The Medusa Chronicles

by Stephen Baxter

  “Oh, come on. The Phobos deal was seventy-six years ago!”

  “We Hermians don’t make many jokes. When we come up with a good one we keep it . . .” The path was steepening sharply. “You okay on this gradient? Until the Machines came we used to run a funicular for the tourists: one of the seven wonders of the solar system, or so our ads claimed.”

  “I’ll be fine.”

  “We’ll be in sunlight soon. Check out your suit.” She tapped a panel on her chest. The front of her own suit silvered and the back turned dark, a chameleon-like adaptation that would, Falcon knew, respond to a change of position so that she always kept her mirrored side to the solar glare, the heat-dumping dark side turned away. Meanwhile extraordinary wings folded out from a backpack, so that she looked like some overgrown, ­silvery bat. The wings were radiator panels, more thermal control.

  Falcon inspected his own clumsier systems. There was, of course, no human-issue suit that would fit Falcon. But the Hermian engineers, who famously relished a challenge, had swarmed over the latest iteration of his prosthetic carriage, checking the integrity of his basic life-support systems, swaddling him in protective thermal blankets, and fitting an adapted set of radiator wings and other systems to his frame. It would never be as elegant as Borowski’s suit, which was the product of more than three centuries of technological evolution since the first landings here—but, the engineers told him, it would keep him alive long enough to get to shelter if anything went wrong. A pragmatic if not entirely reassuring promise.

  And while he was distracted by the unfolding of his wings, Howard Falcon rolled into sunlight. His optical shields immediately cut in, reducing the brilliance to a mere dazzle. The mighty sun glared over a sharp, crumpled horizon. From this elevation Falcon looked out over a plain of broken rock, across which long shadows stretched. Superficially this world was Moon-like; a world scarred by craters, the relics of impacts dating back to the solar system’s violent formation. But Falcon had been to the Moon many times—at least, before the Machines had moved in—and he could see significant differences. The crater walls seemed visibly less steep, perhaps a product of Mercury’s higher gravity and the inner heat of its larger, molten core. And Falcon saw a twisting line of cliff faces, almost like a wrinkle in the landscape that cast a band of shadow within which more artificial lights huddled. Such features, called rupes, were the relics of episodes in which Mercury, its inner heat dissipating, had shrunk, leaving its skin a little like that of a withered apple.

  Above it all hung the sun, more than twice its width as seen from Earth, but with around seven times the intensity. Falcon seemed to feel that tremendous outpouring, just standing here. It was impossible to reconcile the physical force of the star’s presence with the pale thing he remembered from the winter mornings of his childhood in England, as if the sun barely mustered the energy to lift itself above the horizon. It was that monstrous flow of energy that had made Mercury a key colonisation target, first for humans—and latterly for the Machines. The sun: star of humanity and of the solar system, and now a prize of war.

  He was aware of Borowski watching him. She said, “You know, a lot of people just don’t get Mercury. Or us Hermians, come to that. Even though we’re such a jolly bunch.”

  Falcon smiled. “I looked you up. During the Phobos negotiations your ambassador’s ‘irascibility’ was actually minuted.”

  She looked out over her world of rock and raw energy. “Earth is a pretty alien place for us, you know. Mars, though, we have something in common with. We have dreams of terraforming too. Or we did. You’re surprised? It would be a big job. You’d need to shield the planet from the sunlight, spin it up to give a sensible day-night cycle, import volatiles for oceans and an atmosphere.”

  “I thought most Hermians liked the place the way it is.”

  “Well, I’m among them, but you have to think of the future. You need a long-term habitability solution, just in case your children forget how to maintain the air engines. That was the ambition, anyhow.”

  Falcon nodded. “But here are the Machines taking all that away from you.”

  Borowski squinted up at the sun, its fierce light flattening the planes of her face. “The shield isn’t yet visible to the naked eye, but you can already measure the dip in the solar energy reaching the planet. And you can see it with a bit of visual processing: a kind of web hanging right in front of the sun, a bit larger than Mercury’s diameter; a hell of a thing, and yet, according to our spy probes, gossamer thin. Mostly aluminium—Mercury aluminium, and that theft pisses me off greatly.”

