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Posted by baalke on March 22, 2007, 7:14 pm
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Ruth Dasso Marlaire
March 22, 2007
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650-604-4709
E-mail: rmarlaire@mail.arc.nasa.gov
RELEASE: 07-14AR
NASA STUDIES LIFE'S LIMITS IN CHINA'S EXTREME DESERTS
MOFFETT FIELD, Calif. - Searching for clues to the potential for life
on
Mars, NASA scientists recently explored microbial communities in some
of
the world's oldest, driest and most remote deserts, in China's
northwest
region, and found evidence suggesting that conditions there may be
similar
to those in certain regions of Mars.
This is the first comprehensive study of microbial ecosystems in the
extreme deserts of China. Scientists looked for microbial life and
tried to
determine climates effect on the distribution, diversity and abundance
of
that life in extreme conditions. Results of this study were published
recently in the Journal of Geophysical Research.
"Our findings showed that numerous sources of water, such as rainfall
and
snowmelt, characterized how microbial life existed in its
environment,"
said Chris McKay, the principal investigator at NASA Ames Research
Center,
Moffett Field, Calif. "Rainfall amounts primarily dictated the type
of
microbial ecosystems we found across sites, but the effects of
temperature,
humidity and light created a gradient of soil water conditions
suitable for
life as well," added McKay.
In December 2006, NASA published satellite images from the Mars
Global
Surveyor mission that showed periodically changing gullies on the
surface
of Mars. Although no one knows for sure how the martian gullies were
formed, some scientists hypothesize that they may be the result of
surfacing groundwater or melting of ice in the martian subsurface.
According to McKay, single-celled organisms can exist only if there
is
enough water, which determines life's limits. To study the
possibilities of
microbial life on Mars, scientists went to the most arid, Mars-like
environments they could find on Earth - the dry valleys of Antarctica,
the
Atacama Desert of Chile, and now northwestern China.
Scientists who are interested in Mars and its environmental conditions
have
been studying microbial ecosystems in the deserts of Earth for years,
focusing on blue-green algae, or cyanobacteria. The bacteria's green
color
indicates they are capable of photosynthesis, the principal process
by
which organisms produce organic matter from inorganic matter.
According to scientists, microbial photosynthesis can occur within
and
under rocks in the desert. If the rock is porous, like sandstone,
then
cyanobacteria can live within its pores or crevices, where water can
be
held. More commonly, cyanobacteria are found under translucent rocks,
such
as quartzite, where light can penetrate, allowing photosynthesis to
occur.
To broaden understanding of the dynamic physical environments that
allow
for microbial survival, McKays research team traveled to China's
extreme
northwest region in the spring of 2006 for data collecting and
analyses.
Field locations -- including Tokesun, Ruoqiang and Sorkuli - were
selected
based on contrasting temperatures and amounts of regional rainfall.
Tokesun contains the lowest point in China, approximately 500 feet
(152 m.)
below sea level. It was selected because it is hot and dry. Ruoqiang
runs
parallel to the southern edge of the Taklimakan Desert and is hot and
wet.
Sorkuli is a high-altitude desert, ranging between 8,200 feet and
9,840
feet (2500 m. to 3000 m.) that is situated along the Qinghai-Tibetan
plateau. Climate conditions there vary due to changes in altitude and
landscape. It has two types of environments: cold and dry, and cold
and wet.
"Through a comparison of similar available climate data for other
deserts,
we conclude that from a microbial physiological standpoint, although
the
Atacama Desert represents the driest environment recorded, and the
Dry
Valleys in Antarctica represent the coldest desert conditions, the
high-altitude deserts in the Qinghai-Tibetan Plateau represent the
coldest
and driest conditions recorded on Earth," said McKay.
This research was funded under the NASA Astrobiology Science and
Technology
for Exploring Planets program and a joint NASA - National Science
Foundation program, called Life in Extreme Environments.
For more information about NASA on the Web, visit:
<http://www.nasa.gov/home>http://www.nasa.gov/home
-end-
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