and ENGINE ARM. And you'll hit PROCEED.'

'Roger,' says Bado. 'I'll tell you how I'd think of you, man.' Slade looks at him again.

'Out there,' Bado says. 'Floating across the face of the Moon, in all that sunlight. That's how I'd remember you.'

Slade nods. He looks at his instruments. 'Here we go. Nine. Eight. Seven.'

The computer display in front of Bado flashes a '99', a request to proceed.

Slade closes the master firing arm. 'Engine arm ascent.'

Bado has been through enough sims of this sequence. In a moment there should be a loud bang, a rattle around the floor of the cabin: pyrotechnic guillotines, blowing away the nuts, bolts, wires and water hoses connecting the upper and lower stages of the LM.

But they have disabled the guillotines. Bado presses the PROCEED button.

The cabin starts to rattle. The ascent stage engine has ignited, but its engine bell is still buried within the guts of the LM's descent stage.

The over-pressure builds up quickly. Slade says, ‘I think -' But there is no more time.

The ascent stage bursts open, like an aluminium egg, there on the surface of the Moon. Sunlight drenches Bado's face.

Martian Autumn

J will tell the story much as I set it out in my journal at the time. Old-fashioned, I know. But I can't think of any better way to tell how it happened to me.

If there is anybody to read it.

Bob ran one last check of his skinsuit. He did this without thinking, an ingrained habit for a fourteen-year-old born on Mars. Then, following Lyall, he let the lock run through its cycle, and he stepped out of the tractor and onto Martian dirt.

This was Isidis Planitia, a great basin that straddled Mars's northern plains and ancient southern highlands. It was late afternoon, a still day at the start of the long, languid Martian autumn. Everything was a cruddy red-brown: the dirty sky, the lines of shallow dunes lapping against the walls of an enclosing crater.

A cloud of camera fireflies hovered around his head. The moment was newsworthy, Mars's youngest resident visiting the oldest. Bob ignored the flies. They had followed him around all his life.

Meg Lyall was standing with her arms spread wide, as if crucified. She turned around and around, with the creaky, uncertain motions of great age, enjoying Mars.

Bob stood there, hideously embarrassed.

She said, 'You want to know the best thing about modern Mars? Skinsuits.' She flexed her hand, watching the fabric crumple and stretch, waves of colour crossing its surface. 'Back in '2.9 we had to lock ourselves up in great clunky lobster suits, all hard shells and padding, so heavy you could barely take a step. Now it's like we're not wearing anything at all.'

'Not really.'

She looked up at him, her rheumy eyes Earth-blue. 'No. You're right. It's not really like walking over a grassy field, out in the open air, is it? Which is what you think you'll be doing in six months' time.' She looked up at Earth's bright glint. 'Sixty years after the Reboot, Earth is a world of fortresses. Even the grass is under guard. But maybe they'll let you walk on it even so. After all, you're famous!'

Resentment sparked easily, as it always did. 'You won't put me off going.'

'Oh, no.' She seemed shocked at the suggestion. 'That isn't it at all. You have to go. It's very important. There may be nothing more important. You'll see. Walk with me.'

He couldn't refuse. But he wouldn't let her hold his hand.

April 2008

Tricester is in Oxfordshire, England. It is a strange place, I suppose: both old and new, an ancient leafy village in the shadow of a huge particle accelerator facility called Corwell, a giant circular ridge of green landscaping. It is a place crowded with history.

My name is Marshall Reid, by the way. I am a science teacher at the village school.

Here's how it begins for me.

On a bright spring afternoon I lead a field trip of eleven schoolchildren to the Corwell plant. As we troop past the anonymous buildings there is an emergency, some failure of containment, and a blue flash overwhelms us all. I am dazzled but unhurt. Some of the children are still, silent, as if distracted, others very frightened. They all seem unharmed.

There are predictable fears of a radiation leak. The guides quickly herd us into a holding area.

Miranda Stewart is called in, and introduced to us. She is Emergency Planning Officer for the region, the local authority official in nominal charge of such operations, supposedly coordinating the various emergency services. She is 50-ish, a Geordie, a former soldier. I like her immediately; she is a reassuring presence.

But Stewart is overwhelmed by the techs and suits and experts from the environment ministry. Scientists in protection gear crawl scarily over the site with Geiger counters.

We teachers and pupils are held in the middle of all this, sitting

in our neat rows, surrounded by officials and police and medics, our mobile phones besieged by anxious parents. We are all bewildered and scared.

Reluctantly Stewart concedes that the village should be cordoned off, proper tests run on the inhabitants and the local crops, and so on. But no alarm will be raised; there will be a cover story about a chemical leak.

The police set up blocks around the plant and village. There is press attention, and Green protesters quickly appear at the barriers. Emma, my wife, encounters this perimeter, returning from work in London.

Emma, at 31 a little younger than me, is a PR consultant. She misses life in the capital. Emma is seven-months pregnant. To her, the Corwell incident is the final straw; this is not a safe place to raise a kid. Later that day we argue again about moving back to London. But I am devoted to my job, and loyal to the kids. The argument is inconclusive, as usual.

Meanwhile, at the plant (so I learn later), the technicians are finding no signs of radiation damage. But one technician, checking surrounding foliage, finds a nest of mice - a nest without babies.

I have the feeling this is only the start of something larger. Hence my decision to keep this journal.

When Bob looked back, he saw that the tractor had already sunk behind Mars's close horizon. He had no idea where they were going. He wasn't enjoying the oily feel of his suit's smart material as it slithered over his skin, seeking to equalize temperature and pressure over his body. It was like being held in a huge moist hand.

He'd only stepped on the raw surface of Mars a dozen times in his life. It was a frozen desert - what was there to see? He had spent all his life rattling around in the cramped corridors of Mangala or Ares or Hellas, surrounded by walls painted the glowing colours of Earth, purple and blue and green.

Earth! He could see it now, a blue-white evening star just rising, the only colour in this whole rust-ridden landscape - Earth, where he had dreamed of escaping even before he had realized that he was a freak.

He was the youngest child on Mars: the last to be born, as colonists abandoned by Earth dutifully shut down their lives. A

little later he had been orphaned, making him even more of a

He owed Mars nothing. He didn't fit. Everybody stared at him, pitying. Well, another week and he was out of here: the only evacuee Earth would allow.

But first he had to get through this gruesome ritual of a visit with Meg Lyall.

On she talked.

T guess you're used to the fireflies. Surely they are going to watch you all the way home. Just like when I rode the Ares out here, back in 202.9…' More old-woman reminiscing, he thought gloomily. 'There we were in our big ugly hab module, and we were surrounded by drifting cams the whole way out. At first I figured people were watching to see us screw, or take a dump, or fight. But it turned out the highest ratings were for ordinary times, when we were just working calmly, making our meals, sleeping. Like watching fish in a tank. But you've never seen a fish. Maybe even then people were too isolated. Now it's a lot worse, of course. But we're social animals; we need people around us… What do you think?'

'I think you ought to tell me where we're going.'

She stopped and turned, breathing hard, to face him. 'Why, we're already there. Don't you know your history?'

She led him over a shallow rise. And there, under a low translucent dome only thinly coated with Martian dust, sat the Beagle

May 2008

After a couple of weeks the cordon has been lifted. But technicians still patrol the area with their anonymous instruments, and the children and I are subject to ongoing medical checks.

I have tried to protect the children. But there is media attention: unwelcome headlines, cartoons of huge-brained kids glowing in the dark. I am angry, of course. My pupils have already been betrayed by the authorities who should protect them, and now they are depicted as freaks.

The school's pet rabbits have produced no young.

Paul Merrick has shown up, rucksack on his back, looking for a place to stay.

Merrick, 40-ish, is a Jeff Goldblum-lookalike American environmental scientist. He has become something of a maverick, with

controversial theories about holistic aspects of the environment. At college he taught Emma. And they had a relationship.

Now Emma has called him in; she knew Merrick would be intrigued by the accident and she wants to know his views.

I am not pleased to see this ghost from Emma's past.

Merrick and Emma do some unauthorized exploration of Corwell. I suspect Emma, now on maternity leave, wants something to take her mind off the approaching upheaval in her own life: a last youthful adventure.

They find birds' nests without eggs.

They are discovered by Emergency Planning Officer Stewart. She tries to throw them out, and blusters about this being a routine clean-up operation. But Merrick asks probing questions about the instances of sterility, which are already the talk of the village. Stewart points out that the sheep and cattle in neighbouring farms are giving birth as usual. Merrick says this may be because of different gestation periods; if some kind of sterilization effect has occurred, short-gestation creatures would be the first to be affected. Stewart - not a scientist and, I suspect, not kept fully in the know by the ministry types - is disturbed, but is sure there is a 'rational' explanation.

When she tells me this part of the story, Emma rubs her bump thoughtfully.

Merrick, Emma and I talk it over in the pub. To my discomfiture, Emma tells Merrick too much personal stuff: that her conception was an accident while we were on holiday, for example. Merrick, though restrained, is obviously jealous.

Merrick says predictable things. That it is as if we are running a huge, uncontrolled experiment on nature. That England is a small and crowded place, where nature has been saturated by everything we could throw at her - electromagnetic radiation, pesticides, genetic modification, acid rain and now even exotic radiation from the nuclear accident. That we have stressed natural systems beyond their limits. That something strange is happening here as a result - but who knows what?

Meaningless talk. I resolve to focus on the immediate issues before me, on the people I care for, Emma and the field-trip kids.

The Beagle wasn't much to look at. It was just a pie-dish pod that had bounced down from out of the sky under a system of para-

chutes and gasbags. Disc-shaped solar-cell panels had unfolded over the dirt, and a wand of sensors had stuck up like a periscope. And that was it. When people had come looking for it five decades after its landing, Beagle had been all but buried by windblown toxic dust.

And yet, by baking its tiny soil samples and sniffing the thin air, Beagle 2 had discovered life on Mars.

'It was the atmospheric sensor that did it,' Lyall said. 'The probe could directly examine only one little patch of landscape, but a Martian cow could fart anywhere on Mars and Beagle could sense the methane. It took another thirty years before anybody had a sample they could hold in their hand, but Beagle proved it was here to be found.'

Even before Lyall and her crew had left Earth, the findings of unmanned probes had already shattered many ancient dreams of Mars. There were no canal builders, no lusty princesses, no wistful golden-eyed poets, no leathery lung-plants. For a time, Mars had been thought to be dead altogether.

