Io may be running much hotter than scientists thought
Io, Jupiter’s volcanic moon, has long been treated as one of the most extreme worlds in the solar system. It is covered with volcanic depressions known as paterae, shaped by intense internal heating driven by the gravitational tug-of-war between Jupiter and neighboring moons. Now, a new preprint drawing on data from Juno’s Jupiter InfraRed Auroral Mapper, or JIRAM, argues that researchers may have been significantly underestimating the amount of heat these volcanic systems release.
If the result holds, it would matter well beyond a bookkeeping adjustment. Io’s thermal output is central to how scientists understand the moon’s interior, its magma circulation, its heat transport, and the broader consequences of tidal heating in planetary bodies. A hotter Io would imply that some long-standing estimates of how energy is distributed across its volcanic terrain have missed a substantial portion of the total picture.
Why earlier measurements may have missed the bigger signal
The problem, according to the report, lies in how the volcanoes were observed. Previous estimates relied on infrared measurements concentrated in a single wavelength band, the M-band. That band is very good at detecting the hottest zones, particularly the bright outer rings of lava lakes where exposed magma can reach temperatures up to about 900 kelvin. Those peripheral areas stand out clearly because they are thermally intense and therefore easy to identify as hotspots.
But Io’s paterae are not composed only of these blazing margins. They also include much broader central regions covered by a cooler crust, generally in the 220 to 230 kelvin range. That crust forms as lava exposed to the vacuum of space solidifies and thickens over time, creating an insulating lid above the molten material beneath. While cooler than the perimeter, these central areas occupy far more surface area.
The new argument is that earlier M-band observations were effectively biased toward the hottest, most obvious parts of the volcanoes while overlooking the thermal contribution of the larger, cooler crustal zones. In other words, the most visually dramatic regions may not represent the bulk of the heat budget.
