June 28, 2007

Dwayne Brown/Tabatha Thompson
Headquarters, Washington
202-358-1726/3895

Cynthia O'Carroll
Goddard Space Flight Center, Md.
301-286-4647

Nina Stickles
Hampton University,Hampton, Va.
757-727-5457 

RELEASE: 07-145

NASA SATELLITE CAPTURES FIRST VIEW OF 'NIGHT-SHINING' CLOUDS

WASHINGTON -- A NASA satellite has captured the first occurrence this 
summer of mysterious iridescent polar clouds that form 50 miles above 
Earth's surface.

The first observations of these clouds by the Aeronomy of Ice in the 
Mesosphere (AIM) satellite occurred above 70 degrees north on May 25. 
Observers on the ground began seeing the clouds on June 6 over 
northern Europe. AIM is the first satellite mission dedicated to the 
study of these unusual clouds.

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 during the Northern Hemisphere's summer season that 
begins in mid-May and extends through the end of August. They are 
being seen by AIM's instruments more frequently as the season 
progresses. The clouds also are seen in the high latitudes of the 
Southern Hemisphere during the summer months.

Very little is known about how these clouds form over the poles, why 
they are being seen more frequently and at lower latitudes than ever 
before, or why they have been growing brighter. AIM will observe two 
complete polar mesospheric cloud seasons over both poles, documenting 
for the first time the entire, complex life cycle of PMCs. 

"It is clear that PMCs are changing, a sign that a distant and 
rarified part of our atmosphere is being altered, and we do not 
understand how, why or what it means," stated AIM principal 
investigator James Russell III, Hampton University, Hampton, Va. 
"These observations suggest a connection with global change in the 
lower atmosphere and could represent an early warning that our 
Earth's environment is being altered."

The AIM instruments are returning valuable information on the global 
extent and variability of these clouds and preliminary information on 
their particle sizes and shapes. Early indications are that the 
clouds occur at high latitudes early in the season then move to lower 
latitudes as time progresses. The AIM science team is studying these 
new data to understand whether the changes in the clouds may be 
related to global climate change.

When the Northern Hemisphere summer season ends in mid- to late 
August, the AIM science team will not have to wait long before the 
Southern Hemisphere's season starts. This occurs about three months 
later in mid- to late November. The Southern season lasts until 
approximately mid-March of 2008. Early results from the AIM mission 
will be reported at a major international conference focused on PMCs 
and other high altitude layered phenomena to be held at the end of 
August 2007 in Fairbanks, Alaska.

The satellite was launched on April 25, only four weeks before the 
first science observations began. During the satellite-commissioning 
phase and now in routine observations, all three state-of-the-art 
instruments have been working exceptionally well and returning high 
quality data. 

The Cloud Imaging and Particle Size instrument offers a 2-D look at 
the clouds, collecting multiple views from different angles. The 
cameras are providing panoramic PMC images of the Arctic polar cap 
daily. The Solar Occultation For Ice Experiment is measuring new 
information on cloud particles: their variability with altitude, the 
chemicals within the clouds and the environment in which the clouds 
form. The Cosmic Dust Experiment is recording the amount of space 
dust that enters Earth's atmosphere to help scientists assess the 
role this dust plays in PMC formation.

The AIM mission coincides with the two-year, worldwide scientific 
community's International Polar Year, and the mission is expected to 
make unique contributions to the International Polar Year's objective 
of advancing polar research.

AIM is the ninth Small Explorers mission under NASA's Explorer Program 
and is managed by the Explorers Program Office at the Goddard Space 
Flight Center, Greenbelt, Md. The AIM Project Data Center is located 
at Hampton University.

For related images on this story, please visit:

http://www.nasa.gov/aim

	
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