# Io

*In the Solar System*

The most volcanic place in the Solar System: some four hundred active volcanoes, lava lakes and plumes that throw sulphur hundreds of kilometres up, on a moon a little larger than ours. The heat is tidal. Io, Europa and Ganymede are locked in step, going round Jupiter four, two and one times in the same interval, so Io is flexed on every orbit and never allowed to settle. It also sits inside Jupiter's radiation belts, which is why nothing has ever orbited it; Juno flew past at 1,500 km in 2023 and 2024.

| | |
| --- | --- |
| Radius | 1,822 km |
| Around the equator | 11,445 km |
| From the Sun | 794,743,305 km (-771,596 km/d) |
| From the Earth | 869,606,574 km (-2,733,754 km/d) |
| A signal takes | 48 min |
| Goes round | Jupiter |
| Placed to within | 4,264 km |

Distances and speed are computed from JPL Horizons trajectories and are true of 2026-10-09, changing at the rate given beside each. The interpolation itself is good to a few kilometres; what ages these figures is the date, not the arithmetic.

## Elsewhere

- On the live map: https://www.orbitalmap.space/?world=solar-system&focus=io
- This object as a page: https://www.orbitalmap.space/o/io/
- Every object: https://www.orbitalmap.space/o/
- What this site is and what it reads: https://www.orbitalmap.space/llms.txt