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."
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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