Nemoros
Nemoros is a moon orbiting the gas giant Aulea in a single star red dwarf system. Since Aulea is relatively large - between Saturn and Jupiter in size - and Nemoros orbits it closely, the tidal forces acting on it are very strong. This is only made worse by the presence of several other large moons tugging on it, making the moon very volcanically active.
Nemoros has an icy crust and mantle with a core of silicates and iron. Cryovolcanism is common on its surface, and magma eruptions are frequent deep in its interior, under a sub-ice ocean of water and ammonia. Because of this volcanism, the planet has a very dense atmosphere in spite of its small size, about a hundred times as dense as Earth's.
This atmosphere of mostly nitrogen has arisen from the breakdown of volcanic ammonia into hydrogen and nitrogen under sunlight. Most of this hydrogen escapes into space, while the nitrogen remains in the atmosphere. Any ammonia left over condenses out of the atmosphere and freezes. There is also some methane in the atmosphere, which prevents oxygen buildup; when water vapour released from cryovolcanoes breaks down into hydrogen and oxygen under a similar process, reactions with methane prevent it from remaining in the atmosphere in high quantities for long.
With a surface temperature of around minus 170 degrees Celsius, it's cold enough for methane to condense out of the atmosphere, forming large oceans, lakes and rivers. This liquid methane is essential to life; unlike Earth, life on Nemoros uses methane as it's primary solvent instead of water, although ethane is also used to an extent. Although the moon does have liquid water beneath its surface, this underground ocean is uninhabited and very hostile to life on Nemoros. In order to survive, temperatures where methane is liquid are required.
The surface of Nemoros is very dim; not only does it orbit far from a relatively dim star, but its atmosphere filters out a great deal of the sunlight. In the moon's upper atmosphere, UV radiation breaks down methane and allows it to form larger molecules. Over time this has led to the development of a thick, hazy lair of organic tholins, giving the sky its murky orange colour. While this does mean organisms on the surface have less light to utilise in photosynthesis, it also provides its advantages; like Earth's ozone lair, this tholin layer protects life from harmful UV radiation.
Organisms on Nemoros use methane as their primary source of carbon, rather than carbon dioxide, due to its abundance. The moon's equivalent to plant life tends to be very dark in colour to absorb as much light as possible, making up for the low light levels. Chemosynthesis is also used to a great extent, far more so than on Earth, often utilising sulphurous compounds released from volcanoes. These substances are plentiful in the subsurface ocean, supplied by hydrothermal vents, so are often released by cryovolcanoes on the surface.
Properties
Physical properties
Mass: 0.03896 Earth masses
Density: 2.47
g/cm3
Radius: 2822.8 km
Surface gravity: 0.198g
Atmosphere
Nitrogen: 98%
Hydrogen: 2%
Above is the dry composition; there are also variable amounts of methane vapour in the atmosphere
Pressure at sea level: 38 atmospheres
Average surface temperature: -173oC
Orbit and motion of Nemoros
Semi major axis: 500,607
km
Orbital period: 3.061 days
Rotational period: synchronous
Orbital inclination (to Aulea's equator): Negligible
Axial tilt: Negligible
Orbit and motion of Aulea
Semi major axis: 98 million km
Orbital period: 433 days
Rotational period: 12 hours
Axial tilt: 45 degrees
