Locomotion

25 03 2010

Light Rail Channel

“…Project Stephenson, the task of connecting the outposts and mining stations, was the largest planetside undertaking since the construction of Charlotte Station.  Channels were carved through the uneven landscape to provide protection from meteor showers and to streamline loading and unloading of minerals and equipment required elsewhere across Fram.” 

The rail project was the next logical step in the effort to connect the four colonies with each other, and with the various installations scattered about the edge of the main crater. Project Stephenson was prioritised by the First Congress, and work began mere weeks after the close of that meeting. The project represented the most significant capital investment yet undertaken by our fledgling Colony; our other great undertakings – such as Charlotte Station, Port Mayflower, and the cable which connected them – had all been constructed using prefabricated materials, and according to designs drawn up in Sol.

The Stephenson rail network would be almost entirely produced from resources mined from Fram, and designed by us.

The highways of carbon sheeting had been a temporary measure, and one inconsistently applied at that. Each of the colonies had been connected to the central hub, Charlotte Station, although none was directly connected to another. Nor were the open-cut and COIL mines, or the solar field and launch complex, connected to the highway system. Moreover, these were surface roads, with all the problems entailed therein: windstorms would deposit regolith across the carbon sheeting, and these drifts could cut access until they were ploughed to the side.

Light rail was an elegant solution, though not one commenced without thorough consideration. For example, the Conference rejected the use of maglev systems. Most persuasive of the arguments submitted in favour of a light rail electrification scheme was the conservation of power and comparative ease of construction. A magnetic levitation system would involve the construction of high-temperature superconductors and magnetic shielding; moreover, the levitation and propulsion systems would have to be carried onboard the train, reducing cargo space and increasing weight. A light rail network could be connected to and powered by a Colony-wide power board.

We began by digging trenches ten meters deep and thirty meters wide. The inside faces of the channels were strengthened with inlaid carbon mesh. We modified one of our enormous UC-104s: its utility crane was stripped from the chassis and, instead, installed were two load-bearing arms ending in a single rotary bore attachment. Its legs locked in place and the body hung low as its arms dug up the regolith, eerily like a Martian handling-machine plucking victims from the ground in a Wellsian novel.

Our priority, as with the carbon highways, was to connect each of the colonies to Charlotte Station. The elevator ground station was located between each of the colonies and served as a natural terminal. We had to dig over eight kilometres of channels just to fulfil this limited objective.

The closer that we dug to Charlotte Station, the more difficult that task became; Charlotte was located in the base of the large crater in which all the colony pods had landed, and as such there was less regolith between the surface and the bedrock. In places we also struck fractured basalt sheets. Here KOVTARs equipped with portable COIL rigs broke up the densest materials.

It was important that the channels be deep and wide. Deep trenches afforded better protection from meteorites, and we would add a further parapet of exhumed material to the western lip of each channel. The trenches would be widest for the main lines of the network, those between the colonies and the Charlotte Station Terminal – on these lines we would lay two tracks, one for each direction. When we began construction on the ancillary lines, to the spaceport, mines and reactor, we would lay only a single track to accommodate comparatively less traffic.

Three rails were installed for each track. The Stephenson network used a third rail to provide 1,200 V of power to the trains. The conditions of Fram and the depth of the rail channels precluded the use of catenaries and overhead wires, thus necessitating the third rail. Here we used a covered, bottom-contact rail to prevent the kind of disruptions caused by wind-driven regolith that had plagued the carbon highways.

Yet the geographic conditions also gave us certain benefits. The distances between terminals were short – Charlotte Station was no more than three kilometres from any colony – which meant that there was no need to construct feeder stations along the line. Furthermore, our channels followed the general decline of the crater; trains running to Charlotte would run downhill. Our trains would be built with regenerative breaking equipment, which would generate power while breaking and return that power to the rail network for use by trains travelling uphill. Excess energy would be converted to heat and vented into Fram’s atmosphere – our first, if somewhat insignificant, terraforming effort.

