The Arizona planetary scientists, led by Dr . Gregory Hoppa, theorized that Jupiter's huge size _ it is 300 times as massive as Earth _ causes tremendous tidal stresses on Europa.
12.
Large cracks could last for a few thousand years, the researchers say, but as Europa rotates relative to Jupiter, tidal stress points in the crust would change, and cracks would periodically freeze shut.
13.
The moon's icy crust may be just a few kilometers thick _ perhaps thin enough to crack open under tidal stresses and allow life in the oceans below to flourish by absorbing the Sun's energy.
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Alternatively, the orbiter could bounce laser pulses off the moon to measure the effect of tidal stresses _ how much Europa flexes back and forth as its orbit takes it closer to Jupiter, then farther away.
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This is all valid for any Lorentzian manifold, but we note that in general relativity, the electrogravitic tensor controls tidal stresses on small objects, as measured by the observers corresponding to our frame, and the magnetogravitic tensor controls any spin-spin forces on spinning objects, as measured by the observers corresponding to our frame.
