Strange molecule in the sky cleans acid rain, scientist...( WEST LAFAYETTE Ind. - Researchers ha...)

WEST LAFAYETTE, Ind. - Researchers have discovered an unusual molecule that is essential to the atmosphere's ability to break down pollutants, especially the compounds that cause acid rain.

It's the unusual chemistry facilitated by this molecule, however, that will attract the most attention from scientists.

Marsha Lester, the University of Pennsylvania's Edmund J. Kahn Distinguished Professor, and Joseph Francisco, William E. Moore Distinguished Professor of Chemistry at Purdue University, found the molecule, which had puzzled and eluded scientists for more than 40 years.

A technical paper describing the molecule is published this week in a special edition of the Proceedings of the National Academy of Science.

Somewhat like a human body metabolizing food, the Earth's atmosphere has the ability to "burn," or oxidize pollutants, especially nitric oxides emitted from sources such as factories and automobiles. What doesn't get oxidized in the atmosphere falls back to Earth in the form of acid rain.

"The chemical details of how the atmosphere removes nitric acid have not been clear," Francisco says. "This gives us important insights into this process. Without that knowledge we really can't understand the conditions under which nitric acid is removed from the atmosphere."

Francisco says the discovery will allow scientists to better model how pollutants react in the atmosphere and to predict potential outcomes.

"This becomes important in emerging industrial nations such as China, India and Brazil where there are automobiles and factories that are unregulated," Francisco says. "This chemistry will give us insight into the extent that acid rain will be a future concern."

Lester says the molecule had been theorized by atmospheric chemists for 40 years and that she and Francisco had pursued it for the past several years.

"We've speculated about this unusual atmospheric species f
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