But first we had to dig the channels, lay the track, and build the trains. That was many months of work. Still, our impression upon this ancient and dusty planet grew more profound…





Aurorae

25 03 2010

“The MSB Aurora. Can’t remember what the ‘B’ stood for. Modular Service…something. Anyway, controversial things. We set them to work mining the ring of hydrogen and oxygen. There were only a handful of them, and they were small. What amount of volatiles they collected was mostly converted to their own reaction mass. Very low bang for buck. But we didn’t have any other use for them – yet – and we figured it was better to put them to work, see, than have them sitting around in storage…”

The orbiter Ethel Rosenberg rolled over gracefully, exposing its flat belly to the light of Alpha-A.

The payload doors along the orbiter’s dorsal surface opened. Interior light spilled from the joins and illuminated lines of ice crystals. The crystals spun away in a spiral as the Ethel Rosenberg continued its roll.

“Payload bay wasn’t fully depressurised,” Borzęcki spoke into the mike. “No matter.”

Now the fuselage clam-shelled open, and Borzęcki could see straight down into the payload bay of the orbiter. He touched the controls of his MMU, and two of its ten thrusters fired. He inched downward toward the opening doors.

“Payload bay doors show green.”

Borzęcki’s eyes lifted to the bow of the orbiter; there, in the command module, he could see the silhouettes of the commander and pilot. Borzęcki formed two thumbs-up as best he could in the pressurised suit, and waved them toward the shapes of his crew.

“I confirm,” he replied.

The two Auroras were aligned facing one another, and they only just fit into the payload bay. Their hulls were painted a shade of blue Borzęcki had not seen for years – a flat, late autumn afternoon blue – while their manipulator arms, ramscoops and processing modules were painted a pale cream. Borzęcki fired his forward thruster once, cutting his momentum, then twice, bringing him to a stop at the rear of the payload bay.

“I have positive contact.”

Each Aurora was the size of a satellite, maybe twenty-five feet in length. Borzęcki placed his gloved hand against the drive nozzle of the Aurora he stood behind. From his perspective, looking along the length of the craft, the main hull formed the shape of the letter H. There were two internal cargo modules set inside a rounded double-hull; connecting these two pods was the flattened engine. In the gaps formed by the vertically-aligned cargo pods sat the various, mission-specific modules.

Borzęcki crawled forward carefully and moved his way along the dorsal surface of the closest Aurora. Mounted asymmetrically along the upper surface were the AI unit and an articulated manipulator, folded at each of its joints and locked in place. Borzęcki held his wristpad over the AI hub and checked the network signal.

After a few moments, the capcom’s voice came through Borzęcki’s earpiece:

Ethel, Mayflower. Board’s green.”

Borzęcki struggled backwards until his boots made contact with the orbiter hull. The manipulator arm set into the orbiter bay closest to Borzęcki started to whir; he felt this movement through his magnetised boots. The arm began to extend, and the Aurora – secured at its base to the end of the manipulator – rose slowly from the bay.

Borzęcki made a visual inspection of the ventral surface of the Aurora. Here the diffusion plant had been installed. There was a ramscoop mounted forward of the Aurora, a simple, boxy module jutting forward and beneath the bow of the craft like a challenging jaw thrust forward. Behind the ramscoop were twin booms which would deploy perpendicularly downward of the hull. For now, these booms were locked in place beneath the hull.

The orbiter’s manipulator arm was clamped around a load-bearing dock set inside the ventral hull, between the processing module and the drive nozzles.

“Seal looks good,” Borzęcki spoke into the mike. “She’s just popped out of the payload bay.”

A line of light crawled down the Aurora, like a terminator crawling across the face of a globe. The light of Alpha-A was sharply demarcated by the shadow of the payload bay door.

Before the orbiter manipulator disengaged, Borzęcki made a visual inspection that the ramscoop apparatus had properly deployed. Port Mayflower sent the activation signal to the Aurora. The lock holding the twin booms in place beneath the Aurora slid back to where the booms joined the hull. Then they lowered, silently.

These were the magnetic loops: when activated, the wands would generate alternating positive and negative currents. This action created a magnetic field which charged particles within the field and channelled those particles into the ramscoop. The resulting magnetic field was weak, but this weakness helped filter the fines from the solid particles. Once through the ramscoop, the processing module would sort silicate and metal from precious volatiles; oxygen would be converted into lox to fuel the Aurora, the hydrogen would go into storage in the twin cargo modules along the flanks of the Aurora.

