The Planet

The planet is so odd that it's almost difficult to describe it as one planet. Looking at it, one might have to glance again to see that they weren't looking at a planet with a wide spread of rings- and yet it's one discrete body. At the equator its radius (6.4 earth radii) is comparable to a gas giant half its mass, but at the poles it's almost reasonable for a heavy rocky world (2.5 earth radii). Its mass is simply beyond the pale for a world that isn't a gas giant (97.7 earth masses)- hence its rotational period of 2 hours 29 minutes, and the oblateness resulting from it. The only reason the planet is stable is its density gradient- the core is quite dense, while its water remains water. The gravity at the poles is 17.6 times the equatorial gravity of 0.89 gees.

Even beyond that, the poles are thoroughly uninhabitable- the rapid spin causes the many banded convective cells of the planet to be reluctant to mix, making the poles not only large and with high gravity due to the oblateness of the planet but also extremely cold. Dry ice is common on top of the water ice caps, and as one approaches the poles the ocean and atmosphere get as short as 4 kilometres (due to the high gravity) and connect the cold ice of the caps to the pressure ice of the seafloor. The heat gradient between the equator and the poles is almost as bad as the gradient of velocity- the equatorial sea, when not covered by clouds, can reach seventy celsius. Generally, though, the temperature is below forty celsius- safe, if uncomfortable for many. In the ten thousand kilometres between the equator and the poles, a dozen bands per hemisphere go between three levels of precipitation and four levels of temperature. They vary in gravity, too- the highest band before the polar caps set in experiences gravity so high very few forms of large natural life can handle it.

This isn't to say most of the habitable parts of the planet are hot- on a world this large, local climates are hundreds of kilometres wide and other parts of the planet compensate for it. One of these is the ever-present cloud cover- though sometimes incomplete, especially in the higher bands, it can serve to shade the world below for many local days at a time (and it's a mixed blessing, given how many of the clouds are vigorous cyclonic storms). At the equator, the area where clouds can form is over fifty kilometres thick. The atmosphere itself is almost a hundred thirty kilometres thick there, and is breathable up to thirty kilometres above the sea. Most of it is nitrogen, though in a lower proportion than Earth's atmosphere (58%), followed by oxygen (22%), then helium (10%), with argon at fourth (6%). The rest is mostly water vapor, with safe proportions of carbon dioxide and with traces of other gases. Full pressure is 3.17 times that of Earth, low enough to avoid nitrogen narcosis.


Almost eight percent of the planet's surface area is taken up by floating land of a monolithic, roughly ellipsoidal type. Single land-mimic lifeforms can reach almost a thousand kilometres across, filling about a third of a band's north-south extent. While the mechanism for their creation and growth against erosion is mostly unknown, the mechanism for their flotation is- under a layer of land simulant (with exceptions) that can be hundreds of metres thick, great caverns full of high-temperature helium balance out the mass. On the surface, landforms and climates quite typical of real continents and islands exist- mountains, seas, and rivers are extremely common. Temperatures and levels of precipitation on these lands can vary substantially from clear-ocean climates: some of the largest ones high in the equatorial belt even feature glaciers. This variance is especially pronounced when one land passes under another- with the sun fully blocked for up to 70 local days, and with great rivers falling up to several kilometres.

(See also appendices 1 and 2.)

The Star And Orbit

Our star is a K7V dwarf/O8IV fusor (while the planet is a t4o world), though some calls have been made to classify it as a subgiant due to its outsize luminosity- while its actual mass is just 0.591 solar masses, its luminosity is more comparable to a star with a mass of 0.773 solar masses (about 2.5 times brighter).

The world's orbit is eccentric, if mildly- an eccentricity of 0.083 (not the highest the planet experiences, but approaching it) applied to its semi-major axis of 0.803 au shows its current perihelion of 0.7364 au and its aphelion of 0.8696 au. As the most populous planet in the system by a long shot, its inclination defines zero degrees for the other planets- though with regards to the solar equator it is inclined by approximately 4 degrees. Its orbital period is, by a fluke of precession, currently so close to exactly 3500 local days that if one made a calendar that needed to take the deviation into account that the calendar would need a mechanism for handling major changes in the orbital or rotational period of the planet. In Union Days, its orbital period is just under 362 days.

