COOL IMAGES: Glow-in-the-Dark Clouds

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Science  30 Jun 2000:
Vol. 288, Issue 5475, pp. 2279
DOI: 10.1126/science.288.5475.2279a

These glowing wisps high in the Scottish sky are no ordinary clouds: They're noctilucent clouds, a name that means “shines at night.” Thought to be made up of ice crystals illuminated by the sun, these mysterious clouds form about 82 kilometers above Earth in the frigid upper atmosphere–far above storm clouds and nearly as high as the aurora. Noctilucent clouds appear at twilight in summer, usually at high latitudes in places like Russia, Scotland, and Canada. In recent decades they've been spotted more often and farther south. That intrigues atmospheric scientists, as it suggests that the clouds might be tied to the buildup of humanmade greenhouse gases. For more info and photos, visit the Noctilucent Cloud Observers' Home Page run by amateur astronomer Tom McEwan, who snapped the shot above in July 1997 from Glengarnock.

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