Ever since the Miller-Urey experiment in 1953, most scientists have held the view that life arose on the early Earth from simple inorganic molecules. With a suitable energy source (e.g. lightning) and a hospitable environment (e.g. oceans), complex organic molecules such as sugars and amino acids are thought to have originated from methane, hydrogen, and ammonia. These organic molecules then formed the basis of life as we have today.

However, recent astronomical observations have discovered that complex organic molecules exist in stellar environments. Using the European Space Agency's Infrared Space Observatory, astronomers Sun Kwok and Kevin Volk (University of Calgary) and Bruce Hrivnak (Valparaiso University) have found signatures of organic molecules with aliphatic and aromatic structures in the circumstellar envelopes of old stars.

In a paper that they presented at the American Astronomical Society meeting in Atlanta January 12, 2000. They demonstrated that chemical synthesis can occur rapidly. Over a period of only several thousand years, small organic molecules with aliphatic structures are shown to have evolved into large, complex aromatic molecules.

They were able to come to this conclusion by comparing the infrared spectra of very evolved red giants, proto-planetary nebulae, and planetary nebulae. Since only a few thousand years in evolutionary time separate these stars, their different infrared spectra give the most direct evidence of chemical synthesis in stars.

"Although we do not understand how chemical reactions can occur so efficiently in such a low density environment", said Dr. Kwok, "there is no doubt that such complex molecules exist, and the stars are able to make them with no difficulty". In the last 15 years, Drs. Kwok and Hrivnak have pioneered the study of proto-planetary nebulae, and these stars have turned out to be rich in complex molecules.

Since these stars are very short lived, the molecules present in their circumstellar envelopes must have been manufactured recently. The chemical pathway begins with the synthesis of acetylene, which is detected in the envelopes of red giants. Acetylene then serve as the building blocks for aromatic molecules such as benzene and more complicated aromatic hydrocarbons.

Since these molecules are eventually ejected into the interstellar medium, it is quite possible that some of them will end up on planets such as the Earth. If this is the case, life on Earth could have an easier start than previously believed.

The detection of such complex organic molecules in stellar envelopes also leads to the speculation that even amino acids could be synthesised, although the detection of such molecules is beyond the capabilities of the current generation of space telescopes. Should such molecules oneday be found in the envelopes of old stars, they could provide a pathway such that life could indeed be common in the universe.

Valparaiso University

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