Avalon
Currently unofficial lore, and in progress.
 Weather Satellite image of Avalon | |
| Orbital characteristics | |
|---|---|
| 771568 km | |
| Eccentricity | 0.01 |
| 5.322 days (127.7 h) | |
Average orbital speed | 10.53 km/s |
| Inclination | 0° |
| Satellite of | Valaya |
| Star | Solakku |
| Physical characteristics | |
| |
| Circumference | 13,238 kilometres (8,226 mi) |
| |
| Mass |
|
| 2.452 m/s2 (0.25 g) | |
| 3.22 km/s | |
| Tidally locked | |
| Albedo | 0.45 |
Avalon is the fourth and largest moon of Valaya, and the only celestial body orbiting Solakku known to naturally harbor life and one of only three with exposed bodies of liquid on its surface. It is mostly barren, with a majority of the surface taken up by cold deserts, though heavily vegetated areas can be found in coastal regions, with the density of vegetation increasing towards the equator.
Avalon holds on to a thick atmosphere, which consists mostly of nitrogen and oxygen. It plays a vital role on sustaining the habitable surface conditions, as it generates a greenhouse effect that maintains the average surface temperature of −50 °C (−58 °F). Evaporation occuring in Avalon’s oceans generate a consistent cloud cover in the atmosphere, as well as powering global precipitation.
Most notably, Avalon is one of just a few worlds in the galaxy where intelligent life has evolved. Avali have come to inhabit every geographical region of Avalon, having had a profound impact on its biosphere.
Natural History
Avalon formed approximately 2.31 billion years ago, shortly after its parent planet. Similarly to the planets, it coalesced out of a disk of gas and dust, though it formed inside a smaller disk orbiting Valaya, rather than the larger protoplanetary disk surrounding Solakku, though the material composing the former would have been captured from the latter.
The atmosphere of Avalon would’ve formed later from volcanic activity and outgassing, though its initial thickness would’ve been thinner than it is today. After formation, Avalon’s surface rapidly cooled, causing volatile ices, including water and ammonia, to freeze solid. However, pockets of water, having condensed out of the atmosphere during this cooling process, formed underground, where they were kept liquid by tidal heating and geothermal heat.
These underground oceans were left isolated until 1.6 billion years ago, during which time the first Prokaryotic cells would’ve developed around geothermal vents and spread out from there. At the same time, Solakku’s luminosity had been slowly increasing, together with volcanic activity enriching the atmosphere above with greenhouse gases, leading to temperatures rising to above the melting point of ammonia. Eventually, geological activity caused the forming ammonia surface oceans to make contact with the underground water oceans, causing them to mix. This process is known as The Great Nitrification event and lasted until 1.3 billion years ago, when Avalon’s surface temperature largely stabelized and the two sets of oceans became fully mixed with each other.
At the time, the average composition of the oceans would’ve been more skewed towards a higher ammonia content than today, with geological evidence suggesting a ammonia content as high as 80%. The early, water-based life would’ve been forced to adapt to the sudden presence of Ammonia, a toxic substance for those early cells, causing a mass-extinction event out of which the first ammonia-based single-celled organisms emerged. These Prokaryotes would then go on to become the common ancestor to all modern life on Avalon.
It is believed that a number of these cells left their natural environment, floating upwards through the tunnels connecting the oceans until reaching the surface, where they quickly adapted to make use of starlight from Solakku as an energy source. These photosynthetic cells produced oxygen as a byproduct, initiating the Great Oxygenation Event, lasting 600 million years, during which carbon dioxide in the atmosphere was converted to oxygen. This, combined with the outgassing and evaporation caused by the rise in surface temperature, eventually transformed Avalon’s atmosphere towards the composition and thickness it has today.
About 1.3 billion years ago, about halfway through the Great Oxygenation Event, the first Eukaryotic cells developed and filled the oceans. The first multi-cellular life developed much later, about 900 million years ago.