Deep Two-phase, Hemispherical Magma Oceans on Lava Planets

Abstract Astronomers have discovered a handful of exoplanets with rocky bulk compositions but orbiting that orbit so close to their host star the surface planet must be at least partially molten. It is expected dayside such “lava planets” harbors rock-vapor atmosphere flows quickly toward airless nightside—this partial critical interpretation lava observations, transports negligible heat nightside. As result, temperature magma ocean may range from 3000 K near substellar point down 1500 day–night terminator. We use simple models incorporating thermodynamics and geochemistry melt predict physical chemical properties as function distance point. Our principal findings are that: (1) much deeper than previously thought, probably extending core–mantle boundary below an Earth-sized planet; (2) only molten, leading gradients in chemistry ocean; (3) base silicate mantle important temperature. In most extreme cases, interiors could cold enough thermal stratification gravitationally stable. These implications for dynamics ocean, well composition atmosphere.