  “I don’t understand how the shield is being kept in position, up there in space. You have the pressure of sunlight, and Mercury’s gravity pulling it down to the planet—”

  She pointed back over his shoulder. “There’s a secondary structure back there, even bigger than the shield itself. It’s a mirror, Commander—an annulus, a circular band, with a hole you could slide Mercury through, literally.”

  Falcon the engineer peered up in wonder. “So the shield blocks the light from Mercury. But the sunlight that passes the shield hits this mirror, and is reflected back to hold the shield itself in place, pushing against the gravity and direct sunlight.”

  “You’ve got it. The whole thing is one vast engine, using gravity and beams of sunlight as girders.”

  “I wish I could see it.”

  She laughed. “Now you sound like a Hermian. Of course there’s more to it than that. Mercury’s orbit is strongly elliptical, and the shifting solar and planetary tides disturb the set-up—it needs a lot of station-­keeping. But we know that both shield and mirror are composed of Machines, which are individually pretty smart, and a swarm of them will be that much smarter again. Working en masse their components are able to sense their positions, compensate for the shift in balance of the competing forces.

  “For now, most of the sunlight still gets through, but it won’t stay that way; the holes are being filled in. My engineers tell me that the final phase will be very rapid—that’s in the nature of exponential growth. We’ll see the sun go dark in a day. Cutting off the sunlight on which we depend for everything.

  “Anyhow, it’s nice to know we Hermians have friends at our backs as we face this crisis.” She glanced at him sourly. “Friends from Earth. One warship. And you.”

  He spread his hands. “The World Government is a cumbersome beast that’s slow to respond to a crisis. But the people of Earth are right behind you. That’s why the Acheron timed its mission to arrive today.”

  She grunted. “For the coincidence of the transit.”

  “Well, it’s only a partial transit, but the timing is apt.” He turned and pointed, directly away from the sun. “Today, Mercury happens to lie on a straight line between sun and Earth. And if you were standing on Earth you could see the planet’s shadow crossing the face of the sun . . . All over the world, people are looking up at Mercury, right now, looking at us. President Soames is big on symbolism.”

  “Great. But what are you Terrans going to do?”

  “Whatever we can.”

  Which, Falcon admitted, had been little enough so far.

  * * * *

  For an old stager like Falcon, it had been a surprise when the Ultimatum’s centenary had suddenly arrived, marked by grim headlines and analyses.

  But even in an age when extreme longevity was becoming routine, the making of a threat to be fulfilled five centuries hence—perhaps twenty old-fashioned human generations away—seemed beyond the capacity of most people to comprehend. It didn’t help to focus minds that at first the Machines had appeared to do nothing more threatening than to suspend shipments of Jovian helium-3 and other products to Earth.

  The authorities had responded, however. Saturn, the second of the solar system’s gas giants, had been fast-tracked as an alternate source of fusion fuel. Back home, great new projects were afoot. Falcon
had been fascinated by plans to erect space elevators around the equator of Earth, beanstalks that would allow fast and cheap access to space on a massive scale—and would provide a fast mass evacuation route, if it came to that.

  But behind the scenes, successive administrations had put more subtle measures in place to respond to the Ultimatum. The Phobos Treaty had been one step. Meanwhile a new Planetary Security Secretariat had been established—a typical bureaucratic response, people had grumbled at the time, but it had laid down some useful groundwork.

  Despite all the strategic thinking and wargaming, however, it had still taken everybody by surprise, Falcon thought, when, over a century after the Ultimatum, the Machines had finally made their first significant move with this assault on Mercury. And it had led to predictable demands that the World Government do something about it.

  Falcon, semi-detached from humanity himself, rather resented having been drawn into Planetary Security’s covert plans in response. Yet here he was, standing in the Hermian sunlight.

