Juno probe helps scientists solve Jupiter's lightning mystery

While Jovian lightning appears to produce the same radio signals as bolts on Earth, the phenomena are still quite different.
By Brooks Hays  |  June 7, 2018 at 10:07 AM
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June 7 (UPI) -- New observations from Juno prove Jupiter's lightning isn't as different from Earth's as scientists once thought, solving a 39-year mystery.

When NASA's Voyager 1 probe first recorded Jupiter's lightning strikes in 1979, the radio signals produced by the bolts failed to match the signatures created by Earth's lightning.

"No matter what planet you're on, lightning bolts act like radio transmitters -- sending out radio waves when they flash across a sky," Shannon Brown, Juno scientist at NASA's Jet Propulsion Laboratory, said in a news release. "But until Juno, all the lightning signals recorded by spacecraft [Voyagers 1 and 2, Galileo, Cassini] were limited to either visual detections or from the kilohertz range of the radio spectrum, despite a search for signals in the megahertz range."

Scientists tried in vain to explain the discrepancy, but clarity required new observations. Juno, which began orbiting Jupiter in 2016, once again offered scientists the opportunity to observe Jovian lightning.

"In the data from our first eight flybys, Juno's MWR detected 377 lightning discharges," Brown said. "They were recorded in the megahertz as well as gigahertz range, which is what you can find with terrestrial lightning emissions."

Scientists believe Juno was able to pick up the megahertz signatures because its flyby put it closer to the lightning than any spacecraft before it.

While Jovian lightning appears to produce the same radio signals as bolts on Earth, the phenomena are still quite different. The distribution pattern of lightning strikes on Jupiter is the exact opposite of the distribution pattern found on Earth.

"There is a lot of activity near Jupiter's poles but none near the equator," Brown said. "You can ask anybody who lives in the tropics -- this doesn't hold true for our planet."

Heat drives lightning, and the sun's rays cause Earth's equator to heat up more than the poles. Jupiter is much farther away from the sun. And unlike Earth, the majority of its heat is derived from within. The sun still heats up Jupiter's equator more than it's poles, but scientists believe this minimal warming effect is just enough to stabilize its atmosphere and allow warm air to rise from within, creating the convection needed to produce lightning.

"These findings could help to improve our understanding of the composition, circulation and energy flows on Jupiter," said Brown.

Brown and her colleagues published their analysis of Jovian lightning this week in the journal Nature Astronomy.

Though the findings offered clarity, they also yielded new questions.

"Even though we see lightning near both poles, why is it mostly recorded at Jupiter's north pole?" Brown said.

Scientists hope future measurements collected by Juno will helps scientists answer that question and others.

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