But then a meteorite, a fossil-laden scrap of Mars brought to Earth by cosmic chance, had changed all that.

Young Mars and Earth, billions of years ago, had been like sisters: both warm, both glistening with shallow oceans and ponds. And both had harboured life - sister life, as it turned out, spawned on one world or the other and blown across space on the meteorite wind.

Lyall turned around, letting her gloved fingertips trace out the line of the crater walls. ‘I don't think you can imagine how strange this scenery is to me, still. To see a crater like this with water features in it: gully networks and dried river beds and the rippling beaches of ancient lakes ... A crater punched in rock that formed at the bottom of a sea, a crater that later got flooded, over and over. When I was your age, I'd have given anything to be transported here, to stand where you are standing - to know what I know now.' Bob thought she behaved as if she had just stepped down out of that creaky old spaceship of hers.

Mars had been too small. It could not hold onto the gases its volcanoes vented, and without tectonic recycling the atmosphere became locked in carbonate rocks. The air thinned, the oceans and land froze, and the harsh sunlight destroyed the water.

And yet life persisted.

'Slime,' Bob said. 'Life on Mars is pond scum, kilometres down.'

Lyall glared, as if he'd insulted her personally. 'Not pond scum. Biofilms. Martian life is not primitive. It is the result of four billion years of evolution - a different evolution. The anaerobic life forms organize themselves, working together, one living off the output of another. Life on Mars is all about cooperation. Some say that the whole Martian biota, stuck down in those deep thermal vents, is nothing but one vast community…'

'Sure. But so what? You can't eat it. It doesn't do anything.'

Lyall struggled to remain serious, then a grin cracked her leathery face. 'Okay. I felt the same as you, even though I was forty years old before I got here. Once we got through the first phase surface op I made it my mission to find something more.'

'More?'

'More than a damn microbe. Something with a backbone and a brain. Something like me.'

June 2008

Frogs in the school pond have produced spawn, but no tadpoles.

As rumours spread of the sterilities, the children remain the focus of unwelcome attention. Some of them are showing signs of stress - strange paintings and stories, odd games in the playground - they are becoming withdrawn, turning to each other for comfort.

They are just victims of the same hyper-technological accident which apparently triggered the sterility problems. But it is as if the children are being transformed into witches, in some monstrous mass mind. Absurd, paradoxical, frightening.

Meanwhile the ministry scientists are considering pulling out. Their tests have proved inconclusive.

Merrick argues against this. He says that something subtle and strange is unfolding here, which we must study. He walks Stewart, Emma and me through a tree-of-life evolution wall chart; the sterility effects are working their way 'down' the tree, from younger and more complex forms of life, like mammals, to the older. He predicts that reptiles will be the next animal group to show symptoms.

Stewart sticks to her chain of command, determined to keep control and minimize disorder and panic.

But now a personal crisis looms for us. Emma has gone into labour. A doctor and midwife attend.

Merrick, typically, uses the event to gather more data. He asks distracting questions, about instances of human conception in the

village since the accident. The midwife repeats a few rumours.

And meanwhile there are more stories of empty nests, vacant ponds, all over this scrap of ancient English countryside.

She had sent Bob the letter: a genuine letter, written by hand on flimsy sheets of plastic-sealed paper. Bob didn't understand the half of it. But he knew it was about the Reboot, the origin of Earth's disaster.

'I never knew him,' she said. 'Reid, I mean. He was just some English guy. Dead now, I guess. I don't even know why he sent me the letter. We were first on Mars; we got mails from all over. Maybe he saw a bond between us. He was there at the beginning of a new world, as was I.'

'Doctor Lyall -'

She laid her hand on his shoulder - softly, but her fingers were strong, like claws. 'Indulge me a little more. It's important. Believe me.'

She took a few steps away from the memorialized Beagle, and scuffed at ruddy Martian dirt with her toe. 'I learned my fossil hunting before I left Earth. I worked out in the desert heartlands of Kenya. That's in Africa. You've heard of Africa? You know, people have lived in that area for two million years or more. But even there you don't find bones just sticking out of the ground. You have to be systematic. You have to know where to look and how to look.

'The landscape of Mars is billions of years older than Africa. Everything is worn to dust. Fossil-hunting here is unimaginably harder.' She pointed to the distant crater walls. 'But not impossible. I looked in craters like this, at exposed layers of sedimentary rock.'

Bob felt a remote curiosity stir. 'And you found something.'

Lyall smiled. 'It took years.' From a pocket in her suit she dug out a scrap of rock, embedded in a disc of clear plastic. She handed it to Bob.

He turned it over and over. It was like a paperweight. Except for the fact that it contained two bands of shading, divided by a neat, sharp line, it looked like every other rock on Mars.

He was obscurely disappointed. 'I can't see anything.'

'The evidence is microscopic. This is only a show sample anyhow. But they were here, Bob: multicellular life, complex life, a whole community. There seems to have been an evolutionary

explosion like Earth's pre-Cambrian, buried in Mars's deep past - much earlier than anything comparable on Earth. They lived in the oceans. There were squat bottom feeders, and sleek-shelled swimmers that seem to have been functionally equivalent to fish -'

'Why doesn't everybody know about this?'

'Because we are still trying to figure out how they all died.'

He shrugged. 'What is there to figure? Mars dried out and froze.'

'But the extinction was sudden,' she said. She pointed to the line between the different-coloured layers in the rock. 'You find rocks like this on Earth. The lines mark places in the geological record where there have been great extinction events. Below, life. Above, no life - or at any rate, a different life, a sparser life.'

'Like the dinosaurs.'

She nodded approvingly. 'Yes. These are Mars's dinosaurs, Bob. But it wasn't a comet that killed them. It wasn't the freeze - not directly; it happened much too rapidly for that.'

Then Bob saw it; it was as if the ruddy landscape swivelled around the bit of rock. 'It was a Reboot.'

'Yes,' she said.

'Just like Earth.'

'Just like Earth.'

July 2008

Now, Merrick has found, even insects are failing to reproduce, and on the farms crops are failing.

This unfolding environmental disaster is of course impossible to conceal. The cordon is back. Government officials, scientists and the press are crawling over the area. There is a news blackout on the school and heavy security - 'for the children's protection'. I am glad Miranda Stewart is still involved, trying to maintain decent conditions for the children, responding to my requests for normality.

But the children have been isolated. Once more they are subject to scrutiny and endless tests from doctors, social workers, educationalists, psychologists, other scientists. These 'experts' find nothing, of course. I see it as all part of the absurd witch-hunt.

The childrens' parents are agitated, frightened, angry. 'We don't want our child to be special. Why us?' Some are threatening to sue me or the government. But the children have not actually been injured. There is nothing I can say to reassure them.

Joel is one of the field-trip kids. Through him I learn that his family, of farmers, have been badly affected. They blame the government, the kids. Even Joel himself, says the poor child. I .wonder what is happening in his home, away from official eyes.

I am staying with the kids as much as I can. But my situation is difficult. I am delighted with our baby boy, and I think we are both secretly relieved that he is 'normal'. But Emma is scared and thinks we should be planning to get as far from here as possible. My conflict of loyalties deepens.

'When the desiccation came, evolution slowed to a crawl. Life was forced to be thrifty, to evolve towards simplicity, robustness and cooperation. Any fancy multicellular design became a liability. Great communities emerged with a new kind of distributed complexity, with simple, interchangeable components…' 'Instead of people, slime.'

'You got it. But it had to happen fast. On an evolutionary timescale anyhow… Look, I can't tell this story right. There is nothing conscious about the direction of evolution, nothing purposeful. But there was something in the genes, something that found itself activated when the conditions were right, when the stress got too great. Something that shut down what could no longer survive the desiccation.'

'Something?'

'We think we understand the mechanism,' Lyall said darkly. 'Bob, your DNA isn't a seamless piece of genetic machinery. Your genes contain endogenous retroviruses - ERVs.'

'Retroviruses - like HIV?'

'That's right. ERVs were once independent life forms - viruses that invaded the cells of our ancestors millions of years ago. But ERVs liked it so much they decided to stay. They have become integrated into the human genome, reproduced and passed down through the generations. This has been going on for at least thirty million years: maybe one per cent of your genome is represented by ERVs and fragments. And every mammal species we've examined contains ERVs too.

'Cohabitation makes the viruses settle down: it's a poor parasite that destroys its host. But sometimes the tamed viruses turn feral again. Retroviruses seem to be responsible for autoimmune diseases: when they kick in it's like your body is mounting an immune attack against your own cells. And that's not all they can

do. In certain circumstances, it seems, they can stop the replication of DNA molecules altogether…' Lyall shrugged. 'Look, kid, I'm a propulsion engineer - not even a rock hound, and still less a microbiologist. But what I do understand -'

'The Martian Reboot was caused by ERVs.'

She nodded grimly. 'Or something like them. The evidence is iffy - it's been a long time - but that's how it looks.'

Bob struggled to understand what she was telling him. 'Was it an ERV on Earth too?'

'Yes.' She watched him, letting it figure it out for himself.

'Oh,' he said. 'The same ERV.'

'The same ERV

August 2008

Now the plants are dying in earnest - wheat, grasses, weeds. In the very centre, close to Corwell itself, only single-celled organisms are reproducing, the very root of the evolutionary tree. Merrick has followed this grim progression with my classroom tree-of-life diagram, step by step.

There is growing hostility to the children.

It is a hot August, and tempers are inflamed.

It comes to a head.

Some of the locals mount a drunken attack. The soldiers on guard are hesitant, their sympathies split, their orders unclear. Stewart, Merrick, Emma and myself rush to defend the children. Joel's father, drunk and in despair, improvises a petrol bomb and throws it. His own child is his target.

I have never held a lower opinion of the human species. With a possibly terminal catastrophe gathering around us, all we can do is seek someone to blame, and to harass the innocent and helpless. Perhaps we do not deserve to survive.

The children are saved from the fire.

Emma is killed.

I don't know how else to tell such a thing.

She stood there, the lower half of her suit stained bright red by the dust, gazing up at Earth. 'Earth doesn't have to die,' she said. 'That's the point. Earth isn't freezing and drying like ancient Mars. I think that damn ERV got triggered by accident. It was the pressures of that one shithole place in England, the mix of ground toxins and atmospheric pollution and whatever the hell else was

going on there. Our fault, sure - but an accident all the same. It isn't Earth's time.'

