Ganymede and Callisto—which causes the moon to be tugged in different directions during its orbit. The frictional heat buildup in its interior causes constant and widespread volcanic activity.

Europa is beautifully rendered and a refreshing change of pace from The Callisto Protocol’s interior eyesore, but players do not actually spend any legitimate time there. It seems like a ...

And there are tantalizing hints that oceans could exist on Ganymede, Callisto, Titan and other distant moons, too. Now another moon appears ... creates friction in the interior that provides ...