We've been told that water arrived on earth through comets, and asteroids, but a recent study proved that the solar wind is constantly interacting with the earth's atmosphere to create water. This process is small, but over millions and millions of years...it adds up. Here's how it would work, hydrogen ions (H⁺) in the solar wind would break apart ozone (O₃) in our atmosphere and recombine into H₂O misting the earth with water:

H⁺ + O₃ ​→ OH + O₂