Bob, still resentful, was growing frightened of this eighty-year-old, and the huge biological disaster that lay behind her, a billion-year shadow. 'Why doesn't Earth do something about it?'

She sighed. 'Because there is no "Earth". There are only factions and nations and corporations… For a time, even as the disaster unfolded, we were hopeful. We even mounted missions to Mars, for God's sake. I guess we always thought we'd defeat the plague. But we didn't. Hope died. Now there are enclaves, fortresses. And you can't do science from inside a fortress.

'Listen to me. You are Mars's last child. On Earth you will be a sentimental token, a five-minute wonder. You will have a platform. You have to use it.' She closed her hand around his, around the rock. 'Make them listen. Drag them out of their fortresses, their cowering madness. Read the letter. Make them put together the lessons of this ancient rock, and what's going on all around them. We learned more from the first scraping of Martian bugs than in fifty years of one-planet biology, and I believe it can be so again. In a way it's beautiful - the ancient life of one abandoned world coming to the aid of its suffering sister… Make them see that.' She searched his face anxiously. 'Do you understand?'

Bob opened his palm. In the slowly fading light he stared at the innocent bit of rock, longing to see the creatures who had once swum vanished Martian seas.

September 2008

Merrick, my dead wife's lover, has stayed with us. Emma's death has drawn us together.

Merrick's counsel is oddly reassuring, in an abstract way. He says that essentially a 'reboot' mechanism is operating. Just as a crashed computer can be restored from reboot files, so the biosphere, stressed beyond endurance, is 'dumping' higher biological forms, abandoning all but the most basic forms of life, perhaps in the hope of re-evolving to suit the new conditions. Merrick speculates that this mechanism may have operated before, after the great extinction events of the past.

This all seems a little spooky to me; it smacks of Mother Gaia taking revenge. But I know little about the science and I keep my counsel.

The virus is spread by air, water, contact. Merrick hacks into internet sites to find evidence that the virus is already working its effects elsewhere, far from Tricester.

Merrick predicts we have maybe a century left. A hundred years, as humans and other higher forms are discarded like autumn leaves.

I cradle my baby, and wonder how many more like him will be born.

148

Sun God

Apollo drifted between Earth and Moon.

Fifty thousand miles behind Apollo a gibbous Earth loomed, huge and bright. And opposite, a hundred and eighty thousand miles ahead, there hung a tiny crescent Moon, like a Chinese lantern.

The Earth was white. And the Moon was brick red…

… and it was beneath that crimson Moon that I was stationed, as penalty for my heterodoxy, on the surface of the First World: the hell-planet, orbiting less than a solar radius from the surface of the bloated sun itself.

Hell-planet, perhaps. But there was once life here.

We can find traces of complex carbon compounds in the deep, subducted rocks. We can reconstruct how this world's biosphere must have operated, in the youth of the sun, with rich and complex cycles based (unlike our own ammonia-dependent processes) on the unlikely combination of water, carbon dioxide and oxygen.

Yes - oceans of water!

There was even intelligence here.

Oh, after so long, after billions of revolutions of this twin world around its sun, no artefact could remain on the surface: no proud symbol of their presence, for every material used to construct vessels or buildings would long since have crumbled to its constituent chemicals. But, nevertheless, in the deeper layers of the old continents, even in the rock subducted beneath desiccated sea beds, we found traces: layers of metals and pollutants - lead and zinc and cadmium - evidence of mining, deep caches of certain isotopes of uranium.

149

There are even, in places - in the ash from long-dead volcanoes, restored to the surface by tectonic cycles - the remnants of bodies. Artefacts nearby, of gold, platinum and mercury, some ceramics.

Piece by piece we learned much of them: these shambling sacks of water with their unruly, chaotic culture, who so briefly dominated their own planet -

- and, I came to believe, touched the surface of their Moon!

Traces only, granted, and in just six isolated sites, scattered over one hemisphere of that pocked, ancient satellite.

The geological cycle of the First World was my assignment. I was not supposed to be studying the antique intelligence of the First World - still less evidence of voyages to that solitary Moon!

But that - curse my heterodoxy! - is what 1 discovered.

It was difficult to understand how this could be so. How could water-heavy life be transmitted across such a gulf of space? Even if it did, in some form of spaceborne spore, perhaps, why should it be restricted to those six sites? Why should it not spread over the whole satellite?

It made no sense.

Therefore I formed an outrageous hypothesis.

I suggested that the life traces were carried there by conscious intent. The inhabitants of the First World, at the bright dawn of time, travelled to their satellite, and left marks in its shattered soil.

Well, my hypothesis aroused predictable outrage. I already had a reputation for controversy after my original heterodoxy. There was no sign of the use of advanced propulsion technology on that lonely Moon: fusion, zero-point energy, spacetime inflation. Not even nuclear fission! So how did they get here? With chemical rockets, children's toys? And they showed no evidence of the global cultural organization which would have made such an endeavour possible; they were squabbling, territorial creatures.

And why just six landing sites?

Six journeys, and then no more? A tide of life, reaching up from the First World to its satellite at those six points, then falling back? Yes. It was absurd. I needed more evidence.

In my own time, defying my superiors, I began to seek a way to show how such flights could have been achieved, with appropriate technical and cultural logic: flights from the First World to its battered Moon…

... a Moon which rose like a shard of bone in the blue dome of sky over New Mexico scrub, as Slade walked towards the Flight Operations Control Centre.

The DC-X - also known as Sun God - sat on the flat, baked plain of the White Sands Missile Range. The rocket, swathed in boiling hydrogen, was a misshapen cone, like a stubby, isolated minaret maybe forty feet tall. Heat haze shimmered before it. The craft was visibly battered, dinged-up and scorched, after the multiple test flights it had already taken.

A countdown intoned from a primitive PA system, the terse numbers and technical data echoing away across the sands. The sun was directly in Slade's eyes, the light on his head, face and chest a tangible presence; it seemed as unfiltered as if he were in space.

Dream on, he thought.

It was June, 1997.

Slade reached the Control Centre, which was just a ten-yard trailer set up three miles from Sun God's launch pad. He entered and sat in front of a computer screen. Two McDonnell engineers were here waiting for him, with their own consoles and controls. But during the flight phase, Sun God would be Slade's ship, and that suited him just fine.

The countdown proceeded, calm and controlled. And -

Light burst from the base of the craft, the pure, clear glow of burning hydrogen. All of three miles away, the exhilaration of ignition made Slade's soul rise. A billow of white smoke blasted sideways, out across the desert surface, stirring the cryogenic clouds, which were soon stained yellow by kicked-up sand.

The conical craft slid smoothly into the air, soon rising above its support structure. When it had risen out of the hydrogen cloud, that clear flame, lengthening, was all but invisible.

Then the rocket ship slowed to a halt, thirty yards above the ground. It was astonishing. Rockets weren't supposed to do that.

Now the DC-X responded smoothly to its programming, tipping and scooting a few yards back and forth across the desert, moving simply by tilting its four rocket nozzles, directing the thrust. The engineers rattled through their tests.

It looked so easy, Slade thought. But it wasn't.

The problem with spaceflight was, humans were trapped here, on the surface of the Earth, by the laws of physics. If you were going to use chemical engines to get to orbit from Earth, you

needed a ninety per cent mass fraction: ninety per cent of your take-off mass had to be fuel. Back in the sixties, when they first built the Atlas, they could get no better than seventy or eighty per cent.

This little craft, the DC-X, looked good, but its mass fraction was only sixty per cent. It was supposed to pioneer technologies to push up that mass fraction. For this flight it had been given all kinds of fancy modifications, like a new graphite epoxy hydrogen tank, a lox tank made from aluminium-lithium alloy, and an oxygen-hydrogen reaction control system that used excess fuel from the main tanks.

DC-X was a one-third prototype. The full-scale version - a hundred and twenty feet tall, just a little taller than John Glenn's Mercury-Atlas - would weigh in at five hundred tons, and be capable of carrying two crew to orbit.

But it wouldn't be piloted. The crew would be passengers, helpless as babies, stuck in the metal belly of the craft.

Well, it probably wouldn't ever get built. Even if it did, it was so far in the future Slade wouldn't see it.

But here he was anyhow, flying Sun God back and forth, in little arcs over the desert.

Slade, aged sixty-seven, had been in aviation - specifically, rocket craft - all his life. He was an old lifting-body man. After Patuxent, he flew the old X-15 a couple times. When his buddies were applying to NASA in the sixties, for Mercury, he just wasn't interested. He wanted to stick with spaceplanes. He figured those dumb ballistic capsules just weren't the future.

Well, he'd been proven correct. There had been that scare when the Russians had first thrown up their heavy satellites and their cosmonauts, but it was soon obvious that the Soviets' technical lead was only in heavy-lift boosters. Just one American had flown in orbit - John Glenn, in 1961, in his tin-can Mercury capsule atop an Atlas booster - and then the nation had backed off. And when John Kennedy had called for a decade-long programme to reach the Moon - the Moon, with throwaway boosters and ballistic capsules, for God's sake - he had been roundly howled down.

America had gone back to Eisenhower's slow and steady approach. And so, after forty years, the Atlas, steadily upgraded, remained America's only orbital booster system, with a capacity to orbit of a few tons.

But anyhow Atlas was enough for practical purposes like

weather satellites and comsats. You didn't need anything more powerful, unless you wanted to do something seriously dumb like fly to the Moon! The research had gone on into new technologies, slowly and incrementally. There was no rush.

And Slade, to his own surprise, had grown old watching it all go by, waiting for a chance to fly.

Of course this wasn't piloting. The DC-X was completely controlled by the computer. Slade had what the engineers called trajectory command over the bird. He was sending in pre-scripted plays like a gridiron coach, then leaving it to the software to execute the plays.

But that was okay. You didn't need much imagination to believe you were up there, in the tip of that cone, flying.

Sun God stayed in the air by standing on a rocket flame -just like a lunar lander would have worked - in fact, he thought now, he'd have been more than happy to sit on the nose of that thing and ride it down to the surface of the old Moon itself, with Bado.

- And as he framed that idea, he saw Bado again. In his unwelcome memory that treacherous old X-15 came barrelling out of the sky once more, slamming Bado, his good buddy, into the high Mojave - that soft crump, the almost gentle puff of dust.

