That Sweet Scent of Rain

by Anupum Pant

When rain starts falling after a long dry spell, most of us notice a sweet-musky scent around us. Sometimes, it is as if you can smell the rain coming. Have you ever wondered what causes this peculiar smell?

Well, scientists have also wondered the same for a long time and now they have some concrete answers for us. According to them, this evocative scent is a mixture of several individual smells. In essence, there are three factors which combine to form the “petrichor” – The smell of rain.

1. Bacteria – The best (my favorite) of all the three is caused because of a specific type of bacteria in mud called Actinomycetes. The force, with which the rain water falls, disrupts the bacteria-produced-spores in dry mud, and the moisture present in the air carries them to our noses. Most people love this odor and associate it with rain.
   So, spores of bacteria are responsible for the kind of smell you get, when rain falls on dry mud.
2. Plant Oils – A blend of oils produced by plants during the dry spell is another main source of this aroma. When it rains, volatile parts of these oils get released into the air. It is the kind of smell you get when you are getting wet in the woods.
3. Ozone – Another smell associated with the rain, is a minor part of petrichor and it smells like burning wires. This is produced by a reaction caused when lightning strikes, the Nitrogen and Oxygen present in air to form Ozone molecules.

Subjective senses

Besides that, smell is a subjective sensation. That means, you can’t explain a smell to someone, and you can never know what the other person smells. So, it becomes really hard for scientists to communicate to us, which scent is which.

Some of us like the bacteria smell, while others might like the third component of petrichor.

Some like the smell of rain, others don’t. But we’ll never know accurately, if the scent you adore is the same as the one your friend hates. One way to communicate some information about these scents is by comparing them with other popular smells (like I did above). This could probably give you a vague idea, but the exact sensation will remain elusive. It is like trying to explain the color red to a person who’s been blind all his/her life.