NASA’s Juno orbiter has performed over 50 flybys of Jupiter so far. Besides documenting the gas giant, it also took photos during close encounters with its largest moons: Io, Europa, and Ganymede. In the latest flyby on December 30, the spacecraft made the closest flyby in over 20 years! And, of course – it took some fantastic photos.

As Juno passed within about 930 miles (1,500 kilometers) of Io, its instruments gathered plenty of data. Io is the most volcanic world in our solar system, and of course, this isn’t the first time Juno turned its cameras towards its surface. “By combining data from this flyby with our previous observations, the Juno science team is studying how Io’s volcanoes vary,” said Juno’s principal investigator, Scott Bolton of the Southwest Research Institute in San Antonio, Texas. “We are looking for how often they erupt, how bright and hot they are, how the shape of the lava flow changes, and how Io’s activity is connected to the flow of charged particles in Jupiter’s magnetosphere.”

The JunoCam instrument aboard our #JunoMission acquired six images of Jupiter's moon Io during its close encounter today. This black-and-white view was taken at an altitude of about 1,500 miles (2,500 kilometers). More images will be available soon at https://t.co/mGfITRe57Y pic.twitter.com/9GcamrhxPt

— NASA Solar System (@NASASolarSystem) December 31, 2023

During the Io flyby, Juno’s three cameras were all active. JIRAM, which is the Jovian Infrared Auroral Mapper, collected heat signatures emitted by volcanoes and calderas on the moon’s surface in infrared. The Stellar Reference Unit, a navigational star camera, provided valuable scientific data and obtained the highest-resolution image of the surface to date. The JunoCam imager also captured visible-light color images.

JunoCam was installed on the spacecraft to engage the public. While it was meant to function for a maximum of eight Jupiter flybys, the last flyby marked the 57th orbit around Jupiter! The spacecraft and cameras have endured one of the harshest radiation environments in the solar system, and they’re still going strong.

“The cumulative effects of all that radiation has begun to show on JunoCam over the last few orbits,” said Ed Hirst, project manager of Juno at NASA’s Jet Propulsion Laboratory in Southern California. “Pictures from the last flyby show a reduction in the imager’s dynamic range and the appearance of ‘striping’ noise. Our engineering team has been working on solutions to alleviate the radiation damage and to keep the imager going.”

What’s next?

We have another exciting event to look forward to. On February 3, 2024, Juno will perform the second ultra-close flyby of Io. Once again, it will come within 930 miles (1,500 kilometers) of the surface. “With our pair of close flybys in December and February, Juno will investigate the source of Io’s massive volcanic activity, whether a magma ocean exists underneath its crust, and the importance of tidal forces from Jupiter, which are relentlessly squeezing this tortured moon,” said Bolton.

You can check out the complete gallery from the latest flyby on NASA’s dedicated Juno website.