Io’s Escaping Atmosphere: Continuing the Legacy of Surprise

The discovery of Io and her fellow Medicean Stars clearly altered the course of science as a whole. It is equally clear that the discovery of Io’s tidal heating has altered the course of planetary science. One of the most directly observable consequences of Io’s tidal heating is the prodigious escape of a ton per second of volcanically-supplied gases. I will review how studies of Io’s escaping atmosphere since 1972 have advanced our deep understanding of Io itself, and helped formulate our perspective on planetary evolution in our solar system and beyond.