Io looks cold and quiet from far away. But it is the most volcanic world in our solar system. New data from Juno show heat below its surface for the first time. (nasa.gov)
The secret begins with Jupiter’s strong gravity. It pulls Io as the moon travels around the planet. The pull changes because Io’s path is not a perfect circle. So the small moon is stretched and squeezed again and again. This movement causes friction inside it. Friction makes heat when materials move against each other. Scientists call this process tidal heating.
Juno used microwaves to look several meters under the ground. Microwaves are energy waves that can pass through some materials. The machine found warmer ground below the cold surface. This heat may rise slowly through the crust. The crust is the moon’s hard outside layer. Another idea is that young lava stays warm under cooled rock. (nasa.gov)
Think of hot soup with a cool skin. The top feels cooler, but heat still rises from below. Io may work in a similar way. Its surface hides a hot and active world.










