Is the good smell of rain a chemical or cultural result?

There are so many sensations and images that come to mind when we think of the smell that rain leaves after a drought or drought. That summer rain that cools the late afternoon after a full day of sunshine, humidifies the environment, brings fresh air and takes away the dry and polluted weather of the cities.

The pleasure that comes with the smell of rain can be the result of a series of chemical processes occurring on earth. In a 1964 study, Australian geologists coined the term "petricor" to denote the rocky scent of rainfall on dry land.

They determined that one of the reasons we get this particular smell is due to a mixture of secreted plant oils in times of drought. These oils inhibit seed germination and help control competition for water in times of scarcity. With the arrival of rain after a drought period, the plants release this mixture into the air.

Geosmina, the scent of the earth

One of the compounds released with plant oils is geosmin. Earth scent is a chemical produced by classes of microorganisms such as actinobacteria (bacterial spores) and cyanobacteria (bluish-green algae). Geosmin is released into the air when the force of rain hits the soil and causes these bacteria to release compost from their spores. The substance also corresponds to the smell we smell when we move the earth.

Research has shown that human smell is very sensitive to geosmin and that some people can detect the smell of the substance even at concentrations as low as 5 parts per trillion. The compound is generally pleasant to most people and is even used to impart an earthy aroma to perfumes.

The cultural heritage of rain representation

There are scholars in the field of anthropology, however, who analyze the sense of pleasure we get from the smell of rain in other ways. Diana Young from the University of Queensland, Australia, shows that we associate the scent of rain with a series of images with positive representations of life, such as the green color or the figure of plants.

The researcher called “cultural synesthesia” the inheritance of different sensory experiences of life in society according to historical evolution. After all, rain was a necessity for the planting and for the general survival of humanity. The smell of precipitation, by the anthropological hypothesis, causes sensations that are related to the collective consciousness of individuals, recovering senses of satisfaction and pleasure.