Jupiter and its Galilean moons
(Io / Europa / Ganymede / Callisto)
Jupiter’s Galilean moons
Galileo spotted Jupiter’s four biggest moons in the 17th century,
their names from left to right; Io, Europa, Ganymede, Callisto.
- they were discovered in January 1610 by theÂ Italian astronomer, Galileo Galilei.
- Ganymede is the biggest of the Galilean moons – 3,289 miles across, it is larger than the planet Mercury!
- Ganymede looks solid, but under its shell of ice is 563 miles slushy ice and water.
- Callisto is the second biggest moon – 3,004 miles across.
- Callisto is scarred with craters from bombardments early in the Solar System’s life.
- Io is the third biggest moon – Â 2,276 miles.
- the surface of Io is a mass of volcanoes caused by it being stretched and squeezed by Jupiter’s massive gravity.
- the smallest of the Galilean moons is Europa – 1,961 miles.
- Europa has a smooth icy surface full of cracks, but the Galileo space probe discovered an ocean of water under the ice where there might be living creatures.
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