Largest Moon of Jupiter: Why Ganymede is Amazing

Cover image of the article featuring Ganymde

Jupiter is one of the coolest planets in our solar system. It is the largest planet in our solar family, has one of the oldest and largest storms that is still ravaging its gaseous lands. And when it comes to moons, Jupiter is not going to let other planets take the title. The largest moon of Jupiter, Ganymede, is not just the planet’s largest moon, but the largest moon in our solar system. 

There are many Jovian moons, more than 70, and still counting. Some of them don’t even have a name. We’ll list the names of all the moons of Jupiter at the end of this article. Out of the 79 known moons, four moons are the most interesting; Ganymede, Io, Europa, and Callisto. Let’s see what makes Ganymede so interesting. 

Why Ganymede is amazing

Ganymede, as already established, is the largest Jovian moon and the largest moon in our solar system. But that does not really justify how large it is. This does; Ganymede is around 26% larger than the planet Mercury! It is larger than the dwarf planet Pluto and only a tad bit smaller than Mars. So why not call it a dwarf planet? Because it revolves around a planet and not a star. 

Ganymede is also the only moon in our solar system to have a magnetosphere. A part of its magnetosphere is embedded into the magnetic field of Jupiter. A region of Ganymede’s magnetosphere traps charged particles like electrons and this gives the moon a radiation belt. 

Ganymede was not the name of the largest moon of Jupiter. The four moons were first named the Medician planets by Galileo Galilei, with a number assigned to them. This naming was later dropped. Numbering the moon would have been easier but then new moons were discovered. 

So the largest Jovian moon was named Ganymede, after the boy who was taken by Zeus (Jupiter) and later made the cupbearer of the Gods. He took this spot from Hebe, the daughter of Jupiter and Juno. Guess what, Hebe is a large asteroid between Mars and Jupiter, circling around, planetless and parentless. 

The surface of Ganymede 

Ganymede, the largest moon of Jupiter
Ganymede, the largest moon of Jupiter. Image by NASA

Ganymede’s composition has piqued the interest of scientists on Earth. The European Space Agency has planned to launch JUICE in 2022. JUICE stands for JUpiter ICy moons Explorer and it will analyze the three moons of Jupiter, including Ganymede. 

Scientists believe that there is a massive water ocean hidden under the outer surface of the planet. And if we hope a little more, there might be some form of microscopic lifeforms floating in the cup of God’s cupbearer. 

Like our own moon, the surface of Ganymede is scarred. Scarred from all the impacts that it has been taking for billions of years. But there is something more to it. Scientists have reasons to believe that Ganymede may have the largest impact scar on the entire solar system. The current largest scar is on another Jovian moon, Callisto. The scar has a radius of around 1,200 miles or 1,900 kilometers. If the scientists are right about the Ganymede scar, the radius of this scar would be 4,800 miles or 7,800 kilometers. 

Looking at the image of Ganymede, there are two types of shades of surface; one is dark and the other is light. The dark regions are due to the craters created by the impacts while the lighter regions are clear from the impact scars. 

The lighter region has grooves running across them. These grooves are believed to have been created due to the tension between the surface above and the water underneath. In honor of Galileo Galilei, the largest area of the moon is named Galileo Regia. But was it Galileo who discovered the moons?

Galileo and Simon Marius observed the Jovian moons around the same time, Marius being one day behind Galileo. It was done in 1610 and the name Marius gave the moons is still being used today. Here’s the interesting thing. Since the moons other than these four are very small, no other Jovian moons were discovered for the next 282 years! 

Getting back to Ganymede, the underlying oceans of this moon can hold more water than the Earth! The moon takes around 7 Earth days to complete one revolution around Jupiter.  

Since we are done with Ganymede, here are the names of other Jovian moons because large or small, a moon is a moon. Take a look at the list: 

The size of Ganymede compared with Mars, moon and Mercury
The size of Ganymede compared with Mars, moon and Mercury. Image of planets from NASA

Moons of Jupiter









Himalia (group)



Carme (group)

Ananke (group)

Pasiphae (group)

This concludes the article. But this does not mean you have to leave. Take a look at these interesting articles about space and planets, you’ll love them;

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