In late December 2021, the chief explorer of the Juno mission released a 50-second audio clip recorded by a NASA probe as it flew over Ganymede.
Although the track sounded more like the sound of a modem, Ganymede became known online as the “singing moon of Jupiter. We tell you about other unusual facts that make this natural satellite truly unique in the solar system.
Unusual size.
Ganymede is a million kilometers from Jupiter, with the moon’s year lasting only a week. The satellite has a radius of 2,631 km and is currently the largest in the solar system. Ganimed is even bigger than our Moon (R 1 737,4 km) and Mercury, albeit the smallest, but still a planet (R 2 439,7 km).
In fact, Ganimed occupies the 4th place in the ranking of objects in the solar system by size (after the Earth, Venus and Mars). It is noteworthy that the mass of the satellite is twice the mass of the Earth’s Moon.
It was discovered in the XVII century.
Ganymede is one of the four satellites of Jupiter, which was discovered in the XVII century by Italian astronomer Galileo Galilei. At first the scientist mistook them for stars. But while observing the objects, he noticed that the “stars” were orbiting Jupiter. After a few days, the astronomer realized the true nature of these objects. When Galileo realized they were moons, he named them “Medici stars” after the Duke of Tuscany anyway.
From left to right: Io, Europa, Ganymede, and Calisto. Source: Wiki Images/Pixabay
Then another scientist suggested naming them after favorites of the Greek god Zeus. They eventually became known as Io, Europa, Ganymede, and Callisto.
The only satellite with a magnetosphere
Not every planet has a magnetosphere – only Earth, Mercury, Saturn, Mercury and Jupiter. Moreover, they were not found on the moons. At least not until 1996, when NASA’s Galileo spacecraft recorded whistling and static sounds from a satellite. This suggested to scientists that Ganymede has a self-generated magnetosphere.
This suggests that the moon has an active inner liquid core. It is most likely rich in iron and nickel and is between 400 and 1,300 km deep. Convection in the liquid iron, which has high electrical conductivity, just generates a magnetic field.
Just like the magnetic field of the Earth, Ganymede’s magnetosphere consists of charged particles that act as a shield against cosmic radiation, including that of Jupiter. And similarly, the moon’s magnetic field creates glowing auroras at its north and south poles.
NASA’s Hubble Space Telescope image of Ganymede’s polar belts. Source: NASA/ESA.
The electrified gases that form the auroral belts were first detected in ultraviolet images of Ganymede. They were taken by the Galileo spacecraft’s plasma-wave spectrometer and then by the Hubble Telescope spectrograph.
Lots of water.
Ganymede is mostly composed of silicate rocks and water ice. The rocky material sits on top of a metallic iron core and forms several clumps beneath the ice shell. Underneath it is thought to be liquid water. It is salty and saturated with magnesium sulfate.
Signs of the existence of an underground salt ocean were first discovered during NASA’s Galileo mission, and later confirmed by data from the Hubble Space Telescope. Scientists believe that the thickness of the ocean below the surface of Jupiter’s satellite is about 100 km. This is 10 times greater than the depth of Earth’s oceans. Ganymede itself contains more water than all the oceans of our planet combined.
Is there life on Ganymede?
According to NASA, because of the interaction of salt water with rocky materials, it is likely that there is a primitive form of life on the moon. But it can only exist under thick layers of ice where no sunlight enters. This means that any organisms have to survive without it and use alternative energy sources, like the deep sea creatures on Earth. They also have to withstand pressures that are stronger than those in the Mariana Trench. Recall, its depth is more than 11,000 meters.
Ganymede. Source: Pablo Carlos Budassi/Wikisclad
To investigate the potential habitability of Ganymede, the European Space Agency (ESA) will send the JUPITER Icy Moon Explorer (JUICE) probe to collect data from Ganymede as well as from two other Jupiter satellites, Europa and Callisto. The probe will be launched between August and September 2022. It will enter Ganymede’s orbit around 2032. Scientists may find this hardy life on Jupiter’s moon during the mission.
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