NASA's Juno spacecraft began its scientific operations looping around the gas giant Jupiter, providing the most stunning images yet of the solar system's largest planet. But that was in 2016—Juno is still operational, but it's shifted focus to some of Jupiter's many moons. Late last year, Juno completed a close flyby of Io, and now the probe has done it again, zipping over the craggy surface of Jupiter's most volcanic moon to beam back photos of the alien landscape. Enjoy it—these might be the last up-close images of Io we get for a long time.
The Juno team says the latest flyby took place exactly as planned on Feb. 3, offering another glimpse of the moon's surface from a mere 930 miles (1,500 kilometers) above the surface. And what a surface it is—Io is Jupiter's innermost moon, which subjects Io to the intense tug of the gas giant's gravity. This results in tidal heating, which keeps the interior of Io toasty. That's why the moon has an estimated 400 active volcanoes.
Rings of powerful radiation surround Jupiter, and Io is smack in the middle of them. Juno was designed to use a highly eccentric orbit to minimize the time it spent near the planet—the 58th orbit (Perijove 58) took it close to Io for the second time. There's a whole collection of raw Io snapshots from the latest observation if you want to try your hand at processing them. Juno wasn't going to waste the chance to take yet another look at Jupiter, though. The new image set also contains views of Jupiter from the Feb. 3 flyby.
So far, SwRI and NASA have only released the initial raw data from Juno, which is why the below image has no color (it's just the green filter) and some fuzzy details. The image above comes from the new Juno set, but it's been processed and cleaned up by photographer Jason Perry. It approximates the moon's true color and makes the pockmarked terrain look much sharper. NASA might release its own processed versions later.
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NASA hopes that having a pair of similar observations taken a few weeks apart will help determine what's going on inside Io. Some scientists believe a sea of magma could be hiding under the fractured surface, but Juno is the first spacecraft to get close to Io in decades. The last were Voyager 1 and 2, which swung through the Jovian system on their way to the outer solar system and beyond.
This success ends Juno's moon observations. NASA didn't expect the spacecraft's JunoCam to last this long in the high-radiation environment around Jupiter, and there's still much more to learn about Jupiter itself. Although Juno's camera has developed issues with noise and dynamic range, the team believes it will continue to return useful data on Jupiter for the remainder of its mission. NASA currently plans to retire Juno in 2025.
