It’s up there with freshly-baked bread and babies’ skin as one of life’s best smells. But what exactly makes rain smell so good?
You might sometimes think you can ‘smell the rain’ before a storm arrives – you’re right, you can. As Scientific American explains, weather patterns can produce very distinctive scents which, to the sensitive human nose, can be both informative and comforting.
In essence (pardon the pun), the smell of rain can be attributed to three main elements: a mixture of plant oils, bacterial spores and ozone.
According to Scientific American, one of the first odors you might notice before rain arrives is a “pungent zing in your nostrils,” or ozone, which “emanates from fertilizers and pollutants as well as natural sources.
An electrical charge—from lightning or a man-made source such as an electrical generator—splits atmospheric nitrogen and oxygen molecules into separate atoms. Some of these recombine into nitric oxide, and this in turn reacts with other atmospheric chemicals, occasionally producing a molecule made up of three oxygen atoms—ozone, or O3. (Most atmospheric oxygen is made up of two atoms—O2.) The scent of ozone heralds stormy weather because a thunderstorm’s downdrafts carry O3 from higher altitudes to nose level.
2. Petrichor potpourri
A combination of the Greek roots petra (stone) and ichor (the blood of gods in ancient myth), the term petrichor was coined by a pair of Australian mineralologists in 1964 to describe the smell that results “when airborne molecules from decomposing plant or animal matter become attached to mineral or clay surfaces.”
Smithsonian adds: “When a rainstorm comes after a drought, compounds from the oils—which accumulate over time in dry rocks and soil—are mixed and released into the air.” These oils are produced to inhibit seed germination, suggesting that plants likely produce them in response to scarce water supplies during drought.
3. Damp earth
The wet, musty smell of earth you might notice after it rains is probably geosmin, a chemical produced by soil bacteria when they produce spores. When rain hits the ground, it sends the spores airborne, which then make their way to our noses via the moisture in the air.
“Because these bacteria thrive in wet conditions and produce spores during dry spells, the smell of geosmin is often most pronounced when it rains for the first time in a while, because the largest supply of spores has collected in the soil,” Smithsonian explains.
Science aside, it is also suggested that humans might be attracted to the smell of rain for its biological and evolutionary significance. In observing Western Australia’s Pitjantjatjara people, Diana Young, an anthropologist at the University of Queensland found that the Aboriginal community associated the smell of rain with green or new growth, fertility and the bringing of game like kangaroos and emus – food.
“She calls this “cultural synesthesia”—the blending of different sensory experiences on a society-wide scale due to evolutionary history.”
The more romantic among us may connect the smell of rain to pleasure or comfort: reading peacefully on the couch; listening to the meditative sound of drops on the roof from a cosy bed; splashing in puddles as a child.
And to think that you cursed at the dreary weather this morning…
Do you enjoy the smell of rain?
What feelings or memories does it evoke for you?