Google Doodle Today: The Google Doodle of March 19, 2023 is dedicated to Mexican chemist Mario Molina, who is famous for his work on the ozone layer. March 19, 2023 marks the 80th birth anniversary of Molina. Google pays tribute to him through a doodle which depicts the molecular form of ozone, O3, as one of the ‘Os’ of ‘GOOGLE’, and replaces the other ‘O’ with the Sun. The ozone layer protects Earth from the Sun’s harmful ultraviolet radiation.
The doodle also shows the hole in the ozone layer, and denotes the fact that chlorofluorocarbons (CFCs) contributed to the formation of the ozone hole. Chlorofluorocarbons were found in air conditioners and aerosol sprays.
All about Molina’s work on the ozone layer
Molina received the 1995 Nobel Prize in Chemistry, along with two other chemists, for research on the decomposition of the ozone layer. Dutch chemist Paul J Crutzen, American chemist F Sherwood Rowland, and Molina were awarded the 1995 Nobel Prize in Chemistry “for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone”.
Also known as the ozonosphere, the ozone layer is the region of the upper atmosphere, between roughly 15 and 35 kilometres above the surface of Earth, and contains relatively high concentrations of ozone molecules, or O3. The ozone layer protects Earth from dangerous solar radiation, especially ultraviolet rays.
At the University of California, Irvine, Molina and Rowland conducted experiments on pollutants in the atmosphere, and discovered that chlorofluorocarbon gases rise into the stratosphere. There, ultraviolet radiation breaks them into their component elements of chlorine, fluorine and carbon. At the stratosphere, each chlorine atom is capable of destroying about 100,000 ozone molecules before becoming inactive, according to Britannica.
Molina and Rowland discovered that these industrially manufactured gases deplete the ozone layer. Their discovery of how freons, which are colourless, odourless, non-inflammable, non-corrosive gases or liquids of low toxicity introduced as refrigerants in the 1930s, damaged the ozone layer was an important milestone. They called this the “CFC-ozone depletion theory”.
The researchers searched for processes that might destroy the chlorofluorocarbons in the lower atmosphere, but nothing appeared to affect them. However, they knew that the chlorofluorocarbons would eventually drift to sufficiently high altitudes to be destroyed by solar radiation. While exploring the question about what the consequences of the destruction of chlorofluorocarbons are, Molina and Rowland found that the chlorine atoms produced by the decomposition of chlorofluorocarbons would catalytically destroy the ozone.
A few years before, Crutzen had established the role of naturally occurring chlorine as catalysts in the decomposition of the ozone layer.
Rowland and Molina realised that the continued release of chlorofluorocarbons into the atmosphere would cause a significant depletion of the ozone layer. They discussed their findings with Professor Harold Johnston from Berkeley, who had conducted research on the impact of the release of nitrogen oxides from the proposed supersonic transport (SST) aircraft on the stratospheric ozone layer. Johnston told Molina and Rowland that months earlier, two other scientists had arrived at similar conclusions concerning the catalytic properties of chlorine ations in the stratosphere, in connection with the release of hydrogen chloride either from the ammonium perchlorate fuel planned for the space shuttle, or from volcanic eruptions.
On June 28, 1974, the findings of Molina and Rowland were published in the journal Nature.
Their findings sparked a nationwide debate on the environmental effects of chlorofluorocarbon gases, and inspired an international movement in the late 20th century to limit the widespread use of chlorofluorocarbon gases.
In 1985, a region of stratospheric ozone depletion, known as the ozone hole, was discovered over Antarctica, by Joe Farman, Brian Gardiner and Jonathan Shanklin. This discovery validated the findings of Molina and Rowland.
Their research became the foundation of the Montreal Protocol, an international treaty that successfully banned the production of nearly 100 ozone-depleting chemicals, and is considered one of the most impactful environmental treaties ever made.
From 1982 to 1989, Molina worked in the Jet Propulsion Laboratory at the California Institute of Technology. At JPL, Molina, along with other scientists, showed that chlorine-activation reactions take place very efficiently in the presence of ice under polar stratospheric conditions. Molina conducted experiments to understand the rapid catalytic gas phase reactions taking place over the South Pole, by working on chlorine peroxide.
In 1989, he became a professor at the Massachusetts Institute of Technology in Cambridge, where he continued his research on global atmospheric chemistry issues.
Molina moved to the University of California, San Diego, in 2004.
In 2013, he was awarded the US Presidential Medal of Freedom.
On October 7, 2020, he died of a heart attack.