This view combines more than 400 images taken during the first several weeks after NASA's Phoenix Mars Lander arrived on an arctic plain on Mars.

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

"[Thisfinding] caught me by surprise," said Phoenix principal investigatorPeter Smith of the University of Arizona in a Tuesday teleconference withreporters.

Afterrumors spread across the Internet last weekend that Phoenix had foundintriguing findings that werebeing withheld from the public, mission scientists addressed the media toquash what Smith called the "speculation that has become rampant on the Web."

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

Thoughoxidizers can be harmful to life, this isn't the case for perchlorate,scientists said. "It does not precludelife on Mars. In fact it is a potential energy source," said WilliamBoynton of the University of Arizona, who is a co-investigator on the Thermaland Evolved-Gas Analyzer (TEGA), which heats up samples of the Martian dirt andanalyzes the vapors they give off to determine their composition.

On Earth, perchloratesare found in Chile's highly arid Atacama Desert, which is often used as ananalog to the Martian surface. Scientists had originally thought no life couldsurvive in the Atacama, but later research found organics in nitrate depositsassociated with perchlorates. The same could hold true for Mars, the Phoenixresearch team said.

Perchloratesare also highly soluble salts and could help scientists better understand thehistory of water on Mars. The presence of water ice at Phoenix's landing site wasconfirmed in a TEGA analysis last week.

Theperchlorate signal was detected in Phoenix's Microscopy, Electrochemistry andConductivity Analyzer's (MECA) wetchemistry lab, which dilutes dirt samples in water brought from Earth anddetects any soluble salts they contain.

Scientistschecked to make sure the signal was real and could be reproduced. Theperchlorate signal was also seen in a second sample analyzed by MECA.

"Wehave substantial evidence that our soil contains perchlorates," Smithsaid.

The nextstep 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 itwas heated to, which Boynton said some Phoenix scientists though could beindicative of perchlorate, though it could also have indicated several otherchemical species.

Scientistsdecided to look for a chlorine signal in TEGA's next sample on Sunday. If oneshowed up, the evidence for perchlorates "would have been rock solid."?But the analysis showed no evidence of chlorine.

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

They arealso trying to rule out the possibility that the signal was contamination fromthe solid fuel rockets that gave Phoenix its finalpush towards Mars and contained a perchlorate fuel, though Smith said that thescenario was unlikely.