What we feel when we say "smell like rain"

Before a storm, usually in summer, it says "it smells like rain". This shared feeling, of course, has a scientific explanation; although it is useful to specify from the beginning that the rain does not smell. Now, yes, we call it petricor the combination of chemical compounds that come off the plants and the soil by moistening the environment before the rain, which generates this characteristic fragrance.

In fact, the "smell" of the rain is mainly generated actinobacteria, a type of bacterium of great importance for the decomposition of organic materials – such as cellulose and chitin – that become nutrients for plants. From this process emerges the geosminwhich means in Greek "aroma of earth".

In chemical terms, geosmine is a type of alcoholThis allows it to emit a strong aroma, to the point that, even if there are very few molecules in the air, we are able to detect it. Our sense of smell is able to perceive very few geosmin molecules for every trillion molecules that circulate in the atmosphere.

But why is it more common to collect it in summer or on drier ground? It is that, in times of drought, the activity of actinobacteria it becomes slower and focuses. Therefore, when wetting the soil before a rain, the aroma is more intense.

In addition, if the soil is soiled, the first drops will prolong this sensation, because the water will disperse particles called aerosols who will carry the geosmin.

This explanation, developed for years in different studies, adds to the concept that The sense of smell is one of the most complex senses that the human being possesses for the great variety of aromas that we can perceive.