Geodetic Modeling of Gas Giants: An Integrated Approach Applied to Jupiter

Geodetic calculations concerning gaseous giants hold great importance in planetary astrophysics and fundamental physics, as they provide critical insights into planetary structure, dynamics, and evolution. Advancing our understanding of the shape of gaseous planets is essential for improving the precision of radio occultations—a remote sensing technique used to sound the atmospheres of celestial bodies. Accurate shape modeling also contributes to better constraining interior models, allowing for a deeper understanding of the physical processes governing gas giants and other celestial bodies, including Earth. Such advancements are not only key for refining our knowledge of planetary dynamics but also offer valuable insights into the formation of our stellar system and similar planetary systems. Additionally, these developments facilitate the characterization of exoplanetary atmospheres, which is vital for the study of planets beyond.

The shape of a fluid, rotating celestial body is primarily determined by its rotation rate and internal density distribution, which together define the planet's gravitational potential. This shape is further refined by the effects of zonal winds, which introduce an additional centrifugal term, generating perturbations that can significantly deviate from the profile expected for a solid rotating body. These perturbations are particularly pronounced at low latitudes, where the centrifugal component is most significant. We present a method, building on the approaches of Lindal et al. (The Astronomical Journal, Vol. 90, n. 6, 1985) and Galanti et al. (GRL, Vol. 50, e2022GL102321, 2023), to calculate the shape of a gas giant by harmoniously integrating data from gravity experiments, wind measurements, and radio occultation observations. This integrated methodology allows for a precise estimation of the planet's shape, accounting for both its internal structure and atmospheric dynamics. The results obtained from applying this method to a real case will be illustrated, with a focus on Jupiter. This will be done in light of the most recent gravity experiment data and radio occultation measurements from the Juno spacecraft, as well as the latest zonal wind measurements obtained with the Hubble Space Telescope and James Webb Space Telescope.