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Arsenic-based organism redefines search for alien life

by Jorge Hernandez on December 3, 2010

NASA announced its discovery on Thursday of an organism that subsists off the toxic chemical arsenic, redefining the search for life and the scope of the environments that it can thrive in.

"The definition of life has just expanded. As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it," said NASA's Ed Weiler.

NASA researchers discovered the bacterium, which uses arsenic in place of phosphorus in its cells to create proteins and DNA, while conducting tests in Mono Lake, California, known for its unusually high levels of salt, alkaloids and arsenic.

According to the NASA website, phosphorus was previously thought essential to all life and DNA and is one of the six fundamental "building blocks" of all living organisms, in addition to carbon, hydrogen, nitrogen, oxygen and sulfur.

While it behaves much like phosphorus, arsenic is toxic to most all of Earth's life forms.

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new – building parts of itself out of arsenic," said NASA's Felisa Wolfe-Simon, who led the research.

Moving forward, the discovery of this alternative life structure may alter biology textbooks and the methods scientists use to seek extraterrestrial life.

MIT professor Sara Seager told MIT News that the discovery will also prompt researchers to search for a "shadow biosphere," a world, so to speak, filled with life forms we haven't yet recognized due to an alternative biochemistry.

The implication of this could portend a "second genesis," which researchers were already seeking when it was confirmed by the discovery, reports National Geographic. A second genesis, or "Life 2.0," would mean there was an origin of life independent to ours, reports the news source.

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