Washington: It has long been believed that Mars' surface is too oxidised for life to survive. But, a new study has now claimed that the soil on the Red Planet may be less inhospitable than previously thought.

Scientists believe that the Martian surface is packed full of oxidizing compounds, which could make it difficult for complex molecules like organic chemicals -- the building blocks of life as we know it -- to exist.

But the new study, which analysed data gathered by NASA's Mars Phoenix Lander, suggested that is actually not the case.

"Although there may be some small amounts of oxidants in the soil, the bulk material is actually quite benign," said lead study author Richard Quinn of NASA's Ames Research Center and the SETI Institute in Mountain View, California.

"It's very similar to moderate soils that we find on Earth," Quinn was quoted as saying.

NASA's USD 420 million Phoenix lander, which touched down near the Martian north pole in late May 2008, had done a number of observations and interesting soil measurements using its onboard wet chemistry laboratory (WCL). One of those was the Mars dirt's acidity, or pH, level.

Quinn and his team studied the Phoenix data, focusing on measurements of Martian soils' oxidation-reduction potential.

Oxidation refers to the stripping away of electrons. It's a destructive process that can tear up complex molecules like DNA, which is why people need antioxidants as diet.

Scientists had reason to think that Martian soil might be highly oxidising, Quinn said. In the mid-1970s, NASA's Viking landers mixed some organic compounds into Martian dirt and the chemicals appeared to decompose.

But the new results, reported in the journal Geophysical Research Letters, paint a rosier picture of Red Planet soil as far as habitability is concerned.

"When you look at the composite of all the material in there and you measure the overall reactivity of that soil in solution, it's comparable to what you would find in terrestrial soils, Earth soils," Quinn said. So it's not an extreme environment in that regard."

The results do not prove that Martian life exists or ever has existed.

However, they and other findings including evidence from the High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars Reconnaissance Orbiter that liquid water may have flowed just beneath the Martian surface in the last year or so, are making scientists more and more hopeful, Quinn said.
   
"The evidence from the HiRISE team that there may be seasonal water flow at some locations, combined with this measurement that shows that when the soil is wetted it's actually not harsh conditions -- it's very positive in terms of the potential for life to get a foothold," he said.

(Agencies)