What is the Galilean Moon Io?

Io is the innermost Galilean moons of Jupiter. Out of all the moons in the solar system it has the highest density. Io is the most volcanically active body in the solar system with hundreds of active volcanoes.

Io

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Io is the closest moon to Jupiter out of the four Galilean moons. The four moons (Io, Europa, Ganymede, and Callisto) were first discovered by Galileo Galilei in 1610. It is the fourth largest moon in our solar system and the third largest of Jupiter’s moons, after Ganymede and Callisto. Io is slightly larger than our own moon, with a mean radius of 1821 km.

Io is the most geologically active body in the solar system with hundreds of active volcanoes. While the surface is littered with mountains, there are very few impact craters. Scientists were hoping that the impact craters could give them information of the age of Io. Scientists believe there are no impact craters because, geological speaking, the surface of the planet isn’t very old because of the volcanic activity. Io has the highest density of the Galilean moons.

The first spacecraft to pass Io was Pioneer 10 in 1973. Pioneer 10 was supposed to send images back of the moon, but the images were lost due to high radiation the spacecraft encountered. Pioneer 11 sent back the first images of the surface of Io. Since these first missions, Io has been studied by the Voyager 1 and 2 and the Galileo spacecraft. As well as the spacecraft, scientists have also used the Hubble space telescope to study and image the moon. Io’s orbit brings it very close to Jupiter and the moon is affected by the Jovian magnetic field, turning Io into an electric generator.

The four moons are all named by Simon Marius after the lovers of Zeus. Io is a Greek mythological character, the princess of Argos.

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Io Facts

• Orbital Period: 1.8 Earth days
• Rotation Period: 42.5 hours
• Diameter: 3,643 km
• Distance from Jupiter: 422,000 km
• Strength of Gravity: 1.8 N/kg
• Average Temperature: -155° C (-247 ° F)