A new Jupiter: Juno’s first results

The first science results from NASA's Juno mission have revealed Jupiter to be a complex, enigmatic planet.

Oval cyclones up to 1,000km in diameter can be seen at Jupiter’s south pole in this image captured by the Juno spacecraft. Credit: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

NASA’s Juno mission has revealed Jupiter to be a turbulent planet with a strong magnetic field, huge polar cyclones and mysterious atmospheric activity. These are just some of the conclusions drawn by NASA scientists studying early science results from the mission.

Juno launched from Earth on 5 August 2011 and entered Jupiter’s orbit on 4 July 2016.

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It made its first data collection pass as it flew about 4,200km above the planet’s cloud tops on 27 August 2016.

The spacecraft is in an elliptical orbit around the planet and makes a close pass of the planet every 53 days, beginning at the north pole and working its way down to the south.

Images taken by Juno show that both of Jupiter’s poles are covered in massive swirling storms.

“We’re puzzled as to how they could be formed, how stable the configuration is, and why Jupiter’s north pole doesn’t look like the south pole,” says Juno principal investigator Scott Bolton.

“We’re questioning whether this is a dynamic system, and are we seeing just one stage, and over the next year, we’re going to watch it disappear, or is this a stable configuration and these storms are circulating around one another?”

The spacecraft also captured data on Jupiter’s atmosphere by sampling its thermal microwave radiation.

It analysed the bands that give Jupiter its stripes, which are clouds of ammonia in the upper atmosphere.

The lighter coloured bands are ‘zones’ while the darker are called ‘belts’.

Juno data revealed that the belt near Jupiter’s equator penetrates all the way down, while the belts and zones at other latitudes seem to evolve into other structures.

It was already known that Jupiter has the most intense magnetic field in the Solar System, but measurements made by Juno reveal it to be even stronger than anticipated, and ten times stronger that the strongest magnetic field found on Earth.

“Already we see that the magnetic field looks lumpy: it is stronger in some places and weaker in others,” says Jack Connerney, Juno deputy principal investigator.

“This uneven distribution suggests that the field might be generated by dynamo action closer to the surface, above the layer of metallic hydrogen.

Every flyby we execute gets us closer to determining where and how Jupiter’s dynamo works.”

The spacecraft is also analysing Jupiter’s aurorae, which are caused by energetic particles hitting the planet’s atmosphere.

“Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new,” says Scott Bolton.

“On our next flyby on 11 July, we will fly directly over one of the most iconic features in the entire Solar System – one that every school kid knows – Jupiter’s Great Red Spot.

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If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it’s Juno and her cloud-piercing science instruments.”