The air smells good after a rain, and much of the reason is a thing called "petrichor."
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Do you love the good smell of rain? If so, you're not alone.
In fact, some scientists believe that people inherited their affection for the scent of rain from ancestors who relied on rainy weather for their survival.
But what makes rain smell so nice? There are several scents associated with rainfall that people find pleasing.
One of these odors, called "petrichor," lingers when rain falls after a prolonged dry spell. Petrichor — the term was coined in 1964 by two Australian scientists studying the smells of wet weather — is derived from a pair of chemical reactions.
Some plants secrete oils during dry periods, and when it rains, these oils are released into the air. The second reaction that creates petrichor occurs when chemicals produced by soil-dwelling bacteria known as actinomycetes are released. These aromatic compounds combine to create the pleasant petrichor scent when rain hits the ground.
Another scent associated with rain is ozone. During a thunderstorm, lightning can split oxygen and nitrogen molecules in the atmosphere, and they in turn can recombine into nitric oxide. This substance interacts with other chemicals in the atmosphere to form ozone, which has a sharp smell faintly reminiscent of chlorine.
When someone says they can smell rain coming, it may be that wind from an approaching storm has carried ozone down from the clouds and into the person's nostrils.