Where does the earth's water originally come from?

Earthmosphere

Where does the earth's water originally come from? Any idea?

They said that:

I still don't get it. Where does it really come from?

onomatomanic

It depends on what you mean by "originally", I'd think. Water consists of hydrogen and oxygen, as everyone knows. The vast majority of hydrogen was created shortly after the Big Bang. Oxygen is one of the main products of stellar fusion, and is being re-injected into the interstellar medium by means of supernova explosions. The material making up a protoplanetary disk is, in turn, taken directly from the interstellar medium. So there was no shortage of water in the stuff the Earth was assembled from.

The initial problem, I imagine, was that the temperature was too high for water vapour to be retained in the primordial atmosphere, let alone for it to condensate. Hence, the water that's around today must have either been present in a more permanent form early on (that would be the hydrates in the passage you quoted) or arrived later, once things have cooled down sufficiently (that would be the impactors).

Does that help?

Earthmosphere

Yes, absolutely! Thank you very much onomatomanic!