NIGHT-SHINING CLOUDS:

NIGHT-SHINING CLOUDS: Last night a vivid display of electric-blue noctilucent clouds (NLCs) appeared over parts of northern Europe, signaling the start of the 2007 NLC season. Noctilucent or "night-shining" clouds were first reported in the 19th century after the eruption of super-volcano Krakatoa. In those days, NLCs were confined mainly to high latitudes, but they have intensified and spread with sightings in recent years as far south as Utah and Colorado. The origin of these clouds is a mystery; they may be a side-effect of global warming. A NASA spacecraft named AIM is in orbit now to investigate.
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