The cities of Enceladus

Region: Communal Space.
Settlement age: 125 years.
Population: 5 million.
Allegiance: Independent - Saturn Collective.
Distance to Earth: 1.6 billion kilometers

Out of the four gas giants in the Solar System, Saturn is by far the most hospitable, with its resourceful moons, gentle magnetosphere and proximity to Mars and the asteroid belt. Though both Jupiter and Neptune harbour a few permanent settlements, Saturn is home to a true planetary society, spread across its major moons -- Titan, Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus. Founded by Japanese, French and Nigerian migrants of the second space era, at the tail end of the Low Age, the moons of Saturn, contrary to many a Solar System settlement, have prospered into the interstellar century. The spiritual and political home to the Starmoth Initiative, the moons of Saturn are the main population hub of the outer Solar System and a glimpse into what humankind would have achieved, had it settled the surroundings of Sol instead of expanding into the great void. All the moons are linked by the Saturnian kinetic exchange system, a network of mass drivers that allows the moons to swap cargo and energy inside the Saturn system, and towards the inner planets.

Titan

The largest of all moons, Titan was the first and obvious targets of Saturn settlement efforts, more than a century ago. Covered in a petrochemical fog, riddled with methane rivers and lakes, engulfed in ice, Titan is as hostile as it was when the first migrants stepped foot on its surface. Its million inhabitants live in nest cities, not unlike the walled bunker locales of the mid-Low Age. The metropolises of Titan are located near the poles, where methane rains are rarer, or alongside the largest lakes, where liquid hydrocarbons are used to cool the ice and prevent it from giving way. The energy economy of Titan relies on wind turbines, kinetic transfers from Saturn, and the thermal decomposition of tholins in dedicated plants. Over a century of sustained presence, Titan developed a very peculiar architectural style, relying heavily on stilts and bridges, to the point its nest cities have no "ground" to speak of, instead towering under the red clouds as vast fields of bridged platforms. Titan is a world of minarets, aqueducts, arches and belltowers; golden lights seep from stained glass windows, and in the whispers of half-lit alleys, its diligent populace dreams of the cold ocean below.

Mimas

The smallest natural sphere in the Solar System is entirely unremarkable. Protected from solar radiation by Saturn's magnetosphere, it has been carved out by a sect of Selenite gardeners, and houses the galaxy's largest low-gravity forest.

Enceladus

Saturn's crown jewel, this icy moon is home to two million inhabitants, most of which are housed in Babylon Harbour, the O'Neill cylinder in high Enceladian orbit. Covered in ice, Enceladus is tidally heated by Dione and maintains an intense cryovolcanic activity. After Europa proved to be a disappointment, harbouring only bacteria, Enceladus was the seat of humankind's first encounter with complex extraterrestrial life. Its intricate ecosystem revolves around underwater oases located around the hydrothermal vents at the bottom of the global ocean and has been meticulously preserved by the first settlers. Human cities are located alongside deep canyons in the outer crust, with spherical habitats hanging beneath the ice layer, where they enjoy the warmth of the sea, and very liveable pressures, around 5 bars. Sixty-five kilometers below the underwater cities, the seabed allows for direct access to Enceladus' minerals-rich core. For more than eighty years, core mining ensured Enceladus' supremacy in the settlement effort; in recent years, however, mining activity has died down in favour of interplanetary imports through Saturn's kinetic exchange system. The mining techniques developed on Enceladus, which favour laser drilling of extremely narrow holes to limit both geological and environmental impact, have been used with great success on many similar worlds across human space. As the golden age of Saturn waned with the advent of the geometry drive, it turned its gaze towards the outer stars. With its glass libraries hanging above the abyss, its delicate lifeforms, its gold-sewn surface spaceports and its cold gardens carved in billions of years of ice, Enceladus is a haven for scientists and explorers alike.

Tethys

Bombarded by solar radiation, with an execrable delta-v budget and two mundane sub-moons, Tethys is actively hostile to settlement attempts. Even in the interstellar age, it is rarely surveyed, let alone traded with, though recent satellite sweeps indicate that it harbours a small community of Outer Church nuns.

Dione

Enceladus' sister moon is too unstable and its ice layer too thick to allow for settlement. The Starmoth Initiative maintains several laboratories on its surface, however, allowing access to wells that reach into the underground ocean, seventy kilometers below the crust. The planet only harbours basic archaea colonies, whose only oddity is that they bear a striking resemblance to now-extinct Enceladus lifeforms, hinting at panspermia between the two moons. The Starmoth Initiative's hostile environment training program includes deep dives in Dione's waters.

