Concept art by Ryuujin.
Avalon is of the major moon of a gas giant, and is notably the home-world of the Avali. The name was assigned by the first human explorers to discover it. Named after the mythical island of bounty, it was in reference to the planet's wealth of liquid hydrocarbons, water ice and shallow gravity well, which together made it a perfect world for refueling and resupplying interstellar craft.
Characteristics[]
Avalon is located in an outer orbital region around its star, outside what is known as the "circumstellar habitable zone " (a.k.a. the "Goldilocks Zone"). Because of this, its average planetary temperature range is much colder than Earth's, resting between -50ºC to -40ºC or -58ºF to -40ºF. Its surface gravity rests around 2.45 m/s² (roughly 25% that of Earth's). Avalon's atmosphere is denser than Earth's, with a surface pressure about 1.5 times higher. The lower gravity means that its atmosphere is more extended than Earth's, and it is composed primarily of methane, nitrogen, and hydrogen gasses.
The bulk composition of the planet consists of ice and rocky material. Avalon is divided into several layers, on the surface, most notable are the rocky, frozen mountain peaks and the "ice shelves" which cover wide expanses of the surface and are subject to constant shifting, breaking, and movement. Avalon's surface oceans are composed primarily of liquid ammonia.
Cryovolcanism[]
Much of the non-rocky surface of Avalon is dominated by cryovolcanism.
The strong tidal forces exerted on the moon by it's parent planet produce heat and compression that forms a deep layer of liquid water beneath the icey shell. In many ways this system is not entirely unlike that of Earth's surface, with it's silicate shell floating on a soft layer of mantle and liquid interior. However the ice shell is considerably thinner than Earth's lithosphere, often being only a few kilometers thick even on land meaning that psuedo-volcanic activity is far more frequent.
Convection currents from below, where persistent enough can lead to the formation of fissure and hot-spots in the ice which may eventually lead to cryovolcanic eruptions, spewing liquid water onto the planet's surface.
Despite the seemingly harmless nature of water to the human eye, this liquid water is dangerously hot to the local ammonia based life forms and is treated in much the same way as lava would be by humans; with a mixture of awe and a healthy respect for distance. Where water is blown high enough into the air as a geyser it frequently freezes in the frigid atmosphere and falls back to the surface as snow which blankets the surface, frequently combining with the local winds to form fierce blizzards.
Unsurprisingly there is some disagreement between linguists and scholars as to whether to what humans call water and snow, should translate as lava and ash when handling Avali/English translations given the different cultural interpretations of two seemingly mundane forms of water.
Climate[]
With its relatively cold temperatures, liquid water is very rarely encountered, even in the form of water vapor. As such, Avalon's clouds are likely made mostly of ammonia vapor and methane gas. It is known that the planet has arid regions, anologous to desert in the planet's geosphere (Though by human standards they represent arctic tundra) and while temperatures towards the poles can drop low enough to freeze ammonia.
Due to the relatively featureless topography of the planet's ice shelves and dense atmosphere, the planet's jet streams tend to have a significant effect on the surface level airflow, creating consistent winds that tend to travel in roughly the same direction which has a number of useful applications to the native inhabitants, ranging from power generation to navigation.
Orbit & Rotation[]
Avalon orbits its star outside the water-based habitation zone. Specific data could not be found at this time.
Moons[]
Asides from numerous artifical satellites and a number of small rocks trapped at lagrange points, Avalon has no signficant natural satellites of its own.
Life[]
- Main page: Flora and Fauna
Due to the distance from the local star, most plant life on Avalon is not photosynthetic in nature, but are instead symbiotic colonies of microorganisms and bacteria, similar to jellyfish, men-o'-war, slime molds or fungi found on Earth. Others are thermophiles that use the temperature gradient around hot springs to flourish. Precise details about the fauna found on Avalon is relatively scarce. Due to the ammonia based biology of life there, they tend to possess slow metabolisms.