Molina, Mario José << muh LEE nuh, MAH ryoh haw SEH >> (1943-2020), a Mexican-born American chemist, contributed to the discovery that artificial substances called chlorofluorocarbons (CFC’s) damage the protective ozone layer in Earth’s upper atmosphere (see Chlorofluorocarbon ). Ozone, a form of oxygen, shields Earth from the sun’s ultraviolet radiation, which can harm living things. Molina shared the 1995 Nobel Prize in chemistry with F. Sherwood Rowland of the United States and Paul Crutzen of the Netherlands, who identified different threats to the ozone layer.
Molina was born on March 19, 1943, in Mexico City. He was already keenly interested in chemistry when he was sent to a private boarding school in Switzerland at the age of 11. He returned to Mexico to go to university, taking a degree in chemical engineering in 1965. After further study in Germany and back in Mexico, he went to the University of California at Berkeley in the United States in 1968. There he worked on the study of chemical reactions using lasers. He took his Ph.D. at Berkeley in 1972 and joined a research group led by the American chemist F. Sherwood Rowland.
Molina chose to study what happened to the widely used industrial chemicals called chlorofluorocarbons when they were released into the atmosphere. CFC’s were used as the circulating coolant in refrigerators and as the propellant gas in aerosol spray cans. They were valuable because they did not easily combine with other chemicals and so seemed harmless to materials or to living things. Scientists knew that CFC’s accumulated in the atmosphere but believed the chemicals had no significant effect on the environment. Molina wanted to see how they would behave outside the laboratory, in the different circumstances of the atmosphere, where there are a huge range of pressures, temperatures, exposure to solar radiation, and other harsh conditions.
Molina and Rowland developed the CFC ozone depletion theory. This theory states that CFC’s rise into the ozone layer, where they are broken down by the ultraviolet radiation in sunlight into chlorine, fluorine, and carbon atoms. The chlorine atoms contribute to the breakdown of ozone molecules into oxygen molecules. That is, the chlorine atoms act as catalysts, promoting the reaction but not being used up by it. On average, each atom would assist in the breakdown of about 100,000 molecules of ozone.
Molina continued research at the University of California at Irvine, studying compounds difficult to handle in the laboratory but of potential importance in the atmosphere. From 1982, he worked at the Jet Propulsion Laboratory (JPL) in Pasadena, California. In 1989, Molina moved to the Massachusetts Institute of Technology, where he continued his research in atmospheric chemistry.
In the mid-1980’s, the ozone hole —the seasonal reduction in ozone levels over Antarctica —was discovered. Molina and his colleagues at JPL were able to explain the unexpectedly rapid breakdown of ozone by simulating the conditions of the upper polar atmosphere in the laboratory, and by taking account of a newly identified pollutant, chlorine peroxide.
The citation accompanying the Nobel Prize described the three winners as having “contributed to our salvation from a global problem that could have catastrophic consequences.” The consequences referred to were the increase of skin cancer, eye cataracts , and other possible injuries among human beings. Largely as a result of Molina and Rowland’s work, most countries phased out CFC’s by the late 1990’s. Molina died on Oct. 7, 2020.
