NASA’s Juno probe takes a closer look at the lava lakes on Jupiter’s moon Io

New findings from NASA’s Juno probe provide a more complete picture of how widespread lava lakes are on Jupiter’s moon Io, and include the first insights into the volcanic processes at work there. These results were obtained courtesy of the Italian Space Agency’s Jovian Infrared Auroral Mapper (JIRAM), an instrument that “sees” in infrared light. Scientists have published a paper on the latest volcanic discoveries of Juno v Earth and environment communication.

Io has attracted astronomers since 1610, when Galileo Galilei first discovered the Jovian moon, which is slightly larger than Earth. About 369 years later, NASA’s Voyager 1 probe captured a volcanic eruption on the Moon. Subsequent missions to Jupiter with further flybys of Io discovered more clouds – along with lava lakes. Scientists now believe that Io, which is stretched and compressed like an accordion by neighboring moons and massive Jupiter itself, is the most volcanically active world in the solar system. But while there are many theories about the types of volcanic eruptions on the moon’s surface, there is little supporting data.

In May and October 2023, Juno flew by Io and came within about 21,700 miles (35,000 kilometers) and 8,100 miles (13,000 kilometers) respectively. Among the Juno instruments that got a good look at the charming moon was JIRAM.

Designed to capture infrared light (which is not visible to the human eye) emanating from deep within Jupiter, JIRAM probes the weather layer up to 50 to 70 kilometers below the gas giant’s cloud tops. But during Juno’s extended mission, the mission team also used the instrument to study the moons Io, Europa, Ganymede and Callisto. JIRAM images of Io showed the presence of bright rings surrounding the floors of numerous hot spots.

“The high spatial resolution of JIRAM’s infrared images, combined with Juno’s favorable position during the flybys, revealed that the entire surface of Io is covered by lava lakes contained in caldera-like features,” said Alessandro Mura, Juno’s co-principal investigator. from the National Institute for Astrophysics in Rome. “In the region of Io’s surface where we have the most complete data, we estimate that about 3% of it is covered by one of these molten lava lakes.” (A caldera is a large depression created by the explosion and collapse of a volcano.)

Fire breathing lake

The Io flyby data from JIRAM not only highlights the moon’s abundant lava supply, but also provides insight into what may be happening beneath the surface. Infrared images of several of Io’s lava lakes show a thin ring of lava at the boundary between the central crust, which covers most of the lava lake, and the lake walls. Melt recycling is caused by the lack of lava flows at and beyond the lake rim, suggesting that there is a balance between melt that erupted into the lava lakes and melt that circulates back into the subsurface system.

“We now have an idea of ​​what the most common type of volcanism is on Io: huge lava lakes where magma rises and falls,” Mura said. “The lava crust is forced against the walls of the lake to form the typical lava ring seen in Hawaiian lava lakes. The walls are probably hundreds of meters high, which explains why magma is not generally seen pouring out of the paterae.”— bowl-shaped formations created by volcanism – “and moving across the lunar surface”.

The JIRAM data suggest that most of the surface of these Io hotspots is composed of a rocky crust that cycles up and down as one continuous surface due to central magma ascent. In this hypothesis, as the crust touches the walls of the lake, friction prevents it from sliding, causing it to deform and eventually fracture, exposing the lava just below the surface.

An alternative hypothesis remains in play: Magma rises in the center of the lake, spreads to form a crust that sinks along the edge of the lake, exposing the lava.

“We are just beginning to wade through the JIRAM results from close flybys of Io in December 2023 and February 2024,” said Scott Bolton, principal investigator for Juno at the Southwest Research Institute in San Antonio. “The observations reveal fascinating new information about volcanic processes on Io. Combining these new results with Juno’s longer-term campaign to monitor and map volcanoes at Io’s previously unseen north and south poles, JIRAM is proving to be one of the most valuable tools for learning how this tortured world works.”

Juno made its 62nd flyby of Jupiter — which included a flyby of Io at an altitude of about 18,175 miles (29,250 kilometers) — on June 13. The 63rd flyby of the gas giant is scheduled for July 16.