The planetary axial tilt is currently mild, at about 13.3 degrees- while this has little effect on equatorial temperature (the equatorial variance is 25 degrees and due solely to orbital seasons, between roughly 43 and 18 degrees), the permanent habitations furthest north and south (already hard to live under the crushing 7 gee gravity caused by their position so far north north of the 20 degree "hump" of the planetary equator) experience general variances respectively of 36 and 12 degrees. This is because of the mismatch (or match, depending on perspective) of extremes for the axial and orbital seasons, and brings the northern cities between about 32 and -4 degrees while the southern ones are between 20 and 8 degrees. Over a dozen millenia, these switch- meaning at the extreme the larger cap is two and a half times larger in area than the smaller cap. Like today, each cap is about 85% its winter size in the summer.


The airborne ecosystem (excluding birds and similar, which do not take flight permanently; biologists are unsure whether a permanently-flying bird would be part of the airborne or landborne ecosystems) of the planet is the most prominent one, though due to the lack of a long paleontological record means it's unsure if it's the oldest. Leading theories suggest three separate origins of life known as superdomains (with complementary virus-viroid-prion equivalent realms for all)- generally these are coloquially divided by form of reproduction, though much more important and basal differences exist. The group that reproduces asexually is considered likely to have either been modified or imported by some alien species, but aside from marked similarities to abiotic entities of similar size this theory has little specific backing. The group that reproduces fully sexually almost certainly evolved from seaborne life, with obvious strong similarities between the two being known. The group that reproduces in an alternating sexual-asexual pattern (one of many ways they closely resemble plants) likely evolved within the atmosphere itself.

The most famous of the asexual group are the great land-mimic lifeforms that fill the skies- a tenth as numerous as clouds and similar in size, but nowhere near as ephemeral. Twenty-nine subspecies (sorted into seven species in a monotypic superclass) of them exist, averaging one per non-polar band- generally they are quite similar beyond adaptations for gravity, with the northernmost and southernmost species being least similar. They have outcompeted and outlasted not only any of the other elements of their superclass, but also any possible challengers among the three superdomains- only the very largest other lifeforms in the sky rival the hundreds-of-metres of the smallest land-mimics. Their phylum of the asexual group is defined by a strong elastic vascular system which uses both pseudomuscular contraction and pressure differentials to move nearly all internal substances through helium, which is enough to keep most of the smaller members of the group in the air. The same subphylum that contains the land-mimics also contains other classes, which provide clues to the base origins of the entire subphylum- most retain the spherical body shape of juvenile land-mimics, have no "rock" covering, and sustain themselves more through ocean-based feeding than the land-mimics' feeding off of the erosion (and occasionally actual bodies) of other land-mimics. The smallest asexual-group lifeforms are microscopic, and the largest other than the land-mimics are "veiny balloons" of ellipsoidal or spherical shape up to two hundred metres long.

The other two groups have no creatures truly rivaling the land-mimics, but some match the smaller ones. The formerly-seaborne group consists of two kingdoms of creatures derived from seaborne pseudoalgae and pseudofish respectively- the former reproduce asexually, but are difficult to notice if one's not specifically looking for them. These two kingdoms have also diversified into landborne ecosystems, with some even returning to the sea. The airborne forms of pseudoalgae are outcompeted by lifeforms of the plant-like superdomain at small sizes, so the smallest extant forms are small sheets (four phyla colonial, two phyla multicellular) that can "tack" through the air. These are restricted to just a few bands of the amosphere, partially because they're so thin that they break apart at high gravities and partially because they cannot survive most storms, let alone passing the turbulent boundaries between bands. As a result, their larger cousin superphylum consists of pseudolichens- pseudoalgae in a mutualistic relationship with other organisms. Many of these exist on the substrates formed by the bodies of other organisms, including nearly every large form of airborne life. The pseudofish reproduce in a manner generally considered standard among organisms with two general sexes. Their smallest members are considered seaborne, but three phyla are permanently airborne- and one even takes after the other large airborne groups and integrates helium-filled flight bladders. The largest of these match the veiny baloons, with some species even able to integrate photosynthetic pseudolichens into their metabolism- giving them an edge over other large airborne lifeforms, given the others are too dissimilar to the lichens to supplement their own metabolism with them.