Borzęcki  said, “Okay, everything looks good from here. Go for deployment.”

The commander confirmed, followed moments later by capcom. They ran through the checklist. Then manipulator arm disengaged. Centrifugal force imparted by the Ethel Rosenberg’s roll worked on the Aurora, and it drifted up and away to the left.

When the Aurora was obscured by the payload bay door, Borzęcki stepped carefully toward the second craft, and worked his way up onto its dorsal surface…





41, 627, 214, 079, 352 Kilometers

5 03 2010

Two weeks after Cane murdered Gingrich and disappeared into the northern wilderness, a psychologist came to my quarters. He was very friendly but clearly tired. He introduced himself as Jacques.

“Some people I speak to think that we have failed,” Jacques explained, speaking on behalf of the many mental health specialists among the Colonists. “Perhaps we did. But psychology has received more emphasis of late.”

I nodded.

“And if everyone is like me, then you can’t help that people don’t seek out your services.” I gave Jacques a cup of soya. “I guess that’s why you’re here.”

Jacques sipped his drink but didn’t answer. Since the murder, the role of the psychologists had been re-evaluated, and in many cases their services became mandatory. They couldn’t see everyone, of course; instead they focussed on people who had displayed symptoms of poor mental health in their work or social lives.

“Some of your colleagues are concerned,” Jacques stated flatly.

Denunciations. But not made without basis.

“Undoubtedly,” I replied, “but I’m not going to beat someone to death with a wrench.”

Jacques smiled. “That’s not why I’m here. That’s not why we – ” again the royal ‘we’, in reference to the psychologists, as though they were separate from the mentally unhealthy “ – are doing this.”

“This?”

“Coming to people, talking to them.”

“Interviewing them?”

“If you like.” Jacques sipped his soya again, and a look of satisfied, energised relief washed over his face. “On the Quoqasi, we had to worry about cabin fever. Four thousand people cooped up in a starship for five years. But the reality was less of a concern than we had anticipated.”

“Because we all passed the psyche eval.”

“Yes. But also because we had something ahead of us: Planetfall. And this great endeavour of colonising another star system. Something to look forward to.”

I sipped my own soya. I didn’t watch Jacques as he talked, but instead stared absently at the floor. Surely he would jot that down in his mental notepad, maybe underline the comment or star the margin. I felt as though I were in a public bath, for the first time, when my heart skipped a beat as I first appeared naked before everyone.

Jacques continued talking, although I found it difficult to concentrate on what he was saying. Something about the Bottleneck, suggesting that the murder should have happened when we were overworked and fatigued and on rations.

“But we buried ourselves in our work, and looked forward to the Mayflower.”

Mayflower. How long had it been since the arrival of Mayflower? I couldn’t remember. I had trouble conceiving the passage of time. Every soya tasted the same, every shift involved the same tasks, each face stayed the same. When I thought back on the voyage in Quoqasi, sometimes it had felt like decades of my life had passed. But then I had problems remembering much of the trip, and with a spin of somatic dizziness, suddenly the voyage seemed like weeks in my memory.

I shook my head, and asked, “And now?”

Jacques explained that in the absence of something to look forward to, the early fears of psychological trauma were revisited. The murder only evidenced the thesis.

“And that’s what happened to that mechanic, Cane?”

Jacques was sipping his drink as his shook his head. He cleared his throat. “No. No, he and his partner had incompatible personalities, and had been in conflict for a long time. Each had made requests to be reassigned.”

I nodded, still staring at the floor. “They obviously weren’t.”

“I’m not here to talk about him. I’m here to talk about you. Let’s start by talking about her.”

I didn’t need to look up from my space to know what Jacques was talking about. I turned straight to the picture I had on my small desk; the only decoration in my quarters. If my eyes could fade an image like the light of a star, then the picture would have long ago been washed of colour and detail, left only to exist in my faulted memory.

We were both wearing white shirts. She was sitting in front of me and leaning back into my chest, and the top button of my collar was open. She was smiling that resplendent, wide smile of hers; but her eyes were closed, her black lashes pointed downward. Her hair was swept across her forehead. I could almost smell her hair now.

