NASA has released a dramatic image of Jupiter's moon Io, showing a surface covered by hundreds of active volcanoes, which was taken by the Jovian Infrared Auroral Mapper imager on the Juno Spacecraft on 5 July 2022. The image was taken during a close flyby of the moon, when the spacecraft was about 80 000 km from its surface (for comparison, the International Space Station is 408 km above the Earth's surface, while the Earth's Moon orbit's at an average of 384 300 km).
Io is the innermost of the four Galilean Moons of Jupiter (the four large moons discovered by Galileo Galilei in January 1610), and is one of the most distinctive bodies in the Solar System, with a surface dominated by a series of extensive volcanic fields. The volcanism is thought to be caused by tidal forces, as Io is pulled by the gravitational forces of both Jupiter and the other large Galilean Moons, deforming and heating the moon's interior. This has led to a body unlike any other in the Outer Solar System, with no significant ice or hydrocarbon deposits (presumably lost due to the heat of the volcanic activity) and a silicate rock surface surrounding an iron or iron-sulphur core.
The release coincides with another flyby of the Jovian Moon, on 15 December 2022, the first of a series of nine close passes, two of them coming within 1500 km of the moon's surface, over the next eighteen months, during which Io will become a focus of research by the Juno Spacecraft. Previous research has shown that the small moon's numerous volcanoes are a significant contributing factor to Jupiter's spectacular polar aurora's, constantly raining charged particles down upon the atmosphere of the planet, which are then swept toward's the poles by Jupiter's powerful magnetic field.
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