The plant-like airborne group is considerably more diverse than either other superdomain in the air by the virtues of having evolved there and not having a single member that greatly outcompetes all others in a similar niche. However, quirks in evolution and climate have meant that they had been restricted to the northern hemisphere until those rooted to land-mimics crossed the equator (possibly as soon as 300 million years ago)- leaving the southern hemisphere with not only less diverse airborne life, but also less diverse landborne life. Plant-like many-celled life is divided into five superphyla- two non-vascular, with the vascular ones divided by whether they bear spores, seeds, or multi-seed bodies such as fruit. These are all very common ground cover, and are equally common in the skies. Each have large forms- the very largest are spinning wooded plants up to a few kilometres in length (occasionally compared to the much larger spinning trees of zero-gravity megastructures, though those are considerably more amenable to being inhabited by large beings), which produce airborne seeds. The largest spore-producing one is a tenth the size and rotates faster to prevent of its spore load from landing on itself, and the largest fruit-producing ones are small enough that they are capable of active flight rather than just floating.

Life in the sea

Like airborne life, the seaborne ecosystem of the planet has multiple origins. However, as a rule the great planetary ocean is dominated by the single superdomain that evolved in the sea- unlike airborne life, the sea is similar enough worldwide that no other superdomain could evolve before outcompeted by more advanced life. The sea is overall deeper than the sky, and is considerably more difficult to explore- as such, whatever diversity exists below the first few kilometres of the ocean (even that deep is perilous) is practically unknown. It is known that as they die land-mimics descend fully into the sea, scraping off whatever life exists on their surfaces (and giving birth to/carving off many new land-mimics besides). This introduces communities of life that have been separate from the sea for at least a millenium, and further drives evolution both on land-mimics and off of them. They proceed ever-deeper, losing parts to fractures/births and ocean-feeding life... but what happens to them once they approach crush depth is completely unknown.

Most of the diversity of the sea is found nearest the surface, where dead and dying airborne life make up over half of all available nutrients for non-photosynthetic life. Beneath just a kilometre, other seaborne creatures make up the primary source of food- "landfall" is a much larger event, but is extremely infrequent. Across seaborne life, there are many species of extreme size- the very largest known have reached almost a hundred metres, but some may be larger. In the much smaller seas of the land-mimics, most sea life is derived from these forms- but some is derived from landborne life (this will be covered in the landborne life section). Life in the small seas is generally itself smaller, with less access to the constant fall of small airbone life. However, the seafloor and freshwater environs unique to land-mimics provide diversity that would be amazing if most people didn't live on the land-mimics.

Life on the land

Landborne life primarily evolved from seaborne life and plant-like airborne life in the northern hemisphere, but in the southern hemisphere it had its very own abiogenesis. Southern land-mimics are more prone to breaking apart before they fall into the sea (due to a different type of "soil") which means that any new starts for life on these land-mimics have more opportunities to stay in the air rather than eventually reaching the sea and being outcompeted by well-adapted seaborne life. As a result of this separate abiogenesis, land-native life completes the triad of native colors of photosynthesis- deep violet for starved seaborne life, orange for airborne life, and green-blue for landborne life (helped along by the fact that landborne life has no chance of reaching the ozone layer). Land-native life is the most recognizable to someone from a conventional single-abiogenesis world, although nearly all of it here is at least mildly mobile. This is the main way that it can compete with the somewhat more efficient airborne-based orange plants on northern land-mimics- the ability to move to new locations gives it an edge, though it makes land-native "plants" more reliant on either gathering airborne particles for food or the ability to uproot themselves. This means the position of land-native "animals" is more shaky- carnivorous plants are quite common, though in geenral less capable than their non-photosynthesizing counterparts. Land-native vertebrates follow a single primary bodyplan, which is remarkable in comparison to most vertebrates in that its vital organs are largely redundant- a bifurcated brain with extreme crosstalk feeds into two separate nerve cords, with one heart at either end of the body. Eight legs sprout from the sides, useful for keeping the animal stable in higher-gravity climes. Flight is rare due to this predisposition towards elongation, though those creatures that are capable of flight have more ability to grasp things due to their free limbs.

