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Insights into volcanism on Io using sulfur isotopes

Ery Hughes 1,2, Katherine de Kleer2, John Eiler2, Francis Nimmo3, Kathleen Mandt4, Amy Hofmann5, Statia Luszcz-Cook6

  • Affiliations: 1Volcanology, Te Pῡ Ao GNS Science, Lower Hutt, Aotearoa New Zealand; 2Division of Geological and Planetary Sciences, Caltech, Pasadena, CA USA; 3Department of Earth & Planetary Sciences, UC Santa Cruz, Santa Cruz, CA USA; 4NASA Goddard Space Flight Centre, Greenbelt, MD USA; 5JPL, Caltech, Pasadena, CA USA; 6Liberal Studies, New York University, New York, NY USA

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 255

  • Programme No: 1.4.14

  • Theme 1 > Session 4

Abstract

Jupiter's moon Io is the most volcanically active body in our Solar System, but it is difficult to constrain when volcanism started on Io because Io's dynamic atmosphere and high resurfacing rates leave it with a young surface. Io's volcanoes emit vast quantities of sulfur into its atmosphere, which is either lost to space or buried in the crust and recycled. We combine a numerical model of sulfur's isotope cycle with telescope measurements of the sulfur isotope composition of SO2 in Io's atmosphere to model the evolution of sulfur isotopes over time and therefore how long volcanism has been occurring. The highly isotopically enriched signature of Io's atmosphere (δ34S = +347 ± 86 ‰) indicates Io's volcanoes have been active for most its 4.5-billion-year history. Although volcanic processes are not the main cause of isotopic fractionation on Io, volcanism is crucial to cycling sulfur between the atmosphere and the mantle. This means Io's sulfur cycle is well approximated by Rayleigh distillation, enabling extreme isotopic enrichments over time. Also, the heat from volcanism drives SO2 reaction with crustal rocks such that sulfur can be locked into the crust and founder into the mantle. We predict that volcanic plumes on Io may have variable δ34S depending on whether they are sourced from mantle magmas or remobilising sulfur in the crust. Observations of atmospheric variations in δ34S with time and/or location could reveal the average mantle melting rate and hence whether the current volcanism rate is anomalous compared to Io's long-term average.