Washington: A NASA rover on Mars has discovered a toxin in soil on the north pole, diminishing the likelihood of finding life on the Red Planet, space agency officials said on Tuesday.

The Phoenix lander several weeks ago scooped up the dirt samples and extensive analysis confirmed the existence of perchlorate, a highly oxidizing substance that would harm life.

"This is surprising since an earlier ... measurement of surface materials was consistent with but not conclusive of the presence of perchlorate," said Peter Smith, the principal investigator at the University of Arizona.

The NASA scientists would not rule out the possibility that life could have existed on Mars or could exist now, but the findings cast further doubt into the possibility.

"While we have not completed our process on these soil samples, we have very interesting intermediate results," Smith said.

The announcement came after NASA said last week that Phoenix had found water in a soil sample, increasing the possibility the planet could support life.

The spacecraft's robotic arm dug several trenches in the Martian soil near the planet's north pole and have been heating soil samples in a series of small "ovens."

It had earlier spotted chunks outside the rover that scientists had identified as ice, but data sent back by the most recent soil sample for the first time showed water inside Mars' dirt, researchers said.

Phoenix landed on Mars on May 25 and its mission was to last three months. Instead the US space agency will spend another $2 million for a few extra weeks of research. IANS