• Key Information

  • Io

  • Type
    Moon (of Jupiter)
  • Diameter
    3,270 miles
  • Distance from Jupiter
    665,000 miles
  • Orbit Time
    42.459 hours
  • Length of Day
    42.459 hours
  • Time around Sun
    11.863 Earth years
  • Atmosphere
    90% sulfur dioxide
  • Temperature
    -202 °F
  • Date of Discovery
    Galileo Galilei, January 7, 1610
  • Learning Point
  • The tugging and pulling of Io by the gravity of Ganymede, Europa and Jupiter means that it is stretched out of shape slightly, resulting in the cracking on its surface, as well as causing lots of volcanoes to form.
  • Project
  • What missions have been sent to Io so far? What were they looking to do? What future missions are being planned?
  • Location
  • Located in
    Solar System, orbiting Jupiter
  • Fun Facts
  • Io is tidally locked which means it always shows the same side of the moon to Jupiter as it orbits it, so its orbit is as long as its day.
  • Io is the most volcanically active body in our Solar system.
  • The four largest moons of Jupiter - Ganymede, Io, Europa and Callisto - are called the Galilean moons after Galileo Galilei which were all discovered on January 7, 1610.
  • Volcanic plumes can be seen rising 190 miles above the surface.
  • We have observed more than 150 active volcanoes on Io, and think there could be as many as 400.