Origins search looks to Titan

An important step has been taken towards concocting the chemical soup that may have led to the birth of life on Earth.

A team from the Academia Sinica at the Institute of Atomic and Molecular Sciences in Taipei, Taiwan, has successfully tested a way in which some of the key chemical stepping stones to amino acids - called nitriles - could form on a prebiotic world.

The processes involved are thought to be still occurring on Titan, a giant moon of Saturn that is shrouded by a dense atmosphere. The scientists hope that when the European Space Agency/Nasa space probe Cassini-Huygens reaches this mysterious world in 2004, it will detect signs of the substances they are now predicting will be present.

The composition of Titan's atmosphere is thought to be similar to that of the primordial Earth.

Ralf Kaiser, who leads the Taiwanese group in collaboration with theoreticians at Rikkyo University, Japan, and the University of Georgia, Athens, United States, has sought to create some of the key ingredients thought necessary for life with chemicals known to be present on the moon.

"These experiments allow us for the first time in history to identify explicitly the reaction products under well-defined conditions and those molecules that might have been the most important intermediates in the development of life on Earth," said Dr Kaiser.

Life on Earth is based on DNA, a complex organicchemical that is made up of amino acids. One way to create those amino acids is from the complex reaction of nitriles with water and ammonia.

The Taiwanese team used crossed molecular beams to react radicals with organic chemicals already identified in Titan's atmosphere.

So far they have been able to produce seven nitriles in this way, three of which are known to be present on Titan.