Damn, damn. It had always seemed so wrong. Maybe in some other life, he and Bado could really have flown some kind of Mercury capsule down to the surface of the Moon. Maybe that was where his recurring dream came from -

- in which Bado came loping out of a shallow crater, towards Slade, bouncing happily over the sandy surface of the Moon -

- but then there was the other half of his dream, where he was just a kid, toiling in the guts of some huge space rocket factory, forced to speak a guttural European tongue -

Moons and mountains. Recurring dreams. An old geezer thing, evidently.

But the Moon probably would have killed them anyhow. There were scientists who said the mountains there would crumble like meringues if you set foot on them, or the dust itself would explode and swallow you up.

Anyhow, Slade was going to die without ever knowing.

Time to bring her in.

Sun God swept through a smooth arc towards the splash of

concrete that was its landing pad. The bird slid down through the last few feet, as smooth as if it was riding a rail down to the ground, and he let the automatics finish the touchdown. Sun God just stuck out its four landing legs and landed on its pad, as gently as a dragonfly settling on a lily.

Slade got out of his chair. His back and shoulders were stiff; he worked his fingers and arms to loosen up the muscles.

A tech was slapping him on the back. 'How about that,' he said. 'Just as fat as a goose. Outstanding.'

'Yeah. Outstanding.'

Slade stepped out of the trailer. It was still bright morning; the flight had lasted just minutes. And in the sky, that big old Moon hadn't yet set; it just hung there - oh, hell, something must be wrong with his eyes, he spent too much time peering at those damn computer screens - the Moon was bright red…

… red in the light of the sun, which has swollen to a crimson giant in its old age, its hot breath suffocating the First World -and yet, paradoxically, scattering life over our own more remote globe.

How would First World life function?

It is possible water could play the role in a life system that ammonia does for us: a water-based biosphere!

First World life forms would drink water as we do ammonia, and breathe oxygen as we do nitrogen. When we respire, we burn methane in nitrogen, producing ammonia and cyanogen. Similarly, the First World life would burn sugars in oxygen and give off water and carbon dioxide. To close the loop there would be some form of photosynthesis, hydrous plants using solar energy to turn the products of that respiration - water and carbon dioxide - back to sugars and oxygen, as our plants turn ammonia and cyanogen back to methane and nitrogen…

Strange, but not impossible!

What would the First World have been like, in those remote days?

It would be a world of water oceans, perhaps with caps of polar ice, and a clear air, of free oxygen buffered by nitrogen. And there would be clouds, of water vapour…

On such a large world, spinning sixteen times as fast as Home, the climate would be more complex than our own. Powerful Coriolis forces would act on the air, generating swirling storms

… We can only imagine the cultures and ecosystems which evolved in such complex and violent climatic conditions.

There is more. Chemical reactions are dependent on temperature. Reaction rates are increased as the temperature rises. On a world so warm that even water is a liquid the reaction rates rocket, by perhaps a hundred to a thousand times.

Thus, the metabolism of hydrous creatures would proceed at a much faster rate than ours. That would be offset by the increased gravity, but still, life must have proceeded at a frenetic pace.

We can even deduce the colour of the sky, on that strange, lost world.

There was no methane in the air, because it would have reacted with the free oxygen. And because light from the blue end of the spectrum has a wavelength similar in size to the molecules of the air - nitrogen and oxygen - the sky of the First World must have been blue, not green…

At last, the First World was betrayed by the star that gave it life. The end came when the surface grew so hot that the very stuff of water-based life - complex molecules and carbon-based molecular chains - was broken down.

Finally those unlikely water oceans boiled, and huge clouds of vapour were suspended in the atmosphere, driving temperatures higher still, ever faster. But even the clouds did not last forever. At last the water vapour in the air was broken up by energetic sunlight and the hydrogen driven off into space, leaving a planet baked dry, its surface cracked and flattened under a dense, sluggish atmosphere, utterly lifeless -

In any event it seems clear that my putative water-laden Moon voyagers did not have the means to escape their planet, or to avert their ultimate doom.

Trips to the Moon: logic was not enough! My simulation had taught me that, at least. 'Logic' to these creatures meant starving their projects of resources! And besides, nobody logical would attempt to travel between this world and its Moon with such primitive technology. Nobody sensible.

But these people were neither logical nor sensible. I knew I must remember that.

I sought a logical political structure in their reconstructed history, a structure that could have commanded significant resources. I reset the parameters of the simulation -

But I was speaking of my search for evidence of spaceflight by

this antique intelligence, of its travel to the desiccated satellite:

The inner system, at the bottom of the sun's gravity well, is crowded. Conditions are quite unlike Home, which is, of course, the largest satellite of the Fourth World. (Although, it is not well known, once the Fourth World sported a gigantic ring system, made up of chunks of ice and other debris, residue from the formation of the sun. The rings must have been beautiful. But they have long since evaporated, as the sun's heat roared in the faces of its children -) I digress.

The First World, then, swims through a cloud of debris, of thousands of planetesimals left over from the untidy formation of the system, aeons ago. Despite geological smoothing, its surface shows the evidence of repeated bombardment, which has diminished but not ceased with the passing of time. Its airless satellite is scarred still more impressively.

I studied the orbital characteristics of one such planetesimal in particular. Many of these objects had orbits close to or crossing the First World's. But in this case, the parameters were so close to those of the First World that I grew suspicious.

Then excited.

Could this be the artefact I had sought? Not on the surface of either world - but some form of abandoned spacecraft, or space colony, circling the sun with its mother planet?

I scraped together funding for a mission to the anomalous planetesimal: a small ship to sail through the light of the Moon…

… the light of the Moon which shone like a torch beam into the dormitory as Slade woke, reluctantly. Already the older men were moving around him, shuffling, conserving what energy they had. The mornings were the worst.

Everything was slow here - even dressing was slow - and Slade was hungry by the start of his work, at five a.m. And yet he would receive nothing but his soup, at two in the afternoon.

It was 1946. Slade was sixteen years old.

Slade lay in his rat-chewed blanket as long as he could.

Today was worse than usual. He felt - strange.

As if he shouldn't be here.

He couldn't stay on his rough pallet.

Soon would come the rush into the smoking mouth of the tunnel into the mountain, with the SS guards lashing out with their sticks

and fists at the heads and shoulders of the worker herd which passed them. That tunnel was like Hell itself, with prisoners made white with dust and laden with rubble, cement bags, girders and boxes, and the corpses of the night being dragged by their feet from the sleep galleries -

When he got up he had to hurry. Otherwise he would not witness the hangings, and that was against regulations.

Actually, the hangings seemed wasteful to Slade. A victim would be gagged with a metal bar across the mouth, and the bar tied at the back of the head with wire, drawn in so tightly that the metal gag would bend, and the wire cut into the flesh of the face.

So much metal!

It was well known among the workers within the Mittelwerk that Hitler had ordered the production of no less than twenty thousand of von Braun's A-4 rockets - or rather, what the Germans now called their V-2: V for Vergeltungswaffe, revenge weapon. And then there was the demand for thousands more of the ambitious V-3S, the A-4b design with the nuclear-tipped glider on its nose, capable of skipping across the Atlantic and digging more glowing craters into the eastern seaboard of defeated America.

How could this immense production operation spare so much metal on mere hangings?

But then - thanks to those very rockets of von Braun, which had subdued Europe and Asia and fended off America - Hitler could now exploit the resources of two continents. A little hanging wire was nothing.

Slade performed such calculations, even as he reflected on the fact that at the next roll call it could be him, suspended up there like a chicken in a butcher's shop.

At sixteen, Slade was prized by the supervisors for his ability for skilled work. So he was assigned to lighter, more complex tasks. In the process he was forced to absorb a little German. So, gradually, he picked up something of the nature of the great machines on which he toiled, and learned of the visions of the Reich's military planners.

They would construct an immense dome at the Pas de Calais -sixty thousand tons of concrete - from which rocket planes would be fired off at America in batches of fourteen at once. And then there were the further schemes: of hurling rockets from submarine craft, of greater rockets like von Braun's A-9, which might hurl a man into orbit in a glider-like capsule, and - the greatest dream

of all! - of a huge station orbiting five thousand miles above the Earth and bearing a huge mirror capable of reflecting sunlight, so that cities would flash to smoke and oceans might boil.

Thus would be secured the future of the Reich for a millennium.

And when that was done, von Braun talked of flights beyond Earth itself, in new generations of his giant rockets, hurled upwards by brute force: even of a nuclear-launched spaceship called Sun God which would send Germans to the Moon by 1955, to Mars a mere decade later.

Such visions!

But for Slade the V-2 was the daily, extraordinary reality. That great, finned bullet-shape - no less than forty-seven feet long -was capable of carrying a warhead of more than two thousand pounds across two hundred miles! Its four tons of metal contained no less than twenty-two thousand components! And so on.

Slade came to love the V-2.

It was magnificent, a machine from another world, from a bright future - and the true dream inherent in its lines, the dream of its designers, was obvious to him. Even as it slowly killed him.

One day, in the sleek, curving hide of a rocket ship, he caught a glimpse of his own reflection.

He looked into his own eyes unexpectedly, suddenly fully aware of himself. He had a sense of the here and now - or rather of vividness, as if the casual numbness of his life had been lifted, briefly. He hadn't seen a mirror in three years, since the Nazis swept through what was left of Britain, and he was separated from his parents and, as an American, rounded up as an enemy alien.

He saw a skinny, half-bald kid, with blood running down his cheek from some wound he hadn't even noticed.

- and an old man, his face twisted down under a coating of desert gypsum -

- and a gold visor, a glaring landscape reflected there -

- and flames -

Visions. It was probably the hunger. What else could it be? He subsided to numbness, and dreams.

One morning, so early that the stars still shone and frost coated the ground, he saw the engineers from the research facility at Peenemunde - Wernher von Braun, Walter Riedel and the rest, smartly uniformed young men, some not much older than Slade - looking up at the stars, and pointing, and talking softly.

Slade glanced up, to see where they were looking. It was the crescent Moon, dimmed by the smoky light of some town which burned on the horizon. And there was the dream which motivated and sustained these young, clever Germans: that one day the disc of the Moon would be lit up with cities built by men - Germans, carried there by some gigantic descendant of the V-2.

