Meriplaneetat

Meriplaneetat is a term used in speculative exoplanetology to denote a class of planets with global oceans that cover their entire surface. In such worlds there are few or no continents, and the exterior is dominated by a thick water layer over a rocky interior. The name blends a sea-related root with planet, highlighting the central role of surface liquid water in these models. Meriplaneetat are discussed in relation to ocean worlds and aquaplanets as a distinct emphasis on a continuous ocean.

Proposed meriplaneetat would typically have relatively low-lying topography, with ocean depths ranging from hundreds of meters to several tens of kilometers. They are thought to consist of a rocky mantle and iron core, beneath a global ocean. Depending on mass and distance from the star, high-pressure ice layers may lie beneath the liquid ocean, isolating it from the mantle. Formation scenarios include volatile delivery during accretion or migration into the habitable zone while preserving a thick water inventory.

Climate on meriplaneetat would be governed by greenhouse effects, ocean currents, and tidal heating. Hydrothermal activity at the seafloor could provide chemical energy for potential life, though surface conditions would be extreme. Observationally, these planets would be inferred from mass-radius measurements indicating a high water content, and by the detection of water vapor or other volatiles in their atmospheres during transits. The presence of a magnetic field is debated in such interiors.

This term is primarily used in theoretical discussions and fictional settings, and no confirmed exoplanet has been designated a meriplaneetat. See also: ocean world, water-rich planet, aquaplanet, habitable zone.