Scientists have discovered that Jupiter’s volcanic moon Io is emitting far more heat than previously estimated, challenging existing theories about its internal structure. Data from NASA’s Juno spacecraft, while not lacking in detail, had been misinterpreted, leading to a significant underestimate of Io’s fiery output. This revelation paints a hotter, more complex picture of this fascinating celestial body.
The root of the misconception lay in how scientists analyzed data from Juno’s Jovian InfraRed Auroral Mapper (JIRAM). Previous studies focused primarily on a specific infrared light band known as the M-band, which primarily captures extremely high temperatures. This approach, like judging a bonfire solely by its flames and ignoring the cooler embers, provided an incomplete picture of Io’s thermal activity.
“The problem is that this band is sensitive only to the highest temperatures, and therefore tends to favor the most incandescent areas of volcanoes, neglecting the colder but much more extensive ones,” explains Federico Tosi, lead researcher at Italy’s National Institute for Astrophysics (INAF). “In practice, it’s like estimating the brightness of a bonfire by observing only the flames and not the surrounding embers: you capture the brightest spots, but you don’t measure all the energy actually emitted.”
Revisiting the Juno data with a broader perspective revealed that Io’s volcanic heat is concentrated in surprisingly few locations. Around half of the moon’s radiated energy comes from just 17 out of its 266 known volcanic sources. These volcanoes, unlike previously imagined, aren’t uniformly hot; they exhibit a glowing outer ring surrounding a cooler, solid core. While these hotter rings appear brighter in the M-band, the vast expanse of their cooler crusts contribute significantly more to the overall heat output.
This finding has significant implications for theories about Io’s interior. It suggests that a global lava lake, previously theorized as a possible explanation for Io’s intense volcanism, may not be present beneath the surface.
“When this ‘hidden’ component is also considered, the actual heat flux is up to hundreds of times higher than that calculated by analyzing the M-band alone,” says Tosi. “This is a significant leap, because it changes the scale of the satellite’s [Io’s] energy balance.”
While Juno’s flybys in 2023 and 2024 provided unprecedented views of Io, its orbit won’t allow for such close approaches in the future. Future missions like ESA’s Juice and NASA’s Europa Clipper, focused primarily on other Jovian moons, lack the resolution to match Juno’s detailed observations.
However, this study provides a crucial framework for interpreting even more distant observations of Io. It also highlights the need for future missions specifically dedicated to exploring this enigmatic moon in greater detail. Only then can scientists fully unravel the mysteries behind the most volcanically active body in our solar system.
