Noctilucent Clouds (NLCs) turn on every year in late spring, reaching almost full intensity over a period of no more than 5 to 10 days, and the bulb is glowing. These electric-blue ice clouds hang 53 miles (85 km) above Earth’s surface, at the edge of space itself, circling the north and South Pole regions. NLCs over Canada on June 13, 2012. Image credit: flying photographer Brian Whittaker.
“They were visible to the north for about 3 hours as we flew between Ottawa and Newfoundland at 35,000 feet” said Brian Whittaker.
Data from NASA’s AIM spacecraft show that noctilucent clouds are like a great “geophysical light bulb”.
Their origin is still largely a mystery; various theories associate them with meteoric dust, rocket exhaust, global warming – or some mixture of the three.