Beauty in the Dark
October 16, 2007
The photo above shows a breathtaking display of noctilucent clouds above the waters of the Yukon River, near Whitehorse in the Yukon Territory of Canada. It was captured approximately 2:00 a.m. (local time) July 24, 2007. These fascinating clouds are our planet's highest, occurring at altitudes of about 50 miles (80 km). Never visible in daylight, these thin wisps of frozen water vapor seem to appear magically after darkness falls, and glow dramatically with an eerie silver-blue light. They're seen primarily between the subpolar latitudes of 60 and 70 degrees during the late summer but can be occasionally observed in mid latitudes as well. These twilight clouds are poorly understood and though they're thought to consist of ice-covered particles, (possibly meteoritic dust) are objects of continuing scientific research.