Speaker
Description
The cycling of sulphur on the surfaces of Jupiter’s Galilean moons (i.e., Io, Europa, Ganymede, and Callisto) is a key process that may be directly linked to the putative habitability of these moons. This process is largely driven by ionising radiation from Jupiter’s sulphur-rich magnetosphere. Despite the astrochemical and astrobiological importance of sulphur cycling and chemistry on the surfaces of the Galilean moons, there is still much that remains unknown regarding this radiation-driven chemistry. For instance, the source of the solid sulphur dioxide (SO$_2$) observed on the surfaces of Europa and Ganymede is still not known with any certainty, despite the first detection of this species on these moons having been made $\sim$45 years ago. Moreover, the physical and chemical processes involving this solid surface SO$_2$ that are triggered by its interaction with magnetospheric radiation have yet to be accurately quantified, therefore limiting our understanding of sulphur surface and near-surface cycling (and its astrobiological implications) on the Galilean moons.
In this presentation, I will outline recent experimental work performed in the Space Chemistry Group at the HUN-REN Atommagkutató Intézet aimed at addressing some of the unresolved questions regarding the radiation-driven cycling of sulphur on the Galilean moons. Following a contextual introduction to the problem, experiments that were performed to test whether the implantation of sulphur ions from Jupiter’s magnetosphere into the surface ices of Europa and Ganymede could contribute to the SO$_2$ observed there, will be described. This will be followed by a discussion on an alternative mechanism for the radiolytic synthesis of SO$_2$, namely the irradiation of icy surface components in the presence of elemental sulphur, and experiments carried out to determine whether such a mechanism is reasonable in the context of Europa and Ganymede. Finally, new (preliminary) results on the physical and chemical processes triggered in solid SO$_2$ at low temperatures as a result of its interaction with ionising radiation will be shared.