Plant-like airborne life has a major role worldwide on the land, as only seaborne life fills a similar niche (and then only in the north): powered fliers, like ersatz-birds. These are a few phyla of spore-producing non-photosynthetic plant-like lifeforms, and represent the very closest that air-native life has come to omnivores. The most basal forms are full of helium, using fins and jets to control their movement- they filter-feed airborne life and skim the seas for additional sustenance. Most later forms eschew the use of helium in favor of aerodynamic flight and roosting on land-mimics (and occasionally smaller organisms that have "soil" on them), greatly increasing their ability to cross the barriers between bands and allowing a global spread for many species. Having come at the landable powered flier niche from the opposite direction as usual, ersatz-birds have variable numbers of legs- two-legged varieties are the most common, followed by zero-legged bellylanders and one-legged hoppers. They vary greatly in size, but overall are more fragile than bony animals and as such even soaring varieties do not take well to large sizes. With the worldwide spread of land-native, seaborne-derived, and introduced fliers (all bony but relatively short-ranged), plantlike-derived fliers are gradually being outcompeted in the niches available to small non-migratory birds. It may be that ersatz-birds will become the main biological mechanism for movement of organisms between land-mimics soon (evolutionarily), a position currently held by permanently-airborne filter feeders. The largest forms of ersatz-bird diverged soon after the loss of helium, and instead passed air through their bodies to move- but only in the past few million years did they make the leap to biological jet engines, which allow them to prey upon their extremely-high-altitude relatives. The most successful species is a pack-hunting variety- that'll change if many make the decision of attacking more dangerous (especially technological) craft.

Introduced life and people

The planet was first inhabited by modern people in 4409, at a time when interstellar habitation expeditions were extremely commonplace. The people who decided to live on it were, however, different than the average arrival- they were a heterodox faction of the Protection Initiative, a loose organization intended to prevent damage to alien worlds by claiming them before they could be claimed by others. Unlike most other Protection Initiative groups, they not only inhabited the planet without intermediaries such as domes but brought along more easily-controlled domestic organisms. To prevent this from being too close to a normal expedition, each member and ship of the colony was deeply scanned on arrival to make sure that no organisms likely to become dangerously invasive came with them. Some joke that because of this the planet's system is the largest rat-free zone in space.

The cities and technology of modern settlements generally appear almost primitivist (stone or wood buildings, cobble roads, and internal combustion engine vehicles) due to the faction's quirks, though asceticism is uncommon and modern technologies are quite pervasive- just well-disguised. As a result of this foundation, the effective containment of invasive animals has been kept up even through the breakups of land-mimics- only 115 of 1731 land-mimics at or larger than "great island" size host extraplanetary lifeforms other than researchers. This isn't to say that imported diversity on the planet is low for a colony- rather, over 400 extraplanetary species exist (excluding sapients). In the over 5 millenia since colonization, many of these have developed differences from their forebears. For instance, several species of imported bird have adapted so heavily to urban life on the planet that they can memorize the schedules of craft travelling between land-mimics. Likewise, several imported plants have adapted to root themselves on the surfaces of large airborne native lifeforms- necessitating a band-wide net for preventing their escape.

