The American Association for the Advancement of Science: Life linked to light from outer space

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SPINNING light from outer space could have been the spark that fired the evolution of life on earth, scientists said yesterday.

Chemists have known for some time that the crucial carbon-based molecules of life all have a property known as 'chirality' - that is they exist with their atoms arranged in one of two ways. These two states look like the mirror images of each other, left and right- handed pairs best visualised as spiral staircases that turn in opposite directions.

'It is generally agreed that you need either all left-handed or all right-handed molecules for life to get off the ground,' William Bonner, a former chemistry professor at Stanford University, California, told the meeting. But one of the biggest puzzles in unravelling how life began is how this vital imbalance got under way on Earth.

Professor Bonner believes circularly polarised light - spinning around its direction of travel to either the left or the right - could have forced dust in the empty reaches of space to adopt either a left or right-handed state.

Scientists have never succeeded in creating chiral molecules of only one kind in the laboratory. But they have shown that exposing mixtures of right and left-handed molecules to such radiation creates an excess of one kind or another.

The necessary polarised light could have come from collapsing stars, the meeting heard. Shock waves from such explosions, thought to occur about once every 50 years in our galaxy, cause an incredibly violent explosion, called a supernova.

Colossal electric fields around this accelerate electrons in the vicinity to enormous speeds. These racing electrons give off spiralling, polarised 'synchrotron radiation', Professor Bonner said.