Wondering about water

72/82 nice slow rain!! What a beautiful smell and sound. Rain and the water cycle are so amazing. To think that the water molecules we have today are the same water molecules that were here in Ancient Greece and Rome, for that matter of fact, they are the same molecules that the dinosaurs drank and peed. They have been in plants and animals, have been in the sky, the earth, and the oceans. I wonder how they were originally formed?? Joe says the original water molecules were formed in interstellar space.  Surely someone has given this some thought.