The grandfather of active geologic processes in our solar system, which now seem more commonplace than not with active plumes on Enceladus and tantalizingly on Europa, was Io and its volcanoes. Io is host to hundreds of active volcanoes, large and small, and the plume fallout from these eruptions leads to the coloration of its surface and a tenuous atmosphere of sulfur dioxide. Like Europa and other satellite atmospheres, studying these atmospheres helps us to understand the nature of its surface and the interactions with its magnetosphere. However, after more than 30 years of investigating Io, a number of questions still remain about the precious nature, distribution and time variations of the atmosphere.
One of these mysteries is the question of atmospheric support. Two primary sources of SO2 are likely to contribute to the continued replenishment of Io’s atmosphere; the volcanoes and the frost on the surface. Since volcanism is the ultimate source of the atmosphere, perhaps the entire atmosphere is solely supported by the plume emissions of SO2. On the other hand, observations of the density of the atmosphere (in the nanobar range) and the surface temperature show the atmosphere could be supported entirely by vapor pressure equilibrium of the vast reservoir of SO2 frost on the surface.
This talk will tell the story of Io and its enigmatic volcanism through the eyes of its atmosphere. From the ultraviolet to the mid-infrared, from ground-based telescopes to spacecraft flybys, we will review what we know about Io’s SO2 atmosphere, some of the mysteries concerning atmospheric support mechanisms, and how we might better understand resolve these issues in the future.