Io

Description:
Io is the innermost of the four Galilean moons of the planet Jupiter. It is the fourth-largest moon, has the highest density of all the moons, and has the least amount of water of any known astronomical object in the Solar System.

Radius: 1,822 km

Distance to Earth: 628.3 million km

Orbital period: 42 hours

Surface area: 41910000 km2 (0.082 Earths)

Did you know: Io's colorful appearance is the result of materials deposited by its extensive volcanism, including silicates (such as orthopyroxene), sulfur, and sulfur dioxide.