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'Aliens Know There is Life on Earth'

Posted on: Saturday, 2 October 2004, 06:00 CDT

ALIEN astronomers on planets in other star systems almost certainly have the Earth listed as a world teeming with life, a leading scientist claims.

Earth observers are probably no more than 20 years away from identifying distant planets on which life exists.

It was likely that other civilisations among the stars, assuming they exist, have already come to the same conclusion about the Earth, saidDr Roger Angel, from the University of Arizona in Texas.

At America's biggest science meeting in Boston, Massachusetts, he said the Earth had been sending a strong signal into space announcing the existence of life for at least a billion years.

"I'm convinced that, if there were aliens with technology a bit more advanced than ours, they would know that there's life on this planet," Dr Angel told the American Association for the Advancement of Science.

Different chemicals create specific signatures imprinted in light which can be identified when light is divided into its constituent colours.

Astronomers know that any planet whose reflected light contains a strong oxygen signal is virtually guaranteed to support life.

To find small rocky planets such as the Earth and examine their atmospheres requires technology capable of separating their light from the dazzling rays of the stars they orbit.

Two new space telescopes with this abilityare due to be launched in about 15 years.

The European Space Agency's Darwin telescope and Nasa's Terrestrial Planet Finder will allow astronomers to look for the tell-tale signs of life among the stars.

By "cancelling out" the overspill of starlight they will be able to separate and capture reflected light from Earth-like planets.

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