Exploratour - Does Europa have an Ocean?
7.) The final piece of evidence is found in this image of a global pattern of cracks. The pattern suggests to geologists a process called "non-synchronous rotation" of the moons outer crust. In other words, the topmost portion of Europa's surface may have rotated at a different speed than did the interior.
Such a process would require the existence of a subsurface ocean to decouple the lower layers from the upper layers. The process is not well established. In other words, you might ask "how do scientists know that for sure?", and geologists today would not be able to answer.
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