The discovery of molecules linked with a vital ancient biological process, coupled with key DNA ingredients found in meteorites by another team of researchers, supports the idea that life on planet Earth could have started from materials from outer space.

Researchers discovered molecules that make up building blocks of a vital biological pathway, the citric acid cycle, in a number of organic-rich meteorites.

The citric acid cycle is "thought by many experts to be among the most ancient of biological processes," said study co-author and NASA chemist George Cooper told "One function of this cycle is respiration, when organisms give off carbon dioxide."

"It is always exciting to find extraterrestrial and ancient 4.6 billion-year-old organic compounds that might have had a role in early life," Cooper added.

The findings were published online in the Proceedings of the National Academy of Sciences.

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