Specs
| What | Data |
|---|---|
| Name | Io |
| Class | Galilean moon |
| Parent planet | Jupiter |
| Diameter | 3,643 km |
| Mass | 8.932 × 10²² kg |
| Distance from Jupiter | 421,700 km |
| Orbital period | 1.77 days |
| Rotation period | 1.77 days (tidally locked) |
| Surface gravity | 1.80 m/s² |
| Discovered | 1610 — Galileo Galilei |
Volcanic World
Io is the most volcanically active body in the solar system; more so than Earth. It has over 400 active volcanoes, some erupting plumes of sulfur hundreds of kilometres into space. Its surface is constantly being reshaped, which is why it has almost no impact craters: they are buried or destroyed before they can accumulate.
The heat driving this activity comes from tidal flexing. As Io orbits Jupiter, the competing gravitational pulls of Jupiter, Europa and Ganymede squeeze and stretch the moon’s interior, generating enormous amounts of heat.
Surface
Io’s surface is a patchwork of yellows, reds, whites and blacks; the result of sulfur and sulfur dioxide deposits in various states. Large lava lakes and towering volcanic mountains (some taller than Mount Everest) dot the landscape. The volcano Loki Patera, a lava lake roughly the size of Lake Ontario, is one of the most powerful heat sources in the solar system.
Relationship with Jupiter
Io sits deep within Jupiter’s intense radiation belts, making it one of the most hostile environments in the solar system. Its volcanic activity also feeds Jupiter’s magnetosphere: material ejected by Io’s volcanoes forms a torus of plasma around Jupiter that influences the entire Jovian system.