# Where does the earth's water originally come from?

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

They said that:

Some of it was here when the earth was made (but locked into the rocks as hydrates ... much of that released as the Earth became molten.)
And some came from comets and other ice particles that have bombarded the Earth since it was formed.
No one knows which part was the major contributor.

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
Does that help?

Yes, absolutely! Thank you very much onomatomanic!