A study proposes that Jupiter's moon Io has undergone continual transformation due to volcanic eruptions for billions of years — potentially spanning the entire 4.57-billion-year history of the Solar System.
Published on April 18 in the journal Science, the research outcomes carry significant implications for the quest for alien life and for comprehending volcanic bodies like moons and planets, including Earth.
Io stands as the most volcanically active region in the Solar System, boasting hundreds of volcanic structures on its surface. This characteristic poses challenges to unraveling the moon's past. The incessant flow of molten lava and ash, precipitated by volcanic emissions, continuously resurfaces the moon, concealing any tangible traces of its geological evolution. The volcanic phenomenon stems from Io's orbital dance around Jupiter, synchronized with the neighboring moons Europa and Ganymede. Gravitational tugs between these celestial bodies elongate Io's orbit, subjecting it to periodic compression, generating friction and heating within the moon's core.
Sulfur studies
When Io's volcanoes erupt, they discharge sulfur-laden gases into the atmosphere. Katherine de Kleer, a planetary scientist at the California Institute of Technology in Pasadena and a co-author of the study, elucidates that this sulfur serves as "a marker for investigating Io's extensive evolution".
According to de Kleer, the ratio between two sulfur isotopes — sulfur-32 and the marginally denser sulfur-34 — remains relatively consistent throughout the Solar System. Utilizing the Atacama Large Millimeter/submillimeter Array, a radio telescope situated in Chile, she and her colleagues gauged sulfur emissions within Io's atmosphere and computed the ratio between these isotopes.
Their observations unveiled that Io has shed 94–99% of its initial sulfur reservoir. At the atmospheric zenith, the proportion of sulfur isotopes leans towards the lighter variant, and these sulfur-32-enriched gases are "being stripped away from the upper atmosphere at a rate of approximately one ton per second," de Kleer remarks. Across billions of years, this discrepancy has accumulated, resulting in a shift towards a heavier sulfur composition for Io overall. By extrapolating from the ongoing loss of lighter sulfur, the researchers estimated that Io's volcanic eruptions have persisted for the majority of its existence.
Implications for Europa
The study also corroborates theories indicating that Io, Europa, and Ganymede have been ensnared in the same orbital choreography since the inception of the Solar System or shortly thereafter. Katherine de Kleer notes that this suggests Europa may have undergone comparable heating for a similar duration. Europa stands as a promising contender for harboring life within the Solar System. The prolonged heating over billions of years "would augment the habitability of Europa's subsurface ocean in the long run."
The scorching, fluid lava on Io surpasses the temperature of what is currently found on Earth. "However, it is believed to resemble the magma composition prevalent in Earth's early epochs, characterized by colossal volcanic events depositing extensive lava flows rapidly," de Kleer explains. "Io's volcanic activity might offer insight into the mechanisms of volcanism and Earth's primordial era."
Jani Radebaugh, a planetary geologist at Brigham Young University in Provo, Utah, embraces the study's findings. "The notion that Io could exhibit even more remarkable — even more extreme — volcanic behavior is astounding," she remarks. "These findings underscore the importance of further exploration of Io in unraveling the enigmatic histories of other volcanic worlds, including our own planet."
