Where did Earth’s water come from? - Zachary Metz
View full lesson: http://ed.ted.com/lessons/where-did-earth-s-water-come-from-zachary-metz Water covers over 70% of the Earth, cycling from the oceans and rivers to the clouds and back again. It even makes up about 60% of our bodies. But in the rest of the solar system, liquid water is almost impos
