AstroCappella: Noctilucent Cloud
The AIM Mission
(This content from www.nasa.gov/aim)
The Aeronomy of Ice in the Mesosphere (AIM) mission is the first detailed exploration of Earth's unique and
elusive clouds that are literally on the "edge of space." Other space-based and ground-based measurements
have probed some aspects of this unusual phenomenon in Earth's mesosphere (the region just above the
stratosphere), but very little is known about how these clouds form over the poles, why they are being seen
at lower latitudes than ever before, or why they have been growing brighter and more frequent. Some
scientists have suggested that these polar mesospheric clouds may be the direct result of human-induced
Over the course of its two-year mission, AIM will help answer these questions by documenting for the first
time the entire complex life cycle of these clouds. With this information, scientists will be able to
resolve many of the mysteries about how these clouds form and be better able to predict how they will change
in the future.
AIM was successfully launched on April 25, 2007.
Look west 30 to 60 minutes after sunset when the Sun has dipped 6 to 16 degrees below the horizon. If you see luminous
blue-white tendrils spreading across the sky, you've probably spotted a noctilucent cloud. Although noctilucent clouds appear most often
at high latitudes such as Scandinavia and Canada, they have been sighted in recent years as far south as Colorado, Utah and Virginia.
NLCs are seasonal, appearing most often in late spring and summer. In the northern hemisphere, the best time to look would be between
mid-May and the end of August.