How do the “tidal forces warming moons” theories hold when [..] How do the “tidal forces warming moons” theories hold when apart from heating from expansion, there may be also cooling from contraction? I can understand a temporary heating, from the tital forces exerted on the moon but wouldn't there be cooling as well eventually when particles "give in" to contraction? Wouldn't they eventually net a unchanging whole body temperature? i.e. How can Europa's oceans be warmed by that and how can Io's crust be melted by that?