Rhea

Large but light, Rhea is mostly made of ice and dust, and has no core, only a central sphere made of pressurised ice. The surface is riddled with craters, and no underground ocean has been found. Minerals and metals are mixed with the ice and thus easily accessible; for the better part of the previous century, mining on Rhea was extremely cost-competitive compared to asteroid belt imports, and on a par with Enceladus core mining. The planet remains a major mining and manufacturing centre, with its shipyards gleaming above the dusty wastes, and large excavations supplementing the old craters. The moon is home to several ship manufacturers, including the Alsephina Shipyards, and houses rover races alongside its equator.

Iapetus

The furthest of all major moons, Iapetus is the main gate of the kinetic exchange network, with very favourable Hohmann transfer windows towards the inner solar system. Administered by a joint Titan-Enceladus authority, it is a fairly secretive place, where the fierce spirit of the first migrants lives on. It is rumoured to house the Eye of Saturn, a space-to-space particle beam using Iapetus as a heat sink and capable of striking would-be invaders from a light-second away.

llustration by Mark Molnar for Eclipse Phase, distributed by Posthuman Studios under a Creative Commons Attribution Non-Commercial Share-alike 3.0 Unported License.

Planetary type: Rocky world, likely interstellar capture.
Region: Traverse.
Natural satellites: three asteroid moons.
Age: 1.5 billion years (estimated).
Parent star: T-class brown dwarf.
Surface gravity: 0.6 gees.
Atmosphere: 0.5 atmospheres, close to human-breathable.
Average temperature: 12°C
Climate range: Cold arid to hot arid.
Ecosystem classification: Carbon-based, scattered evolution.
Solar revolution length: 15 days.
Day length: Tidally-locked (with terminator precession).
Settlement Type: Isolated cities.
Settlement age: 42 years.
Population: 500,000.
Allegiance: Eloran Ekumen.
Distance to Earth: 578 lightyears

Starports: Styx Port, Urcaguary Station.

Modern interstellar travel notwithstanding, brown dwarfs remain hard to spot and are only systematically explored in dense areas of space. This is the main reason why unlikely or otherwise anomalous habitable worlds seem to be concentrated in the Traverse: the well-travelled region has been thoroughly explored in the past seventy years. In any other place, save for the surroundings of the Sun, Stygia would have been missed -- and the age-old debate concerning the habitability of brown dwarfs would have remained without a conclusive answer. For despite all odds, Stygia harbors carbon-based life: tidally-locked, it is close enough to the brown dwarf to receive enough energy to maintain a biosphere made of dark, scarce plants, fungus, lichen and a thriving pseudoinsect environment. Its cool atmosphere is breathable with a simple oxygen mask and the precession of the brown dwarf at the terminator even allow for a semblance of a day-night cycle at the cool temperatures where human settlements are located. The night side is frozen, with basic life concentrated around sites of geothermal activity, while the day side is occupied by noxious, life-rich swamps and warm but liveable deserts.

In theory, Stygia should not exist. Its T-class brown dwarf is a feeble parent star, whose system is extremely oxygen-poor; its other two rocky planets are classified as "carbon worlds", whose surface is exclusively made of graphite, liquid hydrocarbons and carbon monoxide. Local asteroids are remarkably dry and metal-poor. Stygia itself concentrates 95% of the system's water and the three quarters of its heavy metals. Under the current understanding of planetology, there is no possible way Stygia could have formed in its current system through natural means. In the first years of study, the dominant theory was that Stygia was, to some extent, an artificial creation, not unlike some of the megastructures found in the antispinwards part of the Traverse. It took scientists a good decade to uncover the real origin of Stygia -- and the key was to be found in the fossils contained deep within the cold crust of the planet. Pristinely preserved, they told the tale of an impossible ecosystem; a thriving, complex environment that bore all the hallmarks of a warm planet orbiting a main sequence star, most likely an F or G-class yellow dwarf.

Stygia is an outcast. A former garden world ejected from its parent system by a cosmic cataclysm, having travelled millions of years as a rogue world, its soil and atmosphere frozen barely above absolutely zero, then captured by a brown dwarf and slowly brought back to life by its infrared radiation and tidal heating. A chance in a trillion; a world of death and rebirth, whose current ecosystem evolved over the course of the past half a billion year from pockets of micro-organisms huddled around underground geothermal hotspots during the great journey.

