Tidal Stresses - How Gravity Heats Things Up

Our planet is able to sustain warmth because of its atmosphere and its proximity to the Sun. However, as you may know, most of the other planets aren"t so lucky; nearly all of them have rather frigid temperatures.

For example, take a look at moons like Enceladus or Europa. These moons (of Saturn and Jupiter, respectively) are known as "icy moons." As a result of the extreme temperatures, which are hundreds of degrees below zero, both moons have a thick layer of ice many kilometers deep; however, we know that liquid water still exists on them. How can this be?

Find out at:
http://www.fromquarkstoquasars.com/tidal-stresses-how-gravity-heats-things-up/

Image source before editing:
NASA