Their place in space - Surface conditions - Wildlife - Map of Tarsan’s surface
Tarsan and Reger are twin-planets which orbit their sun Itas in a distance of 2.1 astronomical units. They need roughly 3 earth years to do a full orbit around their host star and about 69 days to orbit around each other. The barycenter of this motion lies between them, with Tarsan - being the heavier of the two - closer to the barycenter than Reger; and the total distance between them being 524670 km.
Tarsan has slighly more mass (1.2 Me) than Earth and it’s rotation is slower, resulting in 32 hours (and 40 minutes) days, wheras Reger has less mass (0.71 Me) and rotates faster, giving it 22 hour days.
While Tarsan is habitable with a mean surface temperature of cosy 280.15 K, Reger is mostly ice, with 252.18 K.
This has several reasons. For one, Reger is smaller and thus cooled faster after it was formed. It’s tectonic plates are congealed and have stopped moving a long time ago. Moreover, it spends a lot of time in Tarsan’s shadow, effectively cooling while no warming light reaches it from it’s sun. Tarsan is big enough to never be completely eclipsed by it’s twin, so there’s always some light of Itas reaching it. And because of its small size, Reger has only a very thin atmosphere left, which can’t retain much heat.
On the other hand, while not completely overshadowed by Tarsan, Reger’s nights are quite bright, since light is reflected from Tarsan’s surface in the twin’s direction.
The ice on Reger is mainly waterice, but while the planet is in complete darkness, temperatures can drop far enough for carbondioxide to solidify from the atmosphere, causing it to fall as snow to the surface. This means that during the the “long nights” most of the surface is covered with a thin layer of CO2 crystals. Later, when the planet moves into sunlight again, it vaporizes back into the atmosphere again.
Tarsan, being the warm habitable planet of the two only cools slightly, when partially overshadowed by it’s twin. It’s rich, earth-like atmosphere is much healthier and can retain more heat than that of Reger. The bigger influence their joined dance through space has, is seen along the coastlines of Tarsan’s continents. Reger exerts a strong tidal force on Tarsan, which can be clearly seen when coastlines fall completely dry, baring massive cliffs during ebb which become completely submerged during flood.
Tarsan still has heathy continental drift, with everything you would expect to find on a geologicly active body. Deep sea trenches, collision orogenes and wandering hotspots, accompanied by earthquakes and tzunamis to name just a few.
Because of the strong tidal changes on Tarsan, something akin to coral reefs could never evolve on the planet.
Fish and land animals were abundant during the planet’s long history, but this changed to a dramatic degree ever since Tarasians began to evolve. Their ancestors quickly became the apex predator of every environment they conquered (beginning with the sea - where the first Tarasianoid evolved from something akin to a shark).
They had a devastating impact on the populations of herbivores and carnivors alike. By the time the Tarasians as we know them today had evolved, only a fraction of the biodiversity the planet once held was left.
Today, the wildernis of Tarsan is nearly devoid of life.
Especially the continents only harbour a few animals, forming a very short food chain. They are all either too non-descript for the early Tarasians to bother with them, or actually such fierce predators that Tarasians don’t hunt them - out of respect.
The oceans are a little different. Early on, the Tarasians realized that the Taryon (above mentioned shark; a living fossil) is an early relative of theirs and they declared the species as well as all of it’s prey-animals to be protected. To some, the Taryon is almost holy and killing one will result in the worst form of punishment a society of nearly immortal beings can come up with (see: Tarasian society).
Tarsan’s skies are equally empty as the continents. Only very few species of bird-fish-like animals inhabits some extreme habitats, such as high mountain ranges or the cold northern ice cap.
 |
 |
Tarasians are very descriptive when naming things. Thus, all continents and cities are named after their most obvious feature.
Gardatok - Volcano (after a chain of volcanos, spanning the coninent in it’s length)
Gereleg - Shipyard (after the first and only starship construction facility on the planet)
Ra-krevek-Regerotuk - Under-hard-snow (= ice; for being covered by the polar ice cap)
Rakotak - Underwater (city on the ocean floor)
Razat-ka-Kotak - On-the-water (for being an island)
Razat-ka-Mitas - On-the-mountain (for it’s topographically high elevation above sea level (plateau of a collision orogene)).
Torrak - Forrest (for the single forrest spanning almost the entire continent. Torrak also means “life”, because the Tarasian civilisation began here)
Vota - Capital (for being the Tarasian’s capital city)
 |
 |
 |
 |
 |
 |
 |
 |