“Her name is Ali.”

“She was a musician?”

I looked back at the picture. The neck of her cello could be seen in the foreground.

“The best.”

“Was she a candidate for the Project?”

“Mmm.”

Where had the years gone? I looked at myself in the picture, then down at my reflection in the syrupy, black surface of the soya. Grey had spread from my temples like solar wind across the magnetosphere; deep lines were carved around my eyes. But there was nothing to show for these years. The feel of her soft, white skin under my fingers; the tensing of her muscles when she came; the lazy stretch of her arm across my chest as she slept; the political arguments; the way her big, blue eyes lit up when she learned something new; the tattered, hardcopy books held so tenderly in her hands. What had I done in those years without these things?

These memories felt so new, so fresh, so important; but really they were old and constantly revisited. What other memories had I lost, to preserve these with such strength?

Jacques was looking at me with a strange expression. I realised that he was waiting for an answer to a question I’d never heard. His soya was empty. Perhaps he had asked the question some time ago.

“I never thought it would be so hard,” I confessed. I saw the tears in my peripheral vision, rather than felt them fill my eyes. “Even when there were five AUs between us, a letter from her was never more than forty minutes away. Now, even if she could write to me, it would take four years to reach me. Four years!”

“You’re homesick,” Jacques said.

“I’m lovesick.”

“No. Lovesickness involves periods of mania, interspersed with depression and obsessive-compulsiveness. You’ve exhibited only depression, almost exclusively, since we left.”

“I’ve never been the most labile of persons,” I replied.

Jacques pressed on. “I also checked the maintenance logs. You’ve never checked out an e-suit, never qualified on a Sprat. You’ve only left this Colony once, for the conference in Alpha-1, and only then because you presumably had to.”

“Fram holds no meaning to me. No significance.”

“I thought not. A symptom. Ali is a proxy for your homesickness.”

I thought of Earth, and the inner system: teeming, crowded, overpopulated, noisy. How could she live there? I’d often asked her that. Government housing, population control, pollution, crime, political unrest; how could Ali possibly represent all of that, in my mind? And how could I miss that?

“No. I miss her. Not Sol. Your set of symptoms can’t be perfect. Or maybe this is just how lovesickness plays out, over light years.”

Jacques appeared shocked, briefly, as though he’d not considered the imposition of distance upon mental illnesses which involved separation. But he recovered quickly.

“Teleology. It doesn’t matter what the mind is acting upon, the effect remains the same.”

I looked down at the floor again.

Jacques said, “And you can’t go home again.”





To Its Limits

5 03 2010

“…Pushing the AMUF to its limits, the Karst-manufactured MREM-C (Multi-Role Earth Mover Component) module was one of the most useful machine upgrades in the colonial motorpool.  Instrumental in carving channels for the intercolonial light-rail system, the MREM featured a robust chassis that offered remarkable durability in the toughest of conditions.  Working in tandem with M10-10 catepillar rigs, the MREM teams were an undeniable asset in infrastructure projects.”

There was the AYLI before us, perhaps fifty meters away, its legs dusted brown with regolith. It was trapped in a pass probably too narrow for the skill of the driver. There were two figures standing at the feet of the walker; their e-suits were dark and clean compared to the legs of the AYLI.

“It’s not an AYLI,” Gingrich said condescendingly.  “An MREM.”

She pronounced it ‘em-rem’. I didn’t much care what random string of letters the super-corporates back in Sol had given the thing.

“Irrespective, these framming Twos shouldn’t have brought the thing so far from the Colonies.”

A quick glance at the GPS showed that we were three kilometres north-west of what amounted to Alpha-2, in the foothills of Henderson Ridge. The ridge had formed from the ejecta spewed out in the impact which created the crater in which our four Colonies were sited. It was relatively rough terrain, as far as Fram went: there were many large bolides scattered about, yet to be worn down by the winds and regolith, and benches of bedrock punched upwards by the force of the impact to the south-east.

The MREM had broken down in the shaded lee of a wadi, where several boulders formed a rough wall of chocolate-brown rock. The suspension on our Sprat worked overtime as we crossed the broken terrain.

