The mesosphere is much cleaner though. The only thing up there is, for the most part, meteor smoke. (It’s theorized that volcanic dust can sometimes help nucleate noctilucent clouds too.) ...

Meteoroids burn up in a part of Earth’s atmosphere called the mesosphere, which is 30 to 50 miles (48 to 80 kilometers) above the ground. Even though the air is thin up there, meteoroids still ...