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, causing it to stretch and compress. This dynamic interaction generates heat, leading to volcanic eruptions that make Io the most volcanically active body in our solar system. Imke de Pater and their team utilized the JWST's Near Infrared Spectrograph to study Io's volcanoes and atmosphere, making groundbreaking discoveries.
In November 2022, the researchers observed an extremely energetic volcanic eruption near the Kanehekili Fluctus lava flow field. They discovered that some Io volcanoes emit an excited form of sulfur monoxide gas, confirming a hypothesis they had held for two decades. Additionally, the JWST detected increased thermal emissions at the Loki Patera lava lake, caused by the lake's solid surface crust sinking into the molten lava beneath.
Nine months later, in August 2023, the team had another opportunity to study the same regions. Io was in Jupiter's shadow, allowing for observations at wavelengths that would otherwise be obscured by sunlight. The new images revealed that lava flows from the 2022 eruption had spread over 4,300 square kilometers, approximately four times the area covered in 2022. A new crust had formed and cooled at Loki Patera, consistent with the lake's behavior over the past few decades.
The 2023 images also captured sulfur monoxide emissions 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 part of the northern hemisphere. The data suggests that these sulfur emissions originated from electrons in Io's plasma torus, an area with high-charged particles, rather than being spewed 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. The findings, supported by data from the Keck Observatory and the Hubble Space Telescope, indicate that the plasma torus-atmosphere system remains stable over decades. The research is published in the Journal of Geophysical Research: Planets and invites further exploration of Io's volcanic phenomena.
