In the 60s and 70s ground-based observations–many made here in Boulder–indicated that Jupiter’s moon Io was peculiar. The innermost Galilean moon triggered radio emissions, appeared to brighten on emerging from eclipse, and optical emissions indicated clouds of sodium atoms and sulfur ions around Io. Further hints of Io’s peculiarity were indicated by the first spacecrafts to visit Jupiter, the Pioneers in 1973-1974. Such strange behavior became understandable when Voyager 1 and 2 flybys of Jupiter in 1979 revealed Io’s remarkable volcanism. When Voyager 1 passed close to Io, perturbations in the plasma and magnetic field showed Io generating magnetic waves propagating away from the moon, carrying electrical currents towards Jupiter. Over the past 40 years the Io-Jupiter system has been explored with telescopes and spacecraft but a major breakthrough came this year when the Juno spacecraft flew directly through Io’s current system.
In this presentation, LASP research scientist and retired CU professor of astrophysical and planetary sciences, Fran Bagenal, will discuss how Io’s strange behavior has been revealed over the years and present the latest results from Juno.