Why does the soil smell so good after the rain?

Are you someone who has ever paused to inhale the delightful scent that lingers in the air after rain has fallen? Have you ever wondered what causes this captivating aroma? If so, then you are not alone. This phenomenon known as petrichor has fascinated both scientists and poets, inspiring curiosity and exploration.

In this article, we will embark on a journey over the secrets of petrichor, examining its origins and unveiling the science behind its irresistible allure. Prepare to delve into the enchanting world of petrichor and discover the magic that unfolds when raindrops meet the earth.

The smell of petrichor is caused by a combination of factors, including the release of volatile organic compounds (VOCs) from plants, formation of a chemical by the microorganisms in soil and also our higher sensitivity of nose to the scent of petrichor.

When it rains, the moisture in the air and on the ground can cause these VOCs to be released into the air, where they combine with other chemicals to create the distinctive smell of petrichor.

Apart from this the most accepted theory of petrichor is rated to the microorganisms.

It turns out that the species of streptomycetes and actinomycetes have the gene for making a chemical substance called geosmin which gives petrichor it’s enigmatic smell.

Geosmin comes from the ancient Greek “geo”, meaning earth, and “osme”, meaning smell. This scent is also used as an ingredient in perfumes and it is what gives beetroot its earthy flavour.

But why is geosmin made in the soil?

In a recent study, it is found that geosmin is part of the chemical language in a mutually beneficial relationship between Streptomyces bacteria and springtails, insect-like organisms that are abundant in the ground.

The benefit for the animals seems to be that the odours lead them to a source of food.

But how does producing these compounds benefit the bacteria? Streptomycetes normally grow as mycelium – a network of long, branching cells that entwine with the soil they grow in. When they run out of nutrients or conditions in the soil deteriorate, the bacteria escape and spread to new places by making spores that can be spread by wind or water.

When raindrops fall on the soil, the moisture functions as an aerosol, and the water vapors carry the spores into the atmosphere.

We breathe in the spores and they have a distinct earthy smell that is commonly referred to as petrichor.

So the next time you enjoy the earthly smell of the petrichor, remember you might be enjoying the chemical love language between the earth and the rain.