The Mysteries of Jupiter: Insights from the James Webb Space Telescope

Somewhere above the largest storm in the solar system, something is glowing that should not be there.

No sunlight explains it.

No known weather pattern predicted it.

When scientists finally figured out what was causing this unexpected glow, they realized that Jupiter has been hiding a version of itself that no telescope had ever managed to see until now.

For nearly four centuries, humans have watched Jupiter’s Great Red Spot through glass lenses.

For most of that time, we assumed we understood it—a giant ancient hurricane twice the width of Earth, spinning quietly in the clouds.

But when the James Webb Space Telescope turned its infrared eye toward Jupiter in July 2022, it exposed something in the atmosphere directly above that storm that nobody expected.

This revelation has forced planetary scientists to rethink what they thought they knew about the gas giant.

The Unexpected Discovery

The instrument responsible for this groundbreaking observation was Webb’s Near-Infrared Spectrograph, known as NIRSpec.

Using its integral field unit, it studied the region sitting just above the Great Red Spot.

The scientists behind the observation, led by physicist Henrik Melin at the University of Leicester, expected almost nothing interesting.

Jupiter receives only about 4% of the sunlight that reaches Earth.

Researchers assumed the upper atmosphere near the equator, far from the energetic auroras at the poles, would be flat and uneventful.

It was supposed to be the boring part of the planet.

However, it was anything but boring.

Webb’s data revealed a tangle of dark curving arcs and bright glowing spots stretching across the entire field of view—an intricate structure nobody had documented before.

Melin later admitted the team had assumed, perhaps naively, that this region would be dull.

Instead, he said it turned out to be just as compelling as the northern lights, if not more so.

Jupiter once again refused to behave the way anyone predicted.

Rethinking the Atmosphere

The obvious first explanation for the glowing patterns was sunlight.

Since incoming solar radiation accounts for most of the glow in Jupiter’s upper atmosphere, it seemed reasonable that sunlight alone might be sculpting these odd shapes.

But the patterns didn’t fit.

The arcs and spots were too structured, too dynamic, too tightly organized to be explained by something as simple and diffuse as scattered starlight.

There had to be another mechanism physically reshaping the atmosphere from below.

The answer researchers arrived at involved something called atmospheric gravity waves.

Despite the name, these have nothing to do with gravitational waves from colliding black holes.

Gravity waves, in this context, refer to a wave motion that occurs when a fluid—in this case, Jupiter’s atmosphere—is disturbed.

Gravity pulls it back toward equilibrium, causing it to oscillate like water rippling after a stone is dropped into a pond or waves crashing and rippling across sand on a beach.

On Jupiter, these waves are generated deep within the turbulent churning lower atmosphere surrounding the Great Red Spot.

As the storm itself grinds through the surrounding gas at ferocious speed, it launches these waves upward.

As they travel higher into the thinner layers of the atmosphere, they carry energy that reshapes the structure and glow of the ionosphere far above.

The Scale of the Phenomenon

What makes this genuinely strange is the scale.

Earth experiences atmospheric gravity waves, too, generated by mountain ranges, storm systems, and other disturbances pushing air upward.

However, the waves we’ve detected rippling above Jupiter’s Great Red Spot are dramatically more turbulent and energetic than anything measured in Earth’s atmosphere.

The Great Red Spot itself is the engine, and its winds, which howl at somewhere between 270 and 425 mph—up to three and a half times faster than a violent tornado on Earth—are apparently powerful enough to send shock waves of energy climbing hundreds of miles upward into space.

These shock waves disturb a layer of the atmosphere separated from the storm by enormous distance and pressure difference.

This finding, published in the journal Nature Astronomy, did more than solve a small mystery about a patch of sky above a storm.

It suggested that Jupiter’s atmosphere is far more vertically connected than scientists had assumed, with energy able to transfer from the deep roiling cloud layers all the way up into the ionosphere—the boundary where the planet’s neutral atmosphere gives way to its colossal magnetic field.

Researchers now hope to track these gravity waves over time to understand how energy moves through Jupiter’s atmosphere as a whole and how that movement drives the visible cloud structures astronomers have been photographing for a century.

Mapping the Great Red Spot

While NIRSpec was uncovering ripples above the storm, a separate set of Webb observations, this time using the mid-infrared instrument, or MIRI, was busy mapping the internal structure of the Great Red Spot itself.

