Jupiter does not sit still.

Its atmosphere races around the planet in more than 20 east-west jet streams, with winds reaching about 100 meters per second, more than three times faster than the strongest jet stream on Earth. Those bands of motion, visible in the planet’s bright stripes and turbulent storms, have been watched for centuries. But only recently have scientists begun to pin down how far those winds reach and what keeps them going inside the solar system’s largest planet.

That question matters because Jupiter is not just a bigger Earth. It has no solid surface, rotates in about 10 hours, and is made mostly of a relatively uniform mix of gases. In some ways that makes it simpler to study. In other ways, it makes the planet harder to understand, because the atmosphere blends into the deep interior.

Recent measurements and computer models now point to a picture that is both clearer and stranger. Jupiter’s jet streams do not stay near the cloud tops. They plunge thousands of kilometers downward, into regions where pressures rise to around 100,000 times Earth’s surface pressure.

At cloud level, Jupiter’s atmosphere already looks unusual. The winds alternate between eastward and westward flow with latitude, creating a pattern unlike Earth’s more limited jet system. At the equator, the winds move in the same direction as the planet’s rotation, a state called superrotation.

That feature poses a basic physics problem. Rotation by itself cannot pile momentum onto the equator. Something has to move that momentum there.

Scientists have tracked Jupiter’s winds since the time of Galileo, first with small telescopes, later with spacecraft including Voyager and Cassini, and now with observatories such as Hubble and the James Webb Space Telescope. A major step came during Cassini’s flyby in December 2000, when repeated images let researchers calculate the two-dimensional wind field at the cloud tops, around the 1-bar pressure level.

Those measurements showed a close link between the jets and turbulent fluxes in the atmosphere. That correlation suggested the winds are at least partly driven by eddies, turbulent motions that can transfer momentum into the larger jets, much as one mechanism does in Earth’s atmosphere.

Still, the deeper layers remained mostly hidden.

The only direct probe into Jupiter’s atmosphere came in 1995, when Galileo dropped an entry probe into the planet. It found heavy elements in greater-than-solar abundances, detected noble gas abundances that helped establish the presence of helium rain, and recorded winds that strengthened below the clouds down to 20 bars. Later work, however, suggested the probe entered a local hotspot, so those results may not represent the planet as a whole.

By measuring tiny changes in Jupiter’s gravitational pull on the spacecraft, Juno allowed scientists to infer details about the planet’s interior structure and the behavior of its atmosphere. The gravity data indicate that Jupiter’s envelope is not uniform. They also support the idea that any compact core is much smaller than once thought.

What seems essential in current models is a dilute core, a region extending roughly 0.1 to 0.5 times Jupiter’s radius where heavy elements are spread through the envelope rather than packed into a sharply defined center.

More strikingly, the planet’s asymmetric gravity field and higher-order gravity harmonics showed that the zonal jets extend deep into the interior. That result answered a long-standing question about whether the visible winds were shallow weather features or part of a much larger structure. Beneath the jets, Jupiter appears to rotate more like a solid body.

Later work found that much of the gravity signal comes from jets near about 20 degrees north and south latitude. Those jets appear to penetrate the interior cylindrically, underscoring how strongly Jupiter’s rapid rotation shapes the atmosphere.

The depth estimate also matches an independent argument based on ohmic dissipation. In this process, electrically conductive gas moving through Jupiter’s magnetic field creates electrical currents that lose energy as heat. Comparing that heating with the heat Jupiter emits gives a limit on how deep the winds can go. Around the same pressure range where the jets seem to end, electrical conductivity becomes important enough that the winds and magnetic field might interact.

Yet observations of Jupiter’s changing magnetic field have not provided clear evidence for that interaction.

Scientists still do not know what keeps Jupiter’s winds from either fading away or digging even deeper.

Several braking mechanisms have been proposed. One is magnetic drag, where the magnetic field acts as a brake on the flow. Others include large density changes and stable layers that resist vertical mixing and suppress convection. Current theory and modeling tend to favor stable layers as an effective way to dissipate the jets, but no one knows for sure where such a layer would come from.

One idea is a helium rain layer at pressures of about a million bars or deeper, in the same broad region thought to host the planetary dynamo. Another is a deep radiative zone at pressures of roughly 1,000 to 10,000 bars. But observations of the jets’ depth have challenged both possibilities, leaving the issue unresolved.

The driving forces may also differ by latitude.

For jets outside the tropics, poleward of about 17 degrees north and south, turbulence is the leading candidate. What remains uncertain is whether that turbulence lives mainly in a shallow weather layer, more like Earth’s baroclinic eddies, or rises from deep convective plumes powered from below. Models of both kinds can reproduce important parts of the observed behavior, suggesting the jets and small-scale turbulence feed back on each other.

The equatorial jet is even harder to explain. Because it is eastward, it needs momentum to be carried into the equator. Researchers have proposed several ways this might happen, including latent heat released by water condensation, wave convergence from north and south, parameterized convection, and organized convection transporting heat upward from the interior. Recent evidence supports the existence of deep heat fluxes, but it still does not settle which process dominates.

Juno’s Microwave Radiometer has added another piece to the story by pointing to deep overturning circulation at midlatitudes. The data suggest alternating cells of rising and sinking motion, somewhat like Earth’s Ferrel cells, but far deeper.

These cells may help move both heat and momentum through the atmosphere. Because they line up with turbulence, scientists have suggested that turbulent fluxes may drive them too. At the moment, this is the only evidence available for deep overturning circulation on a giant planet.

Above the cloud layer, the picture may flip. Temperature measurements from visible and infrared observations suggest a reverse circulation pattern in the stably stratified upper atmosphere. That raises the possibility of stacked meridional circulation, where the same eastward jet is linked to one circulation direction below the clouds and the opposite direction above them.

Nothing like that exists in Earth’s atmosphere.

Numerical simulations can produce such a pattern only when they include friction above the clouds. In the equatorial region, circulation appears to involve upwelling, but the cause remains open. Organized convection is one possible explanation, which would strengthen the case that deep convective processes play a central role near Jupiter’s equator.

Jupiter has become a test case for how giant planets work from the cloud tops down into the interior. The latest findings show that its familiar colored bands are tied to physics operating far below the visible atmosphere, in places where gravity, rotation, heat flow, magnetic effects, and chemistry all meet.

That has practical consequences for future exploration. Long-term observations across visible, infrared, and microwave wavelengths could help track how the jets, vortices, and overturning circulation change over time. New atmospheric probes sent into multiple parts of Jupiter would give much-needed vertical profiles of wind, temperature, and composition. Continued analysis of Juno’s extended mission may also sharpen the search for signs that deep winds interact with the magnetic field.

The modeling challenge is just as important. Next-generation global circulation models will need to combine radiative transfer, cloud physics, condensates, and deep internal heating in a single framework. Better equations of state, and better constraints on where hydrogen and helium separate, may also help scientists locate phase transitions and understand how convection behaves in the deep atmosphere.

Jupiter’s jet streams are no longer just surface weather. They are a window into the planet’s hidden interior, and into the forces that shape giant worlds across the solar system.