NASA satellite captures mysterious 'Night-Shining' clouds

NASA said today its AIM satellite has provided the first global-scale, full-season view of iridescent polar clouds that form 50 miles above Earth's surface known as "Night-Shining" clouds.

Polar sky

Night Shining clouds form at a high altitude which lets them reflect sunlight long after the sun has set. According to NASA, little is known about these clouds at the edge of space, also called Polar Mesospheric Clouds. The clouds consist of ice crystals formed when water vapor condenses onto dust particles in these coldest regions of the planet, at temperatures that may dip to minus 210 to minus 235 degrees F.

The AIM satellite, which is 55 inches tall, 43 inches wide and weighs 430 pounds, reported daily observations of the clouds at all longitudes and over a broad latitude range extending from 60 degrees North to 85 degrees North. The satellite is currently making the first global observations of the Southern Hemisphere cloud season.

New results from AIM's first Northern Hemisphere season observations show:

* The most detailed picture of the clouds ever collected showing that they appear every day, they are widespread, and they are highly variable on hourly to daily time scales.

* That Polar Mesospheric Cloud brightness varies over horizontal scales of about two miles; and over small regions, clouds measured by AIM are ten-fold brighter than measured by previous space-based instruments.

* The unexpected result that mesospheric ice occurs in one continuous layer extending from below the main peak at 51 miles up to around 55 miles.

* Observations of a previously suspected, but never before seen, population of very small ice particles believed to be responsible for strong radar echoes from the summertime mesosphere. This was made possible because of the unprecedented sensitivity of the AIM measurements.

* Polar Mesospheric Cloud structures resolved for the first time that exhibit complex features present in normal tropospheric clouds. This startling similarity suggests that the mesosphere may share some of the same dynamical processes responsible for weather near the surface. If this similarity holds up in further analysis, this opens up an entirely different view of potential mechanisms that can explain why the clouds form and how they vary, NASA said.

* The AIM or Aeronomy of Ice in the Mesosphere satellite mission is dedicated to the study of these clouds. Today NASA said AIM has provided the first global-scale view of the clouds over the entire 2007 Northern Hemisphere season with an unprecedented horizontal resolution of 3 miles by 3 miles.

During its mission, AIM will observe a total of two complete polar mesospheric cloud seasons in each polar region, documenting for the first time the entire complex life cycle of the clouds.

"The measurements show the brightest clouds ever observed with more variability and structure than expected, signifying extreme sensitivity to the environment in which the clouds form. They also show that the clouds exist over a broader range in height than was believed to be the case before AIM was launched," said AIM Principal Investigator James Russell of Hampton University, Hampton, Va., in a statement.

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