Author name: Ashley Gerard Davies

Driven by tidal heating, Io’s extreme volcanism has created a young, impact crater–free surface dominated by hundreds of active volcanic centres. From these volcanoes erupt voluminous, low-viscosity, high-temperature silicate lavas. Volcanic plumes, from venting gas and mobilised surface ices (primarily SO2 and S), contribute to Io’s thin atmosphere. Away from volcanoes, SO2 ice on the surface alternately sublimes during the daytime and condenses during eclipses and at night, resulting in a strong day/night atmospheric dichotomy. Sunlight and radiation bombardment at high altitude breaks the gas molecules apart, leading to the formation of SO, O, O2, S, K, Na, and Cl. These atoms reside as both neutral and charged particles in clouds that are found along Io’s orbit around Jupiter.