A terraformed Titan

Main article: Rocky Planets (Theoretical Models)

A Titanian type planet is a theoretical model of an Outer Planet orbiting close to its parent star. The name is not official and comes from the adjective titanian meaning related to Titan. Ahotter planet will be a Galilean Type Planet.

The Solar System has two giant planets in the are, Saturn and Uranus, with only one large moon with a significant atmosphere, Titan.

Relation with parent star Edit

Around majority of stars, the planet will receive small amounts of heat and light, with aSolar Constant of 0.04 to 0.004. Temperatures on the surface, without an atmosphere, should be of -188 to -127 C.

Around M - type stars (modeled for Barnard's Star):

  • Distance: 60 to 190 million km
  • Visual constant: 0.0002 to 0.002 (for yellow wavelength)
  • Revolution period: 0.57 to 3.23 years
  • Stellar gravity: 0.1 to 1.2
  • Hill sphere (assumed Earth's mass): 1 to 3.2 million km

The planet will have a stable orbit. Light will be too dim for plants, mainly in blue wavelength. Given the low tidal forces, the planet would not be tidal locked and will have stable orbits for satellites.

Around K - type stars (modeled after Epsilon Eridani):

  • Distance: 640 to 2040 million km
  • Visual constant: 0.002 to 0.022 (for yellow wavelength)
  • Revolution period: 9.8 to 56 years
  • Stellar gravity: 0.004 to 0.04
  • Hill sphere (assumed Earth's mass): 6.8 to 22 million km

The planet would be at a significant distance from its parent star, undisturbed by tidal forces. It will have stable orbits for moons. Light will barely be enough for plant life, mainly in blue wavelength.

Around G - type stars (modeled after Sol):

  • Distance: 1050 to 3300 million km
  • Visual constant: 0.004 to 0.04 (equal with solar constant)
  • Revolution period: 19 to 104 years
  • Stellar gravity: 0.002 to 0.02
  • Hill sphere (assumed Earth's mass): 10.5 to 30 million km

Saturn and Uranus fit within the borders.

Around F - type stars (modeled after Procyon):

  • Distance: 3150 to 9900 million km
  • Visual constant: 0.002 to 0.02 (for yellow wavelength)
  • Revolution period: 79 to 440 years
  • Stellar gravity: 0.0003 to 0.003
  • Hill sphere (assumed Earth's mass): 28 to 87 million km

These planets would be as far as the Kuiper Belt from the Sun, but heated as Saturn or Uranus.

Around A - type stars (modeled after Sirius):

  • Distance: 5300 to 16 700 million km
  • Visual constant: 0.0005 to 0.005 (for yellow wavelength)
  • Revolution period: 149 to 831 years
  • Stellar gravity: 0.00016 to 0.0016
  • Hill sphere (assumed Earth's mass): 42 to 132 million km

Plants will hardly survive here, the amount of red light is too low.

Around B - type stars (modeled after Rigel):

  • Distance: 41 500 to 132 000 million km
  • Visual constant: 0.0003 to 0.003 (for yellow wavelength)
  • Revolution period: 960 to 5500 years
  • Stellar gravity: below 0.0003
  • Hill sphere (assumed Earth's mass): 146 to 464 million km

Plants will not have enough light to survive, mainly in red wavelength.

Around O - type stars (modeled after R136a1):

  • Distance: 2 550 000 and 8 000 000 million km
  • Visual constant: 0.000036 to 0.00036 (for yellow wavelength)
  • Revolution period: 126 000 to 698 000 years
  • Stellar gravity: below 0.00001

Hill sphere (assuming Earth's mass): 3700 to 11 700 million km

The planet has by far not enough light for plant life. Still, at this distance, the amount of UV and X radiation is something similar to what Earth receives from the Sun.

Around L - class brown dwarfs:

  • Distance: 2.5 and 7.9 million km
  • Visual constant: 2.9E-9 to 2.9E-10 (for yellow wavelength)
  • Revolution period: 3.5 to 20 days
  • Stellar gravity: 18 to 179

Hill sphere (assuming Earth's mass): 0.07 to 0.2 million km

The planet will have stable orbit and might not be tidal locked. Light is too dim for a person to see.

