A study suggests that Earth's water was imported by asteroids, long after the planet was first formed
Life on Earth first came out of the oceans, but the water itself may have originated from extraterrestrial space rocks. A new study points to a turbulent period when the solar system's giant planets hurled chunks of icy rubble in Earth's direction.
This goes against the more favored scientific theory that Earth's oceans and atmosphere formed from elements within the planet interior, around 4.5 billion years ago. The Nature study argues that the primordial temperatures never dropped enough to condense both volatile elements and water alike, and that the waters of our blue planet must have arrived during a later period of planet building, about one hundred million years after Earth was formed.