ORLANDO, Fla. – Ever step outside, smell the air and thought you could smell the rain coming? You’re not crazy—what you smell is known as petrichor.
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A brief history
During the 1960s, two Australian scientists, Isabel Joy Bear and R.G. Thomas, were studying the smells of wet weather when they discovered the smell of rain.
That smell was deemed petrichor by the duo, after the Greek term “petra” meaning stone and “ichor” meaning the blood of gods in mythology.
Petrichor has a cool makeup of a few things that you smell in the air when it rains.
The science behind the smell
If you’re outside when a gust front passes by, the scent in the air that smells like rain is actually ozone.
Lightning in a thunderstorm splits oxygen and nitrogen. These can recombine into nitric oxide, which in turn interacts with other elements in the air and forms ozone.
The sinking air in a thunderstorm that hits the ground, known as a downdraft, expands outward creating the gust front.
This is the front that carries the ozone that you smell. You may notice is has a faint chlorine scent to it, but that’s what you smell before the rain arrives.
Once the rain arrives, it’s a different story.
During a dry spell, plants create oils to help inhibit growth so they don’t have to compete as much for water. When the rain hits the plant, the odor from the oils is released.
Sometimes the petrichor may smell musky or earthy. This is from bacteria that lives in the soil known as actinomycetes. The secretion from the bacteria gets wet and that’s what you smell.
So there you go—the science behind the smell of rain.