Scientists Say: Petrichor

That lovely smell after a rainstorm has a name

The scent of earth after a rainstorm smells like nothing else. But what is it?

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Petrichor (noun, “PEH-trih-core”)

This is the smell that rises from dry ground when it rains. But it isn’t the smell of water. Instead, petrichor comes from plants and bacteria. Plants release long chain molecules called fatty acids. The chains break down into small molecules that we can smell. Soil bacteria, meanwhile, produce a chemical called geosmin (gee-OZ-men). Combine the broken-down fatty acids and geosmin and you get petrichor. But petrichor doesn’t actually smell until it rains. When water droplets hit the soil, they trap bubbles of air under them. The bubbles rise through the raindrop. When they spray out into the air as a fine mist, they carry the smell of petrichor up into our noses.

In a sentence

The next time it rains, step outside and smell the petrichor.

Here’s the science and history of petrichor.
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Bethany is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology from Wake Forest University School of Medicine.