Ganymede

Ganymede is the biggest moon in the Solar System. It is one of the many natural satellites of the planet Jupiter. Pluto and Mercury are much smaller than Ganymede. The Hubble Space Telescope has detected solid evidence for a subterranean salt-water ocean on Ganymede. The ocean is believed to accommodate much more quantity of water than on the Earth’s surface. It is predicted to be buried beneath a 150km thicker ice crust. The ocean could be 100km thick and ten times deeper than an average ocean on the Earth.

Composition of Ganymede

Ganymede has three primary layers: a spherical outer covering of ice, a spherical mantle of rock and a metallic core made of iron (centre). The visible surface is on the top of the spherical ice shell. Irregular lumps have been discovered beneath its icy surface. Computer-generated models have shown that vast layers of ice and ocean might be stacked up together.

In the 1970s, scientists concluded that it might possess a gigantic underground water body similar to an ocean.

In 1996 spacecraft Galileo detected Ganymede’s magnetic field; this discovery solidified the assumptions about the underground ocean. The Hubble Telescope has also detected much more evidence regarding the underground salt-water ocean and thin oxygen atmosphere. In June 2021, spacecraft Juno captured the latest photographs of Ganymede’s surface.

Ganymede is primarily composed of equal quantities of water and silicate rock. It has a well-defined body with an iron liquid core and an underground ocean that probably holds more water than the entire water content on the Earth. Its outer surface is made of two types of terrain, dark and light regions. Light regions are filled with cross-cuts of ridges and grooves. On the other hand, darker regions are filled with craters, covering about one-third. The reason for light terrain’s distorted geology is not completely known. It might be the result of tectonic movements caused by tidal heating. This points out that its crust is under strong tension from planetary tectonic movements.

Size and Distance

Ganymede possesses a radius of 2,631km, which makes it the largest natural satellite in the solar system. As mentioned earlier, it is even larger than Pluto and Mercury.

It is about 1.08 million kilometres away from Jupiter (5.2 AU from the sun). One ‘AU’ or astronomical unit is the average distance between the Earth and Sun. Sunlight takes around 43 minutes to reach Ganymede.

The icy moon takes seven earth days to complete one orbit around Jupiter. Along with Jupiter, Ganymede completes one orbit around the sun in 12 years.

A video about parallax effect

Ganymede Discovery

Galileo Galilei was the human to observe the Ganymede (January 7, 1610). It was named after the Greek mythology prince ‘Ganymede’.

Pioneer 10 was the first spacecraft to observe it closely. Later, Voyager 1 and Voyager 2 calculated its accurate size and other values. Galileo spacecraft discovered Ganymede’s magnetic field and underground ocean. The next probable mission to Ganymede is JUICE (Jupiter Icy Moon Explorer) by ESA. It will explore every three icy Galilean moons. It will be launched in April 2023. By the third quarter of 2032, JUICE will enter the orbit of Ganymede. No spacecraft has ever orbited a natural satellite other than the Earth’s moon.

Origin and Evolution of Ganymede

Ganymede is believed to be created by accretion in the subnebula of Jupiter. It was a disk of gas and dust surrounding the young Jupiter. While the accretion of Callisto took about 100,000 years, Ganymede’s accretion only took about 10,000 years. The accretion phenomenon is directly connected to gas quantity in the subnebula. During the formation of other Galilean satellites, maybe there was a lack of gas or matter in the subnebula forcing a lengthy accretion time. In the case of Ganymede, it might have been formed closer to the parent planet. Thus, it was much closer to the denser area of the subnebula. This provided ample resources for a faster accretion. The relatively quicker formation might have blocked the removal of recreational heat. This phenomenon probably led to the separation of the ice and rocks. In this regard, Callisto is very different from Ganymede. As there was an evident loss of recreational heat during its formation, there was no differentiation into distinctive layers like Ganymede’s internal structure.

Ganymede and Life

Researchers believe that the interaction of rock and water is the key to the evolution of life. In 2014, a computer-generated model of Ganymede’s interior points that it might support the development of basic life forms. The model illustrated that the moon’s rocky bottom could be in touch with salt-water.

On the flip side, another section of scientists is doubtful about Ganymede’s ability to host life. Even with the lack of a dense atmosphere, there are enough internal properties that are highly favourable to the evolution of life.

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