Slade could understand how these young men from Peenemunde were blinded by the dazzling beauty of their V-2 and what it represented. But Slade was no rocket engineer; he was no more than garbage, just one of the thirty thousand French, Russians, Czechs, Poles, British and Americans who toiled inside this carved-out mountain. And in the dormitories at night would come the whispers, schemes of hidden weapons and tools, the uprising to come which would shatter the Reich.

The duality of it crushed Slade. Was such squalor and agony the inevitable price to be paid for the dream of spaceflight?

But perhaps it was. Perhaps only the organization of all of mankind's resources, under some such system as Hitler's, was capable of breaking the bonds of gravity. Perhaps it was necessary for von Braun's beautiful ships to rise from ground soaked by the blood of thousands of slave workers like himself, with expended human souls burning like sparks in the gaping rocket nozzles.

How he envied the young engineers from Peenemunde, who strutted about the Mittelwerk in their smart uniforms; they seemed to find it an easy thing to brush past the stacks of corpses piled up for daily collection, the people gaunt as skeletons toiling around the great metal spaceships!

He even imagined how it would have been had he been born to become one of these smart young Germans in their SS uniforms. How he envied them! And a part of him hoped that they could achieve some piece of their huge dreams before the inevitable tide of anger rose up and swept them all to the gallows.

When he immersed himself in such dreams, something of his own, daily pain would fall from him, and he could lift his head to the Moonlight…

… the Moonlight which washed over the machined surface of my planetesimal. The object was small. But even at a great distance from it, I could detect its artificial nature.

It was a slim cylinder. One end was domed, the other terminated

by a complex encrustation of equipment, including a flaring nozzle. It bore no markings. It tumbled slowly.

It was extremely old. Sublimation had left its aluminium skin so thin it was, in places, almost transparent. In fact the hull was punctured, after billions of orbits around the sun.

The artefact was fortunate to have survived intact at all.

I approached cautiously. I could see into its interior, through rents and dimples in the hull. There was some form of double chamber in there. There was no sign of activity, of light, of energy.

The cylinder dwarfed my craft.

After circling its exterior, I gathered my courage, and I approached the terminal dome, where an eroded breach afforded me access.

I found myself rising into a cylindrical chamber, up from the cup of the dome. Stars and ruddy sunlight gleamed through hull rents. Far above me, hanging down as if swollen, I saw another dome.

The chamber was all but empty. The walls were lined with small pieces of equipment: spherical casks, ducts, pipes.

I rose through the silent grandeur of the artefact.

I passed through the upper dome, deep into the heart of the artefact. I entered a second chamber, braced with a metal frame. It was much smaller than the first.

There was no sign of occupation, no evidence of life.

I continued my inspection, baffled - at first - as to the purpose of this artefact.

But soon I formed an hypothesis.

My rogue planetesimal was clearly an artefact. But I had misinterpreted its nature.

It was no spaceborne habitat. Those great cylindrical chambers were tanks, which once bore fuel. Liquid fuel.

I came to believe the artefact was a crude rocket. It must have driven itself forward by burning liquid-chemical propellants together, and allowing the expansion of gases through the terminal nozzle. The dimensions of the tanks were consistent with the relative densities of liquid hydrogen and liquid oxygen. These would burn vigorously together, if appropriately controlled.

I elaborated my original hypothesis:

I argued that the creatures of the First World had used chemical rockets like this one to escape from their planet's gravity well, and to travel to their satellite.

Yes - chemical rockets!

Well, I was mocked, as I might have expected. 1 concede it seems absurd that such a journey might be attempted with such limited technology.

But it is not impossible!

I argued my case. I was disciplined, for neglecting my primary studies.

So I determined to prove, by dramatic demonstration, how such a flight could have been achieved! I would reconstruct the chemical Moon ships from the dawn of time, and prove it was this way.

That was the start of it. But soon my simulations were going badly.

Perhaps I continued to miscalculate the natures of my subjects. They were not like us.

We must remember the environment in which these bizarre animals evolved: the ferocious gravitational field of their parent world, the blistering outpourings of the nearby sun. They would be stunted, very alien creatures, warped by these enormous forces into miserably malformed, distorted shapes, crushed until they are blind and tiny. We inhabit a favoured realm, drifting far above the range of those immense forces, on our small moon so far from the sun; we should not envy these creatures their short, pain-filled lives.

But they must have been squabbling, water-stuffed, energy-fat, demon-obsessed monsters! If logic would not motivate them, if they were unable to govern themselves and their resources without brutality and waste, I knew I must try illogic.

I reset the parameters of my simulation once again. I would not rest until I had reconstructed the hydrate creatures from so long ago, sailing to the Moon…

… Sailing to the Moon, Slade was working through a plastic bag of chicken soup. He took a spoonful of the soup, tapped the handle, and the glob of soup floated off, still holding the shape of the spoon. But when he poked the liquid with a fingertip, surface tension hauled it quickly into a perfect, oscillating sphere. Slade leaned over to suck it into his mouth, a little green ball of chicken soup.

It was Slade's fourth spaceflight, in six years. He'd never yet got bored with the zero-gravity environment.

The two other crew - Lunar Module Pilot Bado, and Command

Module Pilot Pond - ate without talking. And that was the way Mission Commander Slade, in his centre couch, preferred it.

It was August, 1967. And Apollo 3 was heading for the Moon.

A splinter of crimson-sunset light, from the Command Module's windows above him, caught Slade's eye. He looked up. Whatever it was had gone; the windows were just rectangles of darkness.

The red of the Moon had been like -

- the red of an old man's rheumy eyes, peering across some Godforsaken desert -

- the red of a kid's blood, toiling in some brutal mountain -Slade tried to focus. He felt disconcerted, unsure, vaguely

disturbed. His instincts were ringing alarm bells.

Maybe it was the ship. There had been a shit-load of problems already on this trip. If this was an aircraft he'd get out before taking her up - peer into the vents and kick the tyres - try to back up his hunch.

But that wasn't an option.

Anyhow the others didn't seem to have noticed anything. The meal over, it was time for work.

Slade toiled steadily through his pre-transposition checklist, throwing switches and recording settings and readings. En route to the Moon, Sun God was still mounted on top of the S-IVB -the spent Saturn V third-stage booster - with its nose pointed forward. Now, to gain access to the Lunar Module - still housed within its adapter cone at the top of the booster - CM Pilot Pond had to uncouple Sun God from the stack, turn it around, and dock it nose-to-nose with the LM, the Lunar Module.

Pond called out a countdown.

Slade heard a muffled thump, a soft push at his back.

Sun God had become detached from the depleted S-IVB booster stage. Pond fired up the reaction-control system, and let Sun God drift away from the booster -

'Uh oh,' Pond said. 'I got a twelve-oh-two alarm.' This was a computer programme alarm, flashing up on Pond's display unit. 'Something to do with a memory overload. It came up when 1 engaged the rendezvous radar. And it - shit.'

The alarm code had changed to 'twelve-oh-one'.

'Houston, are you copying?'

'Stand by, Sun God. We're working on it.' The capcom's voice betrayed nothing.

Slade snorted and slammed the palm of his hand against the

computer. One little glitch and the docking was on hold.

There was nothing he could do now but wait. And all the time, Slade knew, Sun God, on its separate trajectory, was drifting farther from the S-IVB; already the gap had opened up to two miles. To recover now they'd have to go through a full-scale rendezvous procedure.

- and still he had that sense of dislocation: of things being not quite right. As if an engine was running off -

Slade was beginning to think his mission might be snake-bit: doomed to failure. They had had problems with the Apollo since they left the ground. Lousy comms. Computer glitches. Foul stenches from the life support. Scuffed wiring. Stuck hatches. Inoperative reaction-control thrusters.

Slade had followed the evolution of his ship through its manufacture. He had seen the NASA QA report that had called it sloppy and unsafe. He knew there had been twenty thousand failures during its construction and testing. He knew it was just a lousy bucket of bolts that should never had left the factories, at Palmdale and Bethpage.

But here was Slade flying this clunker to the Moon, because that was the timetable of America's mad, impetuous dash into space, and Slade would have been aboard if he had to get out and push.

It was six years since Slade's first flight in space. He'd finished three orbits of Earth on the second orbital Mercury flight, in 1961, following John Glenn. He'd hung in there, piling up flight assignments, while younger, smarter guys came into the programme to compete with him. He'd gotten a Gemini flight, and a seat on the first Earth-orbital Apollo test flight in 1966. He was the only man to have flown all three generations of US spacecraft.

And now here he was - commander of his own lunar ship -on his way to the ultimate piloting test, the Moon landing itself. This would be the best of all, a full-up mission, the crown of his career.

But it seemed to be falling apart.

The capcom came back on the air-to-ground loop. The only solution Houston could come up with was to run the rendezvous manually. 'The coordinates are NOUN 33, 092, 29, 43532 minus 00312. HA and HP are NA. Pitch is -' Slade wrote out the data on the back of a checklist, and read them back down the link.

Pond and Slade rattled through a brief start-up checklist, and

Pond began to throw switches. Bado was appointed timekeeper, and he counted Pond down to the time indicated by Houston. 'Ten, nine, eight -'

Now, framed in the windows, Slade could see the S-IVB. It was a white-painted cylinder, dappled with black panels, the brave scarlet 'USA' emblazoned on its flank. And there, at the nose of the cylinder, was the complex, foil-covered roof of the Lunar Module, now exposed to the sunlight, its docking receptor a dark pit at its centre.

The next item was a couple of short SPS burns, thrusts of the Service Module main engine.

'Three, two, one,' Bado said. 'Fire.'

There was a brief thrust, of perhaps a half-G, which pressed Slade into his couch. It lasted just seconds.

Pond had to fly by eye. The rendezvous radar was still useless. The S-IVB seemed to approach them, then recede, then approach again; it was like stalking some huge, cautious animal.

At last, the S-IVB was looming before them, huge and ungainly and complicated, the LM nestling in its nose. The windows were filled with drifting metal struts and paintwork.

Shadows mingled. The cabin shuddered as Sun God impacted the LM, hard, and there was a groan of metal.

A green light came on. Slade heard the rippling clang of docking latches snapping shut.

'How about that,' Pond whooped. 'Houston, virgin no more.'

Thank Christ, Slade thought. Thank Christ -

But now there was something else. He could smell something.

Smoke.

