“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.
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.