Escape mechanisms from Io’s atmosphere

The enormous tidal forces exerted by Jupiter on its moon Io trigger the strongest volcanic activity within the whole solar system. This volcanism feeds a tenuous and variable atmosphere – mostly consisting of sulfur dioxide. The structure of Io’s atmospheric density is dominated by three primal circumstances: The density is increased in the vicinity of volcanic plumes, it decreases towards the poles and it collapses on the night side. This means, the atmosphere is sublimation-driven. Sulfur dioxide freezes out in absence of solar radiation and sublimates when it enters sunlight. ALMA Observations of Io entering eclipse and coming out of it confirmed this atmospheric dynamic. Furthermore, Io loses around 1000 kg s-1 of material to its environment and is the main particle source for the vast and dynamic Jovian magnetosphere, causing several more effects, when the magnetospheric plasma interacts with the moon’s atmosphere and ionosphere. The neutral escape rate of Io can be related to several effects: Direct volcanic outgassing, thermal escape, photo-chemistrytriggered escape and sputtering, while sputtering from magnetospheric ions with neutral sulfur dioxide molecules is the most prominent part