Juno mission reveals Io's volcanic eruptions dwarf global power
The Juno mission has discovered remarkably strong activity on Jupiter's moon, Io. The hot spot emits eruptions with energy six times greater than the total power of all power plants in the world, NASA's Juno mission scientists caution.
Even by Io's standards—the most volcanically active body in the Solar System—recent observations on Jupiter's moon have been extreme for researchers. Io is the third-largest natural satellite of Jupiter, and scientists have long been fascinated by it. This is mainly because its size is similar to our Moon, and it is renowned as the most volcanically active body in the Solar System, with about 400 volcanoes that continuously eject lava and gases.
Eruptions of unimaginable power
NASA's Juno mission scientists have discovered a massive volcanic area on Io's southern hemisphere. This hot region is larger than Lake Superior on Earth and produces eruptions with power six times greater than that generated by all the world's power plants. This discovery was made possible by the Jovian Infrared Auroral Mapper (JIRAM) instrument, provided by the Italian Space Agency.
"Juno had two really close flybys of Io during Juno’s extended mission," said Scott Bolton, the mission's principal investigator from the Southwest Research Institute in San Antonio, as quoted by NASA. He added, "And while 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 results from its proximity to Jupiter. The gas giant orbits Io in an elliptical path, completing a full orbit every 42.5 hours. Variations in the moon's distance from Jupiter cause gravitational interactions, continually squeezing Io. This results in immense thermal energy generated by friction, which melts the moon's interior and causes 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 (indicated by arrows above). 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 took place in December 2023 and February 2024, when the spacecraft came as close as 930 miles from Io’s surface. The last flyby, on December 27, 2024, occurred from about 46,200 miles, with the JIRAM instrument focusing on the moon’s southern hemisphere.
Scientists estimate that this newly discovered area spans 38,600 square miles, far exceeding the previous record holder, Loki Patera, a lava lake with an area of 7,700 square miles. 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 sulfur and sulfur dioxide.
