A Closer Look at Tidal Effects

Interpreting Europa depends on understanding the four effects of the tides: the effects on heat, stress, rotation, and the orbit.

In considering the heat produced by tidal forces, it may be best to start with an overview of Jupiter's four large moons, moving from the closest to the most distant: Io, Europa, Ganymede, and Callisto.

Also obvious was the clear trend among the Galilean satellites correlating the geological activity with distance from Jupiter. The closer a satellite is to Jupiter,the fewer impact craters and the more the geology is dominated by tidally driven processes. Furthest out and not part of the eccentricity-driving Laplace resonance, Callisto was the archetype of a dead bombarded planet. Closer to Jupiter, and with a resonance-driven eccentricity, Ganymede displayed large Callisto-like areas, but other broad regions showing tectonics and resurfacing. Closer still was the completely resurfaced Europa, and closest to Jupiter was the spewing Io.