NASA’s Juno spacecraft has sent back another batch of jaw-dropping images from its orbit around Jupiter. Along with the stunning detail in its swirling clouds and colorful bands, the school bus-sized probe’s JunoCam also focused its lens on Jupiter’s moon, Io, the most volcanic world in the solar system.
Juno, launched in 2011, arrived at Jupiter in 2016 and has since been sending back images of the gas giant’s spectacular cloud tops every time it dips close to the planet. It’s only an elliptical orbit, so it only gets close to Jupiter about once each month. Each close approach is called a perijove.
A perijove is the only time Juno takes and transmits images to Earth via NASA’s Deep Space Network. These images come from its 64rd perijove on August 18, 2024.
They follow July’s perijove when JunoCam imaged potato-shaped Amalthea, Jupiter’s fifth-largest moon. Amalthea orbits closer to Jupiter than Io.
This month, it was the turn of Io, the innermost of Jupiter’s four giant Galilean moons. About the same diameter as Earth’s moon, Io is covered in volcanoes, some emitting sulfurous plumes hundreds of miles into space.
Io is volcanic because it orbits so close to Jupiter—just 262,000 miles away—and completes an orbit every 42 hours. It’s tugged in all directions during its orbit by the gravity of Jupiter and the three other Galilean moons (Europa, Ganymede and Callisto). The friction builds up heat inside Io and causes, think scientists, an ocean of magma under its rocky surface.
Although these latest images of Io are scientifically valuable, it’s recently proven possible to image the tiny moon from Earth. Using the Large Binocular Telescope on Mount Graham, Arizona, scientists captured features larger than 50 miles across, such as its prominent volcanos Pele, Pillan Patera and Loki Patera.
Since Juno arrived at Jupiter in 2016, it has conducted close flybys of Europa, Ganymede and now Io, but not Callisto. However, that moon will be imaged 21 times during close flybys by the European Space Agency’s JUpiter ICy moons Explorer spacecraft, which launched last year and will reach the Jovian System in 2031.
JUICE will be beaten to Jupiter by NASA’s Europa Clipper, which will launch later this year and reach Jupiter before JUICE in 2030 to tour Jupiter’s moons in 2030, focusing on Europa.
Scientists recently identified 12 new moons orbiting Jupiter, though nine of them orbit in the opposite direction to the inner moons, like Io, which suggests that they are captured asteroids or fragments of comets.
JunoCam—which takes its images at just two-megapixel resolution— suffered radiation damage earlier this year, but it continues to take and return useful data.
However, Juno spins as it orbits, so JunoCam’s data must be carefully processed to get usable images. That job is done by volunteer citizen scientists, who download the raw data from the mission’s special website.
Juno’s next close flyby of Jupiter, perijove 65, will occur on September 20, 2025. The mission is scheduled to end on September 15, 2025, when Juno will perform a “death dive” into the gas giant during its 76th perijove.
Wishing you clear skies and wide eyes.