Metals from space descend on Boulder, Colorado, at dusk and dawn

Enlarge / Morning sun against the foothills of Boulder, Colorado, business area and campus. (credit: Fred Langer Photography | Getty Images)

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.

These layers are not visible to the human eye. So, at the Table Mountain Observatory near Boulder, the team made use of a lidar system-which operates similarly to radar but uses lasers instead of radio waves-to detect the minuscule sodium particles. While the lidar data from the region was taken a few years back, the team analyzed them last December and discovered our atmosphere's metal cycle.

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