Alien life on EarthNew life form -- thriving on arsenic -- found on Earth
“Life as we know it requires particular chemical elements and excludes others—- But are those the only options? How different could life be?” — asks Arizona State University professor Ariel Anbar; researchers find that the toxic element arsenic can replace the essential nutrient phosphorus in biomolecules of a naturally occurring bacterium; the finding expands the scope of the search for life beyond Earth
Evidence that the toxic element arsenic can replace the essential nutrient phosphorus in biomolecules of a naturally occurring bacterium expands the scope of the search for life beyond Earth, according to Arizona State University scientists who are part of a NASA-funded research team reporting findings in the 2 December online Science Express.
It is well established that all known life requires phosphorus, usually in the form of inorganic phosphate. In recent years, however, astrobiologists, including Arizona State University professors Ariel Anbar and Paul Davies, have stepped up conversations about alternative forms of life. Anbar and Davies are coauthors of the new paper, along with ASU associate research scientist Gwyneth Gordon. The lead author is Felisa Wolfe-Simon, a former postdoctoral scientist in Anbar’s research group at ASU’s School of Earth and Space Exploration and Department of Chemistry and Biochemistry in the College of Liberal Arts and Sciences.
“Life as we know it requires particular chemical elements and excludes others,” says Anbar, a biogeochemist and astrobiologist who directs the astrobiology program at ASU. “But are those the only options? How different could life be?” Anbar and Wolfe-Simon are among a group of researchers who are testing the limits of life’s chemical requirements.
“One of the guiding principles in the search for life on other planets, and of our astrobiology program, is that we should ‘follow the elements,’” says Anbar. “Felisa’s study teaches us that we ought to think harder about which elements to follow.”
Wolfe-Simon adds: “We took what we do know about the ‘constants’ in biology, specifically that life requires the six elements CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur) in three components, namely DNA, proteins and fats, and used that as a basis to ask experimentally testable hypotheses even here on Earth.”
From this viewpoint, rather than highlighting the conventional view of the “diversity” of life, all life on Earth is essentially identical, she says. The microbe the researchers have discovered, however, can act differently.
Davies has previously speculated that forms of life different from our own, dubbed “weird life,” might even exist side-by-side with known life on Earth, in a sort of “shadow biosphere.” The particular idea that arsenic, which lies directly below phosphorous on the periodic table, might substitute for phosphorus in life on Earth, was proposed by Wolfe-Simon and developed into a collaboration with Davies and Anbar. Their hypothesis was published in January 2009, in a paper titled “Did nature
