UFO's

[Succubus]

Uh, >>90% of the water in our solar system is not on earth.   If our understanding of the process of planetary formation is correct, then most planetary systems would contain many times more water than present on earth, many of these would have them concentrated on large outer planets and moons.

Apologies for being unclear, what I was stating in a rather vague roundabout way is, why does a starship need water?

Water may indeed be a valuable resource for an interstellar spaceship, growing petunias or whatever but as a reaction mass for a propulsion system then that is one piss poor starship drive they have.

Edit:

Other than water what does planet Earth have that they can't find in the millions of planets much closer to their home world?

Yes I see your point. My bad.