Saturday, February 28, 2004
Scientists Find Ozone-Destroying Molecule
Using measurements from a NASA aircraft, Harvard University scientists have made the first observations of a molecule that researchers believe has a key role in destroying the ozone layer.
Ozone is destroyed when it reacts with one of a variety of chemicals in the stratosphere such as chlorine, nitrogen, bromine or hydrogen.
Analysis of these measurements was conducted using a computer simulation of atmospheric chemistry developed by scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Scientists call the molecule "chlorine monoxide dimer," because it is made up of two identical molecules of chlorine monoxide, which are bonded together.
The dimer has been created and detected in the laboratory, but in the atmosphere it is thought to exist only in the cold stratosphere over Polar Regions when chlorine monoxide levels are relatively high.
"We knew, from observations dating from 1987, that the high ozone loss was linked with high levels of chlorine monoxide, but we had never actually detected the chlorine peroxide before," said Harvard scientist and lead author of the paper, Rick Stimpfle.
The abundance of chlorine peroxide was measured using an instrument that had previously been used to measure levels of chlorine monoxide in the Antarctic and Arctic stratosphere.
"We've observed chlorine monoxide in the Arctic and Antarctic for years and from that inferred that this dimer molecule must exist and it must exist in large quantities," said Ross Salawitch, a co-author on the paper and a researcher at JPL. "But until now, we had never been able to see it."
Chlorine monoxide and its dimer originate primarily from molecules created by humans for industrial uses like refrigeration.
Chlorine peroxide triggers ozone destruction when the molecule absorbs sunlight and breaks into two chlorine atoms and an oxygen molecule. Free chlorine atoms are highly reactive with ozone molecules, thereby breaking them up and reducing ozone. Within the process of breaking down ozone, chlorine peroxide forms again, restarting the process of ozone destruction.
"You are now back to where you started with respect to the chlorine peroxide molecule. But in the process, you have converted two ozone molecules into three oxygen molecules. This is the definition of ozone loss," Stimpfle concluded.
You can find more information on this topic at the following link:
http://earthobservatory.nasa.gov/Newsroom/Nasa
Using measurements from a NASA aircraft, Harvard University scientists have made the first observations of a molecule that researchers believe has a key role in destroying the ozone layer.
Ozone is destroyed when it reacts with one of a variety of chemicals in the stratosphere such as chlorine, nitrogen, bromine or hydrogen.
Analysis of these measurements was conducted using a computer simulation of atmospheric chemistry developed by scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Scientists call the molecule "chlorine monoxide dimer," because it is made up of two identical molecules of chlorine monoxide, which are bonded together.
The dimer has been created and detected in the laboratory, but in the atmosphere it is thought to exist only in the cold stratosphere over Polar Regions when chlorine monoxide levels are relatively high.
"We knew, from observations dating from 1987, that the high ozone loss was linked with high levels of chlorine monoxide, but we had never actually detected the chlorine peroxide before," said Harvard scientist and lead author of the paper, Rick Stimpfle.
The abundance of chlorine peroxide was measured using an instrument that had previously been used to measure levels of chlorine monoxide in the Antarctic and Arctic stratosphere.
"We've observed chlorine monoxide in the Arctic and Antarctic for years and from that inferred that this dimer molecule must exist and it must exist in large quantities," said Ross Salawitch, a co-author on the paper and a researcher at JPL. "But until now, we had never been able to see it."
Chlorine monoxide and its dimer originate primarily from molecules created by humans for industrial uses like refrigeration.
Chlorine peroxide triggers ozone destruction when the molecule absorbs sunlight and breaks into two chlorine atoms and an oxygen molecule. Free chlorine atoms are highly reactive with ozone molecules, thereby breaking them up and reducing ozone. Within the process of breaking down ozone, chlorine peroxide forms again, restarting the process of ozone destruction.
"You are now back to where you started with respect to the chlorine peroxide molecule. But in the process, you have converted two ozone molecules into three oxygen molecules. This is the definition of ozone loss," Stimpfle concluded.
You can find more information on this topic at the following link:
http://earthobservatory.nasa.gov/Newsroom/Nasa
