There’s something special about experiencing the fresh, invigorating smell of a passing rain storm. The small water droplets that leak from the padded clouds seem to carry a swe
et scent with them, but what exactly are we smelling?
It’s tempting to assume that the collection of rain falling from the sky has its own unique smell, however upon closer examination, the powerful smell we experience after it rains is actually a mixture of activated plant oils, bacterial spores in the dirt, and ozone that is reacting with the falling rain.
As rain falls in arid areas, the dry plants secrete oils that are released and carried into the air. The fresh scent is dispursed, in part, by the water cycle, a recycling process that allows water to change into its various forms. Isabel Joy Bear and R. G. Thomas were the first researchers to classify post-precipitation scents in 1964 and gave it the term petrichor.
In addition to the secretion of plant oils, the musky, earthy smell of “rain” can be attributed to damp soil, also know as geosmin. Geosmin is a by-product of bacteria and blue-green algae and creates a very pleasant smell when falling water creates new molecular structures. As the rain evaporates, the fatty acids, alcohols, and hydrocarbons are released, carrying ordorific oils with them.
The third element, which gives rain it’s fresh and energizing smell is ozone, oxygen, or O3. This aromatic smell was observed when three oxygen molecules or O3 drifts from the above atmosphere and settles at lower altitudes.
After recent research that was popularized by writer and researcher, Florence Williams, researchers are discovering that nature smells have many beneficial medical impacts on humans. In chapter 3, The Smell of Survival, she outlines and highlights how smells influence our moods, behaviors, and health.
So, the next time you are enjoying that spring-summer rainstorm, sit back, relax, and let those “rain” smells work their strange magic.
Science Made Simple 