We love the smell of rain due to a combination of factors, primarily the presence of geosmin and volatile fatty acids released from the earth, along with the scent of ozone carried down from higher altitudes.
Here's a breakdown of the components contributing to the pleasing smell of rain:
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Geosmin: This is an organic compound produced by certain bacteria (actinomycetes) in the soil. When raindrops land, they disturb the soil, releasing geosmin into the air. Humans are incredibly sensitive to geosmin, able to detect it at very low concentrations. The "earthy" aroma is largely attributed to geosmin.
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Petrichor: This term, coined by Australian scientists in the 1960s, refers to the unique scent released when rain falls on dry earth. While geosmin is a major component of petrichor, it also includes other volatile organic compounds (VOCs) trapped in the soil during dry periods. These VOCs are released along with geosmin when the rain hits.
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Ozone: During thunderstorms, lightning can split oxygen (O2) and nitrogen (N2) molecules in the atmosphere. These can then recombine to form nitric oxide, which can further react to form ozone (O3). The characteristic "fresh," sharp smell often associated with thunderstorms and rain is ozone, carried down to ground level by downdrafts.
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Volatile Fatty Acids: These compounds, including stearic acid and palmitic acid, are also released from the soil when it rains. They contribute a pleasing, earthy undertone to the overall scent.
In summary, the delightful smell of rain is a complex mixture of naturally occurring compounds released from the earth and the atmosphere, creating a unique and enjoyable sensory experience.
