Jupiter's Moons

Jupiter is the biggest planet in our solar system. It also has the most moons. Scientists have found over 90 moons around Jupiter. The four biggest are called Io, Europa, Ganymede, and Callisto. They were discovered by Galileo in 1610.

The Galilean Moons

The four big moons are called the Galilean moons. Io has more volcanoes than any other place we know. Europa has a frozen ocean with water underneath. Ganymede is the largest moon in the whole solar system. Callisto is covered in ancient craters.

Jupiter's four biggest moons, Io, Europa, Ganymede, and Callisto, lined up together.
Jupiter's four biggest moons, Io, Europa, Ganymede, and Callisto, lined up together. (NASA/JPL/DLR / Wikimedia Commons)

Could There Be Life?

Scientists are very interested in Europa. Its hidden ocean might have conditions for life. The water is kept warm by Jupiter's strong pull. Robots may visit Europa soon to look for signs of life. This could be one of the best places to search.

Fun Facts

  • Ganymede is bigger than the planet Mercury.
  • Io has over 400 active volcanoes.
  • Jupiter's smallest moons are just a few miles wide.

Did You Know?

If Ganymede orbited the Sun instead of Jupiter, it would be called a planet.