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Alternate Life-form: The Arsenic Microbe

different bio-chemistry


Scientists haven't yet found E.T., but the discovery of an Earth microbe that thrives on arsenic should greatly broaden the search for life beyond Earth, NASA announced today (Dec. 2).

In a much-anticipated press conference, NASA announced that the bacterium GFAJ-1, found in a briny California lake, doesn't just tolerate arsenic ? it can incorporate the poisonous stuff into its DNA and other vital molecules in place of the usual phosphorus.

"We've cracked open the door to what's possible for life elsewhere in the universe," said study lead author Felisa Wolfe-Simon, NASA astrobiology research fellow at the U.S. Geological Survey in Menlo Park, Calif. "What else might we find? What else might we want to look for?"

NASA sent out alerts for the conference on Monday (Nov. 29), setting the Internet abuzz with speculation and rumors that life beyond Earth had been found, perhaps on Titan, Saturn's largest moon. The actual discovery ? which is very much terrestrial ? falls short of those expectations, dashing the hopes of some who may have let their imaginations run wild.

"I'm sorry if they're disappointed," Mary Voytek, director of NASA's astrobiology program, told reporters today. "But this is a huge deal. This is a phenomenal finding."

Science fact looks like fiction

Scientists had regarded phosphorus as one of six key ingredients ? along with carbon, hydrogen, nitrogen, oxygen and sulfur ? that all life on Earth needs to survive.

So finding a microbe that substitutes arsenic for phosphorus is like coming face to face with the fictional Horta beast from the science-fiction TV show "Star Trek," one of the scientists said. The Horta was based on silicon rather than carbon.

"In our mind, this is the equivalent," Voytek said. "It will fundamentally change the way we define life, and perhaps the way we look for it."

Search for extraterrestrial life

In particular, scientists hunting for life on Titan,...

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