How far Jupiter's cloud-level zonal winds penetrate into its interior, a question related to the origin of the winds, has long been a major puzzle about Jupiter. There exist two different views: the shallow scenario in which the cloud-level winds are confined within the thin weather layer at cloud top and the deep scenario in which the cloud-level winds manifest thermal convection in the deep interior. We interpret, using two different models corresponding to the two scenarios, the high-precision measurements of Jupiter's equatorially antisymmetric gravitational field by the Juno spacecraft. We demonstrate, based on the thermal-gravitational wind equation, that both the shallow and deep cloud-level winds models are capable of explaining the measured odd gravitational coefficients within the measured uncertainties, reflecting the nonunique nature of the gravity inverse problem. We conclude that the high-precision Juno gravity measurements cannot provide an answer to the long-standing question about the origin of Jupiter's cloud-level zonal winds.

Responding to calls from the National Science Foundation for new proposals to measure the gravitational constant G, we offer an interesting experiment in deep space employing the classic gravity train mechanism. Our setup requires three bodies: a larger layered solid sphere with a cylindrical hole through its center, a much smaller retroreflector which will undergo harmonic motion within the hole and a host spacecraft with laser ranging capabilities to measure round trip light-times to the retroreflector but ultimately separated a significant distance away from the sphere-retroreflector apparatus. Measurements of the period of oscillation of the retroreflector in terms of host spacecraft clock time using existing technology could give determinations of G nearly three orders of magnitude more accurate than current measurements here on Earth. However, significant engineering advances in the release mechanism of the apparatus from the host spacecraft will likely be necessary. Issues with regard to the stability of the system are briefly addressed.