Juno Detects Largest Known Volcanic Outburst on Jupiter’s Moon Io

During a December 27, 2024 fly-by, Juno’s infrared mapper observed an unprecedented volcanic event on Io in which multiple vents brightened at once across a region spanning about 65,000 square kilometers. The team estimates the eruption liberated on the order of 140 to 260 terawatts, a magnitude well above earlier recorded eruptions on Io and orders higher than typical terrestrial analogs. Crucially, the spatial and temporal synchrony of the hotspots points to linked magma reservoirs beneath the surface rather than isolated, independent volcanoes. Investigators propose that Io’s interior contains extensive porous or interconnected melt regions that can route molten material to many surface vents nearly simultaneously. Not every known vent in the area participated, indicating that distinct sub-surface networks may feed different subsets of volcanoes. The detection relied on Juno’s JIRAM instrument, which, although designed for Jovian auroral and atmospheric studies, proved sensitive enough to map thermal anomalies on a satellite’s surface from tens of thousands of kilometers away. Because Juno is now conducting close encounters with Jupiter’s Galilean moons during its extended mission, follow-up passes will search for fresh lava fields and ash deposits to quantify the eruption’s surface footprint and evolution. The observations challenge simplified models of Io’s magma transport that assume largely isolated conduits and suggest a need to incorporate large-scale connectivity and variable reservoir linkage in interior simulations. Beyond Io, the finding offers a natural laboratory for understanding tidal heating, melt migration, and large-scale volcanic plumbing under extreme tidal stresses. The event also highlights the scientific value of multipurpose instruments on planetary missions: devices optimized for one target can deliver unexpected breakthroughs elsewhere. As teams compare these observations with earlier records and forthcoming imagery, they will refine energy budgets, eruption durations, and the mechanics that allow coordinated activity across hundreds of kilometers. This episode reframes Io not just as the solar system’s most volcanically active body but as a place where global-scale subsurface structures can deliver near-simultaneous volcanic output, with implications for planetary geodynamics and melt transport theory.