Updated Jupiter’s Shape Integrating Novel Gravity Experiments and Radio Occultations

Jupiter is the fastest-spinning planet in the Solar System and exhibits a pronounced equatorial bulge. This flattening results from the complex interplay between the planet’s rapid rotation, internal structure, and strong atmospheric winds. Previous estimates of Jupiter’s shape — with uncertainties of about 4 km — were based on a single analysis of radio occultation data from the Voyager and Pioneer missions, conducted nearly five decades ago, and did not account for the effects of Jupiter’s differential rotation. Thanks to the Juno spacecraft, we now have access to a large set of high-precision radio occultation measurements, enabling a more accurate reconstruction of the planet’s shape. By including the effects of zonal winds, we present an updated determination of Jupiter’s shape, achieving an order-of-magnitude reduction in uncertainty. At the 100 mbar pressure level, we find a polar radius of 66,883.7 ± 0.2 km and an equatorial radius of 71,536.37 ± 0.2 km — values that are 12 km and 4 km smaller, respectively, than those derived from earlier analyses. This refined shape has important implications for models of Jupiter’s interior, suggesting higher atmospheric temperatures and metallicity. It also helps resolve long-standing discrepancies between theoretical models, in situ measurements from the Galileo probe, and temperatures inferred from Voyager. Moreover, the improved radius profile enhances spatial referencing in pressure-dependent observations, providing a more precise framework for interpreting Jupiter’s atmospheric dynamics.