The repeated deformation of a body (for example, a moon) due to tides from another body (for example, a planet), which leads to heating of the former’s interior. Tidal forces arise due to variations in the gravitational forces between bodies. For example, tidal forces from the Moon cause tides in the Earth’s oceans of course, but they also very slightly deform the Earth itself. Tidal heating may have resulted in a water ocean under the ice covering Jupiter’s moon Europa.