- The planet Jupiter is the largest planet in the Solar System and has a huge number of moons that orbit around it.
- None of these can be seen with the naked eye, but the four largest moons, Io, Europa, Ganymede and Callisto, can be seen through a small telescope.
Figure 1. Jupiter's 4 moons through a small telescope. Europa is on the right of Jupiter and closer to the planet than Ganymede.
- The four moons are called the Galilean moons because they were first seen and described in 1610 by the great Italian scientist, Galileo.
- Europa is the second closest to Jupiter of the four, after Io.
- Europa looks quite unlike Io, since Europa’s surface is entirely covered by salt water with a thick layer of ice on top.
- Figure 2. An image of the moon Europa from the Apollo spacecraft.
- The length of its orbit right round Jupiter is 2,618,478 miles (4,216,552 kilometres)
- It takes only 3.5 Earth days to complete its orbit, travelling at a speed of 30,724 miles (49.476 kilometres) an hour
- Europa has an average distance of about 417,000 miles (671100 kilometres) from Jupiter.
- The orbit is shaped like an oval, not a circle.
- At its closest point Europa is 412,835 miles (664,792 kilometres) from the planet and at its farthest point it is 420,670 miles (677,408 kilometres) from the planet.
- When Europa moves closer to Jupiter, Jupiter’s gravity causes a higher tide in the sea beneath the ice, which probably causes the ice to crack under the surface.
Figure 3. The icy surface of Europa showing the effects of cracks under the surface ice.
- This movement in the salt water causes it to be less cold than you would expect – Europa is five times as far from the Sun as the Earth.
- Some scientists believe that some form of life could exist in the salt oceans of Europa.
- Like the other Galilean moons, Europa was named after a figure from Greek mythology.
- Europa was the daughter of the King of Tyre and, like Io, was loved by the Greek sky god, Zeus, who was known to the Romans as Jupiter.
- Zeus turned himself into a beautiful and gentle white bull that came out of the sea onto the beach where Europa was playing with her friends.
- Europa was so attracted by the bull that she climbed upon his back.
- Zeus (Jupiter) then swam away with Europa on his back until they reached the Island of Crete, where Europa later became the mother of Minos, King of Crete.
Pictures of the moon from NASA
More information from NASA