Curiosity Corner: Why does rain smell good?

The lovely smell of rain is something that is quite common and familiar, and there is something very reassuring about it too. As soon as the first droplets of rain hit the ground, the atmosphere becomes fresh, cooler, and fills up with the “earthly” smell of rain, which is something many people enjoy and associate very closely. The five reason for the pleasant smell of rain is not just based on sentimental grounds but on some natural principles, which are explained below:

The science behind petrichor

The main of reasons rain smells so good is because of a thing called petrichor. 'Petrichor' is a combination of two words. 'Petra' means stone, and 'ichor' is a reference to a fluid in Greek mythology. Ichor was the bodily fluid of the immortals. It was supposed to be this magical, elixir-like liquid. Really, 'petrichor' is referring to the way in which stone reacts to rain. When there's been no rain for a while, plants give off oils. These oils get sucked up into the ground, the rocks, and the dust in the air. Then, when rain comes, they get re-released, creating petrichor."

Role of the soil bacteria very large

Another important ingredient in the rain smell is a bacterium that lives in the soil. These bacteria are known as actinomycetes. Actinomycetes produce another substance referred to as geosmin. The smell of geosmin is earthy. Whenever rain falls, it disturbs geosmin in the soil, and the earthy smell is emitted into the atmosphere. The human sense of smell is extremely sensitive to this odor even when it is present in minute concentrations. Interestingly, it is the same substance that gives beetroot its earthy smell.

How raindrops spread the smell

As raindrops come into contact with the surface of the earth, they form a layer of air beneath the surface. Air bubbles form and rise to the surface. As the air bubbles burst, they make rain smell aerosols that rise into the air. As a result, the smell of rain diffuses faster and farther. Light rain produces a stronger smell because the smell particles are carried gently and are not washed away by the rain. For this reason, the smell of rain is often the strongest when a drizzle begins.

Ozone adds a fresh note
On other occasions, the scent that comes with the rain is fresh and clean and not earthy. Ozone is the cause of the fresh smell that comes from the rain instead of an earthy smell. Ozone gas is created from the breaking down of molecules that consist of oxygen and nitrogen gas generated from lightning that happens within the atmosphere. The molecules combine to form ozone gas that is then carried down by the rain.

Why humans love the smell of rain

The passion for the scent of rainfall can trace its origins to survival needs. To ancient humans, rainfall translated to water, arable land, and life in general. It is likely that the human brain, over time, paired this scent with a sense of security and renewal life brings. To some extent, it can be argued that even now, this scent brings about a refreshing escape from the scorching and arid conditions associated with the heat, hence the sense of calmness associated with it.





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