Europa's surface ice varies in crystallinity depending on location, indicating complex processes at play. While Earth's water ice typically forms a hexagonal crystalline structure, Europa's surface ice is frequently bombarded by charged particles, disrupting the crystalline lattice and creating amorphous ice.
Raut's team conducted laboratory experiments to simulate these processes and determined how quickly amorphous ice can recrystallize in Europa's chaos terrains-regions of disrupted ridges, cracks, and plains. Coupled with JWST data, these results bolster the hypothesis of a liquid ocean beneath Europa's icy shell.
"For the past two decades, we believed Europa's surface was coated by a thin layer of amorphous ice with crystalline ice underneath," said Raut. "Our findings challenge this, revealing crystalline ice not just below the surface but also exposed in areas like Tara Regio."
Dr. Richard Cartwright, the study's lead author and a spectroscopist at Johns Hopkins University's Applied Physics Laboratory, noted, "We think the surface is porous and warm enough in places for rapid recrystallization. In Tara Regio, a chaos region, we also detect sodium chloride, likely from Europa's internal ocean, along with strong signatures of CO2 and hydrogen peroxide. The chemistry here is both unusual and intriguing."
Raut emphasized, "Our data strongly suggest that materials at the surface are sourced from below, likely from a subsurface ocean some 20 miles (30 kilometers) deep. The fractured surface points to geologic processes that bring materials up from the ocean beneath."
The study also detected both the common carbon-12 isotope of CO2 and the rarer, heavier carbon-13 isotope. "Where is this 13CO2 coming from? It's hard to explain," said Cartwright, "but everything points to an internal source consistent with previous hypotheses about 12CO2 in Tara Regio."
Research Report:JWST Reveals Spectral Tracers of Recent Surface Modification on Europa
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