User:Dante the Ghost/Sandbox

Makes sense.

Atmosphere
Titania's atmosphere is predominantly hydrogen with trace elements of nitrogen, oxygen, ammonia and argon making up less than five percent of the total, and is approximately forty-eight thousand kilometers thick (about one hundred times the size of Lylat's). This atmosphere gives the illusion that Titania is larger than it appears despite the fact it is slightly smaller in size. It maintains a consistent temperature of -550º F, made even colder by the hundred kilometer-per-hour windstorms which rip across the planet. Lightning is common.

Geology
The icy surface—a mixture of metamorphic and igneous rock embedded in ice—is not smooth thanks to tectonic activity brought on by internal pressures. A system of deep canyons and basins cover the landscape, rivers of ammonia-methane liquids mixed with water filling them, along with cracks and streaks from cryovolcanoes breaching the ice shell and internal activity. Beneath the icy shell is honeycombed with tunnels and caverns that connect the surface lakes to the subglacial oceans below. The largest of these surface lakes have breached the shell, creating a five kilometer "hole" and connects the two disparate worlds together—this lake is called Cronus, and is the location of the Titanian Expedition base.

Hydrothermal vents break the ocean floor and shoot upwards to warm the subglacial ocean, producing balmy temperatures of approximately 80º F at certain distances; the bases of these vents are often too hot. They melt through the ice to refresh the atmosphere, create seas on the surface, and have helped form the myriad tunnels which honeycomb the shell. Many of these vents are found in underwater mountains, evidence of volcanism and planetary activity.

Titania's internal composition is similar to Lylat's. Its topmost crust is a twenty-kilometer thick ice shell broken by frozen islands of rock; the subsurface, subglacial ocean beneath is half that. The oceanic crust is about five to seven kilometers thick; the rest follows the typical composition of an ordinary planet.

Native life
Multiple chemoautotrophic and chemoheterotrophic species live in the subglacial oceans and surface lakes, their entire biosphere built inside the subaqueous world. Vast colonies of chemoheterotrophic plants dot the ocean floor, often clustered around a system of hydrothermal vents, while prey and predator animals live and hunt among them. Every species so far observed generate light, possibly influenced from exposure to sunlight.

A single dominant species, the chemoautotrophic Crystaliens, controls the planet; they live in the deepest parts of the subsurface oceans and inside the largest surface lake that connects both worlds.