Mario Molina passed away unexpectedly on 7 October 2020 at age 77.
Mario was born on 19 March 1943 in Mexico City. He studied chemical engineering at the Universidad Nacional Autonoma de Mexico (UNAM) and got his PhD in the University of California, Berkeley, in 1972. From 1973 to 1975 he took a postdoctoral position at the University of California, Irvine, working with F. Sherwood Rowland in atmospheric chemistry. Mario then joined the Department of Earth, Atmospheric, and Planetary Sciences and the Department of Chemistry at MIT as a faculty member. In 1995 he was awarded the Nobel Prize in Chemistry jointly with Paul J. Crutzen and Rowland “for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone.” Above all, Mario should be remembered as a generous extraordinary person who was committed to making this planet a better world.
In 1974 Mario and Rowland published a Nature paper on “Stratospheric sink for chlorofluoromethanes: chlorine atom–catalysed destruction of ozone.” In this paper they proposed that these gases, widely used as refrigerants and propellants, remain in the atmosphere and, when transported upward, are affected by UV radiation, releasing chlorine atoms that destroy the thin ozone layer and in turn allow more radiation to reach the planet’s surface. The studies of the Nobel awardees and others demonstrated the role, complexity, and the importance of understanding the chemical reactions in the atmosphere, particularly in the stratospheric ozone layer. These findings faced a strong backlash from the industry, but by the mid 1980s, evidence of atmospheric ozone layer depletion at the south polar region clearly demonstrated the deleterious effects of these gases. In addition to continuing with his research, Mario became a committed advocate of recognizing the effects of climate change and the importance of protecting the environment. In 1987 a major international agreement, the Montreal Protocol, was signed, establishing a timeline for phasing out the use of these gases.
Mario’s exceptional career and scientific contributions have been widely chronicled and highlighted. Less well known are his wide interests and close links in other fields, including the physical sciences and in Mexico. In the past months we had been organizing a conference series on quantum mechanics and talking about the nature of spacetime and quantum mechanics in the universe. In his biographical account for the Nobel Prize, Mario commented that before enrolling in his doctoral studies he considered his background in mathematics and physics weak, and “subjects such as quantum mechanics were totally alien.” His studies on physical chemistry, stratospheric processes, the ozone layer, and aerosols reflect a multidisciplinary approach, integrating experiments and observations well beyond the atmospheric chemistry. This was a hallmark from the beginning: In the same year that Mario and Rowland published their Nature paper, they also reported on the stratospheric abundances of chlorine species in Geophysical Research Letters; the following year they published in Reviews of Geophysics about chlorofluoromethanes in the environment. Over the years, Mario continued publishing studies on gas‐phase glyoxal and secondary organic aerosol in Mexico City (2007), sea-salt OH uptake (2009), and OH diffusion temperature dependence (2009), while also organizing meetings and workshops, like the 2018 AGU–CAS (American Geophysical Union–China Academy of Science) Joint Meeting on Atmospheric PM2.5 in China: change, impact, mitigation and global perspective, held in Xi’an, China.
Mario had strong interests in international collaboration, as he was active in academies and scientific societies. He was an elected member of the National Academy of Sciences, the Pontifical Academy of Sciences and National Academy of Medicine of the Vatican City, and the TWAS World Academy of Sciences, among others. Mario was a frequent attendee of the Lindau Nobel Laureates annual meetings. He was particularly involved in the 2017 Lindau Nobel meeting, in which Mexico was the invited country in the international program with the Mexican Academy of Sciences. In Lindau, Mario and his wife, Guadalupe, shared their experiences with students and young researchers during the international connecting cultures and get-together evenings. In early October 2020 Mario was an invited speaker in the Science and Technology for Society STS Forum held online from Kyoto, Japan; he actively participated in the discussions and in the sustainable society session. He was also a key participant in the organization of the 2020 Latin America and the Caribbean STS Forum in Mexico.
Although Mario spent most of his working life at various institutions in the US, he developed and maintained strong links with his native Mexico. In 2004 he founded the Mario Molina Center for Strategic Studies on Energy and the Environment in Mexico City, which focuses on projects and initiatives on a wide range of areas of scientific research and public policies. “The Megacity Initiative: Local and Global Research Observations” is a project that seeks to identify and quantify the anthropogenic pollutant emissions in a megacity at local, regional, and global spatiotemporal scales. The project involves several experiments and observational campaigns with different platforms that allow the study of emission, transport, and dispersion of pollutants in the atmosphere. This year Mario devoted considerable efforts to investigate the airborne transmission of the coronavirus. His research was particularly important in designing mitigation policies and the use of face coverings. The COVID-19 pandemic has severely affected Mexico with large numbers of infections and fatalities, and Mario used his influence to highlight the use of scientific research to strengthen the health system and for policy design and implementation.
Mario was also highly committed to strengthening science communication and education in STEM subjects in Mexico. He created the Molina Center education program, focusing on increasing awareness among children and youngsters on science themes such as climate change. Mario was very active and a frequent contributor to initiatives of the Mexican Academy of Sciences and El Colegio Nacional. The latter is an institution that brings together around 40 renowned artists, writers, composers, philosophers, and scientists, with a strong focus on promoting science outreach and promotion of culture. At El Colegio Nacional, Mario organized seminars and meetings on educational programs and outreach activities. His commitment and generosity with his time was reflected in his activities, with frequent conferences and openness to students and young researchers.
Mario benefited from valuable influences during the development of his career, and he was a major force in developing the careers of many others. He had many long-term friends in the academic sphere, with whom he had a shared interest in atmospheric chemistry as well as concerns and worries regarding environmental degradation and climate change. One of them was Ralph Cicerone, with whom he shared not only their research on atmospheric chemistry and stratosphere ozone but also on the broad issues and challenges on science, education, and technology. Mario shared his recollections on Cicerone and their friendship with Eos (23 March 2017). Many aspects of Mario’s character and personality shine through his words.
Mario Molina was a gifted and multifaceted scientist and will be greatly missed. His unshaken commitment for a better world and his legacy will, no doubt, be remembered for years to come.
