Tuluna

Tuluna is a fictional natural satellite frequently employed in science fiction and worldbuilding exercises to explore icy moon environments. In most portrayals, Tuluna orbits a gas giant called Helion in the fictional Valis system.

Naming and origins: The name is typically presented as a portmanteau of lunar imagery and a consonant-heavy constructed language element, underscoring its alien character. Its in-universe history varies by author but commonly situates the moon as one of the outer system's major icy satellites, discovered during early planetary surveys.

Physical characteristics: Tuluna is described as roughly two thousand kilometers in diameter, with an icy, heavily cratered crust over a possible liquid interior. The crust may host cryovolcanic vents and subglacial plumes. Surface temperatures range from extremely cold to somewhat warmer near geologic activity. A subsurface ocean is a common plot element, kept from freezing by tidal heating.

Orbit and rotation: In typical depictions, Tuluna is tidally locked to Helion, presenting the same hemisphere to the planet over time. Its orbit is slightly eccentric, which sustains internal heating and geological activity.

In fiction and media: Tuluna appears in novels, games, and worldbuilding forums as a setting for robotic and crewed missions, sample-return endeavors, and astrobiology research. The moon provides a backdrop for exploration narratives, including tectonics, ice-shell dynamics, and potential habitability in subsurface environments.

See also: List of fictional moons; icy moons; cryovolcanism; subsurface ocean.