Scientists working with NASA's Phoenix Lander are reasonably sure they have detected a toxic chemical in the soil near the north pole of Mars.

But they say hearty strains of microbes might be able to live there anyway -- and even thrive on it.

"This is an important piece of the puzzle as we attempt to determine whether habitable conditions exist for microbes on Mars," said Phoenix principal investigator Peter Smith, of the University of Arizona. "In itself, it is neither good nor bad for life."

The chemical, perchlorate, is an oxidant widely used in solid rocket fuel, but can also be naturally occuring on Earth. It is found in soil of Chile's barren Atacama desert -- generally believed to be one of the most lifeless places on Earth -- but scientists have been able to isolate strains of bacteria living in that soil.

Such organisms are known as "extremophiles," because they have evolved to live in harsh environments. And if it could happen on Earth, why not Mars?

"This desert is a hyper-arid environment that rarely sees rain, and has no vascular plants, and is often used by scientists as a matter of fact as a Martian 'analog' site," Smith said Tuesday.