The smell of rain has a name — petrichor — and it comes from bacteria in the soil
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The distinctive smell after rain falls on dry earth is called petrichor, coined in 1964 by Australian scientists. It comes from at least two sources: geosmin, a chemical produced by Streptomyces bacteria in soil (the same bacteria responsible for the earthy smell of compost), which is released when raindrops disturb the soil; and ozone, produced by lightning reacting with atmospheric oxygen. Human noses are extraordinarily sensitive to geosmin — we can detect it at concentrations of 5 parts per trillion, making it one of the most detectable odours we can sense.
The smell of rain is universally recognised and widely considered pleasant or nostalgic. Finding that it's actually the smell of bacteria released from soil — and that we can detect it at almost unimaginably small concentrations — makes a universal sensory experience suddenly specific and biological.
The Science Behind It
The distinctive smell after rain falls on dry earth is called petrichor, coined in 1964 by Australian scientists. It comes from at least two sources: geosmin, a chemical produced by Streptomyces bacteria in soil (the same bacteria responsible for the earthy smell of compost), which is released when raindrops disturb the soil; and ozone, produced by lightning reacting with atmospheric oxygen. Human noses are extraordinarily sensitive to geosmin — we can detect it at concentrations of 5 parts per trillion, making it one of the most detectable odours we can sense.
Why Your Brain Finds This Hard to Believe
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VerifiedWritten and fact-checked by the OddlyHuman Behavioral Science Team. We verify all psychological, sociological, and historical claims against peer-reviewed journals, primary sources, and established encyclopedias to bring you accurate insights.
Read our Editorial Guidelines →“The smell of rain is called petrichor and comes from bacteria in soil (Streptomyces) released by raindrops. Our noses detect the smell at 5 parts per trillion — one of the most sensitive things we can smell. 🌧️ #OddlyHuman”