Published: Sat, June 09, 2018
Science | By Joan Schultz

Juno Spacecraft Solves 39-Year Old Mystery of Jupiter Lightning

Juno Spacecraft Solves 39-Year Old Mystery of Jupiter Lightning

Jupiter's orbit is five times more remote from the Sun than Earth's orbit, which implies that the giant planet gets 25 times less sunlight than Earth.

"They were recorded in the megahertz as well as gigahertz range, which is what you can find with terrestrial lightning emissions". The spacecraft will continue to orbit the planet till the early 2020s and is set to begin its 13th flyby of Jovian cloud tops next month.

"Until Juno, all the lightning signals recorded by spacecraft were limited to either visual detections or from the kilohertz range of the radio spectrum, despite a search for signals in the megahertz range", Shannon Brown, a scientist at NASA's Jet Propulsion Laboratory and a lead author on the paper, said.

Since then, NASA's Galileo and Cassini, which whizzed near Jupiter on its way to Saturn, validated the initial theories that lightning on Jupiter occurs.

There also seems to be more lightning in Jupiter's northern hemisphere compared to its southern side.

In a second Juno lightning paper published today in Nature Astronomy, Ivana Kolmašová of the Czech Academy of Sciences, Prague, and colleagues, present the largest database of lightning-generated low-frequency radio emissions around Jupiter (whistlers) to date. Spacecraft that have flown by Jupiter over the decades have picked up indications of lightning on the planet. The lightning originates at Jupiter's poles, rather than distributed across its surface, and the researchers attribute that to Jupiter's distance from the Sun. Many theories tried to explain the phenomenon, but none of them could ever visualize traction as the answer. "Even though we see lightning near both poles, why is it mostly recorded at Jupiter's north pole?"

Scientists are now saying that lightning on Jupiter can be as frequent as it is on Earth.

That's a lot to digest, so let's break it down a bit: All the tools on previous spacecraft that tried to listen in to Jupiter's lightning didn't hear the kinds of radio signals that are produced by lightning on Earth.

When Juno flew by the planet in 2016, she used a wide range of highly sensitive instruments to record the emissions of a gas giant.

These differences can be attributed to the different way heat is distributed across the two planets.

The reason for the differences was in the place of occurrence of lightning. With additional funding through fiscal year 2022, the unmanned spacecraft will have additional time to complete its primary science observations of the gas giant and its magnetic field, with the extra time required due to the spacecraft taking longer than planned orbits.

"This will help us better understand the composition, general circulation and energy transport on Jupiter". This is much higher than Voyager previously detected and similar to rates found on Earth.

Jupiter's poles, which aren't warmed by the Sun, have a less stable atmosphere, according to NASA, which allows warm gases to rise and create the recipe needed to produce lightning. Because a group of experts found the results achieved so far satisfactory and seeing how close the mission is to achieving its goals, NASA was able to to extend the life of the machine by 2021.

"This is great news for planetary exploration as well as for the Juno team", said Scott Bolton, principal investigator of Juno, from the Southwest Research Institute in San Antonio.

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