Gingrinch was speaking to the two e-suited figures, although I wasn’t on that frequency and couldn’t hear their conversation. I angrily engaged the footbrake and began to circle the walker on foot. What point was there talking to them? The problem was obvious – not that the teeth of the lead road wheel in the left leg track assembly had been worn smooth, popping out the track sprockets; but that morons from Alpha-2 were given any equipment from the May, when they clearly had not the faintest idea how to use it.

I grabbed some equipment and spares from the stowage bins on the flanks of the Sprat, and went to work levering the remaining track from the guide wheels.

Gingrich eventually walked over, watched me work. She didn’t contribute. Of course. She came onto my freq and explained that the pair driving the MREM had come up into Henderson Ridge to site a good location for a weather station above De Lacaille Chasm.

“What a pair of clowns,” I said, although I looked from the corner of my eye to make sure they weren’t on our freq. “AYLIs, MREMs, whatever, they’re meant for hard-surface duty. In the Colonies. On the highways. What framming idiot takes them out here, into the countryside?”

It was a rhetorical question, of course, but Gingrich answered. She stood there, watching me work, hands on her hips, and actually argued their logic to me. A wretch. God, I was so sick of her.

She was engaging at length about the purpose of humanity to spread life throughout the Universe. Surely there were better places in that Universe for walkers to break down.

“Humanity?” I asked. “Nothing more than a few layers of translucent membrane stretched across a scaffolding of calcium, with some watery, soft tissue sandwiched between. No purpose there at all.”

She tried to rebut.

“And why the fram,” I continued, cutting Gingrich off, “did we even bother bringing KOVTARs? What was the point? If every monkey is going to run about in these fancy new toys, break down somewhere they shouldn’t be, and wait for us to come help them?”

Finally – with a suddenness that made me grunt with overexertion – the track links came off, and tumbled to the ground. I leaned over to pull the tracks out in a straight line. I would have to remove the worn road wheel, clean out the regolith, install a new road wheel with fresh teeth, and then run the tracks back through the idlers.

I struggled with the weight of the track, even in the low gravity. And still Gingrich stood there, watching; still she crapped on about utterly inane stuff. I threw the track back to the ground.

I felt an anger wash over me that I couldn’t stop. “Are you going to help? I mean, at all?”

Gingrich laughed.

“You’re a halfwit,” I said, in a cruel and resigned voice.

“And you’re a framwit.”

The anger exploded behind my eyes like fireworks. My muscles felt like taught steel wires. Somehow, the wrench was back in my hand, and I spun toward her.

And that was all there was – an arm swung, a wrench bloodied, a tight spray of cavalry brown blood over the grey regolith. And I had committed the first murder in the planet’s history.

Oh, God.

The Twos, resting in the shade, suddenly jumped to their feet. I couldn’t hear what they were saying; they were on the general freq. I looked down at Gingrich, motionless, the mask of her e-suit askew and blood oozing from her temple. I felt nothing.

I changed to the general frequency, and walked toward the morons from Alpha-2, those ungrateful, lazy, bloodsucking parasites from Alpha-2. I waved the bloodied wrench. “And neither of you are worth the bullet it would take to shoot you.”

I threw the wrench away. The next thing I knew, I was on the Sprat, driving north, my body shaking uncontrollably…





Selenography

1 03 2010

We looked once more to the sky.

A team from Alpha-1 had made the elevator trip to Port Mayflower. From the observation deck they enjoyed the vertiginous view of Fram spread across the floor of space, and part of the ring slicing toward the horizon. They were looking west, and Amundsen had hours before risen from that horizon. Now it lay above the curve of Fram’s atmosphere, strung along the ring like a bead on a rust-red string.

Fram was a small world; only five and a half thousand kilometres across, not much more than forty percent the size of Earth. But like Earth, Fram had a relatively large moon. Amundsen’s irregular shape was about one thousand two hundred kilometres across, similar to the size of Quaoar or Charon. As Luna was to Earth, so Amundsen was approximately twenty percent the size of Fram. The entire Fram system, planet, ring and moons, would fit easily in the gulf between Earth and Moon.

