Where Does the Smell of Rain Come From?

Do you ever smell the rain coming?  The smell that fills the air as a storm approaches is unique. What causes this smell and where exactly does it come from? A video from YouTube channel ‘It’s Okay To Be Smart’ has the answers.

Three of the main components contributing to the smell of rain are ozone, petrichor, and geosim.

Ozone is a form of oxygen whose name comes from the Greek word ozein (to smell). In a rainstorm, an electrical charge from lightning splits atmospheric oxygen molecules (two oxygen atoms or O2) into separate atoms. Some of these recombine into  a molecule made up of three oxygen atoms—ozone, or O3. The scent of ozone usually comes before stormy weather because a thunderstorm’s downdrafts carry O3 from higher altitudes to nose level.

Petrichor comes from volatile oils that plants and trees release. These oils collect on surfaces such as rocks. The rain reacts with the oil on the rocks and carries it as a gas through the air.

Geosmin is produced by bacteria and algae of various types. They create a compound that can be lifted into the air when soil is disturbed, such as by rain.

When it rains, the air is moist.  This moist atmosphere provides an excellent medium for carrying the scents and fragrances of ozone, petrichor, and geosmin.

While the rain itself doesn’t have a smell, rain interacts with aspects of the environment to produce the scents associated with a rainstorm.

The chemistry behind the smell of rain.

The chemistry behind the smell of rain.

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