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Phoebe, Saturn's largest outer moon

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Celestial bodies between the orbits of Jupiter and Neptune are known as Centaurs. Surface temperature is between 100 and 200 Kelvin(K). They are made of ice or at least contain high amounts of water ice.

Technologies used to paraterraform a Centaur can be used for the small moons of the 4 gas giants. In other solar systems, similar asteroids and moons should exist too.


A centaur is far away from its hosting sun. Temperatures are very low. During day time, the surface is heated to only 70...180 K. During night, the only source of heat remains the cosmic radiation. Centaurs are also exposed to solar winds, but, since they are far away from Sun, the wind is not so dangerous for life and electronics as it is on Earth's orbit. Being still inside the solar magnetosphere, these asteroids are protected from the cosmic, interstellar environment.

Satellites orbiting close to their planets can be protected by their planet's magnetic shields. The inner moons of Neptune (like Proteus) or the inner moons of Saturn (between Titan and Enceladus) are good examples. In other cases (like the inner moons of Jupiter), strong ionized radiation belts can be a real problem to any settlement. The outer moons (like Saturn's moon Phoebe) are too far away to be protected by a magnetic field.

Centaurs are far away from Sun. As a direct result, their Hill Sphere extends far away. This means that a centaur has a higher chance to host satellites then an asteroid in the Asteroid Belt. Indeed, Chiron, one of the largest known Centaurs, has rings. Asteroids have a small gravity, so that they cannot hold all debris resulted from meteorite impacts.

Luminosity is low, but still enough to support plant life. Solar panels will only receive tenuous amounts of light.

Internal Composition

Centaurs are expected to contain high amounts of water ice and probably also other ices. Chiron, at its aphelion, showedCommentary Behavior. It increased its brightness by 75% and formed a small tail. No centaur has been visited by a spacecraft yet. However, Phoebe, one of Saturn's outermost moons, is supposed to be a captured one. Phoebe is made of dirty ice. Also, other moons of Saturn, Uranus and Neptune are made primarily of ice. The largest moons, with a spherical shape, are differentiated, with an internal core made of solid rock, surrounded by a large icy mantle. Some moons might have an underground ocean of liquid water, heated by tidal forces. Centaurs are not heated by tidal forces. Since they are too small, their internal oceans (if ever existed) must be completely frozen. Majority of them should be undifferentiated and made by a mixture of dirty ice.

Temperature is small enough to keep ice solid and prevent it from sublimation. However, many gasses found currently on comets are expected to vanish soon from the surface of a centaur. Examples are methane, carbon monoxide, nitrogen and even ammonia. The fact that Chiron sometimes behaves like a comet means that it has not been for long on its current orbit.

Settlers will find enough water on a Centaur. They will also find other gasses trapped within the ice, providing them with the ingredients needed for life. Also, in the dirty ice, they can find small amounts of other materials.

On a Centaur, settlers will hardly find metals, needed for any human colony.

Reasons for colonization

What could make future settlers to set on a Centaur or a tiny satellite of a giant planet? In case of giant planets, a small, remote satellite can be a good place for building a space station. If one day Saturn will become an independent federation, its government might want to build a large spaceport on Phoebe. All cargo towards Saturn Federation will enter Phoebe International Base, where it will be checked for drugs or other forbidden materials.

Centaurs are floating in the vast immensity of space between the Giant Planets. Despite the technological challenges, they offer some great political advantages. They should be considered neutral territory. So, small communities can create their independent states on the surface of each centaur. Unlike the Kuiper Belt or the Oort Cloud objects, Centaurs still receive some heat and light from the Sun.

We can imagine what kind of new states can form on Centaurs: groups drawn by various ideologies, religious organizations, industrial corporations or even remote colonies of other states. A centaur can be an ideal place for building a prison or a Gulag camp.

Technical challenges

The main problem is the lack of light and heat. Solar luminosity is enough for plants to grow (see Plants on new worlds for more details). Solar panels can be used to generate energy, but they will need to cover a wide area. Ice can offer a good insulation from the extreme cold. Internal paraterraforming can be used. Building a colony on the surface will be more easy, but heating it will be a big challenge. Thermal insulation must be well done because of gas that might exist between the ices.

The main challenge is to provide all light needed for plants and all heat needed for the entire colony. Light can be captured from surface, with large panels, then conducted with optic fiber towards the underground chambers. This way, light from a wide area can be used on a small surface, to mimic the luminosity found on Earth.


The colony will have all ingredients needed for life. However, it will have to import all metals and building materials.

Small temperatures and low gravity can be of great help for industrial corporations. There are many places in industry where low temperatures are required. Also, below 150 degrees Celsius, superconductors are found. So, we can expect that on Centaurs industrial centers can appear.

Agriculture will only produce what is needed for the colony.

Centaurs can be linked in a large-scale transportation network. Since they can host industrial centers, they will need supplies from places richer in metals. Their goods will be then shipped to other places.

Other uses

In other places, religious organizations, charismatic leaders of philosophes will form colonies. Imagine a monastery build on an asteroid, where nobody will disturb you and you will have all silence in the Universe for praying!

Centaurs can be used in many other ways. Let's take the following example: The newly formed Mars state (covering the planet of Mars) wants to expand its borders. It makes a colony on a Centaur, with plans to send space probes in secret, towards other star systems. In the same time, the state of Venus builds a secret laboratory on another centaur. While this happens, the dictatorship of Mercury builds a prison on a third Centaur, where prisoners can be tortured and interrogated without the world even knowing. At the same time, the federation of Uranus (owning the moons of Uranus), is building a secret army on a fourth Centaur.

The Kuiper Belt and the Oort Cloud offer even more remote positions for settlers, but they are far away. Centaurs are closer and can be reached by spaceships more easy.