Local space and moons

The planet's magnetic field is quite robust, and is more similar to a gas giant's magnetic field than to a terrestrial planet's magnetic field. The planet's moons are mostly embedded in the magnetic field, with the magnetopause lying roughly 1.3 million kilometres from the center of the planet. This means that the moons and the magnetic field iinteract strongly, with not only lunar aurorae but lunar plasma production/replenishment being noted facts of the local environment. However, radiation levels are fairly gentle- while the planetary radiation belts are dangerous enough to cause radiation poisoning if not passed through with expedience, most of the moons are outside of these belts and experience less than a tenth the radiation level within the belt (dangerous long-term, but visits are safe). If one does not take standard precautions against radiation, they are advised that a 70 localday vacation to an unshielded moon outside of the radiation belts may incur upon them a radiation dose matching the per-annum recommended maximum dose for people who work with radiation. While not dangerous if one ever goes to a medical clinic, it is not recommended to attempt this twice in one year.

The planet's rings are prominent, but small. While thick enough to be in any good view of the planet, their actual extent is akin to the thin rings of most worlds rather than rare famous rings. The visible breadth of the rings, as seen from the largest moon at its furthest point from the ecliptic, is only about 18 Mm (from 92 Mm above the center to 74 Mm)- less than half the planet's equatorial radius, and only 2 Mm wider than the planet's polar radius. In the outer third, at 86 Mm above the planet's center, the 600 km widest gap lies- it's caused by the 1:2 resonance with the innermost round moon. Other gaps are formed by the weaker resonances of other moons, and in total 9 gaps take 1.3 Mm of breadth from the main rings. Including all dust rings, the full disk stretches to about 500 Mm from the centre of the planet before perturbations from outer moons tear it apart. Included in this space is the 12th greater ring, made of material from the innermost large asteroid moon, plus several incomplete ring arcs and clouds.

(see also appendix 3)

Of the at least 46 moons of the planet, 32 are smaller than 100 kilometres on their greatest axis. Most of these small moons are derived from a series of collisions between larger bodies, whether native to the planet's orbit or from elsewhere. The two permanent moons embedded in the rings are each quite small- the inner one is three dozen kilometres across, and the outer one is only five kilometres across. The inner moon looks almost like a model- a barely pitted icy rock with a saucer-like equatorial ridge made of ring debris, a shape that can be made out with binoculars from the planet's surface. The outer moon is a smooth and very prolate collection of ring fluff with its very own ringlet. Past the main body of the rings, a few ringlets sit- but not enough to form a proper extension of the rings.

Their queen is the 12th greater ring, an almost-colorful assortment of materials that have fallen inward from many other moons. This ring is the daughter of the large asteroid moon that shepherds it, a 260 kilometre sweet potato covered in sulfurs and other compounds that's both visible as a small oval in the sky from the planet's surface and hopelessly in the belly of the stronger planetary radiation belt. The ringlets and the radiation belt give way to the inner round moons, each icy yet mostly unmelted. The first is a 600 kilometre gleaming (in angular size, it's the same size as Luna- but it's twice as bright) ball of ice, prevented from melting by its short orbital/rotation period and its trace atmosphere. However, due to being so close to the parent planet it's moderately prolate- this may be a side effect of the moon coming back together after being blown apart as evidenced by the various geological units that make up its body.

Between it and the next icy moon, there are two smaller moons. Each are made of the same material as their parent, but are protected by thin coatings of particles that have fallen inwards from the many further moons. The next moon would be a normal iceball if it wasn't so close to its star. Its atmosphere is maintained by a shaky equilibrium- higher temperature means more sublimation means more atmosphere means a higher temperature needed for sublimation. If one has a good eye, they might see the forms of white clouds moving across the surface- perhaps contrasted against one of the deep tinted cracks that give away the moon's strong oceanic activity. Snowy dunes cover the plains. The moon is active in other ways, too- cryovulcanism can be seen in the form of geysers, plumes, and transient "lava" lakes. It is large in angular size as well: night skies on the planet are often brought into twilight by the 2300 km moon. Those aren't the only odd features of this moon- while the leading trojan point only holds artificial objects, the trailing one hosts its very own co-orbital moon.

