Smells are known to invoke memories. When I smell pine, I think of camp in Arizona when I was a teenager.
Popcorn can smell either good or bad depending on the space you’re in. Just for the record, burnt popcorn is the worst no matter where you are.
“Smell can instantly trigger an emotional response along with a memory, and our emotional states have a very strong effect on our physical well-being,” says Rachel Herz, a neuroscientist at Brown University who studies the psychological science of smell, from a study in the Harvard Medicine: The Magazine for Harvard Medical School article from Spring 2024 about how our emotions are linked to smells.
So when my 24-year-old daughter asked me “why does rain smell?” during an afternoon storm, I answered her as honestly as I could: soil is the main source.
That got me thinking, certainly there’s a scientific reason to this phenomenon that I must’ve learned during my weather education.
Today, I went back to the books to find answers. And what I found out is much deeper than just surface dirt.
The connection between earth and air
The smell of rain actually has a name - Petrichor.
From Merriam-Webster, Petrichor is: a distinctive, earthy, usually pleasant odor that is associated with rainfall especially when following a warm, dry period and that arises from a combination of volatile plant oils and geosmin released from the soil into the air and by ozone carried by downdrafts.
In 1964, two Australian scientists, Isabel Joy Bear and Richard Grenfell Thomas, combined two Greek words to form the word Petrichor. “Petros” means stone, and “ichor”, in Greek mythology refers to the fluid that flowed in the veins of the gods.
Basically, they identified two compounds (geosmin and 2-methylisoborneol) in soil that causes the earthy smell that occurs when rain falls on dry soil. While this wasn’t a new discovery, they were the first to define, name and publish their findings.
Read the original published article (FYI - there’s a fee to continue reading beyond the Abstract).
Strongest smell after a rinsing rain
Our region has been in a historic drought for almost a year. When the weather is dry, dead leaves and other materials settle on the ground where they become part of the soil. This layer suppresses growth along with the lack of water. Oils are then produced that stop additional growth of seeds and root systems.
According to the Farmers Almanac, actinobacteria grows on moist soil, but as the soil dries out, so does the bacteria causing spores that reproduce as a good rain falls. After they die, geosmin is created: geosim is the earthy smell that rises as the spores are released into the air.
Finding comfort in the smell of rain
I asked around and most of my co-workers find the smell of rain comforting. From the How Stuff Works website, those who like the smell of rain associate it “with positive experiences and emotions, such as relief from hot weather, the nourishment of crops and the soothing sound of rainfall.”
Do you like the smell of rain?
What smell brings back a good memory?