Synchronized volcanic eruptions on Io suggest a spongy interior

Five volcanoes on Jupiter’s moon I erupted at once in a cataclysm of lava. This means they are likely all connected to the same underground magma network, which will help solve the mystery of Io’s interior.

In late 2024, scientists monitoring Io via NASA’s Juno probe saw an unusually large lava flow near its south pole. “There was one gigantic eruption and a lava flow, and that’s what caught our eye the first time, but on a second look, all these other hot spots lit up,” he says. Jani Radebaugh at Brigham Young University in Utah. “There’s so much magma that we can’t wrap it all up.

The erupted lava spread over an area of ​​about 65,000 square kilometers and released more energy than any eruption previously recorded on Io. “Image standing on the edge of one of these formations and a valley that was cold suddenly fills up with an entire lava lake. When it fills up, you turn around and look over your shoulder and another massive fissure opens up in the ground and fills up with lava at the exact same time,” says Radebaugh. “It would be terrifying and so beautiful.

The question, however, is where all that magma came from – we know very little about Io’s internal structure, so it’s hard to answer. Previous work has shown that, contrary to researchers’ long-held expectations, I don’t have a global ocean of magma buried beneath my crust, so it’s unclear how so much magma could burst through the surface at once.

Radebaugh and her colleagues suggest that beneath vast areas of the surface may sit a kind of magmatic sponge that creates an interconnected network of pores that fill with lava and then spew it out through hot spots. However, we’ll need more observations to confirm this, and given that Juno has moved further from Io, we’re unlikely to get them any time soon.

Despite Io’s small size—it’s only slightly larger than Earth’s moon—the extreme nature of these eruptions makes them similar to volcanic events on Earth. “It’s actually like early Earth, when it was much warmer and more active, so it can tell us a lot about our past,” says Radebaugh. While the source of this wildly powerful series of eruptions may remain a mystery for now, when solved, it may help fill a chapter in our own story.

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