Jupiter moon of Io is famed for its volcanoes. NASA just spotted the most powerful one yet

USA Today

06-02-2025

Jupiter moon of Io is famed for its volcanoes. NASA just spotted the most powerful one yet Not only was the hot spot larger than Earth's Lake Superior, but it also was seen belching out eruptions six times the total energy of all the world's power plants combined.
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NASA's Europa Clipper embarks on mission to one of Jupiter's moons
NASA's Europa Clipper spacecraft launched on a six-year journey to Jupiter's moon Europa to observe if life is possible on the icy ocean world.
The hellish surface of a moon of Jupiter known as Io is riddled with hundreds of lava-spewing volcanoes that make the world one of chaos and violence.
The brutal conditions also make Io intriguing to NASA scientists intent on learning more about the innermost and third-largest of Jupiter's four Galilean moons. For nine years, a spacecraft known as the Juno orbiter has divided its time between observing the gas giant of Jupiter and studying its moons, including Io.
And on its third flyby of the celestial body, the orbiter struck gold.
Though it was far from Juno's closest approach to Io, its flyby last December still led to a fascinating discovery: a massive volcanic hot spot on the moon's southern hemisphere.
The volcanic activity spotted on a planet famed for such eruptions was special for two reasons: Not only was the hot spot larger than Earth's Lake Superior, but it also was seen belching out eruptions six times the total energy of all the world's power plants combined, NASA said in a press release.
"This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system," Scott Bolton, the mission's principal investigator at the Southwest Research Institute in San Antonio, said in a statement. "So that's really saying something.'
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What to know about Jupiter's moon Io
Though Io is not much larger than Earth's own moon, the two celestial bodies couldn't be more different.
While our moon is relatively calm, Io is considered to be the most volcanically active world in our solar system. And while Earth, of course, has plenty of active volcanoes of its own, eruptions on the Jovian moon have attracted scientific interest because they are thought to be caused by very different factors.
The rocky moon, which was first discovered by the ancient astronomer Galileo in 1610, is named for a mythological woman transformed into a cow during a marital dispute.
Because Io is so close to its massive host planet, the moon is subjected to a tremendous gravitational pull as it orbits Jupiter once about every 42 hours, according to the Planetary Society. This at times pulls the moon closer to Jupiter, and it times pushes it farther away, weakening the planet's gravitational influence.
The constant stretching and squeezing creates tidal forces that generate heat within the moon, keeping its subsurface crust in liquid magma form that seeks any available escape route to relieve the pressure. As a result, the hectic conditions are perfect for Io's approximately 400 active volcanoes to endlessly spew lava dozens of mile into the air exceeding temperatures of 1,832 degrees Fahrenheit.
Mission scientists hope that by sending Juno on frequent visits to Io, they'll glean more insights into the complex conditions that can create volcanic activity on different worlds.
NASA orbiter spots most active volcano yet on Io
The third and latest flyby, which took place on Dec. 27, 2024, brought the Juno spacecraft within about 46,200 miles of the moon.
Using an instrument known as the Jovian Infrared Auroral Mapper (JIRAM) provided by the Italian Space Agency, Juno trained its sights on Io's southern hemisphere. The instrument is designed to capture the infrared light not visible to the naked eye emerging from deep inside Jupiter, as well as its moons – including not just Io, but Europa, where another orbiter, the Clipper, is bound.
During the flyby, the JIRAM instrument detected a massive hot spot on Io's southern hemisphere "so strong that it saturated our detector,' Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, said in a statement. The hot spot was later determined to in fact be several hot spots located close together that happened to emit at the same time, suggesting that the moon's subsurface is home to a vast magma chamber.
"The data supports that this is the most intense volcanic eruption ever recorded on Io,' Mura added.
The volcanic feature, which has yet to be named, spans a colossal 40,000 square miles – dwarfing Io's previous record holder, a lava lake named Loki Patera that measured about 7,700 square miles, according to NASA.
What to know about the Juno spacecraft
NASA's Juno spacecraft has been probing beneath Jupiter's dense clouds since it arrived in 2016 seeking answers about the origin and evolution of the gas giant.
That mission, which is slated to end in September 2025, also extends to Jupiter's rings and many moons. Juno's trajectory passes by Io every other orbit, flying over the same part of the moon each time.
In December 2023, Juno came within about 930 miles of Io's surface – equal the distance from New York City to Orlando, Florida. The craft's second ultra-close flyby of Io occurred last February, predominantly over the moon's southern hemisphere.
While multiple spacecraft have visited the Jovian moon since the 1960s, those previous two flybys were the closest any had gotten to Io's surface since the Galileo probe made numerous close flybys in the 1990s and 2000s.
Following the third and most recent flyby, Juno will use a more-distant flyby of Io on March 3 to look at the hot spot again and search for changes in the landscape. Earth-based observations of the region may also be possible, according to NASA.
'The intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well," Bolton said.
Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [e-mail]