The experts on Port Mayflower delicately pointed out that we had yet to visit any of the moons. Much of our knowledge of the satellites of Fram had been garnered from observation – by the probes which had visited the system before we had even left Sol, from the Quoqasi as we arrived, or by the orbiters since Planetfall. Some of our knowledge came from the ring system itself. The components of Fram’s ring were pieces of the disintegrating Amundsen, and we had spent weeks crawling over the surfaces of the larger pieces and moving them into safer orbits. There had been some room for science.

“The Fram ring was a good place to start our study of the three moons,” one selenographer explained, and then launched enthusiastically into an explanation.

It was a thin ring; it was about a meter thick, and it was not very opaque. The ring extended from a thousand to six thousand kilometres above Fram’s equator. Our orbiters had spent most of their time in the thousand kilometres beneath the inner ring, that part of the disk closest to Fram. The particles which composed the inner ring were no more than a meter in size, although there were some larger pieces, all of which had been tagged with transponders during the first three months after Planetfall. These larger pieces came from closer to the orbit of Amundsen.

The inner ring was divided from the outer ring by the Sverdrup Division, a sharply defined gap of around four hundred kilometres. The Division was caused by the orbit of Sverdrup, the closest of Fram’s moons, which orbited entirely within the Amundsen ring. Sverdrup was the first of Fram’s shepherd moons; as Sverdrup swam through the ring material on its orbit, its gravity cleared a path through the ring.  Material that drifted into this gap was deflected back into the ring by Sverdrup’s orbit, or accreted onto the mass of the moon.

The Sverdrup Division was not entirely empty. There was a thin, central ringlet which shared Sverdrup’s orbit. This ringlet was knotted by spiral density waves: short, horseshoe-shaped oscillations caused by the resonances of the orbits of Sverdrup and Amundsen.

The selenographer continued. “We really learned a lot about the composition of Amundsen while we were wrapping reflective blankets and installing rockets on the surfaces of the ring bodies.”

The pieces themselves were mostly silicates, a much higher proportion of silicate to iron than we had expected. What iron had been found was in the form of oxides, which explained the reddish colour of the ring. The ring possessed its own sparse atmosphere, only microns thick, of molecular oxygen, hydrogen and even hydroxide. The existence of this atmosphere suggested that the ring once contained quantities of water ice; ultraviolet light from the twin stars had broken down the water ice into its constituent elements.

“And that’s representative of Amundsen?”

“Yes and no.”

When we looked at Amundsen, much of its composition suggested an early bounty of water ice. Spectroscopic studies had shown a rather typical proportion of iron to silicate; moreover, the iron was contained within oxides. UV spectra showed more detail. There were hydrated silicates, which bore magnesium and iron; hydrogen sulphates; sodium sulphates; cyanogens; and carbon dioxide and sulphur dioxide, frozen onto the surface. But the only ices which now existed on Amundsen’s surface were carbon dioxide and volatile ammonia ices; the early water ices suggested by the ring and by the presence of so many sulphates and oxides had long since gone.

The selenographer explained how the water ice might have vanished. It really depended upon which model proved correct to explain the formation of Amundsen. If Amundsen had accreted in orbit of Fram, as the Galilean moons seem to have in the orbit of Jupiter, then it was possible that the surface water ice had simple sublimed under billions of years of ultraviolet light from Alphas A and B. Amundsen lacked any magnetosphere or atmosphere to protect the water ice from the stellar wind.

“There are a number of problems with this hypothesis,” the selenographer continued. “First, if the ice had sublimed, we’d expect to find traces of an atmosphere on Amundsen like we do in the rings. We don’t. A lot of it would escape into space, but not all. The presence of molecular hydrogen and oxygen in the rings suggests that we would find some evidence of the effect of this breakdown. Second, the fact that we find evidence of water ice in the rings suggests that there was water ice on Amundsen when it started to break-up. We think the impact which precipitated that break-up was relatively recent, only tens of millions of years.”

The program director from Alpha-1 nodded. “Not enough time for the ice on Amundsen’s surface to completely break down. I see.”

