Interiors of the Giant Planets

The giant, or Jovian planets—Jupiter, Saturn, Uranus, and Neptune—account for 99.5% of all the planetary mass in the solar system. The internal composition and structure of all these planets thus provide important clues about the conditions in the solar nebula during the time of planet formation. But such information does not come easily. The familiar faces of these planets, such as the cloud-streaked disk of Jupiter, tell relatively little about what lies beneath. Knowledge of these planetary interiors must instead be gained from analysis of the mass, radius, shape, and gravitational fields of the planets. For the majority of giant planets around other stars, at best only the mass and radius can be discerned. Thus for both solar and extrasolar planets, theoretical models of the planetary interiors must be compared to the available data in order to infer what lies within the planets. The study of the behavior of planetary materials at high densities and pressures provides additional constraints for connecting mass, radius, and internal composition. Once constructed, interior models provide a window into the internal structure of these planets and shed light on processes that led to planet formation in our solar system and others.