Chemical pathway links stars, meteorites.

When Thomas J. Wdowiak and Wei Lee zapped a laboratory mixture of hydrogen gas and naphthalene with 9,400 volts, they were seeking to simulate the chemical processes that occur in dusty regions of interstellar space. But their experiment failed to produce any of the hydrocarbon compounds they had hoped for. To add isult to injury, the high-voltage simulation left a yellow-brown residue on their glass discharge tube.

To choose the right solvent for removing the residue, the researchers identified the unwanted material by taking its infrared spectrum. To Wdowiak's surprise, the pattern of ight absorption looked strangely familiar. Searching through recently published data, he and Lee discovered that the spectrum closely resembles that of organic material extracted from the Murchison meteorite, which fell to Earth in 1969.

"This is the best match between the spectrum of a particular meteorite and that a sample synthesized in the laboratory that I've ever seen," notes Louis J. Allamandola, an infared astrophysicist at NASA's Ames Research Center in Mountain view, Calif.

Wdowiak and Lee, researchers at the University of Alabama at Birmingham, describe their serendipitous study in the Nov. 1 ASTROPHYSICAL JOURNAL LETTERS. They say their work suggests a chemical pathway between meteorites and stars.

Naphthalene, notes Wdowiak, ranks as the simplest of a group of organic molecules known as polycyclic aromatic hydrocarbons (PAHs), many of which are found in interstellar space and the outer atmosphere of old, carbon-rich stars. Meteorites also contained PAHs and another group of hydrocarbons known as alkanes. Researchers have suspected that interstellar organic molecules provide the raw materials for the hydrocarbons in meterorites, but they weren't sure of the clinical pathway.

Wdowiak says the new study indicates that PAHs, which are more durable than alkanes, supply both types of hydrocarbons found in meterorites such as Murchison. Traveling through space, the interstellar PAHs would retain their chemical identity until they encountered ionized hydrogen, believed to be plentiful during the formation of the solar system. Wdowiak suggests that the combination of intense outbursts from the young, energetic sun and the presence of ionized hydrogen created conditions similar to those in his high-voltage experiment. He speculates that some of the interstellar PAHs transformed into alkanes and were later incorporated into meteorites as they formed, producing a spectrum like the one detected in the laboratory residue.