Lovely wisps of iridescent clouds in the evening sky are known as noctilucent (NCL), or sometimes they are referred to as night-shining clouds.  On occasion, it is possible for sky watchers to view them above the grandeur of an evening sunset as a serenely beautiful crown of luminance.

They can be seen from space also.  In 2003 astronauts reported seeing them over Australia and the southernmost tip of South America.

Here is a vid from 2009 of noctilucent clouds as seen from space:

http://www.youtube.com/watch?v=AaI8JyAqykQ

Noctilucent clouds are composed of tiny ice crystals in the mesosphere which is 50 miles (80 km) above the Earth in a region of the atmosphere that sits above the stratosphere.  This is literally on the fringe of space.  In the mesosphere the temperature is very cold so that tiny ice crystals that are about the size of particles in cigarette smoke are trapped there and tend to persist over time.

Gary Thomas, a professor at the University of Colorado, reports that:

“The mesosphere is not only very cold (-125 C), but also very dry –  one hundred million times dryer than air from the Sahara desert.”

How those ice crystals got into this cold dry place is a mystery to scientists, and they also wonder why the clouds are becoming more prevalent.  First noticed in 1885, they are increasing in quantity and distribution.  There must be some way that water molecules along with the dust that makes them stick together finessed their way into that space.  In order to investigate these clouds, NASA has launched in 2007 a satellite that will specifically explore this phenomenon and hopefully bring home the answers.

REFERENCE:

http://en.wikipedia.org/wiki/Noctilucent_cloud

http://www.wired.com/wiredscience/2009/07/nightclouds/