Juno spotted an unusual form of lightning which is formed not from water clouds, like lightning is here on Earth, but from an ammonia-water solution. This “shallow lightning” sparks through Jupiter’s atmosphere, creating flashes which were captured by Juno’s Stellar Reference Unit camera.
Scientists had seen these flashes on Jupiter before, back in the 1970s from the Voyager mission, but they assumed these lightning storms were originating in deep water clouds, the same way they would be on Earth. But the new findings, taken from Jupiter’s dark side, show that something more complicated is going on.
“Juno’s close flybys of the cloud tops allowed us to see something surprising — smaller, shallower flashes — originating at much higher altitudes in Jupiter’s atmosphere than previously assumed possible,” lead author Heidi Becker, Juno’s Radiation Monitoring Investigation lead at NASA’s Jet Propulsion Laboratory, explained in a statement.
The Juno researchers believe that lightning is possible at higher altitude on Jupiter than on Earth due to the ammonia in the atmosphere. Violent storms push water-ice up high into the atmosphere where it meets ammonia vapors and forms the ammonia-water solution which gives birth to the lightning.
“At these altitudes, the ammonia acts like an antifreeze, lowering the melting point of water ice and allowing the formation of a cloud with ammonia-water liquid,” Becker said in the statement. “In this new state, falling droplets of ammonia-water liquid can collide with the upgoing water-ice crystals and electrify the clouds. This was a big surprise, as ammonia-water clouds do not exist on Earth.”
These findings also help to explain a mystery about Jupiter, which is why there are varying amounts of ammonia in different parts of the planet’s atmosphere. Another group of researchers has found that ammonia forms into slushy hailstones, called “mushballs,” which are heavy and therefore fall deep into the atmosphere, carrying ammonia down closer to the planet’s surface.
The findings are published in the journal Nature.
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