Juno's astonishing discovery: Io's eruptions outpower Earth
The Juno mission has detected exceptionally intense volcanic activity on Io, one of Jupiter's moons. Scientists from NASA's Juno mission cautioned that the hotspot is releasing eruptions with energy six times greater than the total power generated by all power plants on Earth.
Even by the standards of Io, the most volcanically active body in the Solar System, recent observations of this moon of Jupiter are extraordinary for researchers. Io is Jupiter's third-largest natural satellite. Scientists have long been captivated by it, not least because it is similar in size to our Moon—and is known as the most volcanically active body in the Solar System, hosting about 400 volcanoes that eject lava and gases in almost continuous eruptions.
Eruptions of unimaginable power
NASA's Juno mission scientists have identified a massive volcanic area on Io's southern hemisphere. This hot region is larger than Lake Superior on Earth and produces eruptions with energy six times greater than the total energy generated by all the world's power plants. The Jovian Infrared Auroral Mapper (JIRAM) instrument, provided by the Italian Space Agency, made this discovery possible.
"Juno had two really close flybys of Io during Juno’s extended mission," said Scott Bolton, the principal investigator of the mission from the Southwest Research Institute in San Antonio, as quoted by NASA. He added that "each flyby provided data on the tormented moon that exceeded our expectations, the data from this latest — and more distant — flyby really blew our minds. This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system — so that’s really saying something."
Io's volcanic activity is due to its proximity to Jupiter. The gas giant orbits Io in an elliptical path, completing a full orbit every 42.5 hours. Variations in its distance from Jupiter cause fluctuating gravitational interactions, which continually squeeze Io. This results in immense thermal energy generated through friction, melting the moon's interior and causing continuous lava eruptions and ash ejections into the atmosphere from hundreds of volcanoes scattered across its surface.
Images of Io taken in 2024 by the Juno spacecraft reveal significant surface changes near the moon’s southern pole. These changes were observed between the 66th and 68th close flybys of Juno's orbit around Jupiter.
How has the surface of Jupiter's moon changed?
During the extended mission, Juno flies by Io every other orbit, each time passing over the same area of the moon. Previous close flybys occurred in December 2023 and February 2024, when the spacecraft came as close as 1,500 kilometres from Io’s surface. The last flyby, on December 27, 2024, occurred from a distance of about 74,300 kilometres, with the JIRAM instrument focusing on the moon’s southern hemisphere.
Scientists estimate that this newly discovered area spans 100,000 square kilometres, far exceeding the previous record holder—Loki Patera, a lava lake with an area of 20,000 square kilometres. The total radiated power of this new hot zone surpassed 80 trillion watts.
Io in Flames
An eruption of this scale is likely to leave long-lasting traces. Previous large eruptions on Io have resulted in the formation of various features, such as pyroclastic deposits (composed of rock fragments expelled during an eruption), small lava flows fed by fissures, or particles rich in sulphur and sulphur dioxide.
