Mario Molina and the Hole in the Sky

Have you ever used a spray can or looked behind an old fridge? For many years, they contained gases called CFCs, which seemed perfectly safe. They didn't burn, they didn't smell, and they didn't react with anything. A young Mexican chemist named Mario Molina was the person who showed the world that they had a dangerous secret.

Molina was born in Mexico City in 1943. As a boy, he turned a bathroom in his family's house into a small laboratory. He studied chemical engineering at UNAM, the national university in Mexico City. Then he continued his studies in Germany, and later he earned his doctorate at the University of California, Berkeley.

In 1973, he joined the laboratory of the chemist F. Sherwood Rowland at the University of California, Irvine. Together they asked a simple question: what happens to CFCs after they escape into the air? The answer was frightening. Because nothing destroys them near the ground, CFCs slowly rise high into the sky, to the stratosphere. There, strong ultraviolet light from the sun breaks them apart and frees chlorine, which destroys ozone. Ozone is the gas that protects us from the sun's most dangerous rays, and a single atom of chlorine can destroy thousands of ozone molecules.

In 1974, Molina and Rowland published their results in the journal Nature. Not everyone believed them. The companies that made CFCs said there was no proof, and for more than ten years, the two scientists had to defend their work. Then, in 1985, British scientists reported a huge hole in the ozone layer over Antarctica.

After that, the world acted surprisingly fast. In 1987, countries signed the Montreal Protocol, an agreement to stop making the gases that damage the ozone layer. In 1995, Molina, Rowland and the Dutch scientist Paul Crutzen won the Nobel Prize in Chemistry. Molina was the first person born in Mexico to win it in that subject.

Molina died in 2020, but his work hasn't ended. The ozone layer has been slowly getting better. According to United Nations scientists, it should return to its 1980 levels over most of the world by around 2040, and over Antarctica, where the hole was biggest, by around 2066. The hole that Mario Molina warned us about is closing.