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Scientists finally see Ganymede, a snowball bigger than the planet Mercury

Jupiter's strangest satellite has fascinated us for its magnetic quality.

NASA

Although Jupiter has a whopping 79 moons, none quite stand out as much as Ganymede.

Ganymede is not only Jupiter's largest known moon, it is also the largest across the entire Solar System and it has its own magnetic field.

Ganymede is also the ninth largest object in the Solar System overall, larger than the planet Mercury.

Using imagery collected by NASA's Juno mission, we now have our very first look at Ganymede's icy north pole.

The images were captured on December 26, 2019 as the Juno spacecraft made its way around Jupiter, and flew close to Ganymede's north pole. During its closest approach, the spacecraft was around 62,000 miles away from the moon's surface and captured a total of 300 infrared images.

Juno glimpsed the north pole of the largest moon of the Solar System for the first time, providing the first infrared mapping of this icy region.NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

Ganymede's poles are constantly being bombarded by plasma, a highly electric ionized gas, as it is produced by Jupiter's magnetosphere, that area that surrounds the planet with charged particles that are affected by its magnetic field.

Meanwhile, the magnetic field on Ganymede provides a pathway for the plasma while the moon has no atmosphere to protect it from the incoming plasma the same way Earth's atmosphere shields the planet. As a result, the effects of the plasma were visible on the surface of Ganymede's north pole.

"The JIRAM data show the ice at and surrounding Ganymede's north pole has been modified by the precipitation of plasma," Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome, said in a statement. "It is a phenomenon that we have been able to learn about for the first time with Juno because we are able to see the north pole in its entirety."

The captured images reveal the effects of plasma on the moon's north pole. NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

The north pole is seen at the center of this image, which reveals that the ice near both of Ganymede's poles is amorphous, according to NASA. Due to the ice at the poles being constantly bombarded by plasma from Jupiter, it does not form a crystalline structure, and has a different signature than the ice found at Ganymede's equator.

A lunar mission of its own. The Juno spacecraft launched in 2011. It orbits Jupiter every 53 days, measuring the planet's atmosphere from afar.

The spacecraft is scheduled for a total of 32 close flybys of the gaseous giant, capturing images of the turbulent world underneath, and occasionally, of Jupiter's erratic moons.

However, Ganymede is getting its very own mission soon. The European Space Agency is launching the JUpiter ICy moons Explorer, which will begin exploration of Ganymede, as well as two other moons Callisto, and Europa, in the year 2030.

As Jupiter's strangest satellite, Ganymede has fascinated astronomers who are on a quest to uncover the mystery behind the only magnetic field to exist on a moon.

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