A downpour on the hottest day of summer is a light aroma of freshness and coolness. What could be better?
It turned out that it was not only a pleasant coolness, chemistry was involved here! Scientists came to this conclusion after decades of studying the smell of air after a heavy downpour, writes Express.
The smell of rain in scientific circles is called Petrikor - comes from two Greek words, "petra" - a stone and "ichor" - a golden liquid flowing through the veins of the gods and immortals
The smell of rain was first defined in 1964 by Australian scientists Isabelle Bear and Roderick Thomas. They concluded that the warm, musky smell is the result of a chemical reaction caused by bacteria. Rocks exposed to warm rays and water vapor release a yellow oil, which is also found in the soil. Later it was possible to establish that this oil, it is also the "blood of the gods", is nothing more than oils secreted by plants in drier soil, as well as chemicals released by bacteria. The latter in turn create a molecule called geosmin.
When it starts to rain, the same “chemistry” happens: raindrops absorb air bubbles containing geosmin. After the air bubbles burst and small particles are scattered in the air. In addition, excess moisture helps particles of molecules to linger in the pores of stones and soil - it is these particles that we call "the smell of rain."
In their research, Isabelle Bear and Roderick Thomas also found out why we like the smell of rain so much. It turns out that the human nose is overly sensitive to geosmin and is able to catch it even in micro concentrations - 0.4 parts per billion. That is why Petrikor became popular in perfume compositions back in the 1960s, and it is still actively used today.