NASA's Juno spacecraft, initially tasked with studying Jupiter, has revealed fascinating insights into the volcanic activity on the gas giant's moon, Io.
Through its Jovian Infrared Auroral Mapper (JIRAM) instrument, Juno has captured detailed infrared images showcasing the volcanic plumes and lava lakes on Io, providing scientists with unprecedented data on the most volcanic body in our solar system.
NASA's Juno Discovery and Observations
The recent findings from Juno’s close flybys of Io, conducted in December 2023 and February 2024, have shown that the moon’s surface is dotted with enormous lava lakes. These lakes are characterized by bright white rings in infrared images, indicating temperatures between 450 and 1,350 degrees Fahrenheit (232 and 732 degrees Celsius). The central parts of these lakes are significantly cooler, measuring around minus 45 degrees Fahrenheit (minus 43 degrees Celsius).
Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, explained, “We now have an idea of what is the most frequent type of volcanism on Io: enormous lakes of lava where magma goes up and down.” These observations suggest that Io’s lava lakes function similarly to those found in Hawaii, with magma rising and falling, causing the lava crust to break against the lake's walls.
One significant feature observed is Chors Patera, a notable lava lake on Io. The infrared images of Chors Patera show a distinct hot ring around the edge of the lake, with temperatures much higher than the surrounding area. This ring is formed by the constant breaking of the lava crust against the lake's walls, exposing fresh, hot magma.
Volcanic Processes on Io
Io’s extreme volcanic activity is driven by tidal heating from Jupiter’s immense gravitational pull. This interaction causes internal friction and heat within Io, leading to frequent and intense volcanic eruptions. Some of these volcanoes emit plumes of sulfur and sulfur dioxide that can reach heights of up to 300 miles above the surface. The sulfur compounds also color Io’s surface in vivid hues of yellow, red, white, green, and black.
Scott Bolton, principal investigator for Juno at the Southwest Research Institute, highlighted the significance of these findings: “Combining these new results with Juno’s longer-term campaign to monitor and map the volcanoes on Io’s never-before-seen north and south poles, JIRAM is turning out to be one of the most valuable tools to learn how this tortured world works.”
The Jovian Infrared Auroral Mapper (JIRAM) was initially designed to map Jupiter's aurorae. However, as Juno's orbit brought it closer to Io, JIRAM started delivering high-quality images and data from the volcanic moon. The instrument operates in the infrared spectrum, which allows it to capture thermal images that reveal the temperature distribution across Io's surface.
“The high spatial resolution of JIRAM’s infrared images, combined with the favorable position of Juno during the flybys, revealed that the whole surface of Io is covered by lava lakes contained in caldera-like features,” said Alessandro Mura. “In the region of Io’s surface in which we have the most complete data, we estimate about 3% of it is covered by one of these molten lava lakes.”
The data from JIRAM showed that the lava lakes have a thin ring of exposed lava with no flows beyond or within the rim, indicating a balance between the erupted magma and the magma that flows back underground. This detailed observation helps scientists understand the dynamic nature of Io's volcanism.
Geological Models and Ongoing Research
Researchers have proposed two models to explain the dynamics of Io’s lava lakes. The central upwelling model suggests that heat rises in the center of the patera (a type of volcanic crater), causing the lava to spread radially and then sink at the edges. This model explains the uniform heat distribution but faces challenges regarding the consistency of the magma crust's thickness.
The piston motion model posits that the entire lava lake surface moves up and down like a piston, causing the crust to break against the crater walls and reveal hotter material. This model also has its challenges, particularly in explaining the uniform brightness around the lake perimeter.
NASA's Juno mission continues to provide valuable data that helps refine these models. Future observations will focus on inactive paterae for signs of past lava lake activity and further investigate the mechanisms behind Io’s volcanic phenomena.