Of Jupiter’s 67 moons, Callisto is its eighth and second largest moon. Callisto is close to the size of the planet Mercury, making it the third largest moon in our solar system.
|Discovered By:||Galileo Galilei January 7, 1610|
|Mass:||1.08 x 10^23 kg (1.5 Moons)|
|Orbit Distance:||1,882,700 km|
|Orbit Period:||16.69 days|
|Surface Temperature:||-139 °C|
Callisto was discovered in 1610 by Italian scientist Galileo Galilei and, along with the other three moons around Jupiter that he discovered: Io, Europa, and Ganymede, they are grouped under the name of Galilean moons.
Like many of the planets and celestial bodies, Callisto is named after a mythological Greek creature.
She was a nymph that fell in love with the Greek god Zeus. As the story goes, Zeus’ wife, Hera, became jealous and turned Callisto into a bear and it was then that Zeus changed Callisto into a star and put her in the Ursa Major constellation.
We know this constellation as the Great Bear, and we can see it in our night sky.
Although Callisto is about 99% of Mercury’s diameter its mass is only one third of that of Mercury.
This means that Callisto is less dense. Callisto might be a larger size but it is considered to be a moon because it orbits Jupiter.
The only bodies that can be considered planets are those that orbit the sun. Callisto doesn’t have any atmosphere or tectonic action to protect its surface.
This means that any asteroids, comets, dust or dirt that hits the moon show the damage.
Callisto’s surface is thought to be one of the oldest in our solar system and it is the most heavily-cratered in our solar system. Due to the fact that scientists can’t see any activity on Callisto, it’s thought to be a dead world.
Callisto is made up of around 40% ice and 60% rock and iron. Studies have shown that Callisto also has traces of silicates, carbon dioxide, water ice and even possible compounds that are organic below its surface.
It was the Galileo space mission that revealed the possibility of Callisto having possible liquid water under the surface.
Other moons of Jupiter are affected by each other’s gravitational pull, causing tidal heating. Callisto doesn’t seem to be affected in that way.
Tidal heating allows for the release of the heat through the moons crust and Callisto doesn’t show any signs of melting ice on its surface.
Callisto is affected less by Jupiter because it is millions of miles away.