This moon is over a fifth the size of its partner, but is more rocky and wouldn't need an atmosphere even if it could retain one. These two moons are vacation destinations- the view of the rings isn't as spectacular as from a more inclined moon, but swimming in a natural pool of hot water and looking up at the sky is ever-attractive. Radiation levels are low for moons without magnetic fields, as both experience relatively little magnetic interaction and the second radiation belt only comes into force further out. The third large moon is not so lucky- despite being on the wrong end of a resonance, its eccentricity pushes it fully into being an actively volcanic world. It is a large orange ball in planetary skies- its 2800 km radius and high activity mean that volcanic eruptions are sometimes visible to the eye. Its constant expelling of matter means its radiation situation is a vicious cycle- the planetary magnetic field is encouraged by the moon's magnetic field and ion ring, which is too weak to outcompete the planetary magnetic field at the poles. This causes spectacular low-latitude aurorae.

Beyond the third spherical moon is the ragged outer radiation belt, which stretches almost to the next moon on a "good" day. Within the belt is another large moon- a brownish-grayish asteroid, with an oddly smooth surface between the craters. As such, it looks quite at odds with the normal expectation of an asteroid- though few see it anyway, small and stuck in a radiation belt as it is. From the planet, it is but a star- though its shape is notable through binoculars.

Next out is the grandest moon of them all, a veritable planet even if its smaller fellows weren't. Its orbit is something of a mystery- its inclination and eccentricity are each high for a moon that formed with the planet and low for a moon that was captured, but no culprit has been found yet. In the sky, the planet not only wobbles but grows and shrinks- at its widest (at solar apoapsis and planetary periapsis), the planet is over twenty-two times larger in the sky than the sun, while at its smallest it's "just" thirteen times larger at the equator. The pole is still wider than the sun, so the list of spectacular things this large moon experiences that its companions mostly don't (but gas giant moons do) is at least three items long. The first is enabled by its inclination- the rings of the planet shine in the sky of the inner hemisphere (and especially the third of six lunar poles), even during daytime, and are over two and a half times as wide as the planet itself (when they're not edge-on). The second is enabled by its eccentricity- at periapsis, the moon dips into the planet's vast outer radiation belt. Its magnetic field, strong enough to reconnect even over the moon's northern and southern poles, thus produces extremely strong aurorae over the north, south, and lead (if you think east, you won't be too wrong) poles- almost as strong as the previous moon's aurorae, weaker as its magnetic field is. The third is caused by both combined- the moon's high inclination relative to the planetary equator means that it orbits almost in the planet's own orbital plane (meaning it has a lower effective axial tilt than the planet itself). This means that eclipses are extremely common- despite precession, the size of the planet itself is easily large enough to block the entire sun even in a suboptimal position. This means lunar (solar, on the moon itself) eclipses are more common than their counterparts- about every two orbits (14 earth days), the sun is blotted out and the moon only sees planetlight for up to four hours. Solar eclipses (again, lunar on the moon itself) happen less often due to the much smaller angular size of the moon (at maximum, its 5670 kilometres bring it up to 0.56 degrees in size; at minimum it's only 0.38 degrees- rather lunar, all things considered)- and they're quick on the planet due to its rapid rotation, only 15 seconds long at the very maximum. However, people on the moon can watch their own little disk of shadow slide across the planet for up to two planetary days.

