What it is: Io, a moon of Jupiter and the solar system's most volcanic world

When it was taken: Dec. 30, 2023

Why it's so special: NASA's Juno spacecraft has captured the closest views of Io since NASA's Galileo spacecraft imaged the volcanic world in 2001. Passing within just 930 miles (1,500 kilometers) of Io, the spacecraft snapped six images of the moon's pockmarked surface. This image also shows delicate "Jupiter shine" — sunlight reflected from Jupiter's clouds onto the surface of Io.

Io is the most volcanic world in the solar system; its surface is peppered with hundreds of volcanoes, some spewing sulfurous plumes hundreds of miles high, according to Live Science's sister site Space.com. That's a result of Io's proximity to Jupiter, which the moon orbits every 42 hours. This proximity produces friction, as does Io's gravitational interactions with Jupiter's giant moons Ganymede, Europa and Callisto. The gravitational tug-of-war likely results in a turbulent ocean of magma under Io's rocky surface, leading to volcanic eruptions that are orders of magnitude more powerful than those on Earth.

Planetary scientists hope the images will shed light on how Io's volcanoes vary, including how often they erupt, how bright and hot they are, and how Io's activity is connected to the flow of charged particles in Jupiter's magnetosphere.

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This is the first of two very close flybys of Io. The next one is scheduled for Feb. 3, when Juno will once again get within 930 miles of the volcanic moon.

However, there's a chance that Juno's imaging system, JunoCam, won't last long enough. Seriously degraded by radiation after 56 flybys of Jupiter since Juno arrived in 2016, JunoCam was severely impaired after its most recent orbit of Jupiter in November, according to NASA. In December, engineers used Juno's built-in heater to restore the camera, but it's unknown how long this process, called annealing, will work. Juno is due to be deorbited into Jupiter in September 2025.