These MIRI observations, also taken during the same July to August 2022 window during Webb’s early science phase, allowed researchers to build three-dimensional maps of both the temperature and the chemical composition inside the storm.

This is a genuinely difficult thing to do.

The Great Red Spot isn’t a flat red oval sitting on the surface of the clouds.

It is a churning three-dimensional structure with variation in temperature and composition at different depths and different points across its enormous diameter.

Mapping that structure from 400 million miles away required exactly the kind of sensitivity Webb was built to deliver.

Separately, Webb also caught something else in the same general region—an enormous, previously unknown band of high-altitude clouds sitting above the planet’s main cloud deck at the equator, stretching more than 3,000 miles wide and moving across the planet at roughly 320 mph.

That is faster than the most extreme storm systems ever recorded on Earth, and it was a feature nobody had cataloged before Webb’s infrared instruments picked it out.

The Impact of Citizen Scientists

Before any of these detailed studies were published, it was actually a single processed image that first hinted at how much Webb was about to change our view of Jupiter.

Shortly after Webb’s instruments were calibrated, citizen image processor Judy Schmidt took the raw infrared data and enhanced it into a composite that immediately grabbed the attention of planetary scientists.

In that image, Jupiter’s auroras glowed clearly at both poles, a thin faint debris ring encircling the planet became visible, and several of Jupiter’s smaller moons appeared as pinpoints of light in the surrounding darkness.

It was a reminder that Webb’s infrared vision doesn’t just make Jupiter look sharper; it reveals structures that are effectively invisible in ordinary visible light.

Because the wavelengths Webb detects respond to completely different physical processes than those our eyes are sensitive to, that single image—more than any press release—is what convinced scientists that pointing Webb at Jupiter’s upper atmosphere in detail was worth the telescope’s extremely limited and valuable observing time.

Collaborative Efforts: Webb and Juno

None of this happened in isolation.

Webb’s contribution has to be understood alongside the work of another spacecraft that has been orbiting Jupiter directly since 2016—the NASA Juno mission.

Juno’s job is different from Webb’s.

Rather than observing from nearly half a billion miles away, it swings in extremely close, skimming just above Jupiter’s cloud tops on each flyby to gather data no distant telescope could ever collect.

Together, Webb and Juno have been closing in on the Great Red Spot’s secrets from two entirely different directions—one from space with a wide infrared lens, the other from just above the clouds themselves.

Juno’s own investigation of the Great Red Spot has already overturned prior assumptions.

Two flybys in 2019 allowed scientists to build a three-dimensional model of the storm using gravity measurements, essentially detecting how the storm’s mass subtly warped the spacecraft’s radio signal as it passed overhead—similar to how a car feels a pothole in the road.

These tiny distortions, changes in velocity of about 1/100 of a millimeter per second, allowed scientists to calculate how deep the storm actually extends.

The result was startling.

Rather than being a relatively shallow weather feature confined near the visible cloud tops, the Great Red Spot plunges roughly 300 miles into Jupiter’s atmosphere—somewhere between 50 and 100 times deeper than Earth’s oceans and far deeper than the orbit of the International Space Station would sit if placed above Earth.

Beneath that, atmospheric jets tied to the storm appear to extend even further, to depths of around 3,000 miles, powered by a mechanism involving ammonia gas rising and sinking through the layers—a process fundamentally different from the water-driven weather systems that shape storms on Earth.

The Great Red Spot’s Shrinking Mystery

At the same time that scientists were mapping the storm’s depth, they were also tracking something else: its size is shrinking, and doing so in a way that isn’t fully understood.

Historical measurements show the Great Red Spot used to stretch across more than 24,000 miles—wide enough that three Earths could once fit inside it side by side.

Comparisons of Hubble Space Telescope images from 1995, 2009, and 2014 show a storm that is visibly contracted over that span.

Current estimates put its width at closer to 10,000 miles—room now for only about one Earth.

The storm has also changed shape, becoming noticeably more circular where it was once a clear elongated oval.

The shrinking hasn’t been smooth or steady, either.

In May 2017, the Gemini North telescope caught something unusual: a small hook-shaped cloud peeling away from the western edge of the storm, along with what looked like a wave splitting off the eastern side.

