I think it's valid for any person to ask a question on a subject and have zero idea about what they are asking; I think in a lot of cases it's obvious you wouldn't be asking a question if you knew about things ... people ask questions because they don't know ..... and so, Memphos ... your question is actually a good one, considering ... the real question is, even though water is circulated throughout various earthly systems, does any of it get lost to outer space?.... in other words, can water escape earth's gravitational pull?
When you answer that, you can then answer your initial question.