as per studies water on earth is came along meteor shelling on earth during its formation. these meteors were contain salt crystals that contain water droplets it them..

if collision of theia mixed up all the materiel , and moon is consider a part of earth in some way ,,, then there should be a trace of water on the moon, or need to rethink the theia theory.

 

 

Why do you think there is no water on the moon?

https://en.wikipedia.org/wiki/Lunar_water

Volatile elements, including water, were largely lost from the ejected material from which the moon was formed. This is natural and expected.

 

A small proportion of the water on the Earth is likely derived from dehydration of the mantle. Unlike the water in the ejected material that formed the moon, depth of burial and gravity kept that mantle water available.

 

The bulk of the water on the earth is derived, as you noted, from asteroids, or comets, or both. The moon and the Earth would have received similar amounts, in proportion to their size. The lower gravitational attraction of the moon, however, meant that its water was lost to space. Rather than calling the impact theory into question, the absence of any significant volume of water on the moon is one of the facts that led to and support that theory.