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- Title
Thermal and Chemical Evolution of Small, Shallow Water Bodies in Europa's Ice Shell.
- Authors
Chivers, C. J.; Buffo, J. J.; Schmidt, B. E.
- Abstract
The highly modified surface of Europa's ice shell hides a global, salty ocean that may hold conditions favorable for life, and cycles in the ice shell likely impact those conditions by allowing material transfer between the surface and subsurface ocean. The Galileo spacecraft observed a number of young geologic features that indicated Europa's ice shell was recently or presently active, including lenticulae. Lenticulae, a collection of quasi‐elliptically shaped surface disruptions, have been suggested to form above relatively small bodies of water (∼10 km diameter) emplaced in the ice shell as shallow as 1 km below the surface. Here, we use numerical models to quantify the longevity of small bodies of water in Europa's ice shell and explore their chemical evolution to understand how shallow water impacts the composition of the ice shell and regional surface geology over time. We find that lenticulae are more geologically transient than previously described, and that if the reservoirs contain salts, up to meters‐thick layers of salt may precipitate during the solidification process. Our results imply that, if depressions are the first signs of liquid water emplaced in the ice shell, lenticulae may be actively forming at present day, suggesting liquid water may still be present in Europa's shallow ice which could form water plumes and affect its habitability. Plain Language Summary: The surface of Europa, innermost icy moon of Jupiter, contains recent geologic formations that are clues toward processes that may be presently active or have occurred in the geologically recent past. Among these, lenticulae are small, often dark and dome‐like, elliptically shaped features that may form above saline liquid water bodies inside the ice shell 1–5 km below the surface. How the subsurface water evolves and survives is important for understanding Europa's ice shell, ocean and ability to support life. Using numerical simulations, we find that the shallow water is relatively short‐lived and the geomorphology of some lenticulae may indicate that water currently present in the ice shell. We also show how materials including salts present in the water are frozen into the ice and form distinctive chemical zoning patterns. Key Points: Small, shallow water bodies are shorter lived than previously shown, but Europa's surface expression suggests water may still be presentShallow water leaves a chemical signature in the ice of its thermal and chemical evolutionSalt precipitation caused by concentration during the refreezing of shallow water can leave behind layers of salts in the ice shell
- Subjects
SURFACE of Europa; GEOLOGY of Europa; BODIES of water; GALILEO satellite navigation system; SPACE exploration
- Publication
Journal of Geophysical Research. Planets, 2021, Vol 126, Issue 5, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2020JE006692