Size: Io has a mean radius of 1,131.7 miles (1,821.3 km) making it slightly larger than Earth's moon. It has a slightly elliptical shape, with its longest axis directed toward Jupiter.

The acid yellow moon Io that orbits Jupiter may be less than 30% the size of Earth, but is considered the most volcanic body in our solar system. As demonstrated by explosive news from NASA on ...

Jupiter moon of Io is famed for its volcanoes. NASA just spotted the most powerful one yet Not only was the hot spot larger than Earth’s Lake Superior, but it also was seen belching out ...

Extreme volcanism Io's intense volcanic activity is the result of "tidal flexing," where the moon is continuously being squeezed and released like a stress ball by Jupiter's crushing gravity.

Recent flybys of the fiery world refute a leading theory of its inner structure—and reveal how little is understood about geologically active moons.

Scientists believe that alien life could exist on Io and that it may be hiding in lava tubes beneath the surface of the Jovian moon.

Scientists say Earth's Moon went through a period when it was a lot like Io, a moon of Jupiter that's full of volcanic activity.

Early interactions with the Earth may have heated up the Moon and caused it to remelt, producing new lunar rocks and erasing old craters.

Observations made of Jupiter’s moon Io during the Juno mission’s flybys helped astronomers confirm how and why Io became the most volcanic world in the solar system.

NASA's Juno spacecraft observed powerful volcanic activity on Jupiter's moon Io, the most volcanic world in our solar system.

Extreme volcanism Io's intense volcanic activity is the result of "tidal flexing," where the moon is continuously being squeezed and released like a stress ball by Jupiter's crushing gravity.