The James Webb Space Telescope has made a fascinating discovery on Europa, one of Jupiter's moons. It has found patches of fresh crystalline ice that seem to be rapidly renewed, despite being exposed to Jupiter's intense radiation. This is a significant finding because it suggests that some process is preserving or rebuilding the crystal structure faster than the radiation can disorder it. The key to this discovery lies in the telescope's ability to detect a narrow reflection feature near 3.1 micrometres, known as a Fresnel peak, which is associated with crystalline water ice. This peak was concentrated mainly in Tara and Powys, two southern areas of broken, rearranged terrain on Europa's surface. The presence of this peak indicates that some process is maintaining the crystalline structure in these regions, even though it should be destroyed by radiation in less than 15 days. The study's leading explanation is rapid thermal recrystallisation in a thin layer of porous frost. This process can renew molecular order in existing ice, and it is supported by laboratory spectra and modelling. The finding is particularly intriguing because it suggests that Europa's surface is being processed differently from place to place, with crystalline ice surviving below a thin amorphous skin in some regions, while in others, it persists all the way to the exposed grain surface. The study also highlights the importance of considering the interior of Europa, as evidence from carbon dioxide and sodium chloride in Tara and Powys suggests that the chemistry may be derived from the moon's interior. The discovery raises many questions and will require further investigation, including the use of NASA's Europa Clipper mission, which will approach Europa much more closely and provide more detailed data. The James Webb Space Telescope's discovery of rapidly renewed crystalline ice on Europa is a significant finding that highlights the complexity and dynamism of this moon's surface and interior.
