Every day, the Sun rises and sets on Boulder, Colorado. And, like clockwork, a layer of sodium and other elements trickle down through the sky and hit the ground, a team of researchers at the University of Colorado-Boulder found. These elements hail originally from space and, in various forms, hit the atmosphere before making their trek to the Earth’s surface.

The team published this discovery in Geophysical Research Letters. A decade ago, Xinzhao Chu, the lead author of the research, discovered these metal layers at the McMurdo research station in Antarctica. However, near the Earth’s polar south, these elements appear sporadically, rather than daily. This is the first time researchers have discovered a case where the layers drop at regular intervals. – Source