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Additionally, distinctive chaos terrains—regions where the surface is broken into blocks and covered with reddish material—suggest ongoing geological activity, possibly involving subsurface lakes or pockets of liquid water collapsing and refilling the ice crust.
Evidence of a Subsurface Ocean and Internal Structure
One of the most tantalizing aspects of Europa is the strong evidence for a vast, salty, liquid water ocean beneath its icy crust. Magnetic field data from spacecraft such as Galileo indicate that Europa has an induced magnetic field, implying a conductive, salty subsurface layer—most plausibly a liquid water ocean about 100 km deep, containing more water than all Earth's oceans combined.