Washington, August 13 : Scientists have discovered an unusual molecule in the sky that is essential to the atmosphere's ability to break down pollutants, thus helping combat acid rain.
The team of scientists that found the molecule consists of Marsha Lester from the University of Pennsylvania, and, Joseph Francisco from the Purdue University in the US.
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," said Francisco. "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," he added.
Francisco said that the discovery would 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," he said. "This chemistry will give us insight into the extent that acid rain will be a future concern," he added.
According to Lester, 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 for many years, and then to actually see it and learn about its properties was very exciting," she said.
What makes the new atmospheric molecule so unusual is its two hydrogen bonds, which are similar to those found in water.
The two hydrogen bonds allow the molecule to form a six-sided ring structure.
Hydrogen bonds are usually weaker than the normal bonds between atoms in a molecule, which are known as covalent bonds. In fact, covalent bonds are 20 times stronger than hydrogen bonds.
"But in this case, these two hydrogen bonds are strong enough to affect atmospheric chemistry," said Francisco.
Lester said that the new molecule exhibits its own unusual properties.
"The reaction involving this molecule proceeds faster as you go to lower temperatures, which is the opposite of most chemical reactions," said Lester.
"The rate of reaction also changes depending on the atmospheric pressure, and most reactions don't depend on external pressure. The molecule also exhibits unusual quantum properties," she added.
According to Francisco, this discovery will be used in areas other than atmospheric chemistry.
"Here's a situation where we were studying this purely environmental problem, but, because the findings are so fundamental, it may have broader ramifications to biological systems that depend on hydrogen bonds," he said.