Argh! Popular is not a synonym for common! Change!
Also, it’s not the most common form of precipitation because of what scientists think about it; it would happen with the same frequency (whatever that is) even if there were no scientists to think about it at all, because it’s a natural process and isn’t subject to anyone’s opinion. Delete because.
It rains diamonds on Saturn. Lightning storms turn methane into soot that hardens into diamonds. This could be the most common form of precipitation in the solar system; scientists think it also happens on Jupiter, Uranus, and Neptune.