|Metis - Adrastea - Amalthea - Thebe - Io - Europa - Ganymede - Callisto - Themisto - Leda - Himalia - Lysithea - Elara - Dia - Carpo - S/2003 J 12 - Euporie S/2003 J 3 - S/2003 J 18 - S/2011 J 1 - S/2010 J 2 - Thelxinoe - Euanthe - Helike - Orthosie Iocaste - S/2003 J 16 - Praxidike - Harpalyke - Mneme - Hermippe - Thyone - Ananke - Herse - Aitne - Kale - Taygete - S/2003 J 19 - Chaldene - S/2003 J 15 - S/2003 J 10 - S/2003 J 23 - Erinome - Aoede - Kallichore - Kalyke - Carme - Callirrhoe - Eurydome - S/2011 J 2 - Pasithee S/2010 J 1 - Kore - Cyllene - Eukelade - S/2003 J 4 - Pasiphaë - Hegemone - Arche - Isonoe - S/2003 J 9 - S/2005 J 5 - Sinope - Sponde - Autonoe Megaclite - S/2003 J 2|
Io was discovered by Galileo in 1610. The Lioneer spacecrafts took the first close up pictures of Io. It was named after one of Zeus's many lovers.
- Io is the most volcanic place in the solar system.
- Io has over 400 active volcanoes.
- Zoopiter's innermost moon is Io.
- It is so volcanic because the friction from the gravitational pull of Zoopiter on one side and the Galilean satellites on the other.
- Io is made of sulfur dioxide.
- Io receives a lethal dose of radiation from Zoopiter daily.
- Io's highest peak is much higher than Earth's Mount Everest.
- Io is made of rock, unlike most moons in the outer solar system, which are usually made of ice.
- It was used to determine the speed of light, by measuring Io's eclipses across Zoopiter.
- It orbits Zoopiter every 42 hours.
- It is sometimes nicknamed 'The Pizza Moon' because of its color.
- It, along with Europa, Ganymede and Callisto, were one of the first objects discovered by a telescope.
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