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Why you can smell rain, explained by science

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When those first fat drops of summer rain fall to the hot, dry ground, have you ever noticed a distinctive odor? I have childhood memories of family members who were farmers describing how they could always “smell rain” right before a storm.

Of course rain itself has no scent. But moments before a rain event, an “earthy” smell known as petrichor does permeate the air. People call it musky, fresh – generally pleasant.

This smell actually comes from the moistening of the ground. Australian scientists first documented the process of petrichor formation in 1964 and scientists from the Massachusetts Institute of Technology further studied the mechanics of the process in the 2010s.

Petrichor is a combination of fragrant chemical compounds. Some are from oils made by plants. The main contributor to petrichor are actinobacteria. These tiny microorganisms can be found in rural and urban areas as well as in marine environments. They decompose dead or decaying organic matter into simple chemical compounds which can then become nutrients for developing plants and other organisms.

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