20-EPN-049: The Irradiation of Oxygen-Bearing Ices on Top of Pure Elemental Sulphur Layers (former title: Millimetre-Wave Polarimetry of Space Relevant Ices Exposed to Energetic Ions)
Virtual visit by Olivier Auriacombe, Chalmers University of Technology (Sweden), to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 20 June – 4 September 2022
Report Summary: The chemistry of sulphur in icy extra-terrestrial settings such as the dense interstellar medium and the outer Solar System remains poorly constrained. In particular, the chemical routes towards the formation of SO2 ice (and other volatile sulphur-bearing species) is not completely understood, despite the detection of this species in interstellar icy grain mantles, on the surface of Europa, and on comets. We have therefore explored the possibility of forming SO2 ice as a result of the irradiation of oxygen-bearing ices (including O2, CO, CO2, H2O, and CH3OH) deposited on top of pure elemental sulphur layers, both of which are known to exist in the dense interstellar medium and the outer Solar System where radiation chemistry may be engendered by galactic cosmic rays or the solar wind.
Our results demonstrate that SO2 may indeed be produced after the 1 MeV He+ ion irradiation of O2 and CO2 ices deposited on top of elemental sulphur, but not as a result of similar irradiations conducted using CO, H2O, or CH3OH ices. Other volatile radiation product species incorporating sulphur, such as CS2, OCS, and H2SO4, were also detected in different experiments. Our work should therefore contribute to a better understanding of solid-phase sulphur astrochemistry and the role of elemental sulphur in the formation of volatile sulphur-bearing species in icy extra-terrestrial settings.
