Using data from NASA's Juno spacecraft, researchers at the University of California, Berkeley found that some lightning flashes on Jupiter may be 100 times stronger than lightning on Earth, and possibly even more intense.

The findings come from Juno's microwave radiometer, an instrument that has been studying Jupiter's atmosphere since the spacecraft entered orbit around the giant planet in 2016. The instrument can detect radio emissions produced by lightning, similar to the radio interference created by storms on Earth. Microwaves occupy the high-frequency end of the radio spectrum.

The study was published in the journal AGU Advances.

Why Jupiter's Storms Are So Extreme

Lead author Michael Wong, a planetary scientist at UC Berkeley's Space Sciences Laboratory, said studying storms on other planets can help scientists better understand weather on Earth.

"There's so much we don't know about lightning on Earth," Wong said.

In recent years, researchers have identified several unusual electrical phenomena linked to thunderstorms on Earth. These "transient luminous events" (TLEs) occur high above storms and include sprites, jets, halos, and ELVEs.

On Jupiter, lightning offers insight into convection, the process that moves heat through the atmosphere.

"Convection operates a little bit differently on Earth and Jupiter because Jupiter has a hydrogen-dominated atmosphere, so moist air is heavier and harder to bring upward," Wong explained.

Earth's atmosphere is mostly nitrogen, which is heavier than water vapor. That means moist air on Earth rises more easily. On Jupiter, however, moist air is heavier, so storms require much more energy to rise through the atmosphere. Once they do, they can release enormous amounts of energy, producing intense winds and powerful cloud-to-cloud lightning.

NASA's Juno Spacecraft Measures Jupiter Lightning

Nearly every spacecraft that has visited Jupiter has detected lightning. The bright flashes stand out clearly on the planet's dark side, making them relatively easy to spot.

Earlier missions suggested Jupiter's lightning was exceptionally powerful because they could only detect the brightest flashes. But Juno later complicated that picture when its highly sensitive star-tracking camera revealed many weaker flashes more comparable to lightning on Earth.

According to Wong, one challenge with visible-light observations is that clouds can hide some flashes, making it difficult to determine their true brightness.

Juno's microwave radiometer offered a better way to estimate the energy of lightning because microwave signals can pass through clouds. Although the instrument was not specifically designed to study lightning, it can detect microwave emissions from nearby storms.

Still, Jupiter's atmosphere presented another challenge. Storms often erupt simultaneously across giant cloud belts that circle the planet, making it difficult to determine which storm produced each signal.

Wong compared the problem to hearing popping sounds at a Chinese New Year's parade without knowing whether the noise came from popcorn nearby or fireworks farther away.

"Stealth" Superstorms on Jupiter

Scientists finally got a break in 2021 and 2022 when storm activity in Jupiter's North Equatorial Belt temporarily decreased. That allowed Wong and his team to focus on isolated storms one at a time.

Using observations from the Hubble Space Telescope, Juno's onboard camera, and even images captured by amateur astronomers, the team pinpointed the locations of several unusual storms Wong called "stealth" superstorms.

Like Jupiter's larger superstorms, these systems lasted for months and dramatically altered surrounding cloud patterns. However, their cloud towers remained relatively modest in height.

"Because we had a precise location, we were able to just say, 'OK, we know where it is. We're directly measuring the power,'" Wong said.

During this quiet period, Juno made 12 passes over isolated storms. On four flyovers, the spacecraft came close enough to measure microwave signals from lightning.

Scientists recorded an average of three lightning flashes per second during those passes. In one encounter alone, Juno detected 206 separate microwave pulses.

Out of 613 measured pulses, the team estimated that the lightning ranged from roughly the strength of Earth lightning to more than 100 times stronger.

Wong noted there is still uncertainty in the comparison because Jupiter and Earth lightning were measured at different radio wavelengths. One previous study even suggested Jupiter's lightning could potentially be a million times more powerful than lightning on Earth.

How Powerful Is Jupiter's Lightning?

Determining the total energy of a lightning bolt is complicated, said co-author Ivana Kolmašová, a space physicist at Charles University in Prague, Czechia, and a member of the Czech Academy of Sciences.

Lightning releases energy across multiple forms, including radio waves, light, heat, sound, and chemical reactions.

On Earth, a typical lightning bolt releases about 1 gigaJoule of energy, or one billion Joules. That is enough electricity to power about 200 average homes for one hour.

Wong estimates that lightning on Jupiter may release anywhere from 500 to possibly 10,000 times more energy than Earth lightning.

The Mystery Behind Jupiter's Lightning

Researchers believe Jupiter's lightning forms in a way similar to thunderstorms on Earth. Rising water vapor condenses into droplets and ice crystals that become electrically charged, eventually producing large voltage differences between clouds or between clouds and the ground.

On Earth, thunderstorms are commonly associated with hail. On Jupiter, scientists think the storms may produce icy slush-like objects called "mushballs," formed when water and ammonia combine.

Even with the new discoveries, researchers still do not fully understand why Jupiter's lightning can become so powerful.

"This is where the details start to get exciting, where you can ask, 'Could the key difference be hydrogen versus nitrogen atmospheres, or could it be that the storms are taller on Jupiter and so there's greater distances involved?'" Wong said.

Jupiter's storms can rise more than 100 kilometers high, compared to roughly 10 kilometers for storms on Earth.

"Or could it be that greater energy is available because with moist convection on Jupiter, you have a bigger buildup of heat needed before you can generate the storm to create lightning?" he added. "It's an active area of research."

Wong's co-authors included Berkeley postdoctoral fellow Ramanakumar Sankar along with researchers from the United States, Czechia, and Japan. The research was supported by NASA (80NSSC19K1265, 80NSSC25K0362).