Jupiter Lightning 100x More Powerful Than Earth's

Jupiter, the most massive planet in our solar system, has correspondingly humongous storms, some of which last for centuries. Some of these storms also generate terrific bolts of lightning, according to a new study by University of California, Berkeley scientists. Some flashes are 100 times more powerful than lightning on Earth - and possibly much stronger.

The results come from analysis of data from NASA's Juno spacecraft, which has been orbiting the planet since 2016 and scanning the atmosphere with its microwave radiometer, which can detect radio emissions from lightning similar to the radio interference created by lightning on Earth. Microwaves are at the high-frequency end of the radio spectrum.

Studying storms on other planets sheds light on storms on our planet, which are still not completely understood, said lead author Michael Wong, a planetary scientist at UC Berkeley's Space Sciences Laboratory. His study was published March 20 in the journal AGU Advances.

"There's so much we don't know about lightning on Earth," he said, noting that scientists over the last decade have discovered several new types of "transient luminous events" associated with thunderstorms on Earth. These TLEs - millisecond electrical phenomena in the troposphere above big storms - include sprites, jets, halos and a phenomenon dubbed ELVEs.

On Jupiter, the lightning "tells us about convection, which is how the atmosphere churns and transports heat from below," Wong said. "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."

Air on Earth is mostly nitrogen, which is heavier than water, so added water makes moist air more buoyant. The heavier moist air on Jupiter not only means it takes a lot more energy for a storm to rise, but the storm also unleashes a lot more energy when it reaches the top of the atmosphere, leading to high wind speeds and intense, cloud-to-cloud lightning.

According to Wong, almost every spacecraft passing by Jupiter has detected lightning, mostly because the flashes stand out on the night side of the planet like a lightning bug in the dark. Based on data from previous missions, which could only detect super-powerful dark-side flashes, Jupiter got a reputation for packing more power into its flashes compared to Earth lightning. That was until a highly sensitive star-tracking camera on Juno raised doubts, detecting numerous weaker, Earth-like flashes. The problem with night-side imaging in general is that clouds can block the view of lightning flashes and make their true optical power difficult to pin down, Wong said.

Juno's core instrument, a microwave radiometer, provided a more precise way to measure lightning's power unaffected by obscuring clouds in Jupiter's atmosphere. Even though the instrument was not designed to study lightning, the downward-pointing radiometer can detect microwave emissions from storms nearby.

But storms on Jupiter often occur simultaneously across belts that encircle the planet, making it hard to tell which storm produced the lightning. And without a precise location for the storm, it's impossible to determine the power of the bolts using microwave measurements alone. Wong compared this to hearing a series of pops at a Chinese New Year's parade and not knowing if it was exploding popcorn a few feet away or firecrackers a block away.

Stealth superstorms

Luckily, in 2021 and 2022, there was a lull in storms in the North Equatorial Belt, and Wong was able to focus on one single large storm at a time, pinpointing its location using the Hubble Space Telescope, Juno's camera and images shared by amateur astronomers. He referred to these as "stealth" superstorms. Like true superstorms, their pattern of activity persisted for months and globally transformed the surrounding cloud structure. But unlike true superstorms, their cloud towers only reached the modest heights of small storms.

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

Juno made 12 passes over isolated storms during that period, and was close enough on four of them to measure microwave static from lightning. The flashes averaged three per second during these passes; on one flyover, Juno detected 206 separate pulses of microwave radiation. Of a total of 613 pulses measured, Wong calculated that the power ranged from about that of a lightning bolt on Earth to 100 or more times the power of an Earth bolt. Because he compared Earth lightning emissions at one radio wavelength to Jupiter lightning emissions at a different wavelength, there's some uncertainty in the comparison, Wong cautioned. Based on one study of lightning radio emissions on Earth, Jupiter's bolts could have been a million times more powerful than those on Earth.

Translating microwave power in a lightning bolt into total power is not straightforward, noted co-author Ivana Kolmašová, a space physicist at Charles University in Prague, Czechia, and a member of the Czech Academy of Sciences. Lightning not only emits at radio and optical wavelengths, but also generates thermal, acoustic and chemical energy. On Earth, a single bolt is estimated to release about 1 gigaJoule of total energy, or a billion Joules: enough to power 200 average homes for an hour. Wong estimates that the energy in a Jupiter bolt ranges up to 500 and perhaps as much as 10,000 times that of an Earth bolt.

The lightning is likely generated similarly to lightning on Earth, where rising water vapor condenses into liquid droplets and ice crystals that get electrically charged, leading to large voltage differences between clouds or between clouds and the ground. That's why Earth's thunderstorms are associated with hail. On Jupiter, while water vapor fuels the rise of storm clouds into the upper atmosphere, the charged ice crystals are made of both water and ammonia. One theory is that water and ammonia combine to form "mushballs" that fall like slushy hail.

While more powerful lightning implies higher voltages between clouds, the details of how they're generated on Jupiter versus Earth remain a mystery, Wong said.

"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?'" he said. Jupiter's storms are more than 100 kilometers tall, compared to 10 kilometers 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 include Berkeley postdoctoral fellow Ramanakumar Sankar and colleagues from the U.S., Czechia and Japan. The research was supported by NASA (80NSSC19K1265, 80NSSC25K0362).