Petrichor – The earthy scent when new rain hits the soil

Dry soil and dry leaves & plants everywhere. Sun is too hot. Suddenly as a blessing, when the first rain falls on earth, earth reacts with a pleasant smell – A smell of joy, which we can’t define. All of us say, it’s the smell of new rain. What is the science behind it? New rain has a nostalgic feel. It’s much beyond that.

Petrichor – The impressive smell

Petrichor – the name given to the earthy scent when new rain hits the soil. The name was coined by Isabel Joy Bear and Richard Thomas, and published in an article titled ‘Nature of Argillaceous Order’ in 1964. The name ‘Petrichor’ was coined from 2 words – Petro & Ichor. ‘Petro’ means Rock and ‘Ichor’ is the blood which runs through the veins of Greek gods.

How is Petrichor produced?

When plants are scarce in water, they produce an oil, which flows to the pores of soil and blocks other plants from absorbing water. Over time this oil gets stored in soil, and when first rain falls on soil, this oil rises up to atmosphere. The Streptomyces bacteria present in soil produces geosmin, a metabolic by-product, which mixes with oil in atmosphere producing Petrichor. Geosmin is found in beetroot. That’s the reason why beetroot has the smell of soil.

Geosmin – The fragrant substance produced by Streptomyces bacteria present in soil is the main reason for the smell of petrichor. It’s produced from the chemical substance Farnesyl Pyrophosphate with the help of magnesium ions. When rain falls to soil after a long time, Geosmin mixes with air to give a pleasant smell, which we call as Petrichor.

Ozone layer can also give this smell

During some occasions, before the rain falls, the smell of petrichor can be felt. Ozone is the reason behind it. When lightning happens, oxygen in atmosphere becomes ozone and the smell of ozone gives us an illusion of petrichor.

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