Dusty-Gas Simulations of Io's plumes

Io is the innermost Galilean satellite of Jupiter and is the most volcanically active body

in our solar system. Its largest volcanic plumes can rise up to several hundred kilometers

above the surface. These volcanic plumes are one known source of Io's SO₂ atmosphere,

but additionally the surface of the moon is covered with surface frost which sublimates in

sunlight and condenses during the night and when Io enters eclipse behind Jupiter. There-

fore, Io's atmosphere is a result of the combination of volcanism and sublimation, but it is

unknown exactly how these processes work together to create the observed atmosphere. We

are investigating the flow of SO₂ gas from the source of a plume, into the umbrella-shaped

canopy, and eventually back onto the surface. Additionally, we also study the interaction of

the plumes with an ambient sublimation atmosphere. Both, the gas flow of the plume and

the sublimation atmosphere, are modelled using the Direct Simulation Monte Carlo (DSMC)

method first utilised by G.A.Bird. The DSMC method is the most suitable for this case

because the gas dynamics can be modeled over a great range of gas densities which is es-

pecially important for rarefied gas flows at high altitudes and on the night side of Io. Our

DSMC code is multi-species and also allows the simulation of gas emission from lava lakes

that may also contribution to the atmosphere. Finally, we are also able to implement dust

particles in the plume and analyse the effect for different dust sizes. Our goal is to gain a

better understanding of the plume structure, the interaction with the ambient atmosphere

and the overall contribution of different processes to Io's atmosphere in preparation for future

missions such as JUICE, Europa Clipper and a possible future Io Volcano Observer.