There is growing evidence that life on earth has come from the universe through comets, an eminent British scientist said here.

"Life is cosmically abundant and was brought to the earth by comets and our genes and those of all living forms on earth were brought by comets, neatly-packaged within cosmic microorganisms," professor N Chandra Wickramasinghe, Director, Cardiff Centre for Atrobiology, Cardiff University, said.

The astrobiologist speaking at Nehru Planetarium said, "Our genetic ancestors still lurk amidst the stars, and molecular biology is being deployed to trace connections between different species in search of a Last Universal Common Ancestor (LUCA) for all life on the Earth."

The evidence for organic molecules that may be relevant to life emerged after passage of Comet Halley in 1986. Giotto spacecraft instruments showed that the comet dust contained high molecular weight complex organics that could be connected with degraded biomaterial.

"I shall argue now that comets are responsible for originating life on a cosmic scale, and distributing it through the cosmos," he said. "Deep Impact Mission, 4 July 2004, showed comets to be suitable sites for origin of life, he said. "Comets serve as amplifiers and transporters of cosmic life (bacteria and viruses) in a freeze-dried state.

"Nearly 5 billion years ago, when the solar system formed from a cloud like this, life would have already been widespread in the Galaxy," said the scientist. "The earth and the planets were seeded with bacteria from solar system's comets, they impacted the earth nearly 4 billion years ago bringing the first traces of life to our planet, and thus we have descended from cometary microbes," he said.

When asked can a biological component in comet dust be discovered by present day experiments, he said, such an experiment was carried out a few years ago by ISRO scientists collaborating with the Cardiff University.

The air from the balloon experiment at 41 km in universe revealed signs of microbial life. There were viable but non-culturable micro-organisms indicated by the use of fluorescent dyes, he said. The possibility of an ongoing panspermic input to our planet would have profound implications for biology, Wickramasinghe said.

Source: Press Trust of India