Founded by Eloran settlers, the commune of Stygia is mostly dedicated to studying the peculiar planet; it houses and administers the Styx Research Center, dedicated to uncovering the secret of Stygia's origin and painting an accurate picture of the world it once was -- though the original system has yet to be pinpointed, three candidate G-class stars have been identified in the Traverse and are currently under investigation. The planet is also home to several world-class exobiology laboratories, an unofficial Algorab dig site and a few cooperative farms fruits and vegetables famous for their pitch-black colour.

Illustration by Marc Garlick -- Science Photo Library/Getty Images.

Planetary type: Non-causal Earth-like world.
Region: Deep space, 700 lightyears away from the Serene Sea.
Age: 2 billion years (measured by external observers), 5.6 billion years (measured from the planet).
Parent star: G-class star.
Natural satellites: One moon, two captured asteroids.
Surface gravity: Shifting depending local causal parameters. Averaged at 0.91 gees.
Average temperature: Variable depending on causal shifts. Averaged at 12°C.
Ecosystem classification: Carbon-based, with local pockets of silicon-based life, Sequence remnants and acausal presence.
Settlement Type: Isolated cities, one major continental polity.
Settlement age: 27 years (measured by external observers), varying between 2000 and 550 years for local observers.
Population: 6.7 million (estimated).
Allegiance: Shifting.
Distance to Earth: 970 lightyears.

Starports: The Spire in the East, The Panthalassan Library. 

Sometimes, the world breaks.

I do not know how Armillaire came to be. I will, in time. I have time. We all have time, on this planet. Minutes are hours. Years are decades. Decades are millenia. At first, we thought it was a peculiar case of time dilation, but Armillaire is different. There is no redshift or blueshift in proximity of the planet. The timeline is not extended or retracted on the planet. Rather, it's broken. In the spaceports, we have launchers manufactured three decades ago on a distant planet named Earth, but the walls upon which they stand are a millenium old. The world moves and slithers. Bubbles, pockets and pebbles. Lines, ways and passages. Armillaire is porous.

It used to be different. It used to be a normal Earth-like world, lost in the faint stream of stars between the Sagittarius and Persus arms. I can't tell how long ago this was. No one can. When Armillaire changed, something broke, like a spring ejected from its lodging. The world ceased to work the way it should. We are, in a sense, already familiar with this idea. The geometry drive, the Ladies that Wander, the Moths, they all break reality, but in a gentle way. Scattered rebellions against the world. Not revolution. We know that a million years ago, the Sequence made landfall on Armillaire. They may have tampered with something we have yet to discover, or they may have been simple observers. Who are we to know? On Armillaire, the past doesn't run straight.

A strange world, so it is. In many ways closer to the Earth than other settled worlds, perhaps because our minds shaped the planet this way. Or perhaps because it has always been like this, aware in advance of our arrival. Transbiological creatures roam the deep woods, scorching deserts and well sharpened ruins. Sequence remnants emerge here and there in our histories. They have been changed and shaped by Armillaire, closer to legendary monsters than the civilized shamblers of the Serene Sea. Ladies and weavers reshape lands and societies, casting not spells, but pacts with reality herself, with the speed of light and the architecture of four-dimensional space as their minions. Herbalists and alchemists plant hyperdimensional flowers and whisper to sentient trees. In the west, there is an Empress, sitting on a throne of white mosaics. In the east, ephemeral queendoms build cities of coral by the inner seas. Launchers are covered in runes and paintings. Spaceships are naves, Simurgh birds over the swirling clouds. Swords and bows cut through the tapestry of spacetime. Nuclear fusion is the sun of legends. Deep under the surface, Sequence ruins lie awake, buried in half-truths.

This is Armillaire, the Tangential World.

Illustration by Ekaterina Valinakova, CC-BY-NC 3.0

Planetary type: Icy rocky planet.
Region: Communal Space.
Age: 11 billion years.
Parent star: Kapteyn's Star (red dwarf M).
Natural satellites: Two quasi-satellites (rocky asteroids).
Surface gravity: 2.09 gees.
Average temperature: 8°C, accounting for greenhouse effect.
Ecosystem classification: Developed, in a state of natural decay.
Settlement Type: Scattered ground bases, one orbital station.
Settlement age: 68 years.
Population: 5,000 people.
Allegiance: USRE-Laniakea condominium.
Distance to Earth: 125 lightyears.

Starports: Monolith Station, Omega Centauri Point. 

