Io gets most of its heat flow from tidal pulling and pushing as it orbits Jupiter. Europa also orbits Jupiter
and gets quite a bit of tidal pulling. The heat flow on Europa is around 100 times less than that on Io. The
latent heat of melting from solid ice to liquid water is 3.4 × 105 J/kg. If, as some people have proposed, the
uppermost 100 km of Europa is a thick water ice layer, what is the timescale to melt this layer? Do you
expect Europa to have no, few, some, or many craters on its surface, and why? This surface/interior ocean,
some people think, is the reservoir of water that life on Europa could survive in – but only if there is enough
liquid water that persists for long enough. (Note: The density of ice is around 1000 kg/m3.)
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