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What evidence suggests that Europa has a liquid-water ocean beneath its ice?
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Habitable zone
The habitable zones (green) for stars that are like the Sun (middle), hotter than the Sun (top), and cooler than the Sun (bottom). The red areas are those in which liquid surface water would be lost as a result of a runaway greenhouse effect, and the blue areas are those in which liquid surface water would be completely frozen.
Evidence suggesting that Europa harbors a subsurface liquid-water ocean includes several key observations:
- Induced Magnetic Field: Europa possesses an induced magnetic field that requires the presence of an electrically conducting fluid medium within the moon, implying a layer of salty liquid water beneath the icy crust.12
- Surface Geology: The moonâs surface is remarkably smooth and features few impact craters, indicating it is geologically young and has undergone recent resurfacing. High-resolution images show fractured ice blocks that appear to have rotated and refrozen, suggesting the subsurface was onceâand perhaps still isâsemifluid.12
- Surface Deposits: Mottled regions on the surface contain salt deposits, which scientists interpret as evidence of evaporation from a reservoir located below the crust. Additionally, spatter cones along surface grooves suggest fluid eruptions from the interior.12
- Tidal Heating: Models indicate that tidal energy generated by Jupiterâs gravitational pull could provide the heat necessary to maintain a liquid ocean beneath the ice.12