NASA says Mars toxin find doesn't rule out life

LOS ANGELES (Reuters) - NASA scientists on Tuesday said the surprise discovery of a sometimes toxic chemical on the surface of Mars does not diminish the possibility of finding microbial life on the Red Planet and asked for patience while they study soil samples further.

The space agency also cautioned that further tests were required to confirm that dirt analyzed by the Phoenix Mars Lander contains perchlorate, an oxidizing substance used in rocket fuel that on Earth can be harmful to life, and rule out contamination by the spacecraft.

NASA's initial announcement that Phoenix had detected perchlorate in the soil at the arctic circle of Mars had been greeted in the media and on the Internet by speculation that such a discovery would dampen the likelihood of finding microbial life there.

"This has yet to be verified inside (Thermal and Evolved Gas Analyzer) instruments," Phoenix chief investigator Peter Smith said, adding that even if the discovery were confirmed "this does not preclude life on Mars. In fact it is a potential energy source."

"I ask that the media be patient with us," he said. "Let the science team proceed at a proper pace."

Phoenix is the latest NASA spacecraft sent to Mars to discover whether water ever flowed on Mars and if life, even in microbial form, exists or ever existed there.

Last week NASA said Phoenix had provided definitive proof that water exists on Mars after further tests on ice found by the lander in June.

'WE DON'T HAVE THE ANSWER'

The scientists were seemingly stunned to have turned up perchlorate on Mars. On Earth, the substance is found in such places as Atacama Desert in Chile, one of the driest places on the planet which is used by NASA as a testing ground for Mars missions.

But they noted that on Earth some plants were known to live in relatively perchlorate-rich soil.

"How this perchlorate affects habitability on Mars is certainly a complex question that we don't have a final answer on," Smith said. "It really doesn't limit us in our search

for habitability in this icy soil and if we were lucky enough to see some organic signatures we wouldn't be surprised.

In trying to rule out the possibility that perchlorate could have been brought to Mars by Phoenix, NASA was reviewing its prelaunch contamination control processes.

The agency last week extended the Phoenix mission by five weeks, saying its work was moving beyond the search for water to further exploring whether the planet was ever capable of sustaining life.

The extension will add about $2 million to the $420 million cost of landing Phoenix on May 25 for what was a scheduled three-month mission.

Phoenix touched down in May on an ice sheet and samples of the ice were seen melting in photographs taken by the lander's instruments in June.

Mission scientists said then that Martian soil was more alkaline than expected and had traces of magnesium, sodium, potassium and other elements. They described the findings as a "huge step forward."