Scientists puzzling over chemical found in Martian soil

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.

"These compounds are quite stable in soil and water and do not destroy organic materials under normal circumstances. In fact there are species of perchlorate-producing microbes that live on the energy provided by this oxidant."

Part of the NASA rocket that launched Phoenix to Mars contains ammonium perchlorate, and the team has called in a propellant expert to explore whether or it somehow could have contaminated the science instruments during launch. They consider that possibility remote, however, Smith said.

Researchers are still puzzling over the results, and say they have as many questions as answers right now about what this all means. More data collection, analysis, and review is needed, Smith said.

The team likely would not have announced these results at this time, but Smith said they felt compelled to speak out to squelch inaccurate rumors circulating on the Internet that the White House had been briefed on a significant breakthrough having to do with life on Mars.

"It's not the way we'd prefer to do it," he said. "Unfortunately there was a story out that we were hiding something, and of course as soon as that story goes out people speculate. The speculation leads to all kinds of wonderful stories of discoveries that I wish we'd made, but we haven't."

Even if it turns out perchlorate in the soil makes it unlikely that life could exist there, it does not rule out the possibility that life once existed in the distant past. It is also possible that subsurface life exists there now, perhaps in a deep underground aquifer.

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.