NASA’s Juno spacecraft has captured what scientists are calling the most intense volcanic eruption ever recorded on Io, Jupiter’s most volcanic moon. The event, observed during a recent flyby, revealed a massive hotspot near Io’s south pole, an eruption so powerful that it outshines all volcanic activity on Earth.
Juno’s Mission Extended Beyond Jupiter
Originally designed to study Jupiter’s atmosphere, magnetosphere, and deep interior, Juno has exceeded expectations since arriving at the gas giant in 2016. With its extended mission, NASA has redirected the spacecraft’s attention toward three of Jupiter’s major moons—Ganymede, Europa, and Io—allowing scientists to gather unprecedented data on these celestial bodies.
Io, the innermost of Jupiter’s four Galilean moons, is of particular interest due to its extreme volcanic activity. With over 400 active volcanoes, it holds the title of the most geologically active world in the Solar System.
However, even for a moon accustomed to dramatic eruptions, the latest hotspot detection by Juno’s infrared imager (JIRAM) was unexpected in its sheer intensity.
A Volcanic Hotspot Larger Than Lake Superior
During its December 27, 2024, flyby, Juno’s JIRAM instrument detected an enormous volcanic hotspot at Io’s southern hemisphere, larger than Lake Superior, the biggest freshwater lake on Earth. The eruption released over 80 trillion watts of energy, making it the most powerful volcanic event ever observed on Io.
Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, described the discovery as “a massive hot spot – in Io’s southern hemisphere so strong that it saturated our detector.”
Scientists now believe that the eruption originates from a vast subsurface magma system, potentially connected to multiple volcanic chambers beneath Io’s surface.
The Mechanics Behind Io’s Extreme Volcanism
Unlike Earth’s plate tectonics, which drive most volcanic activity on our planet, Io’s eruptions are fueled by an entirely different mechanism: tidal heating. As Io orbits Jupiter in an elliptical path, the moon is constantly stretched and compressed by the massive planet’s gravity. This gravitational tug-of-war generates intense friction within Io’s interior, melting its rocky mantle and creating an unrelenting cycle of eruptions.
Io’s neighboring moons, Europa and Ganymede, further contribute to this gravitational tugging, intensifying the moon’s internal heat. The result? A landscape covered in molten lava lakes, towering plumes of volcanic ash, and constantly shifting surface features.
Io’s Volcanic History Rewritten
The latest hotspot dwarfs Loki Patera, Io’s previously most famous volcanic feature—a lava lake 126 miles (202 km) in diameter that has been observed since the 1970s. The new eruption site spans an estimated 40,000 square miles (100,000 sq km), making it the largest known active volcanic region on the moon.
Scientists had previously detected Io’s volcanic outbursts from Earth-based telescopes and space probes, but Juno’s close-range infrared imaging provides direct, high-resolution evidence of how these eruptions reshape the moon’s surface in real time.
What’s Next For Juno And Io?
Juno is set to make another flyby of Io on March 3, 2025, allowing NASA to track changes to the moon’s surface over time. Given the scale of the eruption, researchers expect to see long-lasting deposits of pyroclastic material, lava flows, and sulfur-rich layers spreading across the moon.
Understanding Io’s volcanic activity isn’t just about studying one moon—it provides valuable insight into how tidal heating influences geologic activity on other celestial bodies. This process could play a key role in shaping exoplanets orbiting giant stars or icy moons like Europa and Enceladus, which are suspected to host subsurface oceans.
As Juno continues its mission, scientists are eager to uncover more about Io’s volcanic history, the movement of magma beneath its surface, and how its activity interacts with Jupiter’s magnetosphere. Each new flyby brings fresh surprises, reinforcing Io’s status as one of the most extreme and dynamic worlds in the Solar System.
With the largest volcanic hotspot ever observed, Io has once again reminded us that planetary science is full of surprises—and that the Solar System still has many secrets left to unveil.
