These mystifying clouds are called Polar Mesospheric Clouds, or PMCs, when they are viewed from space and referred to as "night-shining" clouds or Noctilucent Clouds, when viewed by observers on Earth. The clouds form in an upper layer of the Earth’s atmosphere called the mesosphere during the summer and can be seen from the high latitudes on Earth.
Image Courtesy of NASA/Veres Viktor

Noctilucent Clouds

Noctilucent clouds (NLC’s) or polar mesospheric clouds (PMC’s) are found very high in the Earth's atmosphere. They are called Polar Mesospheric Clouds when they are viewed from space, and are referred to as noctilucent clouds when viewed by observers on Earth. Unlike lower clouds that are associated with weather, these clouds form at the very edge of space in the atmospheric layer called the mesosphere. Like some of the clouds we see more regularly, scientists think these clouds are made of frozen water or ice crystals.

As you can see from the image, NLC’s are seen best just after sunset. They glow an electric, blue-white. They are normally seen from locations near the poles of the Earth, but in recent years, they have been seen at much lower-latitude locations (like Colorado or Virginia in the U.S.). It’s this change in the locations of NLC’s that makes scientist think they may be a sign of global climate change on Earth, specifically global warming which is influenced by human activity. Scientists will look into this possibility with a new atmospheric mission, AIM (The Aeronomy of Ice in the Mesosphere).

These eerie looking clouds have only been studied in the recent past. Now, people are becoming more aware of NLC's. You too can be an observer of these clouds and can even share that information with others on the Internet!

Last modified February 10, 2009 by Becca Hatheway.

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