All four of our solar system’s gas giants sport stripes. Jupiter’s bands, the most prominent, offer even amateur astronomers a stunning view of the planet’s complex atmospheric dynamics. Planetary scientists are especially intrigued by the areas between the stripes, where east–west winds whip clouds around the planet at up to 150 m/s.
For decades researchers have debated the depth of Jupiter’s jet streams, or zonal jets. Some argued that the winds persist only tens or hundreds of kilometers beneath the visible cloud layer. In their view, Jupiter was a giant, uniformly rotating body topped with a razor-thin tier of atmospheric action. Others maintained that the jets stretch much deeper as part of a rich, complex atmosphere, perhaps sustained by heat from the Jovian interior.
Now, a year and a half after settling into orbit around Jupiter, NASA’s Juno spacecraft has resolved the debate.1 Precise gravimetry measurements reveal that Jupiter’s...
