Io, a moon of Jupiter, is caught in a gravitational tug-of-war, and this intense struggle has a fiery consequence. The heat generated from this cosmic wrestling match has turned Io into a volcanic powerhouse, making it the most volcanically active body in our solar system. But here’s the twist: the James Webb Space Telescope (JWST) has just revealed some surprising secrets about this fiery moon.
In 2022, researchers, led by Imke de Pater, used JWST’s Near Infrared Spectrograph to observe Io and made groundbreaking discoveries. They witnessed an incredibly powerful volcanic eruption near the Kanehekili Fluctus lava flow field, and for the first time, they confirmed the presence of an excited form of sulfur monoxide gas, something they had hypothesized 20 years ago. And that’s not all—JWST also spotted increased thermal emissions at Loki Patera, a massive lava lake, caused by its solid crust sinking into molten lava.
Fast forward to 2023, and the researchers got another chance to observe Io. This time, they noticed something intriguing. The lava flows from the 2022 eruption had expanded significantly, covering over 4,300 square kilometers. And at Loki Patera, a new crust had formed, a familiar pattern in its behavior. But the real surprise was in the atmosphere. JWST detected sulfur monoxide emissions above Kanehekili Fluctus and two other regions, suggesting ‘stealth volcanism’. And for the first time, sulfur gas emissions were observed at wavelengths never seen before in Io’s atmosphere, spreading across the northern hemisphere.
Here’s where it gets controversial: these sulfur emissions didn’t come from volcanic eruptions but were produced by electrons from Io’s plasma torus, an area with high charged particle activity. These electrons penetrated Io’s sulfur dioxide atmosphere, exciting sulfur atoms. The angle of JWST’s observation and the northern hemisphere’s position relative to the plasma torus explain the concentrated emissions. And this isn’t a one-time event; data from other observatories suggest this plasma torus-atmosphere interaction has been stable for decades.
This research, published in the Journal of Geophysical Research: Planets, offers a fascinating glimpse into Io’s volcanic nature and its unique atmosphere. It’s a reminder that even in the vastness of space, there are hidden complexities waiting to be discovered. And who knows what other secrets Io might reveal in the future?