Scott Bolton, Juno's principal investigator, shared these findings on April 16 at a news conference held at the European Geophysical Union General Assembly in Vienna.
During its close approaches in December 2023 and February 2024, Juno navigated within approximately 930 miles (1,500 kilometers) of Io, capturing unprecedented images of its northern regions.
"Io is densely packed with volcanoes, several of which were active during our observations," Bolton explained. "Additionally, we obtained detailed images and data on Loki Patera, which spans about 200 kilometers. The images reveal intricate features, including islands within the lava, surrounded by intensely hot borders."
Juno's Microwave Radiometer (MWR) has produced maps showing that Io's surface is relatively smoother than that of other Galilean moons, with its poles cooler than its equatorial region.
In its extended mission, Juno is focusing more closely on Jupiter's north pole, enhancing the resolution with which it can observe the polar cyclones there. This shifting perspective allows for detailed multiwavelength studies of these storms.
Steve Levin, a project scientist at NASA's Jet Propulsion Laboratory, noted, "A key finding from this study is the varied structure of the polar cyclones. The central cyclone at the north pole, for example, appears visibly distinct but lacks a strong microwave signature compared to other nearby storms. This suggests differences in their subsurface compositions."
Understanding Jupiter's water content is a fundamental objective of the Juno mission. Unlike searching for liquid water, the team aims to quantify hydrogen and oxygen-the components of water-in the planet's atmosphere. Recent findings suggest that Jupiter's equatorial water content is several times richer than solar levels, contradicting earlier models derived from the Galileo probe, which indicated an absence of water and unexpectedly high temperatures during its descent in 1995.
Bolton reflected on the probe's legacy, "The Galileo probe provided crucial data, but it left us with more questions. Now, Juno has confirmed that the probe's landing site was anomalously dry, akin to a desert."
The ongoing analyses of Jupiter's composition, particularly the low water levels at its core, continue to pose challenges to our understanding of the planet's formation. Juno's continued exploration, particularly near the polar regions, aims to provide further insights into these mysteries.
Juno's recent passage by Io, on April 9, brought it within about 10,250 miles (16,500 kilometers) of the moon. The spacecraft is scheduled for its 61st flyby of Jupiter on May 12.
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