Moon of Jupiter
Io
Jupiter's volcanic moon, squeezed by an orbital rhythm with its neighbors.
Io orbits Jupiter in 1.77 days and is locked in a 1:2:4 rhythm with Europa and Ganymede. Those precisely timed tugs keep Io's orbit slightly oval, so Jupiter's tides flex it constantly. That flexing heats its interior and powers hundreds of volcanoes.
How it moves
- Io orbits Jupiter every 1.769 days at about 421,800 km.
- It completes four orbits for every two of Europa and one of Ganymede (a 1:2:4 resonance).
- Pulls from Europa and Ganymede keep Io's orbit slightly elliptical, so its distance from Jupiter keeps changing.
- Changing tides make Io's solid surface rise and fall by as much as 100 meters.
- Io is tidally locked, always showing the same face to Jupiter.
Facts
- Mean radius
- 1,821.49 km
- Mass
- 8.932e+22 kg
- Surface gravity
- 1.8 m/s²
- Rotation period
- 42.459 hours
- Orbital period
- 1.769 days
- Average orbital distance
- 421,800 km
- Eccentricity
- 0.004
- Discovered
- January 8, 1610, by Galileo Galilei
Tides raise and lower Io's solid ground by up to 100 meters, far more than Earth's ocean tides.
Sources: nssdc.gsfc.nasa.gov, ssd.jpl.nasa.gov, ssd.jpl.nasa.gov