JWST Reveals Hidden Activity on Jupiter's Moon Callisto

• James Webb Space Telescope (JWST) data reveals that Callisto, traditionally viewed as a geologically quiet moon, is more active than previously understood.
• Astronomers identified distinct patterns of water ice, dry ice (CO2), and nitrogen-bearing compounds across the moon's surface.
• Findings suggest that magnetospheric plasma and meteorite impacts drive significant surface transformations.

Surface Composition and Distribution

• Water ice: Mapped via the 3.1 µm Fresnel peak, it shows a clear hemispheric divide. On the leading hemisphere, ice correlates with geography and fresh impact basins like Valhalla and Asgard. On the trailing hemisphere, it exhibits a "bullseye" pattern, likely shaped by plasma interaction from Jupiter’s magnetosphere.
• Carbon Dioxide (CO2): Identified by the 4.25 µm spectral band. CO2 signals are anti-correlated with water ice on the trailing hemisphere, suggesting radiation-driven conversion. On the leading hemisphere, high concentrations around younger craters like Lofn and Heimdall indicate impact-sourced deposits.
• Nitrogen compounds: A 4.57 µm absorption feature suggests the presence of carbon-nitrogen (CN) bearing compounds, potentially resulting from nitrogen-rich dust falling onto the moon from other irregular satellites.

Atmospheric and Future Findings

• Atmosphere: A faint, patchy CO2-based atmosphere was detected, with the highest concentrations around the Valhalla basin; the distribution remains inconsistent with temperature or surface ice patterns.
• Future Research: The Jupiter Icy Moons Explorer (JUICE) mission is expected to conduct high-resolution flybys in the 2030s to further clarify these complex volatile processes.