MOON PROFILE - EUROPA

One of the Solar System’s famous ocean worlds is an exciting prospect for further exploration

Europa is one of the four Galilean moons that orbit the Solar System’s largest planet, Jupiter, discovered in 1610 by Italian astronomer Galileo Galilei. Underneath its icy, scarred surface could lie a salty ocean – just like those that make up 71 per cent of Earth’s surface. Europa is tidally locked to Jupiter, meaning the same face of the moon is pointing at the Jovian giant at all times, much like the Moon and Earth. Europa has an equatorial diameter of 3,100 kilometres (1,940 miles), which is 90 per cent of the Moon’s diameter. If you were to replace the Moon with Europa in our sky, to the naked eye they would both seem about the same size. However, Europa would be much brighter on account of its surface ice reflecting 5.5 times more sunlight than the Moon, giving it a higher albedo.

The process behind the creation of Jupiter’s largest moons is still hotly debated, but astronomers largely agree that they formed from leftover debris from the formation of Jupiter roughly 4.5 billion years ago. Fast-forward to today and Europa is a water-ice ball with fractures criss-crossing all over the surface. The number of craters currently found across its cracked terrain indicate that the moon is no older than 90 million years old, suggesting there is likely to be some form of surface replenishment that also brings salts and sulphur compounds to the outer layer. Surrounding the icy world is a thin atmosphere composed of molecular oxygen.