Not often does the Juno space probe aim its sights at the moons of the largest planet in our solar system. This time, the probe first captured the north pole of Ganymede, Jupiter’s largest natural satellite.

On December 26, 2019, Juno flew toward Jupiter. In doing so, he passed the north pole of Ganymede. The probe used the Jovian Infrared Auroral Mapping instrument to take an infrared picture of the northern hemisphere of the moon.

Ganymede is the ninth largest object in the solar system. With a radius of 2634 kilometers, the celestial body is larger than Titan, the planet Mercury, the dwarf planet Pluto and our own moon. In addition, Ganymede is the only moon in the solar system with its own magnetic field. Electrically charged particles from the sun are deflected and reach the poles. Since Ganymede has no atmosphere, the plasma is not held back (like on Earth) and the electrically charged particles reach the surface of the Moon.

Amorphous ice
“We see that the ice on Ganymede’s North Pole is affected by the plasma rain,” says researcher Alessandro Mura. “Thanks to Juno, we are learning more about this phenomenon, because for the first time we can see the North Pole in its entirety.”

The ice on both poles is amorphous. That is, the ice does not have an ordered (or crystallized) structure. This is because the electrically charged particles damage the ice. The frozen water molecules on both poles therefore have a different infrared signature than the crystallized ice near the equator of Ganymede.

What do we know thanks to Juno?
It is special that we now learn more about Ganymede, as the Juno mission is mainly focused on Jupiter. During its mission, the vessel has already collected a lot of information about Jupiter. For example, we already know much more about the core, composition, magnetosphere and poles . Also, thanks to Juno, we finally have a picture of Jupiter’s North Pole . Moreover, we now know that the storms raging on the planet are reaching deep and we have gained more insight into the famous Great Red Spot. We now know more and more about Jupiter’s cyclones. For example, researchers found that five cyclones swirl in a fixed pattern around a central storm at the South Pole. By the way, a sixth cyclone recently joined the club . This type of research sheds new light on the cyclones of turbulent Jupiter and provides astronomers with new insights into how the atmospheres of giant planets work.

End of Mission
At the end of its mission, Juno will be ordered to drill into the atmosphere of Jupiter. That is a deliberate choice: NASA wants to prevent the probe from wandering through space without fuel and thus out of control and possibly landing on one of Jupiter’s moons. Researchers do not consider it impossible that life on those moons is possible. And that’s why they want to leave those moons untouched. We don’t know when the end of Juno is near. The Juno mission was originally scheduled to end on February 20, 2018. But since Juno is in a higher orbit around Jupiter, the space probe receives less radiation. And this has a beneficial effect on the life of the instruments. This allows the mission to be extended until 2021 and astronomers will have the opportunity to collect more data about the gas planet.

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