While primarily a Jupiter mission, NASA’s Juno spacecraft takes any opportunity it gets to look at the gas giant’s moons. In late December, Io was close enough to look at with four of Juno’s cameras. Juno managed to capture images of a volcanic plume in action.
Even at a distance of 300,000 kilometers away from Juno, we can easily make out the plume along the terminator (day/night line). The active area on Io’s surface is shrouded in darkness, but the plume reaches a high enough altitude for sunlight to hit it.
Scott Bolton, principal investigator of the Juno mission, described the pictures as “quite the New Year’s present.”
“We knew we were breaking new ground with a multi-spectral campaign to view Io’s polar region, but no one expected we would get so lucky as to see an active volcanic plume shooting material off the moon’s surface,” said Bolton.
Soon after the above picture was taken, Io fell into Jupiter’s shadow. But Juno managed to keep observing it thanks to the Stellar Reference Unit (SRU). A little moonlight from nearby Europa was enough for the SRU to capture this image.
“As a low-light camera designed to track the stars, the SRU can only observe Io under very dimly lit conditions. Dec. 21 gave us a unique opportunity to observe Io’s volcanic activity with the SRU using only Europa’s moonlight as our lightbulb,” said Heidi Becker, lead of Juno’s Radiation Monitoring Investigation, at NASA’s Jet Propulsion Laboratory.
The plume is still visible inside the smaller white circle on the image. That brighter feature to its left is believed to be a “penetrating radiation signature” according to the Southwest Research Institute. Io’s volcanic eruptions are helping fuel Jupiter’s magnetosphere.
NASA’s Juno probe wrapped up its 16th science pass on December 21. Every 53 days, it swings in close to gather science from Jupiter. That 16th flyby marks the halfway point for the spacecraft’s mission.
Raw images from the 16th science pass are up over at Juno’s official website. If you have Photoshop, why don’t you try processing an image? Who knows, NASA might feature it. Here’s a short video that can help you get started.