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Jupiter’s moon Io is a world of volcanoes. In fact, it is the most volcanic body in the entire solar system. But how did it become that way? We know Jupiter’s powerful gravitational pull heats Io’s interior, melting rock and feeding the 400 known volcanoes. But is there a global ocean of magma beneath the surface? Or does each volcano have its own lava pool? Scientists with NASA’s Juno mission said on December 12, 2024, that it’s likely the latter. Io’s raging volcanoes are self-powered.
The researchers published their peer-reviewed paper in Nature on December 12, 2024. While peer-reviewed and accepted for publication, the paper is a preview version and still undergoing editing.
The results were also discussed at the American Geophysical Union’s annual meeting this month in Washington, D.C.
With Io having so many volcanoes – at least 400 known – scientists theorized there might be a global ocean of magma beneath the surface. Many of the volcanoes are active at any given time, blasting lava and plumes into the extremely thin atmosphere. So there must be an on-going supply of magma below ground. Imaging scientist Linda Morabito at NASA’s Jet Propulsion Laboratory (JPL) in California first saw signs of volcanic activity in Voyager 1 images in 1979.
But is that magma global, or is it localized beneath each volcano?
Scott Bolton is the principal investigator for the Juno mission. He said:
Since Morabito’s discovery, planetary scientists have wondered how the volcanoes were fed from the lava underneath the surface. Was there a shallow ocean of white-hot magma fueling the volcanoes, or was their source more localized? We knew data from Juno’s two very close flybys could give us some insights on how this tortured moon actually worked.
So, does Io have a magma ocean? The answer appears to be no.
Juno, which orbits Jupiter, made extremely close flybys of Io in December 2023 and February 2024. It came within 930 miles (1,500 km) of the scorched and roiling surface. Juno measured Io’s gravity by calculating how it affected the spacecraft’s acceleration. This can provide clues about the moon’s interior.
Io experiences what scientists call tidal flexing, or tidal heating. That’s due to Jupiter’s gravity squeezing and pulling on Io’s insides. This creates heat and melts subsurface rock, forming magma. The scientists wanted to know if that subsurface magma was global or just under each volcano. Bolton explained:
This constant flexing creates immense energy, which literally melts portions of Io’s interior. If Io has a global magma ocean, we knew the signature of its tidal deformation would be much larger than a more rigid, mostly solid interior. Thus, depending on the results from Juno’s probing of Io’s gravity field, we would be able to tell if a global magma ocean was hiding beneath its surface.
The results suggested that Io does not have a global magma ocean. The deformation of Io’s interior from the tidal flexing did not match what would be expected from a global layer of magma. Instead, each volcano is self-powered with its own localized pool of magma.
Animated tour of Jupiter’s volcanic moon Io. Video via NASA/ JPL-Caltech/ SwRI/ Koji Kuramura/ Gerald Eichstädt.
Scientists can also apply the results to their studies of other moons. Instead of magma, some other moons in the outer solar system – such as Europa and Enceladus – have subsurface oceans. On both moons, those oceans are global. And on Enceladus – and maybe also Europa – there are huge geyser-like jets of water that erupt through the outer ice surface and into space. These are cryovolcanoes, which spew water, ice and ammonia (gas) instead of lava. Scientists can use the same techniques from Io in studying those moons as well, because they also experience tidal flexing. Lead author Ryan Park is a Juno co-investigator and supervisor of the Solar System Dynamics Group at JPL. He said:
Juno’s discovery that tidal forces do not always create global magma oceans does more than prompt us to rethink what we know about Io’s interior. It has implications for our understanding of other moons, such as Enceladus and Europa, and even exoplanets and super-Earths. Our new findings provide an opportunity to rethink what we know about planetary formation and evolution.
Last September, scientists spotted a new volcano on Io, added to the hundreds it already has. They first saw it in Juno images from February 2024. And it’s big, covering an area about 110 miles by 110 miles (180 km by 180 km) wide.
Bottom line: Does Jupiter’s moon Io have a global subsurface magma ocean? A new study said no, and that Io’s raging volcanoes are self-powered with their own magma pools.
Source: Io’s tidal response precludes a shallow magma ocean
Read more: Jupiter’s moon Io has a new volcano! See pics here
Read more: Jupiter’s moon Io as you’ve never seen it
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