THE WORLDS OF JUPITER

Jupiter has at least 16 moons revolving around it, more than any other planet in our solar system. Many of them are only a few kilometers in diameter. The four outermost moons have retrograde orbits (they move around Jupiter in the opposite direction that most moons and planets orbit.) It is probable that these four moons are captured asteroids and did not form with Jupiter at all.

Io, Europa, Callisto and Ganymede are known as the Galilean moons because they were discovered by the 17th century astronomer Galileo Galilei when he first turned a telescope to the night sky. These moons are easily seen with even binoculars and their movements around Jupiter can easily be tracked.

IO: A WORLD TURNING INSIDE OUT

EUROPA: SMOOTH AND ICY

GANYMEDE: OLD, DARK AND IN THE GROOVE

CALLISTO: ANCIENT AND CRATERED