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Why do scientists think Europa may have an ocean beneath its icy crust?
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Jupiter
Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7 million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud bands and Great Red Spot (lower centre).
Scientists hypothesize that Europa harbors a subsurface ocean based on several lines of evidence gathered by space missions:
- Magnetic Fields: Europa possesses an induced magnetic field that appears to require an interior, electrically conducting fluid layer, such as a salty liquid water ocean, beneath the icy crust.12
- Surface Features: The moon’s surface is remarkably smooth and features very few impact craters, suggesting it is geologically young and has been resurfaced by fluid activity from the interior. Observations of mottled regions containing salt deposits further suggest the evaporation of water from a reservoir below the surface.12
- Geological Evidence: Images from the Galileo mission revealed areas where the icy crust has fractured and shifted, indicating that the subsurface was once semifluid. Additionally, spatter cones and grooves suggest fluid eruptions from below.21
- Tidal Heating: Scientists believe that tidal energy generated by Jupiter’s gravity could provide the heat necessary to maintain a liquid ocean beneath the ice.12