Io

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Learn about Io, Jupiter's moon with the most active volcanoes in the solar system

global mosaic of Jupiter's moon Io

Io's Tvashtar volcano

volcanic plumes on Io

Io, in Jupiter's shadow, photographed by the Galileo spacecraft on May 6, 1997. The relative brightnesses of Io's features are enhanced with added colour, red being the most intense, yellow-green moderate, and blue the faintest. Small red and yellow-green spots are probably lava flows or lakes, while the bright area extending from Io's left limb corresponds to the plume from the volcano Prometheus. The diffuse glow on the right limb also has plumelike characteristics.

Jupiter's four Galilean moons

Io, moon of Jupiter. A massive volcano can be seen on the horizon.

Jupiter's atmospheric blemishes

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Io: Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

News •

NASA’s Spacecraft Reveals Io To Be A Hellishly Active Volcanic Moon • May 7, 2025, 5:36 AM ET (Forbes)

NASA’s Juno Mission Gets Under Jupiter’s and Io’s Surface • Apr. 29, 2025, 9:13 AM ET (NASA Jet Propulsion Laboratory (JPL) (.gov))

Photos and Videos

global mosaic of Jupiter's moon Io

Io's Tvashtar volcano

volcanic plumes on Io

Io, in Jupiter's shadow, photographed by the Galileo spacecraft on May 6, 1997. The relative brightnesses of Io's features are enhanced with added colour, red being the most intense, yellow-green moderate, and blue the faintest. Small red and yellow-green spots are probably lava flows or lakes, while the bright area extending from Io's left limb corresponds to the plume from the volcano Prometheus. The diffuse glow on the right limb also has plumelike characteristics.

Jupiter's four Galilean moons

Io, moon of Jupiter. A massive volcano can be seen on the horizon.

Jupiter's atmospheric blemishes

volcanic eruption on Io

Learn about Io, Jupiter's moon with the most active volcanoes in the solar system

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