If Earth didn’t start off with water when it was born, how did water arrive on this Earth? Minute Earth explains the mostly likely origins of H2O on our planet.
That water in your Evian bottle came from outer space. Water wasn’t formed on Earth, so it most likely came from bodies like meteoroids and comets that originated in the outer solar system. The planet’s water probably did not come from comets, because comet water is far richer in heavy hydrogen than Earth water. That leaves meteoroids that formed beyond the sun’s frost line as the main source for water the Earth.