Juno Spacecraft Unveils Secrets of Jupiter’s Volcanic Moon Io #

New Insights into the Solar System’s Most Active Volcanic Body #

Flybys of Jupiter’s fiery moon Io by NASA’s Juno spacecraft are helping to solve the mystery of why this small moon is the most volcanically active body in our solar system. Similar in size to Earth’s moon, Io has an estimated 400 volcanoes that continuously release plumes and lava, coating its surface.

The Juno mission, orbiting Jupiter and its moons since July 2016, made incredibly close flybys of Io in December 2023 and February. The spacecraft zipped within 930 miles of the moon’s surface, capturing images and data. These flybys have enabled an unprecedented look at the smoldering moon, including observations of its poles for the first time.

New data suggests that Io’s numerous volcanoes are each likely powered by their own chamber of hot magma, rather than being fed by a global ocean of magma beneath the surface. This finding could change the way astronomers understand moons dominated by subsurface global oceans in our solar system, such as Jupiter’s moon Europa and planets beyond our solar system.

Italian astronomer Galileo Galilei discovered Io on January 8, 1610. However, the moon’s wild volcanic activity wasn’t detected until Voyager 1 flew by Jupiter and its moons in 1979, revealing Io’s dynamic surface that resembled a pepperoni pizza.

Io orbits around Jupiter, the largest planet in our solar system. The moon’s orbit is imperfect, meaning that sometimes it comes closer to Jupiter during its orbit, and other times it is farther away. Io completes one orbit around the planet every 42.5 hours.

Jupiter’s massive gravitational influence squeezes Io as it orbits the planet, like a hand squeezing a rubber ball, which warms up the moon. This phenomenon is called tidal flexing, or friction from tidal forces that generate internal heat. The constant flexing of Jupiter’s tug on Io generates immense energy, which would melt part of the moon’s interior.

During its close flybys, Juno captured high-precision Doppler data, which measured Io’s gravity by tracking how zipping closely to the moon affected the spacecraft’s acceleration. The data was compared with observations from previous missions and ground-based telescopes.

Together, the observations point to a rigid, mostly solid interior beneath Io’s surface, rather than a global magma ocean. Instead, the volcanoes are powered by more local sources, and each one has its own pocket of magma beneath it.

The mission has also helped to capture an array of imagery that showcases Io’s primordial fantasy land surface. The images are bringing different features on Io into focus like never before, including islands spotted on massive lava lakes, such as one called Loki Patera, which is so large that astronomers compare it more to a lava sea sitting on Io’s surface.

The Juno spacecraft continues to contribute new insights about Jupiter and its moons, having recently completed a flyby over Jupiter’s swirling cloud tops on November 24. Next, Juno will swing by 2,175 miles above Jupiter’s center on December 27, logging 645.7 million miles since beginning its investigation of Jupiter eight years ago.