Despite its long rotational period (baffling to those who've lived on the planet for a long while), the strong magnetic field and thick atmosphere (thicker than the planet's, in fact) make the moon perhaps more habitable- the gravity is 0.677 gees, the oceans are only 6 kilometres deep in the trenches, and the global climate is overall much more hospitable. The orbital seasons are as strong as on the planet, bringing the planet's temperature from an average maximum of 31 celsius to an average minimum of 7 celsius. However, this makes for diverse growing seasons and the temperate regions are kept warm by the thickness of the atmosphere- even during the long nights. Unlike on the planet, life and biodiversity are fairly similar worldwide- the air is thick and the seas low, so the continents are almost spiderwebbed by island chains and what life can fly (quite a lot of it) can go very far. The fourth large moon also has two co-orbitals, the larger in the leading trojan point and the smaller in the trailing point. This happens to mean that most of the moon can see at least one mostly-stationary object in the sky at all times- while almost 65% of the moon can see some part of the planet, 55% each can see one (or, near the inner pole, both) of the two trojan bodies, meaning only the area immediately around outer pole lacks such a body in the sky. The larger co-orbital is comparable to a standard terrestrial moon- rugged gray highlands, with a few flatter basaltic regions. At 2040 kilometres in radius, it is easy to see in the moon's sky when lit properly and is still an obvious disk in the planet's sky. It also features large cracks in its surface likely due to core cooling-related shrinkage. The smaller one is a a remarkably cubic 300 kilometre rock, complete with one rather large crater. From the moon its squarishness can be seen, and from the planet it is a bright star.

Next out is a batch of small moons, likely perturbed by both a close encounter with one of the larger moons and an impact- all seven of them share similiar surprisingly stable orbits. The moon beyond them is another large inclined eccentric moon, though it's smaller- this one is 3900 kilometres in radius, and was likely wider due to spin before it was captured. Its inclination is high, but its eccentricity and rotational period are relatively low- almost certainly due to interaction with the odd shape of the parent planet and the larger inner moon. Its spin (about 70 local days, much like the other high-mass moon) also allows it to be warmed by tidal strain, preventing it from cooling off. As such, it is something of a desert moon- trench seas and a somewhat thin atmosphere ensure that. It is noticeably cratered- while many craters have eroded, a few large and recent ones remain. This moon can have even better views of the rings than the other, but rarely experiences eclipses.

From the fifth moon, the gleaming rings can be up to four degrees wide and as thin as three degrees. Its widest gaps can barely be seen, while the divisions between the 12th and 11th greater rings plus between the 1st greater ring and the planet are more prominent. The planet can't see the moon as well, but its ruddy disk is still noticeable even at apoapsis. Beyond this moon, the rest of the hill sphere is filled with small families of captured asteroids and similar bodies. Two of these are particularly interesting- one is an icy ball both pitted with craters and covered in dark carbon dust, while the other was nearly shattered by an ancient impact. The first also sheds quite a lot of its dust, which spirals inwards and can be found even on inner moons. The second is a sphere with a large bite taken out of it, and cracks and cliffs cover much of the rest of the body. Both are stars in the sky, but their shapes can be discerned with amateur telescopes.

Life on the moons

The fifth large moon, despite its tiny size, may be most recognizably similar of the moons to those who were born on the planet. This is because like the planet it has multiple extremely different life zones- dark bluish thick-atmosphere trenches, scraggly green mid-pressure plains, and red-white highlands. The first two are tolerable for most people from other worlds- the equatorial plains go between roughly 36 and 14 celsius across the year and have just enough oxygen to exercise, while the deep northern trenches go between 51 and 25 celsius and an atmosphere nearly 1/3rd thicker than the plains atmosphere. Along with the long winding trenches, there are other deep cracks- a few great tidal chasms gather much of the planetary water, and several vast craters reach just as deep to provide bowls of diverse rainforest. The plains, what would be seabed on a world with a more reasonable quantity of water, host shallow but wide seas... and deserts, too. Highlands gather small lakes at the foothills and calderas of vast mountains, but this moon is more active than worlds with Tharsis-style mountains- volcanic spots move a bit too quickly to build atmosphere-rending peaks.

Unlike the planet, evolutionary history is possible to trace- and easier than on the fourth large moon due to the fact that tectonic activity is less common. As such, it is known that an ancient eastern sea likely gave rise to life- from there, it quickly rose onto the land and spread both to the mountains and to the rich trenches. This breeds global diversity unseen on either the planet or the fourth moon- in particular, flight has evolved eleven times (thrice on the plains, eight times in the trenches). As far as can be ascertained, soon after life developed the moon's core began to cool- causing a great die-off. However, this was exactly when the moon was captured by the planet- causing strong tidal stresses to act upon the moon, increasing activity and heating it until the situation stabilized.

