The Fragrance of Petrichor – The Seductive smell of rain


It’s raining after a very hot few months. There are predictions about the hottest time periods that are about to come in the next few weeks, but we all appreciate this sudden rain. There is a famous poem that I learned in high school by H.M Kudaligama.

“ගන වැහි වළා ඉගිළි එන විට දී අඩා

මට මහා සොම්නසක් ඇත මොනරෙකුට වඩා” 

H.M Kudaligama

I still love the smell that comes with the rain that earthy smell. Do you know why the first rain smells so good? Let me tell you a bit more about it. 

Why does rain smell so good?


Did you know there is a scientific term for that smell of rain? Well, it’s called Petrichor. But where does this name come from? It’s quite interesting, actually.

Petrichor is derived from two Ancient Greek words: “petros,” meaning “rock” or “stone,” and “ichor,” which is the ethereal fluid in Greek mythology representing the blood of the gods. This unique name was not just whimsically chosen; it was formally described in the renowned scientific journal Nature.

The Science & Mechanism Behind Petrichor

If something does have a scientific name, obviously some scientists are behind it. Let me tell you about the Science behind this Petrichor. The scent we perceive after rainfall comes from a combination of fascinating compounds. 

Two key players here are geosmin and 2-methylisoborneol. These compounds are responsible for that earthy aroma we all know and love. But here’s the thing: it’s not just about chemicals; bacteria play a significant role, too. 

Specifically, certain bacteria called Actinomycetes & actinobacteria, such as Streptomyces, contribute to producing this distinctive scent. When rain hits the ground, these bacteria release spores, enhancing the smell we associate with rain. Additionally, during lightning storms, ozone may also be present, adding another layer to the olfactory experience.

When raindrops land on surfaces like soil, they create small bubbles in the air pockets. These bubbles, in turn, release tiny particles called aerosols. These aerosols carry not just the scent but also bacteria and viruses from the ground.

It’s remarkable how sensitive our noses are to geosmin; we can detect it even at incredibly low concentrations, as low as 0.4 parts per billion. This sensitivity to geosmin contributes to our ability to appreciate the scent of rain.

Historical and Modern Perspectives of Petrichor


Humans are very curious creatures. They want to solve the mysteries of Nature. The smell associated with rain is one of these interesting mysteries. 

The quest to find Petrichor is obviously not a recent phenomenon. But did you know it goes back to the 1800s? To be exact, in 1891, researchers like Thomas Lambe Phipson were already intrigued by this unique scent, just like every human ever felt a first rain.

Phipson’s observations, along with discussions at the French Académie des Sciences meeting in the same year, shed some light on the matter. Their paper, titled Sur l’odeur propre de la terre,” delved into the scent associated with rain-dampened soil, hinting at the complexities of Petrichor long before its formal scientific description.

Scientific Contributions

Fast forward to 1964, where Australian researchers Isabel Bear and Dick Thomas made groundbreaking strides in unraveling the mysteries of Petrichor. Their publication in March of that year marked a turning point in the scientific understanding of this phenomenon.

Through meticulous research, they revealed the chemical composition and biological origins of the rain’s scent. Their work defined Petrichor and sparked further investigations into its intricacies.

Recent Research

In 2015, a team of researchers at MIT took a closer look at Petrichor using modern high-speed cameras. Their study aimed to uncover the mechanisms behind the Petrichor scent’s dispersal.

By capturing raindrops in action, they made a remarkable discovery: the formation of aerosols. These tiny particles, propelled by raindrop impact, carry the scent of Petrichor and bacteria and viruses from the soil. 

Sometimes, there is more than one smell of rain. Because of various factors of Nature, these smells tell us different stories about the rain itself. 

Acidity of Rain

Have you ever noticed how rain sometimes has a tangy smell? Well, that’s because of its acidity. When rainwater falls, it interacts with organic debris on the ground, triggering chemical reactions.

These reactions lead to the release of minerals and chemicals trapped within the debris. As a result, we get a medley of distinct smells that add to the overall aroma of rain.

Volatile Oils and Aromatic Materials

As raindrops hit the ground, they disturb the serene abode of plants and trees. In response, these green guardians release volatile oils into the air. These oils and other aromatic materials mingle with rainwater, creating a symphony of fresh and pleasant scents. I mean, we could call it nature’s own air freshener, straight from the sky to our noses.

Why Do We Enjoy the Smell of Rain?


Have you ever taken a deep breath after a refreshing rain shower and felt an instant sense of calm and happiness? It’s not just your imagination; there are real reasons behind why we love the smell of rain. Yes, people, it’s Science. 

“සුළගින් ගසා ගෙන එන මිහිරි බව රැදී

සිතුවිලිවලට මුළු හදවත ම ඉඩ මදි”

H.M Kudaligama

Biological and Psychological Reasons: Our love for the smell of rain goes beyond just enjoying a pleasant scent. It’s deeply rooted in our biology and psychology. Scientists believe that our attraction to this aroma may be linked to evolutionary survival instincts. 

Back in our hunter-gatherer days, rain meant the end of drought and the promise of fresh water, essential for our survival. So, our brains may have learned to associate the smell of rain with relief and abundance.

Positive Associations with Rain: Rain is often associated with positive experiences and emotions. Think about it – rain brings relief from scorching hot weather, nourishes crops, and creates a cozy atmosphere indoors. 

These positive associations can make the smell of rain even more enjoyable. It’s like nature’s way of giving us a little boost of happiness when we need it most. Personally, I think we all can use a little bit of happiness right now. 

Personal Experiences and Associations: Beyond the biological and psychological aspects, our love for the smell of rain is also influenced by personal experiences and associations. 

For many people, rainy weather evokes memories of childhood adventures, cozy days spent indoors with loved ones, or romantic moments under an umbrella. Even the writer has few memorable memories associated with the rain. So yeah, I can relate. 

These personal connections to rainy weather can deepen our appreciation for the smell of rain, making it even more enjoyable.

Another wonderful thing about this Petrichor fragrance is the way this fragrance is tied to human evolution. Since the distant past, water is one of the most important factors that people have used to build their habitats. 

So, the man who has become familiar with this Petrichor scented water has developed his eva to this scent. This Petrichor is known as the most sensitive smell of humans because of the way humans have evolved to find this water over hundreds of thousands of years.

So, the next time you take a stroll in the rain and catch a whiff of that familiar scent, take a moment to appreciate the biological, psychological, and personal reasons why we love the smell of rain. It’s not just water hitting the ground – it’s nature’s perfume, delighting our senses and lifting our spirits.

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