Lack of craters on the surface
- surface is 10 MY or younger?
- rarity of craters determined by (>24 months of) careful study of
- reflected light from the surface
- Analysis of small cracks adjacent to large topographic loads implies a layer of brittle ice, less than 1 km thick above the supposed ocean
- Preponderance of internally caused pits, moats, and domes
- depressions formed locally where the ice has collapsed due to internal geologic activity.
- that activity may be subsurface solid state convection
- if convection is determined to be the process creating the pits, moats, and domes, then the possibility of a water ocean is more remote, or perhaps it exists at lower depths
- theory can help but there is a lack of constraints; i.e. rates of creep must be determined by the actual material composition which is unknown rates of creep are difficult to determine from the flyby pictures
- water has reached surface to form once-again-frozen "ponds"
- there are many examples of "lobate" flow
- Magnetometer detected near surface currents
implies the presence of convecting/circulating currents in a salty ocean
- what is needed to form a magnetic field?
- electric currents, => electrically conducting material in motion
- electrically conducting materials include:
- iron (iron core of a planet)
- salt water
- implies the presence of convecting/circulating currents in a salty ocean
To read more this subject, you may leave the tour and read our section on the recent findings about this moon, or take the Exploratour on the question Does Europa have an Ocean?
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