The US scientists have discovered an evidence that could prove that the existence of former Martian life. By using the data provided by Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter, the researchers found 200 individual places in the Martian southern hemisphere that show spectral characteristics consistent with chloride minerals.

These salt deposits occur in the middle to low latitudes all around the planet within ancient, heavily cratered terrain and they could be a proof that, once, there was life on Mars.

The team, led by Mikki Osterloo, of the University of Hawaii, has published a report about the findings in the March 21, 2008 issue of the scientific journal Science.

Lead author Osterloo found the sites by looking through thousands of THEMIS images processed to reveal, in false colors, compositional differences on the Martian surface.
"I started noting these sites because they showed up bright blue in one set of images, green in a second set, and yellow-orange in a third," she explained.

According to Philip Christensen, a Regents' Professor of Geological Sciences at ASU's School of Earth and Space Exploration in the College of Liberal Arts and Sciences, many of the deposits lie in basins with channels leading into them,

“This is the kind of feature, like salt-pan deposits on Earth, that's consistent with water flowing in over a long time," he added.

The new findings could mean a new direction of research. Until now, it was believed that the signs of past life on Mars should be searched mainly on a handful of places that show evidence of clay or sulfate minerals. The reasoning is that clays indicate weathering by water and that sulfates may form by water evaporation.

"By their nature, salt deposits point to a lot of water, which could potentially remain standing in pools as it evaporates." That is crucial, Christensen says. "For life, it's all about a habitat that endures for some time."

NASA is currently studying potential landing sites for its Mars Science Laboratory (MSL), a new-generation rover due for launch in fall 2009. In the light of new discovery, the salt deposits in topographic basins within the oldest rocks on Mars should also be considered as an alternative mineralogy for MSL or future rovers to explore, the scientists added.