Volcanic eruption on Jupiter's moon Io covers area larger than Lake Superior

Jupiter’s moon Io has once again demonstrated why it holds the title of the most volcanically active body in the solar system. NASA’s Juno mission has detected an enormous volcanic hot spot in Io’s southern hemisphere, which has undergone an eruption unlike any seen before.

The feature, which is larger than Earth’s Lake Superior, releases energy equivalent to six times the total output of all power plants on Earth.

The discovery was made possible by the Jovian Infrared Auroral Mapper (JIRAM), an instrument provided by the Italian Space Agency.

Io’s biggest volcanic eruption

Juno’s extended mission has allowed it to make multiple close flybys of Io, and capture data that continues to surprise scientists.

The most recent observation, conducted from a greater distance, provided unexpected and extraordinary results.

“Juno had two really close flybys of Io during Juno’s extended mission. And while each flyby provided data on the tormented moon that exceeded our expectations, the data from this latest – and more distant – flyby really blew our minds,” ,” said Scott Bolton of the Southwest Research Institute.

“This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system – so that’s really saying something.”

Io, which is roughly the size of Earth’s Moon, undergoes immense tidal stress due to its close orbit around Jupiter. The gravitational forces from the gas giant stretch and squeeze Io, which generates intense internal heat.

This process fuels its continuous volcanic activity, with the moon’s more than 400 active volcanoes spewing lava and gas into space.

Io’s changing landscape observed by Juno

Images taken by JunoCam in 2024 highlight dramatic surface changes near Io’s south pole. These images, captured between Juno’s 66th and 68th closest approaches to Jupiter, provide clear evidence of Io’s ever-changing geological features.

The arrows in the images indicate newly formed volcanic deposits, suggesting that fresh eruptions reshaped the terrain within a short period.

Juno’s JIRAM instrument was originally designed to study Jupiter’s atmosphere by detecting infrared light that emerges from deep within the planet’s weather layer.

Since the mission extension, JIRAM has also been used to investigate Jupiter’s largest moons, including Io, Europa, Ganymede, and Callisto.

With each flyby, Juno gathers more data on these dynamic celestial bodies, revealing new insights into their composition and activity.

Close flybys and infrared observations

Juno’s orbital trajectory brings it close to Io every other orbit, allowing repeated observations of the same regions.

During previous flybys in December 2023 and February 2024, the spacecraft came within approximately 930 miles (1,500 kilometers) of Io’s surface.

The latest flyby, conducted on December 27, 2024, occurred from a greater distance of 46,200 miles (74,400 kilometers).

Despite the increased distance, JIRAM successfully detected an intense volcanic eruption that surpassed all previous records.

The detection of this new hot spot represents one of the most significant findings of Juno’s mission.

JIRAM’s ability to capture infrared light enabled scientists to observe the eruption’s thermal signature, and provide critical data about the intensity and scale of Io’s volcanic activity.

Magma chamber beneath Io

“JIRAM detected an event of extreme infrared radiance – a massive hot spot – in Io’s southern hemisphere, so strong that it saturated our detector,” said Alessandro Mura from the National Institute for Astrophysics.

“However, we have evidence what we detected is actually a few closely spaced hot spots that emitted at the same time, suggestive of a subsurface vast magma chamber system. The data supports that this is the most intense volcanic eruption ever recorded on Io.”

The estimated size of this feature is staggering; it spans 40,000 square miles (100,000 square kilometers).

This makes it the largest known volcanic hot spot on Io, surpassing even Loki Patera, which is a well-known lava lake that covers about 7,700 square miles (20,000 square kilometers).

The total power output of the eruption exceeded 80 trillion watts, making it the most powerful volcanic event recorded on the Jovian moon.

The discovery suggests the presence of a vast subsurface magma system beneath Io’s crust. Scientists believe that multiple volcanic hot spots erupted simultaneously, and Juno’s observations indicate that magma movement deep inside Io could be far more complex than previously thought.

Io’s surface and volcanic signatures

JunoCam’s visible-light images provided further confirmation of the eruption’s impact.

By comparing images from previous Io flybys with the latest ones from December 27, scientists identified noticeable changes in surface coloration around the newly discovered hot spot.

While these images were taken from a greater distance and at lower resolution, the alterations in the landscape were still evident.

Large volcanic eruptions on Io often leave lasting geological signatures. The moon’s surface is frequently reshaped by pyroclastic deposits, which consist of fragmented rock ejected by volcanic explosions.

Other features include fissure-fed lava flows and volcanic-plume deposits that are rich in sulfur and sulfur dioxide. These elements contribute to the constantly evolving appearance of Io’s surface.

What happens next?

Juno’s upcoming distant flyby of Io on March 3 will provide another opportunity to study the new hot spot.

Scientists plan to use this next observation to monitor any changes in the region and determine whether the eruption is still ongoing.

Earth-based telescopes may also contribute additional data by capturing images of Io’s active volcanic zones.

“While it is always great to witness events that rewrite the record books, this new hot spot can potentially do much more,” said Bolton. “The intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well.”

The findings from Juno’s latest observations could provide insights into volcanic activity beyond the solar system.

Understanding Io’s volcanic processes may help scientists interpret similar geological phenomena on exoplanets and other celestial bodies.

With future missions to Jupiter’s moons planned, including the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) and NASA’s Europa Clipper, continued exploration of these dynamic worlds will likely uncover even more surprises.

Information for this article came from a NASA press release.

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