If you ever thought that the smell of rain was in the air after you left your home one day, you are not alone. But apparently, not everyone can detect the smell of approaching rain. So you might be wondering if this is really backed up by science.
The claim that it is possible to smell the rain before it comes has divided people into two. A quick glance at social media makes it clear that some insist on their ability to predict rain by smell, while others seem far more skeptical. But perhaps surprisingly, there is some evidence to support these claims. There are several factors that contribute to why it can be smelled before the rain arrives, and the most important of these includes something called a petrichor.
What does petrichor mean?
The word petrichor comes from the Greek petros, meaning stone, and ichor, the fluid that flowed in the veins of the ancient gods. It refers to that familiar, oddly satisfying scent that emanates from the ground after heavy rain, especially after a long period of drought. The term was first used in 1964 by mineralogists Isabel Joy Bear and Richard Thomas.
Petrichor is considered among many people’s favorite fragrances in the world. But until relatively recently, no one was quite sure why we found it so pleasant. In 2020, a team of scientists discovered that the scent is particularly attractive to other animals as well.
This is because Streptomyces, a common soil bacterium, produces a compound called geosmin. What attracts us in a very strange way is actually the smell of geosmin. In fact, the human nose is so good at detecting traces of the compound that it outperforms sharks’ ability to smell blood in water. Bacteria produce geosmin to lure creatures that become coated with their spores and then disperse them over larger distances.
When it rains, water droplets crash against a surface and then flatten, creating air pockets in the ground’s pores, as researchers showed in 2015. These pockets then blast out of the water, basically breaking down into very small aerosols. During this process, they carry away traces of everything found in the soil, including geosmin. These can then be carried by the air for miles beyond the rain clouds. These aerosol particles are probably what people notice when they smell rain on the horizon. It may also explain why bacteria are present in high concentrations in the atmosphere, while tiny microorganisms are swept away by the winds.
Presence of ozone in the wind
Another contributing factor to the smell of impending rain is the presence of ozone in the wind. This particular chemical has a sweeter odor than the slightly more earthy odor associated with petrichor.
Ozone is made up of three oxygen atoms and gets its name from the Greek word ozein, meaning “to smell”. It is a naturally occurring gas but can also be produced by man-made fertilizers or other pollutants. It can be formed by an electrical charge (such as lightning or lightning) that separates nitrogen from the atmosphere from oxygen molecules. Some of these molecules will recombine to form nitric oxide, which can sometimes turn into ozone after reacting with other chemicals in the atmosphere.
The odor of ozone in the air may indicate that heavy rain is approaching, as a stormy draft can send ozone to ground level where it can be detected by humans.
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