Europa is the fifth moon of jupiter and the second of the galilean moons.
Europa was discovered by Galileo and Marius in 1610.

Europe and Io are somewhat similar in composition to the terrestrial planets. They are also primarily composed of silicate rock. Unlike Io, Europe has a thin ice crust. The satellite has an internally layered structure, with probably a small metallic core.

Europa has a very smooth surface. No features higher then a few hundred meters exist. There are also very few craters on Europa. Only a few craters are larger then 5 km in diameter. This indicates a very young and active surface.

Europa has a very thin atmosphere. It contains oxygen, but not the biological oxygen as we know it on earth. This oxygen probably comes into the atmosphere when water vapor is split into hydrogen and oxygen. The hydrogen leaves the atmosphere, leaving the oxygen behind.