Did you know that… petrichor is the name given to the smell that is perceived when it rains?

Surely, anyone will have noticed that when it starts to rain, a peculiar smell can be perceived outside closed places. This odor is called petrichor and is produced when molecules derived from the decomposition of plants or animals join with surfaces and recombine. When the rain falls and the air lifts the molecules, the petrichor aroma is perceived, especially if there was a long period of drought before.

When it comes into contact with the rain, the petrichor is released in a process described by MIT researchers that consists of hitting a porous surface, creating small bubbles inside the drop that increase in size and float until it reaches the surface. where it breaks up and releases an “aerosol fizz” into the air, which carries the aroma.

When it rains, the bacterium Streptomyces coelicor, some filamentous fungi and cyanobacteria found in the soil generate a molecule called geosmin (smell of earth), which is responsible for the smell of wet earth that we perceive.

The odor that is noticed changes depending on the place. In cities, for example, the molecules come from concrete and asphalt; while in the field they come from the earth and plants. The name petrichor was first used to describe this phenomenon in 1964, by Australian scientists Isabel Joy Bear and R. G. Thomas.

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