JWST Peeks at Callisto’s Ancient Scars

• The James Webb Space Telescope (JWST) discovered water ice and dry ice (CO2) on Callisto, revealing a complex surface composition. The data, published in the Planetary Science Journal, showed water ice on the leading hemisphere and CO2 on the trailing hemisphere, with anti-correlated patterns suggesting particle radiation converts ice and carbon-rich grains into CO2.
• The JWST data revealed a 3.1 µm Fresnel peak indicative of water ice, mapped in detail, and a 4.25 µm spectral band representative of dry ice, concentrated at the center of the trailing hemisphere. The ice on the leading hemisphere tracks with geography, while the trailing hemisphere shows a bullseye pattern, possibly shaped by plasma blasting.
• The findings suggest that Callisto's surface is more active than previously thought, with CO2 and water ice present in distinct patterns, indicating complex processes involving particle radiation and volatiles. The data also highlights the challenges in modeling the behavior of volatiles on icy moons, and the upcoming Jupiter Icy Moons Explorer (JUICE) mission will provide more detailed observations.

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