“It's almost unimaginable thinking a gas giant would have a lush and diverse ecosystem, but universe has it's wonders, and Aurantia is one of them.” -Unknown Traveller.
Aurantia is the third planet orbiting the stars of Aura and Lumina in the highly prominent Auralumina System of the Cosmoria Galaxy. Aurantia is the largest and most massive world out of the seven worlds in it's system. It is the capital of economy in the Collective Systems of Cosmoria.
Aurantia is a temperate gas giant primarily composed of hydrogen, but helium comprises around one quarter of its mass and one tenth of its volume. It has a solid, rocky core of heavier elements, but like the other giant planets, Aurantia lacks a well-defined solid surface. Because of Aurantias rapid rotation, the planet's shape is that of an oblate spheroid. The outer atmosphere is divided into several bands at different latitudes, with turbulence and storms along their interacting boundaries. A prominent result of this was the Great Hyades Storm, a giant storm that lasted for around two million years and disappeared in the year of 64,721 CE.
Surrounding Aurantia is a faint planetary ring system and a powerful magnetosphere. Aurantia's magnetic tail is nearly 800 million km long. Aurantia has a little over hundred known moons and possibly many more, including the three large major moons. The first of these major moons, Grenuria, is entirely neglected as it has no interesting features and such, except a lifeless subsurface ocean. The second of the large spherical moons, nicknamed Chilia is was ice world, and has been terraformed into an oceanic moon. Chilia has many species of marine life residing within it. The last moon, named Dauradia is an ecumenopolis with a large population of over five trillion.
Aurantia is host to a complex and diverse ecosystem of multicellular fauna and flora. It all started approximately 2.4 billion years ago, when an ancient meteor known as Vielay struck the storms of Aurantia. The meteor held simple single-celled lifeforms on it. After it hit Aurantia, the meteor disintegrated falling deeper into the dense atmosphere of the gas giant.
By luck, many unicellular lifeforms managed to escape off of the meteor, and quickly started evolving in the upper clouds of the vast gas giant. They quickly reproduced before sinking deeper into the gas giant. Soon, tiny multicellular species started to thrive, having a pressurized 'bag' of light elements to help them float within the atmosphere.
This evolution led to many floater organisms to evolve, feeding off of gliding plankton species. To control the population of floaters, specialized hunters evolved, with the ability to swiftly destroy the 'bag' of light elements, in some cases letting the floater to sink into the gas giant, while in most cases the hunters will just consume the floater.
While many hunters were satisfied with the amount of their daily nutrient intake, many hunters were essentially starving to death. This prompted many hunters to evolve into scavengers, feeding off of the sinker organisms that were still present on the world. In the course of many millions of years, this simple ecosystem essentially stayed the same, untouched by any life outside Aurantia.
Grenuria is one of the neglected moons of Aurantia and is the third and last major one from the magnificent gas giant. As a primarily mining world, Grenuria has never been quite popular among scientists, due to it having no interesting features to speak of, except it's lifeless subsurface ocean. Grenuria is a fairly recently captured moon.
The moon used to once have subsurface oceans filled with life when it was a planet, but as the core gradually cooled down, so did the subsurface oceans. Now the only evidence remaining of it's ancient ecosystem are massive fossils frozen in water-ice, littered across what was once the seabed. One such fossil is known as the "Gargantuan Fossil", and is the fossil of a possible apex predator of the ancient ecosystem, as even the teeth on the fossil are each 6 meters long. On account of the low gravity, the life would evolve to be much larger than usual.
When in a long time the outer layer of rock and metal is fully mined away, the moon is planned to be heated up with solar mirrors, causing the water-ice to melt, creating an oceanic world, which is giving rise to a new and lush ecosystem of fauna and possibly flora. Many aquatic species are planned to be exported to the moon too.