Mario Jose Molina
Molina, Mario José (1943-), a Mexican-born American chemist who contributed to the discovery that artificial substances called chlorofluorocarbons (CFC's) damage the protective ozone layer in the earth's upper atmosphere. Ozone, a form of oxygen, shields the earth from the sun's ultraviolet radiation, which can harm living things. Molina shared the 1995 Nobel Prize in chemistry with American chemist Frank Sherwood Rowland and Dutch chemist Paul Josef Crutzen. Crutzen discovered that nitrogen oxides accelerate ozone reduction.
Molina was born in Mexico City and became interested in chemistry as a young boy. At age 11, he went to a private boarding school in Switzerland, returning to Mexico to go to the National University of Mexico (Universidad Nacional Autonoma de Mexico, UNAM), earning a degree in chemical engineering in 1965. He received a postgraduate degree in polymerization kinetics from the University of Freiburg, Germany, in 1967. In 1972, he earned his Ph.D. degree at the University of California at Berkeley. He became a postdoctoral associate that same year, researching the chemical laser measurements of vibrational energy distributions during certain chemical reactions. In 1973, he left Berkeley and joined a research group led by Rowland.
Molina and Rowland were interested in the impact of widely used industrial chemicals when they were released into the atmosphere and designed experiments to determine the outcome when chemical pollutants reached not only the atmosphere directly above the earth, but also the stratosphere. The stratosphere is a layer of the earth's atmosphere that begins about 6 to 10 miles above the earth. It contains ozone, which serves as a filter to screen out much of the sun's most damaging ultraviolet radiation.
Molina focused on what happened to the widely used industrial chemicals called chlorofluorocarbons (CFC's) 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. Because they did not easily combine with other chemicals, it was thought that CFC's were harmless to materials or to living things. Scientists also believed that CFC's had no significant effect on the environment. Molina wanted to see how CFC's behaved when exposed to variables such as the range of pressures, temperatures, exposure to solar radiation, and other harsh conditions outside the laboratory.
Molina and Rowland developed the CFC ozone depletion theory that states that when CFC's are exposed to massive ultraviolet radiation, such as that from sunlight, they break down into chlorine, fluorine, and carbon. The chlorine atoms act as catalysts, promoting the breakdown of ozone molecules into oxygen molecules without being used up by the process. Each chlorine atom is capable of destroying as many as 100,000 molecules of ozone. They realized that with the production of CFC's for commercial and industrial use, the amount that would ultimately be released into the atmosphere and the resulting effect on the ozone layer could be life-threatening.
A few years after Molina published the results of the study in 1974, CFC's became a topic of widespread concern and he was invited to testify before Congress. Manufacturers began searching for alternative propellants for their products.
In the mid-1980's, the “ozone hole”—the seasonal reduction in ozone levels over Antarctica—was discovered. To explain the unexpectedly rapid breakdown of ozone, Molina and his colleagues at the Jet Propulsion Laboratory (JPL) in Pasadena, California, demonstrated the process in an experiment in which they simulated the conditions of the upper polar atmosphere in the laboratory. They also took into account a newly identified pollutant, chlorine peroxide.
He continued his research over the next several years and published additional data on the destructive effects of CFC's on the ozone layer. He joined the staff at the JPL in 1982. In 1989, he became professor of atmospheric chemistry and professor of chemistry at the Massachusetts Institute of Technology (MIT). In 1993, he held a chair at MIT established by the Martin Foundation to support research and education activities related to the studies of the environment. In 1994, he was elected to the President's Committee of Advisers on Science and Technology.
Primarily because of Molina and Rowland's work, most countries phased out the use of CFC's by the late 1990's. However, there remain skeptics as to whether the depletion of the ozone layer is caused by chemicals released by humans or is a natural phenomenon.