This session aims at understanding deep interiors and atmospheres of solar system bodies and massive extra-solar planets, their associated internal processes and corresponding material behaviour at extreme pressures and temperatures. These will have important implications for structural models (e.g. location of layer boundaries), evolution scenarios (e.g. demixing phenomena, diffusion), and magnetic field generation (e.g. nonmetal-metal transitions). This session also bridges the geophysical knowledge of bodies in the Solar System to rocky exoplanets by considering the potentially observable signatures associated with geologically-active worlds. Potentially fruitful targets are molten or volcanically-active planets, where the atmosphere and interior are tightly coupled through the exchange of heat and mass.

The session will include solicited and contributed papers addressing observational, laboratory, and theoretical studies of matter under planetary interior conditions.

Included subtopics are:
(1) Ab initio simulations and laboratory studies for matter under extreme conditions
(2) Interior structure, composition, and evolution
(3) Equation of state, melting, and phase transformation at extreme states
(4) Volcanism and magma ocean modeling
(5) Novel observational signatures of active worlds