TA Visit: Searching for the mysterious source of sulphur dioxide on Jupiter’s icy moons
This week, Duncan Mifsud, PhD student at the Centre for Astrophysics and Planetary Science of the University of Kent, and Zuzana Kanuchova of INAF Osservatorio Astronomico di Roma, will be taking part in a Transnational Access (TA) visit funded by the Europlanet 2024 Research Infrastructure (RI). If you would like free access to any of the TA planetary field analogues and laboratory facilities offered by Europlanet 2024 RI, the Second TA Call for Applications is now open until 6 January 2021.
Our visit is scheduled to take place between 30 November and 11 December at the Ice Chamber for Astrophysics-Astrochemistry (ICA) in Debrecen, Hungary. The study involves implantation of high-energy sulphur ions in pure frozen carbon and nitrogen oxides at several temperatures between 20 and 80 K (-253 to -193 degrees Celsius).
Carbon oxide ices are known to exist on the surfaces of Europa and Ganymede, which are two of the most interesting moons of Jupiter due to their hypothesised large, habitable subsurface oceans. These moons are thus prime candidates for astrobiological studies. They do, however, orbit within Jupiter’s giant magnetosphere, and so are continuously subjected to bombardment by high-energy ions and electrons.
Sulphur dioxide (SO2) has also been detected at the surface of these moons, although it is not certain where the sulphur atoms in these molecules are sourced from. In our experiment, we shall be testing the hypothesis that sulphur magnetospheric ions can implant into carbon oxide ices at the Europan and Ganymedean surfaces and subsequently react to form SO2. Previous experimental and computational studies have provided inconclusive results, and so we hope that our results will be a step forward in determining whether the observed SO2 is formed primarily as a result of these sulphur ion implantations, or alternatively via other reactions between molecules native to the icy moons.
We have also proposed to implant sulphur ions in nitrogen oxide ices to determine if any new molecules are formed. To the best of our knowledge, such an experiment has yet to be performed. We are particularly interested in whether or not the molecule Nitrogen Sulphide (NS) can be formed, as this molecule has been hypothesised to be a reservoir of sulphur in dense interstellar molecular clouds, which are known to be severely depleted in sulphur compared to the total cosmic abundance.
We will determine the formation of new molecules by monitoring the physico-chemical changes within the ice using Fourier Transform Infrared (FTIR) spectroscopy, which will allow us to quantitatively determine the nature of molecules present within the ice both before and after sulphur ion implantation.
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