A recent TED-Ed lesson by Zachary Metz examines different theories about how the Earth got its water. One theory says that although Earth had water when its rock first formed it would have lost it all due to the young planet’s lack of atmosphere, so the current water must have come from comet or asteroid impacts. Another says that the young Earth would have had enough water to retain it despite the lack of an atmosphere.
The lesson also explains how elements were formed in stars and dispersed through the Universe by exploding supernovae.
