One of the most intriguing problems in the study of planetary magnetospheres is the electrodynamic interaction between Io, a satellite of Jupiter, and the planet's magnetosphere. The first indication of this unique relationship was found in remote observations of radio emission from Jupiter's magnetosphere, first detected in 1955. Observations of Jovian decameter radiation (DAM) at Earth had established a correlation between the probability of observation of DAM and the position of Io in its orbit about Jupiter. Io's influence on the generation of Jovian DAM was attributed to the workings of an electric generator of enormous scale [Goldreich and Lynden-Bell, 1969]. Now, images of Jupiter's disc reveal a localized infrared emission feature associated with this interaction (Figure 1).