NASA's Juno spacecraft has measured subsurface temperatures on Io for the first time, capturing data that reveals the violent thermal landscape beneath the volcanically active moon's crust. During two close flybys, Juno's instruments detected substantial heat in Io's shallow subsurface, confirming that this Jovian moon operates as the solar system's most extreme volcanic forge.
Io's surface churns with over 500 active volcanoes, yet scientists knew little about the thermal dynamics just beneath the visible terrain. Juno's infrared sensors penetrated the outer layers to quantify this subsurface heat, producing measurements that reshape understanding of how Io's internal engine drives its relentless volcanic activity. The moon's tidal heating from Jupiter's gravitational pull compresses and flexes the interior constantly, generating the energy that powers its spectacular eruptions.
The data also revealed that Io's surface is far smoother than expected across much of the moon. Rather than jagged, impact-scarred terrain like the moon or Mercury, Io presents relatively uniform, gently rolling topography punctuated by volcanic features. This smoothness reflects the constant resurfacing that volcanic activity delivers. Lava flows continuously bury older terrain, erasing impact craters and reshaping the landscape on timescales of millions of years rather than billions.
Juno conducted these observations while orbiting Jupiter, using its close approach trajectory to gather high-resolution thermal data. The mission's primary goal focuses on Jupiter itself, studying the gas giant's atmosphere and interior structure. Yet Juno's powerful instrument suite allows it to conduct opportunistic science at the Galilean moons during passages.
These subsurface temperature readings establish a foundation for future missions targeting Io. NASA's upcoming Europa Clipper will launch later this decade to study Jupiter's ocean moon, and future Io-dedicated or