Imagine giant slushy hailstones made of ammonia and water wrapped in a shell of ice, plunging through Jupiter’s atmosphere in fierce thunderstorms lit up by flashes of lightning.
These bizarre frozen balls—called “mushballs”—might sound like science fiction, but scientists now believe they’re very real and may be common not just on Jupiter, but on other giant planets like Saturn, Uranus, and Neptune.
Researchers at the University of California, Berkeley, have confirmed the existence of mushball hailstorms on Jupiter.
Their findings, published in Science Advances, help explain strange patterns in Jupiter’s atmosphere and deepen our understanding of weather on gas giants.
The team also created the first 3D map of Jupiter’s atmosphere, revealing how most of its weather systems are surprisingly shallow, but some storms punch much deeper into the planet, stirring things up in dramatic ways.
The idea of mushballs was first proposed in 2020 to explain why there are areas in Jupiter’s upper atmosphere with much less ammonia gas than expected.
At first, UC Berkeley scientist Chris Moeckel and his advisor, planetary scientist Imke de Pater, were skeptical. The theory seemed too complicated.
But after years of testing and analyzing data, they couldn’t prove it wrong—and eventually found strong evidence to support it.
Using observations from NASA’s Juno spacecraft and ground-based radio telescopes, the team discovered signs of deep atmospheric mixing caused by powerful storms.
Some of these storms are capable of creating mushballs, which form when water droplets are carried high into Jupiter’s atmosphere.
There, they freeze, mix with ammonia (which acts like antifreeze), and turn into icy slushballs that grow larger as they rise and fall. Eventually, they become so heavy that they plunge deep into the atmosphere, carrying ammonia and water with them.
This process helps explain why the upper layers of Jupiter’s atmosphere appear to lack ammonia—it’s being pulled deep into the planet by mushballs. The team spotted unique signals in the radio data that pointed to the presence of these slushy hailstones melting and releasing ammonia deep inside the planet.
Their 3D reconstruction of Jupiter’s atmosphere showed that while most weather only affects the top 10 to 20 kilometers, these powerful storms dig much deeper—over 150 kilometers down—redistributing material that scientists once thought was evenly mixed.
Moeckel compares the top of Jupiter’s atmosphere to the surface of a boiling pot. It looks turbulent, but below, it’s much calmer. This new understanding changes how scientists interpret what they see on other planets, including distant exoplanets.
The research also connects with past theories. Ten years ago, de Pater found that ammonia was missing down to 50 kilometers. Now, thanks to Juno’s deeper radar scans and Moeckel’s methods, scientists can trace these patterns even further down.
They also discovered that water condensation plays a major role in controlling how deep storms can go. Only the most intense weather systems can break through that barrier and send material deeper into the planet.
Interestingly, mushball storms could be a universal feature of gas giants, meaning similar weather could occur on Neptune, Uranus, or even giant exoplanets outside our solar system. That makes these findings especially valuable for interpreting telescope data from distant worlds.
To create a more complete picture, the team combined Juno data with images from the Hubble Space Telescope and radio measurements from the Very Large Array in New Mexico. Moeckel developed a special technique to convert radio signals into 3D images, which helped reveal the hidden structure of Jupiter’s atmosphere.
The research wasn’t easy. Moeckel had to recreate some of Juno’s data processing tools from scratch because they weren’t yet publicly available. He’s since shared them online to help other scientists move faster in future studies.
This new insight into mushballs not only solves a long-standing mystery about Jupiter’s atmosphere but also opens the door to a better understanding of how weather works on worlds far beyond Earth.
Source: UC Berkeley.