Around T - class brown dwarfs:

  • Distance: 1.4 and 4.45 million km
  • Visual constant: 8E-14 to 7E-15 (for yellow wavelength)
  • Revolution period: 1.5 to 8.4 days
  • Stellar gravity: 56 to 570

Hill sphere (assuming Earth's mass): 38 000 to 120 000 km

The planet will have stable orbit. Given the strong tidal effect, it will be tidal locked. Light is too dim for a person to see.

Around Y - class brown dwarfs:

  • Distance: 0.223 and 0.7 million km
  • Visual constant: around 1E-30 (for yellow wavelength)
  • Revolution period: 0.09 to 0.5 days
  • Stellar gravity: 2300 to 22 000

Hill sphere (assuming Earth's mass): 6000 to 19 000 km

The planet will be below or very close to the Hill sphere, so there will be a high chance it will break apart and become a ring.

Physical and chemical composition Edit

Titanian planets are cold places. The only known similar object is Titan. The vast majority will contain a high amount of water ice, probably with a subsurface ocean. Because atmospheres are more stable, there is a high chance these planets will also contain other volatiles in high amounts, like methane. Ammonia should be solid.

If the planet has a low mass and is unable to support volatiles, it will still contain high amounts of water ice and volatiles trapped in the ice. Heavier elements might be found deeper.

Titanian type planets should contain a rocky core. However, since this core is smaller then for an inner planet, the amount of radioactive materials is smaller and the heat generated will also be smaller. It will cool faster or it might not had melted itself. Still, not much internal heating is required to maintain a subsurface global ocean.

Atmosphere Edit

It is known that all outer moons and dwarf planets have atmospheres that are slowly escaping into space. Solar wind is not so powerful to erode them fast, so the process will keep on going for a long time, even with no magnetic field. These atmospheres tend to contain also methane and other organic gasses, that are transformed by ultraviolet radiation into tholins. The presence of nitrogen is also known.

Carbon dioxide should be completely frozen. Other gasses might also exist on the surface or in the ices.

Terraforming Edit

Terraforming a Titanian planet is not impossible. The first step is to insert greenhouse gasses in high amounts, then to wait for the ice to melt. Except for a few theoretical planets that might be inner planets moved outwards, the majority should have large amounts of water ice. The second step, depending on available technology, is to use artificial continents, ground insulation or to transform the planet into an oceanic world. During this phase, the oceans will be colonized with algae and bacteria. Also, this is the moment when, with the use of chemistry, the oceans will be made suitable for Earth-like life. The third phase will require the transformation of atmosphere and the insertion of plants and animals.

Climate simulation Edit

A Titanian planet would look interesting, with low climate variations. The following is a model for an Earth-sized planet, located at the orbit of Saturn:

Latitude T(C)
90        8
75        14
60        15
45        16
30        16
15        17
0         17

The following is a temperature model for a terraformed planet, the size of Earth, orbiting where Uranus is:

Latitude T(C)
90        10
75        14
60        15
45        15
30        16
15        16
0         16

The values for the poles are in fact the temperatures expected to be reached during a polar night. As one can see, differences of temperature caused by latitude are too small. Day-night fluctuations will also be very small. Basically, there will be a single type of climate for the entire planet. During day-night cycle, changes of temperature are negligible, even if the rotation period is over 30 Earth days.

As a direct result, the atmosphere will accumulate moisture up to saturation level, but because temperature does not drop fast, it will not rain, except for rare exceptions. Winds will be very slow. Since greenhouse gasses are more heavy then oxygen and nitrogen, they will tend to accumulate closer to the ground. The use of sulfur hexafluoride should be a bad idea, since this gas is heavy. Nitrogen trifluoride, a much lighter gas (similar to carbon dioxide in mass), should be still lifted by air currents.

The lack of strong winds has another implication. There will not be lightning, which is required to create nitrates from atmospheric nitrogen, which are vital for plants.

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