The Science Behind That Fresh Rain Scent : Short Wave (Encore episode.) Scientists have known for decades that one of the main causes of the smell of fresh rain is geosmin: a chemical compound produced by soil-dwelling bacteria. But why do the bacteria make it in the first place? Reporter Emily Vaughn answers this mystery.

Read the paper on which this episode was based.

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Other scent mysteries driving your nose wild? Email the show at shortwave@npr.org and we might track down the answer.

The Science Behind That Fresh Rain Scent

The Science Behind That Fresh Rain Scent

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A meadow reflects in a raindrop hanging from a blade of grass in Dresden, Germany. Robert Michael/dpa/AFP via Getty Images hide caption

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Robert Michael/dpa/AFP via Getty Images

A meadow reflects in a raindrop hanging from a blade of grass in Dresden, Germany.

Robert Michael/dpa/AFP via Getty Images

Encore episode! Scientists have known for decades that one of the main causes of the smell of fresh rain is geosmin: a chemical compound produced by soil-dwelling bacteria. But why do the bacteria make it in the first place? Reporter Emily Vaughn answers this bacteria-based mystery.

In this episode, we hear from Klas Flärdh, a professor of microbiology at Lund University in Sweden; Mahmoud Al-Bassam, a researcher at University of California, San Diego; and Paul Becher, a chemical ecologist and a researcher at the Swedish University of Agricultural Sciences.

You can find their paper in Nature Microbiology here.

Other scent mysteries driving your nose wild? Email the show at shortwave@npr.org and we might track down the answer.

This episode was produced by Rebecca Ramirez, edited by Viet Le, and fact-checked by Berly McCoy and Emily Vaughn.