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: 07-84
NASA AIMS TO CLEAR UP MYSTERY OF ELUSIVE CLOUDS AT EDGE OF SPACE
WASHINGTON - NASA is preparing to launch the Aeronomy of Ice in the
Mesosphere (AIM) spacecraft, the first mission dedicated to
exploration of mysterious ice clouds that dot the edge of space in
Earth's polar regions. These clouds have grown brighter and more
prevalent in recent years and some scientists suggest that changes in
these clouds may be the result of climate change.
The first opportunity for launch is on Wednesday, April 25 from
Vandenberg Air Force Base, Calif., aboard a Pegasus launch vehicle.
AIM will conduct the first detailed probe of this unusual phenomenon
typically observed approximately 50 miles above the Earth's surface
in the mesosphere. The mesosphere is the region just above the
stratosphere. Researchers know very little about how these polar
mesospheric clouds form, why they are being seen at lower latitudes
than ever before or why they have recently grown brighter and more
frequent.
"These clouds are indicators of conditions in the upper reaches of the
Earth's atmosphere, and are an important link in the chain of
processes that result in the deposition of solar energy into Earth's
atmosphere," said Mary Mellott, AIM program scientist, NASA
Headquarters, Washington. "AIM will provide an understanding of how
and why these clouds form, an important contribution toward the NASA
goals of understanding the fundamental physical processes of our
space environment and how the habitability of planets is affected by
the interaction of planetary magnetic fields and atmospheres with
solar variability."
The clouds are noctilucent, meaning they can be seen from the ground
only at night, when they are illuminated by sunlight no longer
visible from the Earth's surface. The brightest of these clouds are
now known to be primarily composed of water ice. Their seasonal
lifecycle is controlled by complex interactions between temperature,
water vapor, solar activity, atmospheric chemistry and small
particles on which the cloud crystals form. Human-induced factors
such as carbon dioxide cause a warming in the lower atmosphere but a
cooling in the mesosphere.
The clouds form in the coldest part of the Earth's atmosphere at the
summer season in the polar regions. In the northern hemisphere they
begin appearing in mid-May and last through mid-August, in the
southern hemisphere beginning mid-November and lasting through
mid-March.
"The occurrence of these clouds at the edge of space and what causes
them to vary is not understood," said AIM principal investigator
James Russell III, Hampton University, Hampton, Va. "One theory is
that the cloud particles grow on 'seeds' of meteoric dust or dust
lofted up from below. AIM will provide the comprehensive data needed
to test current theories for cloud formation or develop new ones, and
allow researchers to build tools to predict how they will change in
the future."
AIM will be comprised of three instruments: the Solar Occultation for
Ice Experiment; the Cloud Imaging and Particle Size Experiment; and
the Cosmic Dust Experiment. The satellite will simultaneously measure
air pressure and temperature, moisture content and cloud dimensions,
providing data needed to determine the role of polar mesospheric
clouds as an important indicator of the planet's changing climate.
The clouds appear to be a relatively recent phenomenon, first reported
in the late 19th century shortly after the volcanic eruption on the
Indonesian island of Krakatoa. The first daytime observations of the
clouds were made by satellite in 1969. Regular space-based
observations began in 1982 with NASA's Solar Mesosphere Explorer
using instruments primarily designed for other purposes.
"This Small Explorer mission is a good example of the huge science
returns we can get for a relatively small cost investment," said
Vicki Elsbernd, program executive for the AIM mission, NASA
Headquarters.
For more information about NASA and the AIM mission, visit:
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