There was smoke coming from a compartment at the foot of his couch. Maybe there was some new piece of scuffed wiring, shorting down there, some piece of equipment to do with the docking. And now there was a flare of light; it looked as if a spark had caught the nylon netting underneath their couches.

It spread quickly.

Christ, there was fire everywhere.

Velcro pads stuck to the walls just exploded into flame and dropped away, showering them with sparks. Even materials that were normally flameproof were burning as if they had been dunked in kerosene: checklists, insulation, aluminium, the fabric of his suit.

Even the skin on- his hands.

It was pure oxygen in here, at five psi.

Oddly, there was no pain. And he could still smell that smoke. The double-domes said Moon dust would smell like that, like ash -

He had a crushing sense of unfairness. He was going to lose his mission, the full-up flight he'd intended. It was all meaningless, like another crashed simulation.

Slade remembered so much: his father, Fay and the girls, the ranch house in Clear Lake. Such memories comprised him, his soul. But in a moment the memories would be gone. As would he.

He felt a rush of warmth, within him. His thoughts seemed to soften, guttering like candle wax.

Slade tried to focus on Fay. But he could no longer remember her face.

The air was full of light.

Red light.

Empty, its systems dormant, the glowing Apollo sailed on, towards the brick-red Moon…

… the Moon over which I sailed, in triumph! For my hypothesis was confirmed.

And in the destiny of these stunted creatures there is a profound lesson for our own future.

The First World formed deep in the hostile maw of the new sun's gravity well. It is a ball of rock.

But our Home, at a comfortable distance from the sun, was born half rock, half ice. A giant among moons, its huge mass caused it to heat as it collapsed. The primordial ices were melted and vaporized. The rock settled to the centre. Thus, Home is a ball of silicate, overlaid by a shell of water ice.

Home's first ocean was a mixture of ammonia and methane. A dense methane-water-ammonia atmosphere was raised over that ancient sea. The new world was a cauldron, with air pressure hundreds of times its present level, and searing temperatures.

And in the organic soup of the ammonia-water ocean, complex chemistry seethed…

Life arose. Yes, so long ago, at the dawn of the solar system itself!

But the new ocean and atmosphere were not stable. Ultra-violet flux from the young sun beat down on the atmosphere, shattering

its ammonia molecules; planetesimals continued to fall, blasting away swathes of Home's atmosphere; the atmospheric gases dissolved in the ocean…

Perhaps, in the brief time they were allowed, those primeval life forms reached a high degree of complexity. We cannot tell. But they could not survive these changes. All we can find are chemical fossils, the decomposed elements of a life that was snuffed out as Home settled into its billion-Revolution Freeze. Home was a world of darkness, of haze and clouds, of sticky organic slush: a land of mud and crater lakes - a world utterly alien to the clement orb which sustains us now!

After the time of the hydrous First-Worlders, the evolution of Home continued.

As the sun brightened, at last the Freeze receded. The ethane lakes boiled, evaporated. The gases trapped there - nitrogen, methane, hydrogen - exsolved, thickening the atmosphere. Eventually the ice shells over the magma, the ancient ammonia oceans, melted, exposing the old seas once more. Ammonia and water vapour enriched the air still further…

And life, after its epochal suspension, began to stir once more. After hundreds of millions of Revolutions, our true history had begun.

But Home, too, is under threat of destruction!

Even now, our air is leaking away; for our world is fundamentally too small to retain its thick atmosphere even at today's prevailing temperatures. And we can postulate a time when the rising temperatures caused by the sun's expansion will once more cause the loss of our air, the evaporation of our ammonia oceans.

But the sun's ballooning growth will not stop there. When the red giant growth reaches its climax, even our bedrock water ice will become liquid.

Think of that! We have used water ice as the staple of our structures: the cities, the spires, the gleaming bridges. When the ice softens, our buildings will collapse.

Worse: our very bones will melt!

And, at last, even the water will boil away… It will take only a few thousand revolutions, no more. Then, nothing will be left of Home but its rocky core.

Long before then, we will be forced to make a choice: to submit to extinction, or to flee Home. We have millions of Revolutions before us, of course.. Some argue that is enough. I say that when

the destiny of the species is at stake, only eternity will suffice!

… But let us draw back, from the end of Time itself.

Before the final destruction, for a brief period, Home will have new lakes and oceans - but of liquid water.

That is why we should cherish the hydrous Astronauts, these silent ambassadors of the past. That is why we should endeavour to reconstruct them, to revive and study them.

For one day the circle of destruction and birth may close. One day we may be forced to share Home - with them!

… But 1 digress.

My historical reconstruction complete, I froze the simulation.

In the light of its Moon the little, glittering ship was really quite beautiful. So shiny and new, silver and white and black. Like a toy. But so lethal, of course.

How entertaining it had been. The interplay, the language. So authentic! And so ingenious. The very idea of reassembling the craft by hand, here in cislunar space!

To impose such defects seemed hardly fair. But this was not a game. Fairness was not a factor. Given this level of gadgetry, even multiple defects must have been common.

Of course, it might not have been quite like this. Perhaps more sacrifice was necessary. If that oxygen fire had occurred before a launch, for instance, subsequent generations of spacecraft might have been rebuilt for greater safety. The beings who performed these flights did not think logically, in an orderly fashion. Logically, they should never have flown into space at all! Perhaps they needed some such catastrophe as this to occur, regularly, to guide them on their path.

But it was really quite remarkable. These hydrate creatures were really not up to this. Not yet; perhaps, in the end, not ever. They just were not smart enough. Why, they must even have navigated by eye, by the stars! And yet they persisted. There was something to admire, in this grandiose, doomed enterprise.

Well, I felt tired but happy. My simulations had converged. A mission to the Moon with chemical rockets, so I had proven, was foolish but feasible, given supportive historical logic. Already I had sufficient documentation; it was not necessary to adjust the parameters once more, to follow the sequence through to its conclusion.

I could allow the simulation to dissolve.

Yet I lingered.

I basked in my triumph. But I felt -Complicated. Guilty?

Perhaps. Those simulacra were fully sentient, of course. It was necessary for verisimilitude.

But in the end they were distressed. "Well, of course they were distressed. Believing their world to be real, their lives and memories to be genuine, they had undergone a cessation of consciousness. Still, I meant to honour them - their ingenuity and bravery - not cause them harm.

Perhaps, I reflected, I should reconsider. Complete the exercise.

But after all, they were only simulacra.

Yes. Only simulacra. But of beings who once took halting steps in Moon dust…

… Moon dust which seemed to crunch beneath Slade's feet, like a covering of snow. His footprints were miraculously sharp, as if he'd placed his ridged overshoes in fine, damp sand. He took a photograph of one particularly well-defined print; it would persist here for millions of years, he realized, like the fossilized footprint of a dinosaur.

Or, he thought vaguely, not.

He felt dreamlike.

He was floating over this bright landscape. The tug of gravity was so gentle he couldn't tell which way was vertical. And when he closed his eyes he saw things: a bleeding boy, a bitter old man, a fire -

It was probably the low G. Yeah, that was it. The low G. He looked around.

The LM, standing in a broad, shallow crater, was a glistening, filmy construct of gold leaf and aluminium. Low hills shouldered above the close horizon. There were craters everywhere, ranging from several yards to a thumbnail width, the sunlight deepening their shadows.

Bado came loping out of a shallow crater, towards Slade. Bado had one glove up over his chest, obscuring the tubes which connected his backpack to his oxygen and water inlets. His white oversuit was covered in dust splashes. His gold sun visor was up, and inside his white helmet Slade could see Bado's face, with its four-day growth of beard.

Bado said, 'Hey, buddy. Look up.'

Slade dipped back on his heels and looked at the sky.

The sky was black, empty of stars. In the middle of the sky the Earth was a fat crescent, four times the size of a full Moon. And there, crossing the zenith, was a single, brilliant, unwinking star: the orbiting Sun God, with Pond, their Command Module Pilot, waiting to take them home.

It was July, 1969.

Holy shit, Slade thought. I really am here. I made it. Holy shit.

He felt a rush of affection for his buddy, the glowing reality of him, here on the Moon. Those fragmentary visions fled, leaving him with a sense of here and now and tightness.

This was his place. This was where he was meant to be.

He tilted forward and eyed Bado. 'Pretty sight. But we got to hustle, boy; we got a fat checklist to get through. We're going for a full-up mission here, and don't you forget it.'

Through his visor, Bado grinned. 'Yes, sir!'

Sun-Cloud

To human eyes, the system would have been extraordinary:

The single, giant sun was so vast that its crimson flesh would have embraced all of Sol's scattered planets. Across its surface, glistening vacuoles swarmed, each larger than Sol itself. There was a planet.

It was a ball of rock no larger than a small asteroid. It skimmed the sun's immense photosphere, bathed in ruddy warmth. It was coated with air, a thick sea.

The world-ocean teemed with life.

Beyond the sun's dim glow, the sky was utterly dark.

She rose to the Surface. Thick water slid smoothly from her carapace.

She let her impeller corpuscles dissociate briefly; they swam free of her main corpus in a fast, darting shoal, feeding eagerly, revelling in their brief liberty.

She lifted optically sensitive corpuscles to the smoky sky. The sun was a roof over the world, its surface pocked by huge dark pits.

She was called Sun-Cloud: for, at her Coalescence, a cloud of brilliant white light had been observed, blossoming over the sun's huge, scarred face.

Sun-Cloud was seeking her sister, the one called Orange-Dawn.

Sun-Cloud raised a lantern-corpuscle. The subordinate creature soon tired and began sending quiet chemical complaints through her corpus; but she ignored them and waited, patiently, as her sphere of lantern light rolled out, spreading like a liquid over the oleaginous Surface.

The light moved slowly enough for a human eye to follow.

Sun-Cloud's people were not like humans.

Here, people assembled from specialized schools of corpuscles: mentalizers, impellers, lanterns, structurals, others. Obeying their own miniature imperatives of life and death, individual corpuscles would leave the aggregate corpus and return to their fish-like shoals, to feed, breed, die. But others would join, and the pattern of the whole could persist, for a time.

Still, Sun-Cloud's lifespan was finite. As the cycle of corpuscle renewal wore on, her pattern would degrade, mutate.

Like most sentient races, Sun-Cloud's people sustained comforting myths of immortality.

And, like most races, there was a minority who rejected such myths.

Sun-Cloud returned to the Ocean's deep belly.

