When Galileo Galilei discovered Europa and Jupiter’s three other large moons – Io, Ganymede, and Callisto – it showed Earth was not the center of all motion in the universe and profoundly changed our view of the cosmos.

Abundant liquid water, energy, and the right chemical elements make Europa one of the best places in the solar system to seek present-day life beyond Earth.

Europa is primarily made of silicate rock and has a water-ice crust and probably an iron-nickel core. Cracks and streaks striate its surface but it has relatively few craters.

Most of Europa's surface consists of bright water ice. It also has reddish-brown cracks slicing the surface, which give Europa the look of a veiny eyeball.

Europa has an extremely thin oxygen atmosphere – far too thin for humans to breathe.

Europa's subsurface ocean might contain more than twice as much water as Earth's global ocean.

Europa is slightly smaller than Earth’s Moon and barely one-quarter the diameter of Earth.

Europa orbits Jupiter, the fifth planet from the Sun. Jupiter orbits the Sun at a distance of roughly 500 million miles (780 million kilometers).

Europa rotates once on its axis and completes one orbit of Jupiter every 3.5 Earth days, so the same side of Europa always faces Jupiter.

Europa has been visited by several spacecraft and more missions are planned, including NASA’s Europa Clipper.