The fourth large moon has more biomass than the fifth, but the ease of movement around means biodiversity suffers. Rainforests and coral reefs form unbroken strips between shores- meaning that while the fifth moon's dozens of isolated seas have duplicate niches for life, any fish or bird making the journey from one end to the other on the fourth moon may just find more members of its species. In fact, many species manage this- in the thick air, it's easy to soar thousands of kilometres. While flight is even easier than at the planet's equator, life only developed once on the fourth moon. This evolution followed a broadly similar pattern to most other high-water oxygen worlds. As such, it has its very own photosynthesis color- a warm greenish-yellow, redder than the plains plants of the fifth moon but greener than the orange of the airborne "plants" of the planet.

Plant life is one of the most diverse forms of life on the world, but the standard trimodal form is missing its third- only introduced forms matching the broad definition of fungi exist. Animals are a distant second- sea animals are fairly uniform. Small land-based animals are the peak of animal diversity, because they don't have the reserves to walk halfway across a continent. On the other hand, flying animals are underspecialized... until they become flightless. The planet is host to nearly as many species of formerly-flying animals as there are genera of flying animals in total. The fourth moon does boast one thing otherwise unseen- pseudo-native sapient species. The people who originally settled this moon were a different odd (and concerning in ethics) faction of the Protection Initiative- they believed that "uplifting" native near-sapients was the best way to protect planets. As such, many of the system's native sapients are from the fourth moon. The local cities are constrained affairs due to (and perhaps causing) the fact that nearly all of the population of 3 billion is native to the world, and they prefer to travel under their own power.

Other planets in the system


(see also appendix 4)

Appendix 1:

this is up in the air (hah) cuz i don't think it's plausible but i imagine the life cycle is

the funniest part is that of all the representations of such things in media, the best is this one minecraft map i found once- the under-construction pics for red tern island

Appendix 2:

a friend asked "how in the world do continent-sized single organisms maintain a uniform metabolism? I got the pneumatic helium vascular system but on a cellular level it would be much harder to maintain homeostasis across something that large"

my response is: but stuff like homeostasis and thermoregulation is significantly easier with ground cover, which is part of the reason for the layers of rock- if we're pretending it's possible for them to exist without alien intervention, i think it's plausible for them to have an evolutionary history along the lines of "very large veiny balloon scoops up some seaborne and airborne muck derived from other forms of asexual-group life, eventually a symbiotic relationship emerges and they merge as closely as lichen with the muck organism losing independent structure in exchange for being much larger and having a cooperative substrate, eventually mutations that cause gigantism become possible to survive due to the use of the new rock/dirt/muck as a faster more easily repaired metabolic system" because one of the keys is that there isn't really a central nervous system, it's all distributed around the veins- so the integration of a life form with smaller veins that don't need to carry everything important provides a way to actually regulate across that size

Appendix 3:

Tiny, over 1/under 20 km; Small, under 100 km; Medium, non-rounded; Large, rounded

total of 7* round and 17-35 largeish asteroidal of various sorts

Appendix 4:

There can be no other planets (aside from lucky trojans) between 0.425 and 1.179 au orbiting the planet's star, because the gravitational influence of such a highly eccentric heavy world completely rules that out. (I checked with the calculator- either Earth destabilizes nearly to the surface of Sol, which we know is false, or Earth barely destabilizes anything. I chose to be optimistic). Multiplying (number of earth masses orbiting sol) by (star mass in solar masses) by (metallicity) gives me a conservative mass of local bodies of 220 earth masses and a liberal mass of local bodies of 730 earth masses. I think the liberal mass is more useful- if only because I like oort cloud bodies.

So that's about 130 earth masses dedicated to far belt, disc, and cloud bodies- one ejected mesogiant, two smaller giants, a handful of earth-to-mars bodies, several dozen luna-to-ceres bodies, and a ridiculous amount of tiny bodies. Of the 500 remaining, well- that's suited for a few other giants, plus their moons and any other rocky or watery worlds.

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