Sulfur Ion Implantations Into Condensed CO 2 : Implications for Europa

• Published in: Geophysical research letters 2022-12, Vol.49 (24)
• Main Authors: Mifsud, D. V., Kaňuchová, Z., Herczku, P., Juhász, Z., Kovács, S. T. S., Lakatos, G., Rahul, K. K., Rácz, R., Sulik, B., Biri, S., Rajta, I., Vajda, I., Ioppolo, S., McCullough, R. W., Mason, N. J.
• Format: Article
• Language: English
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL100698

The ubiquity of sulfur ions within the Jovian magnetosphere has led to suggestions that the implantation of these ions into the surface of Europa may lead to the formation of SO 2 . However, previous studies on the implantation of sulfur ions into H 2 O ice (the dominant species on the Europan surface) have failed to detect SO 2 formation. Other studies concerned with similar implantations into CO 2 ice, which is also known to exist on Europa, have offered seemingly conflicting results. In this letter, we describe the results of a study on the implantation of 290 keV S + ions into condensed CO 2 at 20 and 70 K. Our results demonstrate that SO 2 is observed after implantation at 20 K, but not at the Europa‐relevant temperature of 70 K. We conclude that this process is likely not a reasonable mechanism for SO 2 formation on Europa, and that other mechanisms should be explored instead. SO 2 ice is known to exist at the surface of one of Jupiter's moons; Europa. However, the method by which this ice forms is still uncertain. Due to the orbit of Europa being within the giant magnetosphere of Jupiter, it has been proposed that sulfur ions within the magnetosphere could implant into the cold surface ices on Europa and subsequently react to form SO 2 . However, laboratory experiments looking into the implantation of such ions into H 2 O ice (the dominant ice on Europa's surface) and CO 2 ice have either failed to yield SO 2 or have provided inconclusive results. We have therefore performed an experiment in which we have implanted high‐energy sulfur ions into CO 2 ice at two temperatures. Our results indicate that such implantations are unlikely to be the mechanism by which the SO 2 on Europa is formed, and that other chemical processes should be considered instead. Sulfur ions were implanted into CO 2 ices at 20 and 70 K to simulate Jovian magnetospheric radiation chemistry at the surface of Europa SO 2 was observed to be among the radiolytic products at 20 K, but not at the more Europa‐relevant temperature of 70 K Alternative explanations for the formation of SO 2 on the surface of Europa should be considered