Composition and internal structure of giant planets - an evolutionary perspective

The composition and internal structure of gas giants determine their observed parameters, such as radius-mass relation, and atmospheric metallicity. Often giant planet interiors are modeled as 2-layer (core-envelope) structures, in both formation and evolution models, for simplicity. However, new planet formation models suggest that composition distribution in the interior is gradual in some cases, depending on the formation conditions. I will explain the importance of the composition and its distribution to the thermal evolution of the planet. I will discuss whether the internal structure changes in time by thermal evolution, and how it affects the observed parameters. Finally, I will discuss the implications for our solar system gas giants and show that gradual composition structures for Jupiter and Saturn are feasible.