Stunning noctilucent clouds over North Atlantic

Dorinda Todd, an American Airlines flight attendant, shared this beautiful image captured from from the flight deck of electric blue noctilucent clouds shining over the North Sea on a recent overnight flight from RDU to London.

Posted 9:24 p.m. Aug 2, 2022 — Updated 9:24 p.m. Aug 2, 2022

Tony Rice

, NASA Ambassador

polar mesopheric clouds, also known as noctilucent clouds, are made up of microscopic ice crystals high in the mesophere, Earth's coldest region. This photo was taken from the flight deck of a flight from RDU to London before sunrise. (Photo: Dorinda Todd)

Dorinda Todd shared a beautiful sight captured on a recent flight from RDU to London.

American Airlines flight 174 was about 700 miles south of Iceland late Thursday night when wispy cloud filaments glowing electric blue appeared on the northern horizon around 4:30 am local time.

These are noctilucent or “night-shining” clouds made up of tiny grains of ice, about the size of a flu virus (100 nanometers). They are formed in the upper reaches of the mesosphere.

Not unlike International Space Station passes, these clouds can appear in the sky at any time, but are only visible during twilight when the ground and lower reaches of the atmosphere are in shadow but upper reaches are lit by the rising (or setting) Sun.

noctilucent clouds reflect sunlight high in the atmosphere while it is still dark at ground level and even at 39,000 feet, cruising altititude for airliners crossing the Atlantic.

Ice forms in cold regions of the atmosphere when water vapor collects around a dust particle in a process called nucleation. A NASA mission, Aeronomy of Ice in the Mesosphere (AIM), has been studying where those two things come from since its launch in 2017.

Scientists looking at sunlight shining through these crystals via the Solar Occultation for Ice Experiment (SOFIE) aboard AIM have concluded that they are forming around meteor smoke.

Earth sweeps up about 20 tons of material from space each day, mostly very small rocks and dust. When that burns up in the atmosphere it leaves a thin haze of even smaller particles about 50 miles up.

Astronauts on board the ISS took this picture of noctilucent clouds near the top of Earth's atmosphere on July 13, 2012.

AIM data has shown ice crystals growing around meteoritic dust ranging in size from 20 to 70 nanometers. For comparison, the ice crystals in thin wispy cirrus clouds in the lower atmosphere where water is abundant are 10 to 100 times larger.

The small size of the ice crystals explains the clouds' blue color. Small particles tend to scatter short blue wavelengths of light.

NLCs begin forming each summer, peaking in early August, and are usually seen in the upper latitudes of Canada and northern Europe. But they've been seen more frequently recently and further south. Scientists have a few reasons why.

Noctilucent clouds appeared in the sky above Edmonton, Alberta, in Canada on July 2, 2011.
Credits: NASA/Dave Hughes

A recent paper by Michael H. Stevens of the U.S. Naval Research Laboratory and Cora Randall, an atmospheric scientist at the University of Colorado Boulder's Space Weather Technology Center, points to rocket launches, which have doubled worldwide in the last decade as a possible contributor.

Research has shown rocket exhaust plumes not only deposit water vapor directly into the normally dry mesosphere where NLCs form, but are also transported there from the lower thermosphere.

They are a regular scene over Florida after launches and have been seen far south as Arizona, new Mexico and Texas following a 2013 SpaceX Falcon 9 launch from Vandenburg Space Force Base in California.

James Russell from Hampton University's Center for Atmospheric Sciences , and principal investigator for the AIM mission, has another theory: climate change, specifically methane released from landfills, natural gas and petroleum systems, agricultural activities, and coal mining.

"When methane makes its way into the upper atmosphere, it is oxidized by a complex series of reactions to form water vapor. This extra water vapor is then available to grow ice crystals for NLCs."

It Russel's idea is correct, noctilucent clouds could serve as a "canary in a coal mine" for one of the most important greenhouse gases.

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