The light here was complex and uncertain. Above Sun-Cloud the daylight was already dimming. And below her, from the Deep at the heart of the world, the glow of a billion lantern-corpuscles glimmered up, white and pure.

Sun-Cloud watched as Cold-Current ascended towards her.

They were going to discuss Sun-Cloud's sister, Orange-Dawn. Orange-Dawn was a problem.

Cold-Current was a lenticular assemblage of corpuscles twice Sun-Cloud's size, who nevertheless rose with an awesome unity. The ranks of impellers at Cold-Current's rim churned at the thick waters of the Ocean, their small cilia vibrating so rapidly that they were blue-shifted.

The Song suffused the waters around Sun-Cloud, as it always did; but as Cold-Current lifted away from the Deep the complex harmonics of the Song changed, subtly.

Sun-Cloud, awed, shrank in on herself, her structural corpuscles pushing in towards their sisters at her swarming core. Sun-Cloud knew that she herself contributed but little, a few minor overtones, to the rich assonance of the Song. How must it be to be so grand, so powerful, that one's absence left the Song - the huge, world-girdling Song itself - audibly lacking in richness?

Cold-Current hovered; a bank of optic corpuscles swivelled, focusing on Sun-Cloud. 'You know why I asked to meet you,' she said.

'Orange-Dawn.'

'Yes. Orange-Dawn. I am very disturbed, Sun-Cloud. Orange-Dawn is long overdue for Dissolution. And yet she persists; she prowls the rim of the Song, even the Surface, intact, obsessed. Even to the extent of injuring her corpuscles.'

'I know that Orange-Dawn wants to see out another hundred Cycles,' Sun-Cloud said. 'Orange-Dawn has theories. That in a hundred Cycles' time -'

'I know,' Cold-Current said. 'She believes she has Coalesced with ancient wisdom. Somehow, in a hundred Cycles, the world will be transformed, and Orange-Dawn will be affirmed.'

'But it's impossible,' Sun-Cloud said. 'I know that; Orange-Dawn must see that.'

But Cold-Current said, absently: 'But it may be possible, to postpone Dissolution so long.' Sun-Cloud, intrigued, saw a tight, cubical pattern of corpuscles move through Cold-Current's corpus; individual corpuscles swam to and fro, but the pattern persisted. 'Possible,' Cold-Current said. 'There is old wisdom. But such a thing would be - ugly. Discordant.' Perhaps that cubical pattern contained the fragment of old knowledge to which Cold-Current hinted.

Cold-Current rotated grandly. 'I want you to go and talk to her. Perhaps you can say something… Nobody knows Orange-Dawn as well as you.'

That was true. Orange-Dawn had helped Sun-Cloud in her earliest Coalescence, as Sun-Cloud struggled towards sentience. Orange-Dawn had hunted combinations of healthy corpuscles for her sister, helped her coax the corpuscles into an orderly shoal. Together the sisters had run across the Surface of the Ocean, their out-thrust optic corpuscles blue-tinged with their exhilarating velocity…

Cold-Current began to sink back into the glimmering depths of the Ocean, her disciplined impellers beating resolutely. 'You must help her, Sun-Cloud. You must help her put aside these foolish shards of knowledge and speculation, and learn to embrace true beauty…'

As Cold-Current faded from view, the light at the heart of the world brightened, as if in welcome, and the Song's harmonies deepened joyously.

The world was very old. Sun-Cloud's people were very old. They had accreted many fragments of knowledge, of philosophy and science. A person, on Dissolution, could leave behind fragments of

insight, of wisdom, in the partial, semi-sentient assemblies called sub-corpora. Before dissolving in their turn into the general corpuscle shoals, the sub-corpora could be absorbed into a new individual, the knowledge saved. Or perhaps not.

If they were not incorporated quickly, the remnant sub-corpora would break up. Their component mentation-corpuscles would descend, and become lost in the anaerobic Deep at the heart of the world.

Sun-Cloud returned to the Surface of the Ocean.

She saw that the sun had almost set; a last sliver of crimson light spanned one horizon, which curved sharply. Above her the sky was clear and utterly black, desolately so.

Her corpuscles transmitted their agitation to each other.

She raised a lantern; cold light bloomed slowly across the sea's oily meniscus.

She roamed the Ocean, seeking Orange-Dawn.

At last the creeping lantern light brought echoes of distant motion to her optic corpuscles: a small form thrashing at the Surface in lonely unhappiness.

With a rare sense of urgency Sun-Cloud ordered her impeller corpuscles into motion. It didn't take long for her to accelerate to a significant fraction of lightspeed; the impellers groaned as they strained at relativity's tangible barrier, and the image of the lonely one ahead was stained with blue shift.

Wavelets lapped at her and air stroked her hide; she felt exhilarated by her velocity.

She slowed. She called softly: 'Orange-Dawn?'

Listlessly Orange-Dawn raised optic corpuscles. Orange-Dawn was barely a quarter Sun-Cloud's size. She was withered, her corpus depleted. Her corpuscles lay passively over each other, tiny mouths gaping with obvious hunger.

'Do I shock you, Sun-Cloud?'

Sun-Cloud sent small batches of corpuscles as probes into Orange-Dawn's tattered carcase. 'Orange-Dawn. Your corpuscles are suffering. Some of them are dying. Cold-Current is concerned for you -'

'She sent you to summon me to my Dissolution.' Sun-Cloud said, 'I don't like to see you like this. You're introducing a harshness into the Song.'

'The Song, the damnable Song,' Orange-Dawn muttered. Moodily she began to spin in the water. The corpuscles' decay had so damaged her corpus's circular symmetry that she whipped up frothy waves which lapped over her upper carapace, the squirming corpuscles there. She poked optic corpuscles upwards, but the night sky was blind. 'The Song drowns thought.'

'What will happen in a hundred Cycles, Orange-Dawn?'

Orange-Dawn thrashed at the water. 'The data is partial…' She focused wistful optic corpuscles on her sister. 'I don't know. But it will be -'

'What?'

'Unimaginable. Wonderful.'

Sun-Cloud wanted to understand. 'What data}'

'There are some extraordinary speculations, developed in the past, still extant here and there… Did you know, for instance, that the Cycle is actually a tide, raised in our Ocean-world during its passage around the sun? It took many individuals a long time to observe, speculate, calculate, obtain that fragment of information. And yet we are prepared to throw it away, into the great bottomless well of the Song…

'I've tried to assemble some of this. It's taken so long, and the fragments don't fit more often than not, but -'

'Integrate? Like a Song?'

'Yes.' Orange-Dawn focused her optic corpuscles. 'Yes. Like a Song. But not the comforting mush they intone below. That's a Song of death, Sun-Cloud. A Song to guide you into non-being.'

Sun-Cloud shuddered; little groups of her corpuscles broke away, agitated. 'We don't die.'

'Of course not.' Orange-Dawn rotated and drifted towards her. 'Watch this,' she said.

Quickly, she budded off a whole series of sub-corpora, each tiny body consisting of a few hundred corpuscles. Instantly the sub-corpora squirmed about the Surface, leaping and breaking the meniscus, blue-shifted as they pushed into lightspeed's intangible membrane.

Sun-Cloud felt uneasy. 'Those sub-corpora are big enough to be semi-sentient, Orange-Dawn.'

'But do you see?' said Orange-Dawn testily. 'See what?'

'Blue shift. The sub-corpora - see how, instinctively, they strain against the walls of the prison of lightspeed. Even in the moment

of their Coalescing. Light imprisons us all. Light isolates us…'

Her words filtered through Sun-Cloud, jarring and strange, reinforced by bizarre chemical signals.

'Why are you doing this, Orange-Dawn?'

'Watch.' Now Orange-Dawn sent out a swarm of busy impeller corpuscles; they prodded the independent sub-corpora back towards Orange-Dawn's corpus. Sun-Cloud, uneasy, watched how the sub-corpora resisted their tiny Dissolutions, feebly.

'See?' Orange-Dawn said. 'See how they struggle against their immersion, in the overwhelming Ocean of my personality? See how they struggle to live}'

Sun-Cloud's own corpuscles sensed the suffering of their fellows, and shifted uneasily. She flooded her circulatory system with soothing chemicals. In her distress she felt a primal need for the Song. She sent sensor corpuscles stretching into the Ocean beneath her, seeking out the comfort of its distant, endless surging; its harmony was borne through the Ocean to her by chemical traces.

… But would she struggle so, when it came time for her to Dissolve, in her turn, into the eternal wash of the Song?

It was, she realized, a question she had never even framed before.

Now, gathering her corpuscles closely around her, Orange-Dawn turned from Sun-Cloud, and began to beat across the Surface with a new determination.

'You must come with me, Orange-Dawn,' Sun-Cloud warned.

'No. I will see out my hundred Cycles.'

'But you cannot…' Unless, she found herself thinking, unless Cold-Current is right. Unless there is some lost way to extend consciousness.

'If I submit to Dissolution, I will lose my sense of self, Sun-Cloud. My individuality. The corpus of knowledge and understanding I've spent so long assembling. What is that but death? What is the Song but a comfort, an anaesthetic illusion to hide that fact?…'

'You are damaging the unity of the Song, Orange-Dawn. You are - discordant.'

Orange-Dawn was receding now; she raised up a little batch of acoustic corpuscles. 'Good!' she called.

T won't be able to protect you!' cried Sun-Cloud.

But she was gone.

Sun-Cloud raised lantern-corpuscles, sending pulses of slow light

out across the Ocean's swelling surface. She called for her sister, until her corpuscles were exhausted.

In some ways, Sun-Cloud's people resembled humans.

Sun-Cloud's component corpuscles were of very different ancestry.

Mentation-corpuscles - the neuron-like creatures that carried consciousness in tiny packets of molecules - were an ancient, anaerobic race. The other main class, the impellers and structure corpuscles, were oxygen breathers: faster moving, more vigorous.

Human muscles usually burned glucose aerobically, using sugars from the air. But during strenuous activity, the muscles would ferment glucose in the anaerobic way evolved by the earliest bacteria. Thus human bodies, too, bore echoes of the earliest biosphere of Earth.

But, unlike a human body, Sun-Cloud's corpus was modular.

Despite their antique enmity, the two phyla within Sun-Cloud would cooperate, in the interests of the higher creature in which they were incorporated.

Until Sun-Cloud weakened.

A mass of corpora, sub-corpora and shoals of trained impeller corpuscles rose from the Deep in a great ring.

