Ongoing studies of
Martian analog habitats on Earth
include some of the iciest regions and the driest areas. A new
study, published in the
Feb. 2007ref
Journal of Geophysical Research-Biogeosciences,
is the first comprehensive look at the microbial life in the
extreme deserts of China.
Results of
this study of China’s remote deserts could help
astrobiologists refine their maps
for uncovering Martian life. |
ref-
Warren-Rhodes, K.
A., K. L. Rhodes,
S. Liu, P. Zhou, and C. P. McKay,
Nanoclimate environment of cyanobacterial communities in China's
hot and cold hyperarid deserts,
J.
Geophys. Res.,
112,
1029 (2007). |
Kimberley
Warren-Rhodes, et al
in their
paper
examined the abundance and diversity of
blue-green algae called cyanobacteria
in several spots in the extreme deserts of China. They
analyzed linkages between cyanobacterial community
abundance and climate across a wide range of environmental
conditions and geographical distances in China's northwest
region, an area containing some of the
world's oldest, driest and most isolated
deserts. |
|
This aerial view shows a hyper-arid
desert near the Tianshan Mountain
Range in northwest China, where the Warren-Rhodes surveyed for
microbial life.
photo by NASA |
The Dry
Valleys in Antarctica (arguably the coldest place on Earth) and
certain areas in the Atacama Desert of Chile (some of the driest
places on Earth) previously provided a combination of of
conditions which are similar to those on Mars indicated lead
author Kimberley Warren-Rhodes and
Chris McKay of NASA
Ames Research Center. In the China deserts they
chose three locations based on temperatures and amount of
rainfall. One site, called Tokesun,
was warm and dry and located about 500 feet (152 meters) below
sea level, making it the lowest point in China. Another site,
called Ruoqiang, runs parallel to
the southern edge of the Taklimakan Desert and is hot and wet.
The last site, Sorkuli, is situated
along the Qinghai-Tibetan plateau and lies between 8,200 feet
and 9,840 feet (2,500 meters to 3,000 meters) above sea level.
This high-altitude desert included two climates: cold and dry,
and cold and wet.
Like green plants, cyanobacteria
capture the sun’s energy to carry out
photosynthesis and turn inorganic
CO2 into organic sugars needed for growth. On
Earth,
water is the limiting factor for
carrying out photosynthesis, and this would be particularly true
on the parched planet of Mars. But ecologists suspect that
microbes can live within rock pores
or beneath translucent rocks where moisture is most likely to
remain, possibly on both planets. Current monitoring and
long-term climate data show that extreme heterogeneity in liquid
water availability characterizes the
cyanobacteria environment with rainfall and snowmelt
being the main moisture sources. Warren-Rhodes measured
micro-climate conditions, including the relative humidity,
moisture, temperature and light levels in the soil, beneath
rocks and within pore spaces of rocks. Mean annual precipitation
(MAP) primarily dictated cyanobacteria
ecology across sites with an increase in rainfall being
typically associated with a spike in cyanobacterial density, but
the effects of temperature, humidity and light created a
gradient of soil water conditions suitable for life as well.
There appears to be certain climatic characteristics that make
it more probable to find microbial life in these really China
harsh deserts. One feature is rock size, with the larger rocks
supporting higher densities of
cyanobacteria, presumably because they can store more
water.
A major
conclusion of the research was that the high-altitude deserts in
the Qinghai-Tibetan Plateau of China offers the coldest and
driest recorded extremes for cyanobacteria on Earth and might be
a model for Martian habitat studies.
|
Kimberley A. Warren-Rhodes -
NASA-Ames Research Center,
Moffett Field, California,
USA.
Kevin L. Rhodes
- Department of Agriculture, Forestry and
Natural Resource Management,
University of
Hawaii, Hilo,
Hawaii,
USA.
Shuangjiang Liu
and Peijin Zhou
- Institute of Microbiology,
Chinese Academy of Sciences,
Beijing,
China.
Christopher P. McKay -
NASA-Ames Research Center,
Moffett Field,
California,
USA
|