Petrichor

Have you ever wondered why does rain smell so good? Do you know what is that smell called? And, why do many of us find that earthy scent so pleasant?

So, the pleasant smell produced when rain falls on dry soil is called “Petrichor”. The term “Petrichor” is made up of the Greek words “petra” and “ichor” where “petra” means “stone” and as per the Greek mythology “ichor” means the fluid that flows in the veins of the Gods.

This warm, earthy fragrance got its name in 1964 from two Australian researchers, Isabel Joy Bear and Richard G. Thomas. In one of their articles, they described this earthy scent as a combination of plant oils and the chemical compound geosmin which are released from the soil when it rains. Geosmin has a distinct earthy flavor and aroma produced by certain bacteria, and contributes to the strong scent petrichor. The human nose is extremely sensitive to geosmin and is able to detect it even at very low concentrations. Geosmin has now become more common as a perfume ingredient.

In 2015, using high-speed cameras, scientists from the Massachusetts Institute of Technology (MIT) observed when a raindrop hits a porous surface, it traps tiny air bubbles at the point of contact. These bubbles then shoot upward, ultimately bursting from the drop in a fizz of aerosols. (Aerosols are minute particles suspended in the atmosphere.) Such aerosols carry the scent, as well as bacteria and viruses from the soil. Petrichor is more common after light rains because raindrops that move at a slower rate tend to produce more aerosols.

Why do we like petrichor so much? Because, many of us believe that our ancestors may have relied on rainy weather for survival.