  The nature and structure of the observed east-west flows on Jupiter and
Saturn has been one of the longest-lasting mysteries in planetary science. This
mystery has been recently unraveled due to the accurate gravity measurements
provided by the Juno mission to Jupiter and the Grand Finale of the Cassini
mission to Saturn. These two experiments, which coincidentally happened around
the same time, allowed determination of the vertical and meridional profiles of
the zonal flows on both planets. This paper reviews the topic of zonal jets on
the gas giants in light of the new data from these two experiments. The gravity
measurements not only allow the depth of the jets to be constrained, yielding
the inference that the jets extend roughly 3000 and 9000 km below the observed
clouds on Jupiter and Saturn, respectively, but also provide insights into the
mechanisms controlling these zonal flows. Specifically, for both planets this
depth corresponds to the depth where electrical conductivity is within an order
of magnitude of 1 S/m, implying that the magnetic field likely plays a key role
in damping the zonal flows.