1 - Weird backyard

While part of the galactic halo, Kapteyn’s star is merely 12.5 lightyears away from the solar system, which puts its firmly into Communal Space, among the Earth’s stellar backyard. In present day, it could almost be considered as a holiday destination — the system is just one or two translations away for a short-range interstellar vessel. Kapteyn’s Star itself is fairly unremarkable — it is classified as a variable red subdwarf, a small and very cool star belonging to one of the most common stellar classifications in the Milky Way. What makes the Kapteyn system exceptional is the presence of Kapteyn B.

Kapteyn Beta, or simply Kapteyn, has been known to astronomers since the 20th century, but was considered by most to be an artefact due to imprecise measurements. As such, the discovery of the planet by an automated probe at the beginning of the interstellar age came as somewhat of a surprise — one that probably triggered a few resounding “I told you so!” in USRE universities. Kapteyn B is a small, cold super-Earth, orbiting its parent star right inside its minuscule habitable zone. Covered in a thick atmosphere maintaining acceptable temperatures on the surface, Kapteyn is eleven billion years old and, as such, the oldest inhabitable planet in the known universe.

2 - Ancient Life

Kapteyn B is so old that it likely comes from another galaxy — as a former member of the Omega Centauri globular cluster, its parent star appeared in one of the numerous dwarf galaxies swallowed by the Milky Way billions of years ago. Born under such divergent auspices, life on Kapteyn B is unlike anything else in Communal Space, to the point many of its lifeforms are hard to qualify as such. It is considered as the clearest example of what xenobiologists classify as natural decay ecosystems, that is to say biospheres that are so ancient they have all but exhausted the resources of their planet and, while the light of their parent star is dwindling, have entered a form of hibernation with very limited natural selection going on. Life on Kapteyn is slow and serene, living at the pace of millennia, undisturbed by the frenetic rummaging of the small humanoids that explore its surface. When they return to their homes, human travellers of Kapteyn recall vivid sights of sentient fog, oceans made of fungi and wide-eyed eels turning into dark-leaved plants as they age.

Interestingly enough, Kapteyn is one of the rare exoplanets that does not require any specific antigenic treatment or vaccines before landfall — local pathogens are so different from Earth-based life that they are simply unable to affect humans in any way.

3 - Monoliths

Kapteyn was the first contact of humankind with non-human ruins — excluding the geometry drive itself. Well, contact might be a bit of a strong word here. Whoever lived on Kapteyn five to six billion years ago did not leave a lot behind. Even their fossils have disappeared, and xenobiologists have not been able to narrow down their physical shape. All that remains are towering structures in Kapteyn’s landscape, smooth and pitch black, as if carved in fragments of the deep sky. The monoliths of Kapteyn are made of a thick carbon-silicon alloy, strengthened with unknown components that are reminiscent of artificial coral. Though most of them have fallen prey to wind, rain and meteorites, the few that remain escape all of our attempts at understanding them. They do not bear any inscription. They do not house any machinery. They just are. Silent and useless, except as a reminder that sometimes, in a distant past, Kapteyn housed a great civilisation.

Though the birthplace of xeno-archaeology, Kapteyn is now mostly empty of scientific endeavours. The frustration of its silent monoliths has worn down everyone, from the exalted nuns of the Omphal to the patient researchers hailing from prestigious USRE universities. The planet only houses a single permanent research center, the Kapteyn University of Extrasocial Sciences (KU-ES), a joint Laniakea-USRE training center for xenohistorians and xenoarchaeologists. It is often said that the only thing the Kapteyn University truly teaches is resilience in front of the frustrating silence of the unknown — though that might be the most precious lesson for an interstellar historian.

The USRE High Fleet maintains a single vessel in polar orbit of Kapteyn at all times, officially to discourage illegal exports of local artefacts — in practice, this assignment is just an officious punishment for sloppy commanders.

We don’t talk about the second ship up there, however.

Illustration: Ph03nix1986, CC4.

Planetary type: Rogue gas giant.
Region: Near Arm's End (see human space maps).
Age: 3 billion years (estimated).
Parent star: Free-floating object.
Natural satellites: 6 icy moons system.
Surface gravity: 2.8 Earth masses.
Average temperature: Variable. Cloud tops near absolute zero, lightning channels and internal activity create pockets of life-tolerable temperatures in lower zones.
Ecosystem classification: Lightning-sustained, organic, possibly Forgotten Traveller seeded.
Settlement Type: Orbital bases and floating needle-stations.
Settlement age: 19 years.
Population: 70,000 people.
Allegiance: None, but extensive ties with Eloran qiths.
Distance to Earth: 10,500 lightyears.