Juno photographed something similar around the same period—images that appear to show reddish material physically detaching from the Great Red Spot and drifting into the surrounding atmosphere.

Researchers have since confirmed that chunks of material, some as large as 60,000 miles across—roughly the size of a country like Portugal or Iceland—really do break away from the storm and scatter.

The Forces at Play

The leading explanation involves how Jupiter’s vortices interact with one another.

On Jupiter, anticyclones, which rotate in the same direction as the Great Red Spot, tend to be drawn toward each other and can merge, with a smaller storm essentially absorbed into a larger one over time.

However, when an anticyclone encounters a cyclone spinning in the opposite direction, the interaction is far more violent.

Their opposing rotations collide, momentarily arrest each other, and then burst apart with tremendous force, flinging fragments in different directions.

Rather than merging cleanly with the Great Red Spot, these smaller storms appear to be shattering against it, tearing loose pieces of the giant vortex as they collide.

This may explain the erosion astronomers have been documenting.

Based on the current rate of contraction, some researchers have floated the possibility that the storm could theoretically disappear within a couple of decades, though this is treated cautiously rather than as settled fact.

Data from Hubble, covering 2009 through 2020, actually shows something that complicates a simple story of decline.

Average wind speeds around the storm’s edge increased by roughly 8% over that period, meaning the vortex isn’t simply running out of energy.

It’s possible the storm could stabilize, shrink further, or even swell again—particularly since Jupiter has generated replacement storms before.

In 2000, three smaller white oval vortices merged into a single storm, which by the end of 2005 had turned red and became known informally as the Little Red Spot.

It briefly grazed the Great Red Spot in 2006 without major consequence.

The Great Cold Spot

Whatever happens next, most scientists agree that Jupiter itself won’t be meaningfully destabilized if the Great Red Spot eventually fades.

What remains unclear is whether the storm has been suppressing other atmospheric processes that could reshape the visible face of the planet once it’s gone.

Jupiter’s other extreme storm system, sitting quietly opposite its famous red counterpart, deserves attention too.

Known as the Great Cold Spot, it is a region in the planet’s upper atmosphere near the poles that runs roughly 200° C colder than its surroundings.

It can span an area comparable to the Great Red Spot itself, though it behaves completely differently.

Rather than being a stable, long-lived storm, the Great Cold Spot appears and disappears—a cycle scientists have linked directly to Jupiter’s auroras.

As charged particles pour into Jupiter’s atmosphere near the poles, generating light shows even more intense and persistent than Earth’s aurora, because Jupiter draws particles from both the solar wind and its volcanic moon Io, they deposit energy unevenly.

The uneven heating appears to drive the formation of a swirling vortex of cooler air nearby, distinct from the auroral glow itself but tied to the same underlying process.

Because the phenomenon seems locked to the age of Jupiter’s polar light activity, researchers estimate the Great Cold Spot in some form has likely existed for thousands of years, continually reforming rather than persisting as one unbroken structure.

Unraveling Jupiter’s Auroras

Speaking of Jupiter’s auroras, they are unlike anything Earth produces, and Juno’s instruments have helped explain why.

On Earth, auroras form when charged particles streaming from the Sun collide with our atmosphere near the poles.

Jupiter’s auroras draw on that same solar wind, but they also draw enormous additional power from the planet’s moon, Io, which is the most volcanically active body anywhere in the solar system, home to more than 400 active volcanoes constantly ejecting material into space.

As Io orbits roughly 262,000 miles from Jupiter, it cuts directly across the planet’s ferocious magnetic field lines, effectively turning the small moon into a natural electric generator capable of producing 400,000 V and a current of about 3 million A.

The current follows Jupiter’s magnetic field lines down toward the planet’s poles, contributing directly to the auroral display.

Juno’s flybys over Jupiter’s poles also detected electrons being accelerated downward into the atmosphere with energies reaching 400,000 eV—roughly 30 times more powerful than the strongest auroral electron acceleration ever recorded on Earth.

Layered on top of this, Juno data revealed that Jupiter produces a distinct burst of X-rays approximately every 27 minutes—a rhythm traced back to a specific physical process.

