Nasa finds arsenic-loving ‘aliens’ in California lake
‘The definition of life has just expanded’ says Nasa - but not as much as space buffs had hoped
THE MYSTERY surrounding Nasa's much-trailed 'astrobiology discovery' - which prompted speculation that alien life had been found on a moon of Saturn - has been dispelled.
Scientists have found a new form of life which, unlike every living creature we currently know, can use arsenic instead of phosphorus to build and power its cells.
The earth-shaking discovery has only one downside for space buffs: this 'alien' micro-organism lives in a lake in California.
The news comes in a scientific paper published in the December issue of Science Express and was the subject of a press conference which prompted the feverish speculation about alien life when the invitation was sent out earlier this week.
Humans - like all other forms of life - use the element phosphorus to create ATP (adenosine tri-phosphate), a molecule used in respiration as a kind of 'energy carrier'. Phosphorus is also needed as a building block to produce DNA - which our bodies use to create our proteins - and phospholipids, which are needed to produce body cells.
One of the reasons why arsenic is such a poisonous element is because it is chemically similar to phosphorus. If eaten, it can replace phosphorus and disrupt our metabolic processes.
The Nasa scientists have discovered a new type of bacterium that, if no phosphorus is available, can use arsenic to make DNA, proteins and cell membranes.
A Nasa spokesman said: "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."
Creatures that utilise a different suite of elements to build their body cells are a staple of science-fiction. In the 1960s TV series Star Trek, Captain Kirk and his crew land on a planet inhabited by a life-form that, unlike the carbon-based organisms of earth, is made of silicon.
The new microbe announced by Nasa is not quite that impressive. For a start, 'strain GFAJ-1' is a member of a common group of bacteria, the Gammaproteobacteria, and was found in Mono Lake, a body of water just east of California's Yosemite National Park which boasts one of the largest concentrations of arsenic on earth.
The new bacterium is a significant find, suggesting that organisms can exist in a place where there is no phosphorus - previously considered an element essential to life.
Felisa Wolfe-Simon, a Nasa astrobiology research fellow in residence at the US Geological Survey, and the research team's lead scientist, said: "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?" ·
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