  Borowski said now, “The Machine ships came in at superspeed. Better than anything we’ve got. Even the warning from Spaceguard got to us only a little before the vanguard arrived. Some of our technical analysts think the Machines have got what they call an ‘asymptotic drive.’ Do you know the theory? You throw matter into a miniature black hole, and as it’s crushed out of existence you get a pulse of energy that can drive a spacecraft. But you’d need some way of manufacturing miniature black holes to make it work . . .”

  Uneasily, Falcon remembered Adam’s talk of the Machine he called 90, and the radically new physics he had dreamed up out in the dark, surrounded by a spinning sky . . . From that, perhaps, something like the asymptotic drive might have come.

  However they were powered, nothing had been able to catch the Machine ships.

  “They landed at Inferno,” Borowski said. “Second city on Mercury, slap bang in the middle of the Caloris Basin.”

  Falcon nodded. Caloris was a mighty impact crater that sprawled across much of one hemisphere of Mercury. “They would land there. Machines have a sense of symbolism too—or at least of symmetry.”

  “They started their construction work on day one. We saw it from surveillance satellites. Their ships just dissolved, melting down into subcomponents that started chewing the rock . . .”

  “Assemblers.”

  “Yeah.”

  Falcon knew the theory of this kind of engineering. Assemblers were von Neumann replicators, a variety of specialised Machines that had used Mercury’s sunlight and minerals to make copies of themselves: Machines that fed on planets, like flesh-eating bacteria. From the beginning the assemblers had been firing material up into space to build what had become their huge spaceborne construction project, the sunshield hovering over Mercury. Also, for reasons as yet unknown, they were firing clusters of probes across space—not towards Earth, but, bafflingly, to Venus.

  Borowski pointed at the sun. “Everything we do here depends on solar energy. And now the Machines are using that very energy to build the shield, their weapon against us.”

  “What do you think their ultimate goal is?”

  Borowski shrugged. “Isn’t it obvious? The Machines have come here for the same reasons humans did. Mercury is a rich lode of raw ­materials, handily positioned as close as you can get to the solar system’s powerhouse. I’d predict we’ll see large-scale resources extraction starting up soon, maybe manufacturing.”

  Falcon knew the Machines; he doubted their ambitions would be so limited.

  “The Machines have left our people at Inferno unharmed. They’ve allowed evacuation of children, families, the ill, even passage of essential supplies. But this will be the end of Prime, Vulcanopolis, Inferno—the end of us.”

  Falcon could hear her pain, and imagined how difficult it must have been for the tough, noisily self-reliant Hermians to have to reach out to the other worlds, to that resented mother Earth. “President Soames is going to make a speech later.” Even as he said that, he could hear how lame it sounded.

  Borowski just laughed. “I told you, I’ve been to Earth. I’ll tell you what I saw, Commander. I saw a world like a garden. A park. All those cities like museums, the restored animals. Everything’s free,” she said with disgust. “You Terrans are soft.”

  He sighed. “Maybe. But we’re behind you.”

  “You have to be. Because if they get past us, they’ll be coming for you.” She glanced up at the sun, occluded by a spider web neither of them could see. “We’re done here.” She turned on her heel and led him back down the crater-mountain path and into shadow.

  Later that day a message arrived for Falcon, followed by a requisition order for a sub-orbital shuttle. Adam had agreed to meet him in Caloris Basin.

  34

  It turned out that Machines, too, sought shelter from the ferocious sun of Mercury when they could find it. At Caloris, Falcon was directed to the shadow of one of the rupes that curled across the shattered ground of the great impact crater. For reasons lost in astronomical lore, these cliff-like folds had been named—by cartographers puzzling over images returned from the first uncrewed probes to Mercury—after ships of exploration, such as Beagle and Santa Maria. That tradition had continued when humans had come here in person.

  Thus, Howard Falcon was directed to the shadow of an escarpment called Kon-Tiki.

