Science / Medicine : Comet Dust May Have Sparked Life

Dust from disintegrating comets, rich in the molecular building blocks of life, may have rained onto Earth in the distant past, providing a relatively gentle way for such chemicals to reach the surface without being burned up, it was reported last week.

How such molecules could have survived the fiery heat of atmospheric entry to reach Earth’s surface has been a major stumbling block for those who believe chemicals formed in deep space may have played a role in the origins of life.

But Kevin Zahnle and David Grinspoon of NASA’s Ames Research Center in California, writing in the British journal Nature, argue that the breakup of giant comets in the inner solar system could have produced clouds of dust rich in the chemicals.

As Earth sailed through those clouds in its orbit around the sun, amino acids and other chemicals could have made it to the surface without the excessive heating associated with violent impacts.

The researchers arrived at their conclusion after studying the distribution of specific amino acids above and below a layer of sediment associated with the impact of a giant meteorite about 65 million years ago.