You have ever perceived a particular smell in the air just before it starts to rain or immediately after A storm? That fresh and earthy scent that many find relaxing and familiar has a very precise and fascinating scientific explanation. It is not simply the water that bathes the ground, but one combination of chemical and biological phenomena involving the soil and some special microorganisms.
At the basis of this characteristic aroma we find a compound called geosminaa substance produced by some soil bacteria belonging to the genre Streptomyces. These microorganisms, which are part of the group of Actinomicetslive in the soil and contribute to the decomposition of organic matter, playing an essential role in the balance of natural ecosystems.
The role of geosmina and the effect of the rain
The name geosmina derives from the Greek geō (earth) and osmḗ (smell), and perfectly describes its function. This compound It is released into the soil in normal conditionsbut his presence becomes particularly evident when he begins to rain.
When the first drops of water affect the ground, they create tiny air bubbles Which, going back to the surface, free the particles of Geosmina and other volatile substances present in the ground in the atmosphere. This process, similar to an aerosol effectspreads in the air the characteristic perfume of the rain that we perceive so distinctly.
Geosmina is not only responsible for the smell of the earth after the rain, but it can also influence the flavor of some foods. For example, it is the same substance that gives a earthy aftertaste to some fresh water fish such as carp or catfish that live in environments rich in these bacteria.
Why is our nose so sensitive to geosmina?
Human beings are particularly sensitive to Geosmina: minimal concentrations are enough because our sense of smell detect it immediately. This ability is thought to have evolutionary origins, linked to the fact that the scent of the wetland could have helped our ancestors find sources of water in natural environments.
The smell of rain is a sensory experience that many associate with Moments of peace and nostalgia. It is the scent of the first drops that fall on a country path, fresh air after a summer storm, of the nature that awakens after an autumn aquazzone.
It is a reminder of how much We are connected to the natural elementseven in the smaller details and apparently insignificant. The next time you feel that unmistakable perfume, you will know that it is the result of a small miracle of nature, triggered by the bacteria who work silently under our feet.
