The chemical NASA's Phoenix Mars Lander found in a sample of Martian dirt, as announced on Monday, may not be harmful to any potential life there and could in fact be a boon to it, mission scientists said today.

"[This finding] caught me by surprise," said Phoenix principal investigator Peter Smith of the University of Arizona in a Tuesday teleconference with reporters.

After rumors spread across the Internet last weekend that Phoenix had found intriguing findings that were being withheld from the public, mission scientists addressed the media to quash what Smith called the "speculation that has become rampant on the Web."

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The Phoenix team announced Monday that one of Phoenix's instruments had detected perchlorate, a highly oxidizing substance.

Though oxidizers can be harmful to life, this isn't the case for perchlorate, scientists said.

"It does not preclude life on Mars. In fact it is a potential energy source," said William Boynton of the University of Arizona, who is a co-investigator on the Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples of the Martian dirt and analyzes the vapors they give off to determine their composition.

On Earth, perchlorates are found in Chile's highly arid Atacama Desert, which is often used as an analog to the Martian surface.

Scientists had originally thought no life could survive in the Atacama, but later research found organics in nitrate deposits associated with perchlorates. The same could hold true for Mars, the Phoenix research team said.

Perchlorates are also highly soluble salts and could help scientists better understand the history of water on Mars. The presence of water ice at Phoenix's landing site was confirmed in a TEGA analysis last week.

The perchlorate signal was detected in Phoenix's Microscopy, Electrochemistry and Conductivity Analyzer's (MECA) wet chemistry lab, which dilutes dirt samples in water brought from Earth and detects any soluble salts they contain.

Scientists checked to make sure the signal was real and could be reproduced. The perchlorate signal was also seen in a second sample analyzed by MECA.

"We have substantial evidence that our soil contains perchlorates," Smith said.

The next step in confirming the findings was to see if TEGA also detected perchlorates. The first sample delivered to TEGA released a large amount of oxygen when it was heated to, which Boynton said some Phoenix scientists though could be indicative of perchlorate, though it could also have indicated several other chemical species.

Scientists decided to look for a chlorine signal in TEGA's next sample on Sunday. If one showed up, the evidence for perchlorates "would have been rock solid."

But the analysis showed no evidence of chlorine.

The team plans to analyze another sample in TEGA taken from the same spot as the MECA sample that gave off the perchlorate signal to see if it will confirm the finding. (The Phoenix team had intended to wait for the TEGA results before announcing the perchlorate finding.)

They are also trying to rule out the possibility that the signal was contamination from the solid fuel rockets that gave Phoenix its final push towards Mars and contained a perchlorate fuel, though Smith said that the scenario was unlikely.

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