Theoretical planetology, also known as theoretical planetary science is a branch of planetary sciences that developed in the 20th century.
Theoretical planetologists, also known as theoretical planetary scientists, use modelling techniques to develop an understanding of the internal structure of planets by making assumptions about their chemical composition and the state of their materials, then calculating the radial distribution of various properties such as temperature, pressure, or density of material across the planet's internals.
Theoretical planetologists also use numerical models to understand how the Solar System planets were formed and develop in the future, their thermal evolution, their tectonics, how magnetic fields are formed in planetary interiors, how convection processes work in the cores and mantles of terrestrial planets and in the interiors of gas giants, how their lithospheres deform, the orbital dynamics of planetary satellites, how dust and ice are transported on the surface of some planets (such as Mars), and how the atmospheric circulation takes place over a planet.
Theoretical planetologists may use laboratory experiments to understand various phenomena analogous to planetary processes, such as convection in rotating fluids.