NASA Mission Finds New Clues to Guide Search for Life on Mars
PASADENA, Calif. - 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 a square kilometer (0.4 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 colors, 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 sulfate minerals. Clays indicate
weathering by water, and sulfates 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."
JPL, a division of the California Institute of Technology, Pasadena, manages
Odyssey for the NASA Science Mission Directorate. Lockheed Martin Space Systems,
Denver, is the prime contractor for the project and built the spacecraft. Additional
information about Odyssey is at http://www.nasa.gov/mission_pages/odyssey
information about the camera and the new findings is at http://themis.asu.edu
Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Robert Burnham 480-458-8207
Arizona State University, Tempe
Tara Hicks-Johnson (808) 956-3151
University of Hawaii, Manoa