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Heavens above, secret of life is all in the stars.

Astronomers have found evidence in a cloud of gas 1,500 light years away that life on Earth originated among the stars.

The discovery backs theories that the organic components of life hitched a ride to Earth on comets and meteorites.

It also helps solve a mystery about the molecular structure of living things that has puzzled scientists for 150 years.

Louis Pasteur discovered in 1848 that some molecules can exist in two mirror image forms known as right-handed and left-handed.

But instead of being a mixture, molecules in living organisms tend to be all one form. Amino acids, the building blocks of proteins, are nearly always left-handed while sugars are right-handed.

Why this is so has been a major conundrum for scientists but some experts have claimed it is linked with life's extraterrestrial origins.

Last year scientists at Arizona State University discovered large amounts of left-handed amino acids in the Murchison meteorite, which fell to Earth in 1969 in Victoria, Australia.

This seemed to indicate that one-handed organic molecules existed before life began on Earth and may have been present in the material from which the Solar System was formed.

Yesterday astronomers using the Anglo-Australian telescope at Siding Spring Mountain near Coonabarabran, New South Wales, announced a discovery which begins to make the picture clearer.

They found high levels of circularly polarized light in a region of the Great Nebula in the constellation of Orion, a star birthplace 1,500 light years away.

In the 1930s scientists discovered that circularly polarized light can destroy molecules of a particular handedness depending on its polarity. If right-handed amino acids were destroyed, for instance, only left-handed molecules would be left.
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Publication:The Birmingham Post (England)
Date:Jul 31, 1998
Words:278
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