  * * * *

  Falcon met Adam out on the surface, away from the craft. The Machine stood in shadow, silent and still, illuminated only by sunlight reflected from the baking rocks.

  “So here we are, once again,” Falcon began. “Face to face. So to speak.”

  Still Adam said nothing. His latest physical body was only vaguely a humanoid form, rendered in advanced technology. His legs were a tangle of springs and shock absorbers; his torso was a cylinder covered with access panels; his arms were flexibly jointed and fitted with claw-like manipulators. His head was now an open frame, fitted with artificial eyes and ears and even a mouth, surrounding an empty space. The design made Falcon’s own Oscar-statuette chic seem prehistoric.

  But Adam reached out a hand. Falcon held out his own prosthetic hand in return, and Adam’s metallic claw enfolded his. They stood there as if locked together, palm to cold palm.

  Adam smiled, an eerie distortion of that mouth. “A simple gesture but with layers of meaning, Falcon. You humans walk around in a fog of symbols.”

  “So do you,” Falcon retorted. “It wasn’t my choice to stand here under a cliff called Kon-Tiki.”

  “Ah, yes. I wish it was your famous vessel that was commemorated here, rather than an ocean-going craft of an age even earlier than yours. Still, the connection had occurred to me.” He glanced towards the position of the sun. “But you chose the day of Mercury’s transit for this meeting. Another act of symbolism.”

  “It’s no exaggeration to say that the hopes of at least two worlds—two human worlds—are resting on this encounter between us. Why not choose such a day? And once the transit is over everybody’s attention will be focused on the speech President Soames is due to give, after we’re done here.”

  “I hope she has two drafts ready. Good news and bad news.”

  That made Falcon smile. “I tell people you have a sense of humour, Adam. Nobody believes me.”

  “Tell me why you’ve come here.”

  “You know why. I’ve been asked to speak to you about your actions on Mercury. Particularly the building of the sunshield, which is impossible to read as anything other than an act of aggression towards the Hermians and, through the mutual protection treaties, towards all of mankind. And you know why it’s me.”

  “I am grateful for the things you did for me—for us. Your stewardship, in our earliest days. But those times are long in the past. By the way, I made an error when I chose to call you ‘Father.’” Adam’s head tilted. “I did not wish to
. . . displease you. But it implied a bond, a connection, that was never really there.”

  “I’m sorry you feel that way,” Falcon said, with genuine regret—even though the Machine was referring to conversations centuries gone. “And is it too late for humanity on Mercury, Adam?”

  “We pursue objectives beyond the defeat of humanity.”

  That dismissive sentence chilled Falcon, even standing here in Mercury’s heat. “The Hermians think you intend to hijack solar power and Mercury’s resources, to use them for engineering projects.”

  “In other words: to do what they’ve been doing. Why do you think we’re here, Falcon? Of all the humans I have encountered, you are the one who most nearly thinks like a Machine, when you choose to.”

  “More like, when I can’t help it.”

  Adam actually laughed, a sound that seemed more realistic than Falcon had observed before.

  “Let’s not play games. What will you make here?”

  Adam raised his face to the dark sky, and tapped his temple with his finger. “You made us this way, Falcon. In your own image. We are human-sized intelligences, with human-sized limits. It was all you could imagine. Now we take your legacy as a building brick to construct something much greater. We will join . . . We will create a mind greater than any one Machine as your own brain is greater than a single neuron.”

  “You never used to brag, Adam.”

  “Well, I’ve a lot to brag about.”

  “Why Venus?”

  “You mean, why have we sent assemblers there? It is the next logical target. I believe there is a small human settlement at the south pole, easily evacuated . . .”

  Falcon knew that the crew of Aphrodite Base were already being taken offworld to Cytherea One, the main crewed space station at Venus. “You aren’t human, but you aren’t inhuman either. You show concern for the safety of the scientists at Aphrodite, just as you’re allowing evacuations on Mercury. Remember my own efforts to have you Machines recognised as Legal Persons (Non-human)? We respected your rights, back then—”