This image of Jupiter's moon Europa was taken by NASA's Galileo spacecraft. It shows the trailing hemisphere of the ice-covered moon. The crust of Europa is believed to be composed mainly of water ice. The dark brown areas represent rocky material that have either been uplifted from the interior or has been impacted by meteors. The long, dark lines are fractures in the ice. Astronomers believe that there is an ocean of liquid water about 60 miles (96 kilometers) deep underneath the icy crust. It is believed that this ocean could possibly support some type of life.