NASA’s Juno mission has solved a 44-year mystery about the source of Io’s volcanism, revealing that its eruptions are fueled by localized magma chambers rather than a global magma ocean. Data from Juno’s close flybys of Io in 2023 and 2024 showed tidal flexing—caused by Io’s orbit around Jupiter—generates immense internal heat, melting parts of the moon’s interior. These findings not only reshape our understanding of Io but also have implications for studying other moons and exoplanets.