We Just Learned A Lot Of Unexpected Things About Jupiter

NASA / JPL / MSSS / Gerald Eichstädt / Justin Cowart

Forget everything you knew about gas giants, because based on the latest results from the Juno mission, we were wrong. We were so wrong.

Well, that’s a bit extreme. But NASA's Juno spacecraft is upending a lot of our models of the gas giant Jupiter, including what we thought it was like on the inside, the strength of its magnetic field, and what its poles look like. And that has implications for our Solar System and others, too.

Juno has been in orbit around Jupiter since July 4, 2016, completing an orbit every 53.5 days. In Science today, the first batch of results from Juno have been released, in this and this paper, after we got a sneak peak earlier this month.

“These first results are sort of telling us that some of our ideas are wrong and need to be corrected,” Scott Bolton, the principle investigator for the Juno mission, said in a Science podcast.

How so? Well, let’s take the first paper, on which Bolton is the lead author. On August 27, 2016, Juno dived over the poles of Jupiter just 5,000 kilometers (3,100 miles) from the cloud tops, the first spacecraft ever to observe this region. On the rest of the planet, storms are divided into iconic bands. At the poles, though, it looks like a hodgepodge of meteor craters.

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The north and south poles of Jupiter. Weird, huh? J Connerney et al / Science

Except these aren’t craters, but rather raging cyclones. This is the first time we’ve seen the poles, and they’re completely unlike anything we’ve seen before. On fellow gas giant Saturn, for example, its north pole is dominated by a large hexagonal storm. Jupiter looks much more weird.

“The surface patterns found near the poles, are highly different from what was expected,” John Leif Jørgensen from the Technical University of Denmark, and a co-investigator on Juno’s Magnetometer (MAG) instrument, told IFLScience. “The distribution [of vortices] came as a surprise.”

Rather interestingly, Juno also spotted a massive cyclone rising above the cloud tops of Jupiter. Spanning 7,000 kilometers (4,350 miles), the huge cloud was seen at the boundary between night and day, known as the terminator. It was sticking up like a tornado, casting a shadow over the clouds, which was a huge surprise to the scientists.

Then we’ve got Jupiter’s rather crazy magnetic field. Juno has been using its magnetometer to measure the strength of the magnetic field and map it across the planet. The team found it reached up to 7.766 Gauss in places, which is twice as strong as models predicted and about 10 times the strength of our own magnetic field.

“Previous spacecraft visiting Jupiter were observing from a great distance, in order to avoid the fierce radiation from particles from the Sun trapped by Jupiters magnetic field,” said Jørgensen. “Juno, designed to dodge the main part of the radiation by flying in under the main radiation belts, gets much closer, and delivers a very detailed map of the magnetic field.”

On Earth, the interaction between our magnetic field and the solar wind creates stunning aurorae at our poles. They glow in glorious light as solar particles make their way down the magnetic field lines, hitting atoms in our atmosphere.

But on Jupiter, a very different process seems to be taking place. While the solar wind plays a part, it seems that Jupiter’s rotation plays a much greater role. Juno saw the southern aurora for the first time, discovering that downward-travelling electron beams are showering energy into the upper atmosphere, which may power the aurorae.

A gif of Jupiter from Juno. J Connerney et al / Science

One of Juno’s ultimate goals is to find out if Jupiter has a solid core, which may have big implications for the origins of our Solar System. Theories predict that there should be something solid at its center, but we don’t know for sure. As Jupiter was thought to be the first planet to form in our Solar System, this could give us new clues on how solar systems take shape.

To examine the core, Juno has been studying Jupiter’s gravitational field. While there isn’t enough data yet to fully comprehend what’s going on (another four orbits or so are needed), we are getting closer to an answer.

“What Juno’s results are showing us is that our ideas of gas giants maybe are a little bit oversimplified,” said Bolton. “It’s changing in the most fundamental way how we think solar systems are formed, and how giant planets work.”

Juno is expected to continue its primary science mission around Jupiter until July 2018, during which it will complete 12 flybys. A failure with one of its valves meant it was unable to enter a lower orbit around Jupiter, which would have increased the number of flybys to 37 in a shorter time up to February 2018.

But the spacecraft is still expected to meet its goals, and the longer orbit actually means it spends less time in Jupiter’s intense radiation belts – so it may even survive longer than planned. That would be rather good, as it turns out Jupiter is even more weird and wonderful than we’d hoped.

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