The James Webb Space Telescope (JWST) has revealed fascinating insights into Io's volcanic activity and sulfurous atmosphere. Io, a moon of Jupiter, experiences intense gravitational forces from Jupiter and other Jovian moons, leading to constant stretching and compression. This results in extreme volcanic activity, making Io the most volcanically active body in our solar system. Using the Near Infrared Spectrograph, Imke de Pater and their team made groundbreaking discoveries about Io's volcanoes and atmosphere.
During their initial observation in November 2022, they detected an energetic volcanic eruption near the Kanehekili Fluctus lava flow field. This observation confirmed a 20-year hypothesis, as it revealed the emission of excited sulfur monoxide gas from some volcanoes on Io. Additionally, JWST identified a rise in thermal emissions at the Loki Patera lava lake, caused by the sinking of its solid surface crust into the molten lava beneath.
Nine months later, in August 2023, the researchers had another opportunity to study the same regions. This time, Io was in Jupiter's shadow, allowing for the capture of emissions at wavelengths otherwise obscured by sunlight. The new images showed that lava flows from the 2022 eruption had expanded to cover over 4,300 square kilometers, approximately four times the area covered in 2022. At Loki Patera, a new crust had formed and cooled, consistent with the lake's behavior over the past few decades.
The images also captured sulfur monoxide emissions in Io's atmosphere above Kanehekili Fluctus and two other regions without clear volcanic associations, attributed to 'stealth volcanism.' A significant discovery was the detection of sulfur gas emissions at wavelengths never before observed in Io's atmosphere. Unlike sulfur monoxide, sulfur gas was distributed more evenly across the northern hemisphere.
The data suggests that these sulfur emissions originated from electrons in Io's plasma torus, an area around its orbit with high-charged particles, rather than directly from volcanoes. The angle of JWST's observation and the northern hemisphere's position relative to the plasma torus explained the concentration of detected emissions over the northern hemisphere. These findings, supported by data from the Keck Observatory and the Hubble Space Telescope, indicate a stable plasma torus-atmosphere system over decades.
The research, published in the Journal of Geophysical Research: Planets, opens new avenues for understanding Io's volcanic activity and atmospheric composition. The team's continued exploration of Io promises further revelations about this fascinating moon's geological and atmospheric dynamics.
