Wikijunior:Solar System/Jupiter/Io
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Io Facts:
- Io is the most volcanically active body in the Solar System.
- Io is one of the few moons to have an atmosphere although it is very thin.
- At any given time, there are approximately 9 volcanoes erupting on Io.
- Io is so close to Jupiter that Jupiter causes "tides" in its surface. These "tides" might be what makes it so volcanically active.
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[edit] How big is Io?
Jupiter has over 20 moons and Io is one of the largest. Io is 3642.6 km, or 0.28 Earths, wide. It only has a mass of about 1.4% of the mass of Earth. It is a similar size to our moon (but a lot more exciting!).
[edit] What is its surface like?
Unlike most moons, Io has a "young" surface. Because there is so much volcanic activity, the surface is almost free of craters. Also, its volcanoes are quite unusual. Instead of erupting like a normal volcano, they erupt more like geysers do on earth.
The temperature of Io varies wildly. At some spots, near volcanic eruptions, the temperature is very hot. But most of Io is very cold, as it is so far away from the sun. The average temperature of Io is -143°C. This is much colder than −90°C, the coldest it gets in Antarctica.
In addition to volcanoes, Io also has many mountains, lakes of molten sulfur, calderas, and flows of molten sulfur or silicate hundreds of kilometers long. The colour of the surface is due to sulfur being at different temperatures. When sulfur warms up and cools down, it changes colour. This is why the surface of Io has so many colours!
[edit] How long is a day on Io?
It takes 42 hours (1¾ Earth days) for Io to rotate on its axis. It also takes 42 hours for Io to complete one orbit around Jupiter. Since these numbers are the same, it means that the same side of Io always faces Jupiter. (Earth's moon is the same way, which is why you can always see the Man in the Moon.)
[edit] Who is it named after?
Io is named after one of Zeus' (Jupiter's) 1000 lovers. If you notice, allbig of Jupiter's moons are named after characters from Shakespeare plays.
[edit] How would Io's gravity pull on me?
If you stood on the surface of Io, you would weigh less than you do on Earth. A person who weighs 100 pounds (45kg) on Earth would weigh about 18 pounds (8kg) on Io.
[edit] How was it discovered?
Io was discovered by both Simon Marius and Galileo Galilei. Galileo discovered it on January 7, 1610, and Marius discovered it around the same time.