Not five Cycles had passed since Sun-Cloud's failed attempt to bring Orange-Dawn home. Now, they had come for Orange-Dawn.

Sun-Cloud found her sister at the centre of the hunt. She was shrunken, already fragmented, her corpuscles pulsing with fear. 'I don't want to die, Sun-Cloud.'

Anguish for her sister stabbed at Sun-Cloud. She sent soothing chemical half-words soaking through the Ocean. 'Come with me,' she said gently.

Exhausted, Orange-Dawn allowed herself to be enfolded in Sun-Cloud's chemical caresses.

Commingled, the sisters sank into the Ocean. Their ovoid bodies twisted slowly into the depths; light shells from curious individuals washed over them as they passed.

The light faded rapidly as they descended. Soon there were few free sub-corpora; and of the people they saw most were linked by corpuscle streams with at least one other, and often in groups of three, four or more.

The Song was a distant, strengthening pulse from the heart of the Ocean beneath them.

Now Cold-Current rose up to meet them, huge and intimidating, her complex hide pulsing with lantern-corpuscles. The rim of her slowly rotating corpus became diffuse, blurred, as her corpuscles swam tentatively towards Orange-Dawn.

Cold-Current murmured, 'You are old, yet very young, Orange-Dawn. Your unhappiness is caused by ignorance. There is no other Ocean. Only this one. There is no change and never has been. These facts are part of what we are. That's why your speculations are damaging you.

'You have to forget your dreams, Orange-Dawn…'

Orange-Dawn hardened, drawing her corpuscles into a tight little fortress. But Cold-Current was strong, and she forced compact biochemical packets into Orange-Dawn's corpus. Sun-Cloud, huddling close, picked up remote chemical echoes of the messages Cold-Current offered.

… Hear the Song, Cold-Current's corpuscles called. Open up to the Song.

Their bodies joined, her impeller-corpuscles herding Orange-Dawn tightly, Cold-Current began to guide Orange-Dawn deeper into the lattice of mingled persons.

Sun-Cloud followed, struggling to stay close to her sister. Orange-Dawn's pain suffused the waters around her with clouds of chemicals; Sun-Cloud suffered for her and with her.

As they descended, individuals became less and less distinct, and free corpuscles swam through the lattice's closing gaps. At last they were falling through a sea of corpuscles which, with endless intelligent grace, swam over and around each other. Sun-Cloud's structurals and impellers felt enfeebled here, in this choking water; the effort of forcing her way downwards seemed to multiply.

Perhaps this was like Dissolution, she thought.

At last there was only one entity, a complex of mingled bodies that filled the Ocean. The living lattice vibrated with the Song, which boomed around them, joyous and vibrant.

'The Deep,' Cold-Current whispered to Orange-Dawn. 'The Song. Now you will join this, Orange-Dawn. Uncountable billions of minds, endless thoughts straddling the world eternally. The Song will sustain your soul, after Dissolution, merged with everyone who has ever lived. You'll never be alone again -'

Suddenly, at the last, Orange-Dawn resisted. 'No! I could not bear it. I could not bear -'

She was struggling. Jagged images filled Sun-Cloud's mind, of being crushed, swamped, stultified.

Immediately a host of sub-corpora and corpuscles, jagged masses of them, hurled themselves into Orange-Dawn's corpus. Sun-Cloud heard a single, agonized, chemical scream, which echoed through the water. And then the structure of the corpus was broken up. Corpuscles, many of them wounded, came hailing out of the cloud of Dissolution; some of them spiralled away into the darkness, and others rained down towards the glowing Deep. Sub-corpora formed, almost at random, and wriggled through the water. They were semi-sentient: bewildered and broken images of Orange-Dawn.

Sun-Cloud could only watch. Loss stabbed at her; her grief was violent.

Cold-Current was huge, complex, brilliantly illuminated. 'It is over. It is better,' she said.

Sun-Cloud's anger surged. 'How can you say that? She's dead. She died in fear and agony.'

'No. She'll live forever, through the Song. As will we all.'

'Show me what you know,' Sun-Cloud said savagely. 'Show me how Orange-Dawn might have extended her life, through another ninety Cycles.'

'It is artificial. Discordant. It is not appropriate -'

'Show me!'

With huge reluctance, Cold-Current budded a tight, compact sub-corpora. It bore the cubical pattern Sun-Cloud had observed earlier. 'Knowledge is dangerous,' Cold-Current said sadly. 'It makes us unstable. That is the moral of Orange-Dawn's story. You must not -'

Sun-Cloud hurled herself at the pattern, and forcibly integrated it into her own corpus. Then - following impulses she barely recognized - she rose upwards, away from the bright-glowing Deep.

She passed through the cloud of Orange-Dawn's corpuscles, and called to them.

The Song boomed from the Deep, massive, alluring, stultifying; and Cold-Current's huge form glistened as she called her. Sun-Cloud ignored it all.

She ascended towards the Surface, as rapidly as she could.

Orange-Dawn's fragmentary sub-corpora followed her, bewildered, uncertain.

The place Sun-Cloud called the Deep was an anaerobic environment. Only mentation-corpuscles could survive here. They lay over each other in complex, pulsing swarms, with neural energy flickering desultorily between them.

The Song was a complex, evolving sound-structure, maintained by the dense shoals of mentation-corpuscles which inhabited the heart of the world, and with grace notes added by the Coalesced individuals of the higher, oxygen-rich layers of the Ocean.

At the end of their lives, the mentation structures of billions of individuals had dissolved into the Deep's corpuscle shoals. The Song, they believed, was a form of immortality.

Embracing this idea, most people welcomed Dissolution.

Others rejected it.

Sun-Cloud gathered around her central corpus the cubical pattern of Cold-Current, and Orange-Dawn's sad remnants, integrating them crudely. She grew huge, bloated, powerful.

And now, as she broke the thick Surface of the Ocean, she made ready.

She wondered briefly if she had gone mad. Perhaps Orange-Dawn had infected her.

But if it were so, let it be. She must know the answer to Orange-Dawn's questions for herself, before she submitted to - as she saw it now, as if through her sister's perception - the sinister embrace of the Song.

She enfolded Cold-Current's compact data pattern, and let its new wisdom flow through her… Of course. It is simple.

She began to forge forward, across the Ocean.

A bow wave built up before her, thick and resisting. But she assembled her impellers and drove through it. At last the wave became a shock, sharp-edged, travelling through the water as a crest.

And now, quickly, she began to sense the resistance of light-speed's soft membrane. The water turned softly blue before her, and when she looked back, the world was stained red.

At length she passed into daylight.

The day seemed short. She continued to gather her pace. Determined, she abandoned that which she did not need:

lantern-corpuscles, manipulators, even some mentation components: any excess mass which her impellers need not drag with her.

A bow, of speed-scattered light, began to coalesce around her.

The day-night cycle was passing so quickly now it was flickering. And she could sense the Cycles themselves, the grand, slow heaving of the Ocean as her world tracked around its sun.

The light ahead of her passed beyond blue and into a milky invisibility, while behind her a dark spot gathered in the redness and reached out to embrace half the world.

Time-dilated, she forged across the surface of her Ocean and into the future; and ninety-five Cycles wore away around her.

Light's crawl was embedded, a subtle scaling law, in every force governing the structure of Sun-Cloud's world.

The sun was much larger than Sol - ten thousand times more so - for the fusion fires at its heart were much less vigorous than Sol's. And Sun-Cloud's world was a thousand times smaller than Earth, for the electrostatic and degeneracy pressures which resisted gravitational collapse were greatly weaker.

Lightspeed dominated Sun-Cloud's structure, too. If she had been a single entity, complete and entire, it would have taken too long for light - or any other signal - to crawl through her structure. So she was a composite creature; her mind was broken down into modules of thought, speculation and awareness. She was a creature of parallel processing, scattered over a thousand fragile corpuscles.

And Sun-Cloud's body was constrained to be small enough that her gravitational potential could not fracture the flimsy molecular bonds which held her corpus together.

Sun-Cloud, forging across the Surface of her Ocean, was just two millimetres across.

At last, a new light erupted in the bow that embraced her world.

With an effort, she slowed. The light-bow expanded rapidly, as if the world were unfolding back into its proper morphology. She allowed some of her impeller corpuscles to run free, and she saw their tiny wakes running across the Surface, determined, red-shifted.

Now that her monumental effort was done she was exhausted, depleted, her impellers dead, lost or dying; unless new impellers joined her, she would scarcely be able to move again.

Ninety-five Cycles.

Everybody she had known - Cold-Current and the rest - all of them must be gone, now, absorbed into the Song's unending pulse.

It remained only for her to learn what mystery awaited, here in the remoteness of the future, and then she could Dissolve into the Song herself.

… From the darkling sky, the new light washed over her.

Her optic corpuscles swivelled upwards.

She cried out.

Sun-Cloud felt her world shrink beneath her from infinity to a frail mote; the Song decayed from the thoughts of a god to the crooning of a damaged sub-corpus.

Above her, utterly silently - and for the first time in all history - the stars were coming out.

To human eyes, the skies of this cosmos would have seemed strange indeed:

The stars spawned from gas clouds, huge and cold. Hundreds of them formed in a cluster, companions to Sun-Cloud's sun. Light and heat crept from each embryonic star, dispersing the remnant I- wisps of the birthing cloud.

It took five billion human years for the light to cross the gulf between the stars.

And at last - and as one speculative thinker among Sun-Cloud's : people had predicted, long ago - the scattered light of those remote [ suns washed over an unremarkable world, which orbited a little I above the photosphere of their companion…

I The stars were immense globes, glowing red and white, jostling in a complex sky; and sheets and lanes of gas writhed between them.

Orange-Dawn had been right. This was wonderful, beyond her 1 imagining - but crushing, terrifying.

Pain tore at her. Jagged molecules flooded her system; her corpuscles broke apart, and began at last their ancestral war.

She struggled to retain her core of rationality, just a little longer. Exhausted, she hastily assembled sub-corpora, and loaded packets of information into them, pale images of the astonishing sky. She sent them hailing down into the Ocean, into the Deep, into the belly of the Song itself.

Soon a new voice would join the Song: a merger of her own,

and Orange-Dawn's. And it would sing of suns, countless, beyond imagining.

Everything would be different, now.

She fell, gladly, into the warm emptiness of Dissolution.