20-EPN-043: A Systematic Study of Sulfur Ion Radiolysis of Simple Oxide Ices
September 5, 2021

20-EPN-043: A Systematic Study of Sulfur Ion Radiolysis of Simple Oxide Ices.

Visit by Zuzana Kanuchova (virtual participation), Astronomical Institute od Slovak Academy of Sciences (Slovakia) and Duncan Mifsud (in-person participation), University of Kent (UK) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 30 November – 4 December 2020 and 25-29 January 2021

Report Summary: We have implanted 290 keV S+ ions in a variety of simple oxide ices, including CO, CO2, H2O, N2O, O2, and CO:N2O at 20 K, as well as CO2 and H2O at 70 K. Our aim was to determine whether such implantations could result in the formation of sulfur-bearing product molecules, particularly SOwhich has been detected at the surfaces of several icy Solar System moons. 

The performed experiments suffered from initial setbacks in the form of unexpected and significant sputtering of the astrophysical ice analogues during irradiation. In order to mitigate this sputtering, we made use of two different experimental techinques; (i) via simultaneous deposition and irradiation of the ice analogue in cases where we knew gas phase chemistry to be negligible, and (ii) via creation of a very thick (~3-5 μm) ice and a slow rate of implantation. Once these initial problems were solved, we were able to successfully carry out implantations into the six ices mentioned above. 

Our work has indicated that although sulfur-bearing molecules (such as OCS and H2SO4 hydrates) may form as a result of such implantations, SO2 formation was not detected in most experiments, except at high fluence (~1016 ions/cm2) implantations in CO. Such results have important implications for the icy Galilean satellites of Jupiter, suggesting that the SO2 present there may be formed by endogenic processes at the lunar surfaces.

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