Atmospheric metal layers appear with surprising regularity

Twice a day, at dusk and just before dawn, a faint layer of sodium and other metals begins sinking down through the atmosphere, about 90 miles high above the city of Boulder, Colorado. The movement was captured by one of the world's most sensitive 'lidar' instruments and the regularly appearing layers promise to help researchers understand better how earth's atmosphere interacts with space, even potentially how those interactions help support life.

from Latest Science News -- ScienceDaily https://www.sciencedaily.com/releases/2021/06/210602091411.htm