Starports: Xango Disco Point, Arm's End Hub. 

1 - Rogue World

Rogue planets are relatively common in the galaxy -- at least 10,000 of them have been identified by Starmoth Initiative surveys, albeit many have been missed, given how little energy they radiate. Xango, formerly known as CFBMOTH-2456-067, was discovered three decades ago by survey vessel Axial Tilt Zero through direct imaging -- one of the most random discoveries made by the Initiative, but also a very lucky one. While rogue planets are almost universally devoid of life, CFBMOTH-2456-067 showed telltale signs of active organic life in its lower atmosphere. Two years after its discovery, Axial Tilt Zero came back with a full expedition complement that unveiled the numerous oddities of a world that would come to be known as Xango, the Yoruba deity of thunder and a revered figure in the Moon Communes.

Xango is characterized by thunder -- though lightning strikes are common in gas giants, the temperature difference between the planet's frozen top clouds and its warmer depths, combined with magnetic activity and dust storms, mean that the cold body is constantly covered in lightning storms. From orbit, the equatorial belts and jet-stream lines are permanently highlighted by whitish-blue sprites and pillars, giving the planet a striking, albeit eerie appearance. Permanent lightning enables the rogue world to support life, under the shape of vast strains of pseudo-lichen drifting in the wind, feeding on the energy emitted by lightning storms. Various species of bacteria and pseudo-viruses also populate the atmosphere, floating between storms and jet-stream channels. Life on Xango has evolved to develop very specific solutions to its energy conundrum, including a capacity for extremely fast (millisecond-scale) photosynthesis and biological batteries feeding on residual static electricity in dust-rich regions. Some pseudo-lichen species follow a plasma-based life cycle, exposing themselves to lightning at the end of their existence, which vaporizes them and spreads their spores all over the atmosphere. Such vaporizations are called "spore flares" by the locals -- they can lit up entire storms with bright plasma lines for hours on end.

2 - Forgotten World

Deep in the atmosphere, the Starmoth Initiative found ancient ruins, aero-statically suspended in-between the calmest layers of the world. Low-density cubes made of bone and carbon compounds, bearing telltale signs of transbiological enhancements. They were remnants left behind by the Forgotten Travellers -- surprising, that far from the galactic core, but ultimately possible, considering that they once possessed AFAL (As Fast As Light) propulsion. More specifically, this variety of Forgotten Travellers seems to have been part of some kind of isolated settlement, perhaps made of outcasts or deep space dwellers. Though there is no solid evidence to confirm this hypothesis, it is highly possible that this planet's life has been partially selected, maybe even engineered, by the cube-like transbiological aliens. A recent Algorab report even suggested that the Forgotten Travellers were using lightning to test or engineer the high-efficiency batteries that are one of their technological hallmarks. A few kilometer-long structures, perhaps laboratories, remain buried within the atmosphere but they are not accessible to human vehicles and as such shall keep their secrets for the time being.

3 - Electric Bass

There is not enough photosynthetic life on Xango to produce a breathable atmosphere, and this dark, lightning-haunted gas giant isn't friendly to human life, though it did not discourage a commune from settling the planet. Based on free love, darkness and a touch of unhinged science, the Xango Communal Interest owns several space stations around the planet, as well as floating settlements installed in close proximity to the largest concentrations of pseudo-lichen lifeforms. The commune harvests energy from the lightning storms, through the use of "needle stations" deploying vast strings of superconductive material through Xango's atmosphere. Most of these stations are used for research -- lightning strikes on Xango are unparalleled in their intensity, and as such are ideal power sources for stress-testing battery and accumulator technology. It is speculated that the Xango Communal Interest is actively experimenting with Forgotten Traveller technology, or human copies thereof -- several unexplained detonations observed on Xango in the past few years could be thus linked to accidental explosions of Forgotten Traveller batteries. In any case, Xango-made accumulators and electricity-based weaponry are renowned in the Traverse and beyond -- extremely expensive and almost artisanal, they are only bought by high-end military communes such as qith Sahaak.

Another key aspect of Xango is that it vibes. In order to maintain a semblance of psychological balance in this dim, cold gas giant, the local communes have turned towards music -- and preferably the kind that makes noise. Electronic music is not just a practice on Xango, it's an art and a planetary industry that exports singles way beyond the rogue planet. The finest variety of Xango music uses the pace and intensity of lightning strikes as planet-wide bass -- it is called Xango Beat, and is sometimes considered as the likely precursor of interstellar rave culture.

Credits: NASA/Caltech.