The sky over Antarctica has turned an electric blue recently, which indicates the start of noctilucent, or night-shining, cloud season in the Southern Hemisphere. And it’s come early this year.

Noctilucent clouds are the highest clouds on Earth, sitting about 50 miles above the ground in the mesosphere, just outside of the reaches of space. This is where meteors disintegrate and ice crystals grow a brilliant blue as they reflect sunlight, according to a NASA statement.

NASA’s Aeronomoy of Ice in the Mesosphere (AIM) spacecraft took the image above. It studies noctilucent clouds to better understand the mesosphere and how it impacts our atmosphere and subsequently the weather and the climate.. AIM spotted the start of the noctilucent cloud season on Nov. 17, which would be the earliest start ever in the AIM’s record of the Southern Hemisphere, which could indicate earlier seasonal changes at lower altitudes.

“Data from NASA’s Aeronomy of Ice in the Mesosphere, or AIM, spacecraft shows the sky over Antarctica is glowing electric blue due to the start of noctilucent, or night-shining, cloud season in the Southern Hemisphere – and an early one at that,” the NASA statement reads. “Noctilucent clouds are Earth’s highest clouds, sandwiched between Earth and space 50 miles above the ground in a layer of the atmosphere called the mesosphere. Seeded by fine debris from disintegrating meteors, these clouds of ice crystals glow a bright, shocking blue when they reflect sunlight.

“AIM studies noctilucent clouds in order to better understand the mesosphere, and its connections to other parts of the atmosphere, weather and climate. We observe them seasonally, during summer in both the Northern and Southern hemispheres. This is when the mesosphere is most humid, with water vapor wafting up from lower altitudes. Additionally, this is also when the mesosphere is the coldest place on Earth – dropping as low as minus 210 degrees Fahrenheit – due to seasonal air flow patterns.”