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Title: Using Io's Sulfur Isotope Cycle to Understand the History of Tidal Heating
Abstract Stable isotope fractionation of sulfur offers a window into Io's tidal heating history, which is difficult to constrain because Io's dynamic atmosphere and high resurfacing rates leave it with a young surface. We constructed a numerical model to describe the fluxes in Io's sulfur cycle using literature constraints on rates and isotopic fractionations of relevant processes. Combining our numerical model with measurements of the34S/32S ratio in Io's atmosphere, we constrain the rates for the processes that move sulfur between reservoirs and model the evolution of sulfur isotopes over time. Gravitational stratification of SO2in the upper atmosphere, leading to a decrease in34S/32S with increasing altitude, is the main cause of sulfur isotopic fractionation associated with loss to space. Efficient recycling of the atmospheric escape residue into the interior is required to explain the34S/32S enrichment magnitude measured in the modern atmosphere. We hypothesize this recycling occurs by SO2surface frost burial and SO2reaction with crustal rocks, which founder into the mantle and/or mix with mantle‐derived magmas as they ascend. Therefore, we predict that magmatic SO2plumes vented from the mantle to the atmosphere will have lower34S/32S than the ambient atmosphere, yet are still significantly enriched compared to solar‐system average sulfur. Observations of atmospheric variations in34S/32S with time and/or location could reveal the average mantle melting rate and hence whether the current tidal heating rate is anomalous compared to Io's long‐term average. Our modeling suggests that tides have heated Io for >1.6 Gyr if Io today is representative of past Io.  more » « less
Award ID(s):
2238344
PAR ID:
10533477
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
American Geophysical Union
Date Published:
Journal Name:
Journal of Geophysical Research: Planets
Volume:
129
Issue:
4
ISSN:
2169-9097
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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