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Image: Soil on Mars
NASA via AP file
This image provided by NASA shows a scraped area on Mars known as "Snow White," photographed on July 8. Two samples from Snow White were delivered to the Phoenix Mars Lander's wet-chemistry lab, and tests turned up evidence of a type of chemical known as perchlorate.
By Alan Boyle Science editor
msnbc.com
updated 8/5/2008 8:11:52 PM ET 2008-08-06T00:11:52

Would Martian soil be good for living things, or bad? After going back and forth on the question, the scientists behind NASA's Phoenix Mars Lander say it could be either.

The most surprising thing is that some of Phoenix's soil samples appear to contain chemicals that are found in rocket fuel — and in the natural soil of Chile's Atacama Desert, one of the places on Earth considered most like Mars.

That was the mixed message emerging from Tuesday's teleconference for journalists, which NASA organized in the wake of leaked reports that the Phoenix team had come upon unexpected findings about Mars' potential habitability.

The mission's top scientists admitted that the results were unexpected — so unexpected that they didn't exactly know what to make of them. The University of Arizona's Peter Smith, principal investigator for the Phoenix mission, said the discovery of perchlorates in the soil surrounding the lander in Mars' north polar region was "something that caught me by surprise."

"It doesn't limit us in our search for habitability in this icy soil," Smith said. "And if we were lucky enough to see some organic signatures, it would not be a huge surprise, I think, that they were co-existing with perchlorates."

So do Phoenix's findings make it more or less likely that Mars was once hospitable to life? "It probably comes down on the positive side rather than the negative," Smith said.

Twists and turns in Phoenix's tale
The findings, which still have to be confirmed, represent the latest twist in the tangled tale of Phoenix's scientific search. Smith and other researchers have repeatedly stressed that the probe's onboard laboratories can't detect life directly, but they can check the Red Planet's soil and ice for chemicals that might point to organic processes.

In June , the scientists in charge of Phoenix's wet-chemistry lab — part of an instrument suite known as the Microscopy, Electrochemistry and Conductivity Analyzer, or MECA — announced that the soil was alkaline and had the kinds of minerals that would make it suitable for growing asparagus if it were brought to Earth.

Last Thursday , results from a different mini-lab on Phoenix — the Thermal and Evolved-Gas Analyzer, or TEGA — confirmed the claim that water existed on Mars, albeit in frozen form. For years, scientists have been building a case that water was once abundant on the planet and could have sustained life. However, Phoenix's findings marked the first time that a probe had actually "tasted" the water.

Then, on Friday, Aviation Week reported that the White House had been alerted about an upcoming announcement on the "potential for life" on Mars, based on fresh findings from the MECA team. The report set off an Internet-driven buzz that grew in volume over the weekend — prompting denials from Smith, NASA and the White House on Monday. Later that day , researchers issued a statement about the detection of perchlorates and said such chemicals diminished the prospects for habitability.

Perchlorate's pluses and minuses
The views expressed at Tuesday's teleconference were much more nuanced. "How this perchlorate in the soil affects habitability is a complex question that we certainly don't have the final answer on," Smith said.

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On Earth, perchlorates are considered toxic contaminants requiring environmental cleanup. They're the main ingredient in solid rocket fuel and can be found in fireworks and other explosives. In fact, scientists still have to rule out the possibility that the perchlorates actually came from the Delta 2 rocket that sent the Phoenix spacecraft out of Earth orbit. (The lander itself used a hydrazine fuel that didn't contain perchlorates.)

Slideshow: Month in Space Brown University geologist John Mustard, who had no role in the Phoenix mission, told The Associated Press that perchlorates are "not usually considered an ingredient for life."

However, some organisms actually thrive on perchlorates and have been enlisted for cleaning up chemical spills. Perchlorate-loving microbes have been found in Chile's Atacama Desert and Antarctica — two of the places that have been compared to the Red Planet's cold, dry environment.

"There are some microbes that use it as an energy source, and there are some microbes that just co-exist with it and there are no problems," said Richard Quinn, a chemist at the SETI Institute and NASA's Ames Research Center who is an expert on the Atacama Desert.

Tufts University's Sam Kounaves, a member of the MECA team, said he still thought asparagus would grow well in soil from Mars, even with the perchlorate. "At this point, I still don't have any reason why it wouldn't," he told msnbc.com.

What it all means
Quinn said past Mars probes hadn't picked up evidence of perchlorates because they weren't designed to. The $420 million Phoenix mission was the first one with the onboard laboratory facilities capable of making the detection, he said.

There are several types of perchlorates with different properties, and scientists have not yet determined which types exist on Mars. Magnesium perchlorate, for example, tends to soak up water and could conceivably act as an antifreeze, said the MECA team's lead scientist, Michael Hecht of NASA's Jet Propulsion Laboratory.

"Certainly the way, say, magnesium perchlorate and water interact is interesting and could affect many things, from how landforms formed to whether, in the distant past, there was ever precipitation," he told msnbc.com. "Widespread implications, and they may turn out to be nothing or they may turn out to be very important. It's just that this has opened up a whole new research chapter for us."

Phoenix's researchers will have five extra weeks to study that chapter, thanks to a NASA decision to extend the probe's 90-day mission through the end of September. They stressed that they still have to confirm their findings about the perchlorates by running more tests. So far, the TEGA lab has not yet detected perchlorates, but more samples will be tested from the same area where the MECA lab made its find.

If the researchers had their way, they would have waited at least another couple of weeks before announcing any results.

"We don't want to come to you in the media and say we found chocolate on Mars, and two weeks later flip-flop and say, uh, we made a mistake, it was strawberry," Hecht told journalists. "That hurts our reputation, that hurts your reputation. So we want to make sure we get it right. Now, when we see something on the Internet that in fact is speculation that is attributed to us — and it's wrong — that does indeed change the equation a little bit."

Hecht hinted that there might be further announcements in the coming weeks, based on observations by Phoenix's atomic force microscope. On Tuesday, however, he focused almost exclusively on the perchlorate story.

"I certainly hope this isn't the last big, interesting story from Phoenix, and I hardly expect it will be. ... They will come out, as in this case, when we feel confident about the particular conclusions," he said.

This report includes material from The Associated Press.

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