NASA Mission Finds
New Clues To Guide The Search For Life On Mars
(20 March 2008) NASA's Mars Odyssey
orbiter has found evidence of salt deposits.
These deposits
point to places where water once was abundant and where evidence might exist of
possible Martian life from the Red Planet's past.
A team led by Mikki
Osterloo of the University of Hawaii, Honolulu, found approximately 200 places
on southern Mars that show spectral characteristics consistent with chloride
minerals. Chloride is part of many types of salt, such as sodium chloride or
table salt. The sites range from about half of a square mile to 25 times that
size.
"They could come from groundwater reaching the surface in low
spots," Osterloo said. "The water would evaporate and leave mineral deposits,
which build up over years. The sites are disconnected, so they are unlikely to
be the remnants of a global ocean."
Scientists used Odyssey's Thermal
Emission Imaging System, a camera designed and operated by Arizona State
University, Tempe, to take images in a range of visible light and infrared
wavelengths.
Thermal infrared wavelengths are useful for identifying
different mineral and rock types on the Martian surface. Osterloo found the
sites by looking through thousands of images processed to reveal, in false
colours, compositional differences on the Martian surface.
Plotted on a
Mars map, the chloride sites appear only in the southern highlands, the most
ancient rocks on Mars. Osterloo and seven co-authors report the findings in
this week's issue of the journal Science.
"Many of the deposits lie in
basins with channels leading into them," said Philip Christensen, co-author and
principal investigator for the camera at Arizona State University. "This is the
kind of feature, like salt-pan deposits on Earth, that's consistent with water
flowing in over a long time."
Scientists think the salt deposits formed
approximately 3.5 to 3.9 billion years ago. Several lines of evidence suggest
Mars then had intermittent periods with substantially wetter and warmer
conditions than today's dry, frigid climate.
Scientists looking for
evidence of past life on Mars have focused mainly on a handful of places that
show evidence of clay or sulphate minerals. Clays indicate weathering by water,
and sulphates may have formed by water evaporation. The new research, however,
suggests an alternative mineral target to explore for biological
remains.
"By their nature, salt deposits point to a lot of water, which
potentially could remain standing in pools as it evaporates." said Christensen.
"That's crucial. For life, it's all about a habitat that endures for some
time."
Whether life ever has existed on Mars is the biggest scientific
question driving Mars research. On Earth, salt is good at preserving organic
material. Bacteria have been revived in the laboratory after being preserved in
salt deposits for millions of years.
"This discovery demonstrates the
continuing value of the Odyssey science mission, now entering its seventh year.
The more we look at Mars, the more fascinating a place it becomes," said
Jeffrey Plaut, Odyssey project scientist at NASA's Jet Propulsion Laboratory,
Pasadena, Calif.
"This is a wonderful and scientifically exciting result
obtained from a relatively low cost NASA Mars orbiter mission which still has
years of life left.," said Alan Stern, associate administrator for NASA's
Science Mission Directorate in Washington. "Hold on to your hats, more exciting
results from Mars are sure to be coming."
(source: NASA)
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