I have heard some people mention it may have came from the theoretical Oort Cloud or comets, ect... I'm wondering why a common guess as to where it comes from is from isn't within a lighting storm itself. Hydrogen and Oxygen are pretty much abundant in a lightning storm. The first crack of lightning is sometimes accompanied by a downpour, and lightning has recently been discovered to give off anti-matter signatures. I am no physicist, but isn't anti-matter a signal that matter has been produced? Where did all the Earths water come from and why is not an obvious thing to think the water could be manufactured in the clouds? Just some of it, not all of it, not the clouds themselves which are formed by evaporation, but perhaps lightning contributes to the total mass of a storms rain through matter production?