Another big problem with the accretion model, the selenographer clarified, is that it was highly unlikely a moon so relatively large and massive to the planet it orbited could accrete in so close an orbit. If it did, we would expect each body to share a mutual barycentre; that is, to rotate around a common point external to each body, like the dwarf planets Pluto and Charon. Amundsen was very large, relative to Fram, and orbited very closely, relative to their radii. The accretion model simply didn’t account for these facts.

“But Charon did not accrete around Pluto,” the director protested.

The selenographer winced. “A poorly chosen example. But we have only two star systems to draw upon for examples.”

The most likely model, perhaps unimaginatively, was the same which accounted for the formation of Earth’s moon: the giant impact theory. A large object had smashed into Fram in the distant past, spewing material into orbit. The remnants of this object accreted together with the displaced material from Fram, coalescing into Amundsen. Such an impact could explain the angular momentum of Fram and Amundsen; that they did not share a mutual barycentre, and that Fram should continue to rotate so quickly. In the absence of such an impact, Fram might well have become gravitationally locked to Amundsen. This had happened to Pluto and Charon: both dwarf planets kept the same face to each other.

There was other evidence supporting the impact model. Fram’s crust was highly anorthositic, and basalt sheets a common feature of the fractured bedrock; this suggested a catastrophic period of global magmatic activity, of a scale far out of proportion to Fram’s size and geological inactivity. It was likely that Amundsen had also once had a magma ocean; that evidence would only be found by a mission to the moon.

“Of course, if this model is proven, then Amundsen is a particularly unlucky celestial body,” the selenographer said.

Because it had been struck again, catastrophically, tens of millions of years ago. The most recent impact had been the one that shattered Amundsen’s crust, and probably accounted for the lack of water ice. It had been a traumatic experience for Amundsen – Fram’s ring demonstrated that – and while it had not led to the creation of another magma ocean, the impact would have melted away exposed water ice, then lost to space.

“But how did it get the ice, between the impact that formed it and the impact that destroyed it?”

The selenographer explained the benefits of having a moon so massive and close to Fram. It acted, in a local way, like Jupiter acted to the Solar System – is spun along its orbit and scooped up other nearby bodies, effectively protecting the inner system. In the billions of years between major events, Amundsen had been bombarded by asteroids and comets, the latter of which had deposited water and volatile ices on Amundsen’s surface. These deposits were built up laboriously over a period of some four billion years; what the suns stole through ultraviolet sublimation had been replenished by further impacts. Until the latest, most dramatic impact.

The selenographer explained that the break-up of Amundsen was probably not entirely a result of the impact; rather, that whatever hit the moon had fractured its crust and then pushed the moon beyond its Roche limit.

The farthest of the moons from Fram was Nansen. Like Sverdrup, Nansen was a small shepherd moon, regulating the ring which surrounded Fram. Nansen orbited at the far edge of the ring, defining its outer edge. At first we thought both Sverdrup and Nansen were larger pieces of Amundsen, but spectroscopic studies suggested otherwise. Both were captured asteroids, probably carbonaceous chondrites, caught up in the interacting gravities of Fram and Amundsen.

The selenographer pointed out Nansen to the team from Alpha-1. It was a small lump, highlighted by the suns, a grey potato tinted terracotta by the colour of the fuzzy ring. Nansen was the larger of the captured asteroids, just under fifty kilometres on its longest side. Both Nansen and Sverdrup were much larger than the chunks which made up the ring, and were easily distinguished from the surface.

“Far down the line,” the selenographer continued, “we want to capture a third body and use it to stabilise the inner ring, like Nansen stabilises the outer edge. Because Wilbur is far too small.”

But there would be problems. The three moons were already in a precise Laplace resonance: for every one orbit that Sverdrup completed, Amundsen completed two, and Nansen four. Moreover, any shepherd moon placed underneath the ring would be at risk of being pulled apart by the tidal forces of Fram. One solution to this would be to shape an orbit below the synchronous orbit radius. Such a fast orbit, faster than Fram’s own rotation, would stave off the risk of tidal deceleration – for a few million years, at least.

“And there are any number of asteroids out there,” the program director waved an arm in the microgravity out beyond the Fram system, “from which to choose.”

“Indeed. The moons first, however.”