Anyone who's ever seen a noctilucent cloud or “NLC” would agree: They look alien. The electric-blue ripples and pale tendrils of NLCs reaching across the night sky resemble something from another world.
Researchers say that's not far off. A key ingredient for the mysterious clouds comes from outer space.
"We've detected bits of 'meteor smoke' imbedded in noctilucent clouds," reports James Russell of Hampton University, principal investigator of NASA's AIM mission to study the phenomenon. "This discovery supports the theory that meteor dust is the nucleating agent around which NLCs form."
NOCTILUCENT CLOUDS IN MOTION: "Last night (July 17)some nice noctilucent clouds appeared over Stockholm," reports Swedish photographer Peter Rosen. "Watching NLCs this summer has made me take an interest in their intricate movements--so I decided to create some close-up timelapse movies using a telephoto lens."
"What looked like a serene view from a distance behaves more like a stormy sea with wave after wave rolling in," he observes.
When NLCs first appeared in the 19th century, the mysterious clouds were confined to the Arctic, most often seen in the same places as Northern Lights. In recent years, however, their "habitat" has been expanding, rippling as far south as Colorado, Virginia, Kansas, and Utah. There is growing evidence that the expansion is a sign of climate change, although this remains controversial.