As Jupiter’s rapid rotation drags its magnetic field through the surrounding solar wind, the field compresses, heating trapped ions and triggering electromagnetic ion cyclotron waves that guide those ions along the magnetic field until they slam into the planet’s polar atmosphere, producing the recurring X-ray flashes.

Investigating Water Content

It isn’t only the auroras and the storms that Webb and Juno have re-examined.

Jupiter’s water content has also come under fresh scrutiny.

Water vapor was first confirmed in Jupiter’s atmosphere back in 1995 by NASA’s Galileo spacecraft using its near-infrared mapping spectrometer during a close atmospheric probe descent.

More recent analysis puts water at approximately 0.25% of the atmosphere near Jupiter’s equator, and while that fraction sounds small, Jupiter’s sheer size means it likely holds more total water than exists on Earth.

Because Jupiter is thought to have been the first planet to fully form in the early solar system, understanding exactly how much water and other volatile material it locked away is central to reconstructing how the entire solar system came together.

Researchers have specifically identified a substantial water signature within the Great Red Spot itself.

Now, water plays a direct role in one of Jupiter’s most violent phenomena—lightning that can flash roughly a hundred times brighter than lightning on Earth.

Some of it forms the way terrestrial lightning does, through collisions between water droplets and charged ice particles within water clouds.

But Juno also detected fainter lightning occurring much higher in the atmosphere, at altitudes where temperatures plunge to around -87° C—far too cold for liquid water to exist.

The explanation turned out to involve ammonia acting as a natural antifreeze.

High in the atmosphere, ammonia vapor mixes with water ice crystals and lowers their melting point enough to form a slushy liquid.

As these ammonia-water droplets collide with falling ice crystals, they build up an electric charge that triggers lightning.

As these droplets continue colliding and growing heavier, they eventually form large, dense, hail-like objects that scientists have nicknamed “mushballs,” which sink deeper into the planet’s atmosphere, carrying ammonia and water down and away from the layers where they formed.

This process may help explain why ammonia levels measured throughout Jupiter’s atmosphere are so uneven.

A New Understanding of Jupiter’s Interior

Beneath the clouds, the storms, and the lightning lies a structure scientists are still actively rewriting.

For decades, the standard model assumed gas giants like Jupiter formed around a solid, well-defined rocky core.

Data gathered by Juno, however, points towards something messier.

Instead of a clean rocky ball at the center, Jupiter’s interior appears to have a fuzzy or diluted core, where heavy elements are mixed gradually into the surrounding hydrogen and helium over an enormous region rather than sitting in a sharply defined layer.

Researchers estimate that within Jupiter’s deep interior, only around 18% of the material by some measures is rocky in composition, spread through a vast transitional zone rather than concentrated in a compact center.

Laboratories, such as the Center for Matter at Atomic Pressures—a partnership involving the University of Rochester—use powerful laser systems to compress material samples to pressures and temperatures resembling Jupiter’s interior, helping scientists interpret what Juno’s gravitational and magnetic field measurements are actually telling them about that hidden structure.

Roughly 10% of the way down toward Jupiter’s core, the crushing pressure transforms ordinary hydrogen gas into an exotic state called liquid metallic hydrogen—a fluid that conducts electricity and heat the way metals do while still flowing like a liquid.

This immense layer, believed to be tens of thousands of kilometers thick, combined with Jupiter’s remarkably fast rotation of roughly 10 hours, is what generates the planet’s colossal magnetic field—the strongest of any planet in the solar system, roughly 20,000 times stronger than Earth’s, and extending millions of kilometers into space.

The Magnetic Field Anomaly

The magnetic field, it turns out, isn’t uniform, either.

Unlike Earth’s comparatively tidy dipole-shaped field, Jupiter’s magnetic field emerges from a broad region in the northern hemisphere and reenters closer to the south pole in a lopsided pattern.

Juno’s magnetometer data revealed an unexpected feature within this field—a concentrated intense patch of magnetism just south of the equator that researchers have nicknamed the Great Blue Spot.

This anomaly effectively functions like a second unofficial magnetic south pole positioned nowhere near the planet’s actual geographic pole.

Its strength fluctuates by as much as 1% per year, and because it sits at roughly the same latitude as the Great Red Spot, some scientists have raised the question of whether the two features—one atmospheric, one magnetic—could be connected in ways not yet understood.

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