Jupiter’s moon Io, through an analysis of the sulfur and chlorine isotopes present in its atmosphere, offers information about its continuous volcanic activity spanning the entire 4.57 billion-year history of the Solar System. It is worth mentioning that Io stands out as the most volcanically active celestial body in the Solar System.
The volcanic phenomena observed on Io are attributed to the effects of tidal heating resulting from friction generated within the moon due to gravitational forces exerted by Jupiter and neighboring moons such as Europa and Ganymede. However, there remains a significant gap in our understanding of the duration for which this moon sustained such extensive volcanic activity. The ongoing volcanic processes on Io contribute to a dynamic surface that undergoes continuous reshaping, thus presenting a geological chronicle that mainly reflects the most recent millions of years of its evolution. Investigating stable isotopic measurements of volatile elements in Io’s atmosphere holds promise for unraveling the volcanic history imprinted on this enigmatic moon.
A prominent volcanic fluids geochemist at GNS Science, Dr. Ery Hughes, affirms Io’s status as an exceptionally active moon of Jupiter, characterized by intense volcanic manifestations. Notably, Io’s orbital resonance with the larger moons Europa and Ganymede plays a key role in shaping its volcanic landscape. This resonance pattern determines that for each orbit completed by Ganymede around Jupiter, Europa completes two orbits and Io completes four orbits.
Consequently, Io’s elliptical orbit around Jupiter, influenced by the different gravitational forces exerted cyclically by the neighboring moons, triggers tidal heating mechanisms in the interior of Io, similar to the tidal phenomena observed on Earth due to the gravitational pull of the Moon.
However, the temporal extent of Io’s volcanic activity remains a subject of uncertainty, along with questions about possible variations in this volcanic behavior over Io’s extensive 4.57 billion year history. The sheer magnitude of volcanism on Io results in a constant renewal of its surface, erasing substantial traces of its geological past. Fortunately, investigations focused on sulfur and its isotopic compositions offer a window into Io’s volcanic legacy.
In recent research, Dr. Hughes, in collaboration with Caltech researcher Dr. Katherine de Kleer and her scientific cohort, employed the Atacama Large Millimeter/submillimeter Array (ALMA) to examine the gases present in Io’s sparse atmosphere. . Through this observational campaign, researchers aimed to discern the stable isotopic ratios of sulfur- and chlorine-containing molecules in Io’s atmospheric composition.
The researchers determined that both elements exhibit a significantly high concentration of heavy isotopes compared to typical values observed in the solar system. This phenomenon arises from the depletion of lighter isotopes in the upper atmosphere, as materials undergo continuous recycling processes between Io’s interior and its atmospheric layers.
Study results suggest that Io eliminated approximately 94% to 99% of the sulfur involved in this continuous outgassing and recycling mechanism. This deduction implies that Io must have sustained its current level of volcanic activity throughout its existence. According to Dr. Hughes, the release of sulfur from Io’s interior into the atmosphere occurs due to tidal heating generated by volcanic activity.
A portion of the sulfur escapes into space due to the influence of Jupiter’s magnetosphere, characterized by a multitude of charged particles orbiting Jupiter and impacting Io’s atmosphere incessantly. The remaining sulfur is eventually reabsorbed into Io’s interior, setting the stage for the cyclical process to resume. During this cycle, isotopes of the same element exhibit distinct weight characteristics, leading to subtle variations in their behavior.
Notably, the sulfur lost to space by Io tends to be somewhat isotopically lighter than the sulfur that is recycled back into Io’s interior, causing the sulfur content on Io to become progressively heavier over time. The high presence of isotopically heavy sulfur in Io’s atmosphere, exceeding the solar system average, suggests that Io has likely eliminated almost all of its original sulfur.
Through numerical simulations, it is inferred that Io has remained volcanically active for billions of years, indicating that tidal heating and orbital resonance have prevailed throughout most of Io’s history. In the future, the fluctuation in the sulfur isotopic composition of Io’s atmosphere could serve as a valuable indicator for determining the average rate of tidal heating experienced by Io.
Source:
Study: Jupiter’s Moon Io Has Been Volcanically Active for All of Its History
