The sky over Antarctica is now glowing electric blue with noctilucent, or night-shining, clouds. That’s according to recent images from NASA’s AIM spacecraft (Aeronomy of Ice in the Mesosphere), which monitors these clouds for the whole Earth. The season for night-shining clouds in the Southern Hemisphere is November to April, so they are right on schedule. These are ice clouds, and Earth’s highest clouds, located some 50 miles (80 km) above the ground in a layer of the atmosphere called the mesosphere. The clouds – made of ice crystals – are seeded by fine debris from disintegrating meteors.
The season for noctilucent clouds in the north is May to September. In both hemispheres, they happen when it’s summertime, when water vapor wafts up into the high atmosphere, providing the moisture needed to form these spectacular ice clouds at the edge of space.
As for the electric-blue glow, it comes from sunlight shining through the high clouds.
Cora Randall, a member of the AIM science team at the University of Colorado’s Laboratory for Atmospheric and Space Physics, said:
The current season began on November 19. Compared to previous years of AIM data, this season seems to be fairly average, but of course one never knows what surprises lie ahead, particularly since the southern hemisphere seasons are so variable.
If you were in Antarctica now, would you see these clouds shining overhead? Not likely, since there’s 24-hour daylight shining on that part of the globe now. But we’re past the December solstice, meaning that summer is waning in the Southern Hemisphere. People outside the Antarctic, at relatively high Southern Hemisphere latitudes, might be able to glimpse the clouds, especially as their sunsets come earlier and night lengthens on that part of the globe.
We frequently see images of noctilucent clouds, taken from the ground, during the northern summer. Our friends at high northern latitudes – typically from northern Europe and Scandinavia – capture them. Examples below:
Bottom line: NASA AIM image of notilucent clouds, shining in the high atmosphere, or mesosphere, over Antarctica in early January, 2018.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.