On March 1, 2023, NASA’s Juno spacecraft flew past Jupiter’s moon Io, coming within 51,500 km (32,030 miles) of the innermost and third largest of the four Galilean moons. The stunning new images offer the best and most detailed view of the most volcanic moon in our solar system since the New Horizons mission flew by Io and the Jovian system on its way to Pluto in 2006.
Jupiter’s moon Io as seen by the JunoCam instrument on Juno on March 1, 2023. Credit: NASA/JPL-Caltech/SwRI/MSSS/ edited by Kevin M. Gill.
Sure, Io still looks like a pizza. The mottled and colorful surface is from volcanic activity, with hundreds of vents and calderas on the surface creating a variety of features. Volcanic plumes and lava flows above the surface show up in all sorts of colors, from red and yellow to orange and black. Some of the lava “flows” stretch for hundreds of kilometers.
In its expanded mission, Juno has now orbited Jupiter 49 times and is on course to study several of Jupiter’s moons. This latest flyby of Io was the third of nine flybys of the volcanic moon over the next year, with the first occurring in December 2022. An upcoming flyby next year on February 3, 2024 will come as close as 1,500 km (930 miles) from Io.
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Jason Perry, an Io observing expert who has worked with the Cassini, Galileo, and HiRISE imaging teams, said on Twitter that his first looks at these images show some subtle changes from the New Horizons images.
“Surface changes are pretty subtle, but there are at least two,” Perry wrote. “The first is a small river from the east end of East Girru. That is a [volcanic] Hotspot first seen by New Horizons in the midst of a mini-outburst. According to Juno JIRAM still active.”
The Jovian InfraRed Auroral Mapper (JIRAM) is a dual instrument consisting of an imager and a spectrometer sharing the same telescope.
Perry said other data showed reddening of Chors Patera, a bowl-shaped volcanic crater. “Reddish material on Io indicates the presence of S3-S4, short-chain sulfur that needs to be periodically replenished by active high-temperature volcanism,” he explained.
JunoCam is a high-resolution visible-light instrument that is not actually part of the spacecraft’s primary science payload. It was included on the mission as a public-facing camera, and its images are being processed by members of the public, many of whom have been actively processing Juno’s images since it reached Jupiter in 2016. However, with the abundance of JunoCam images, it turned out that the images were also used for science.
Images here are courtesy of Andrea Luck, Kevin M. Gill, and Jason Perry.
Juno’s next encounter with Io occurs during Perijove 51 on May 16, 2023 at a distance of 35,000 km.