Petrichor is the Smell After Rain: Definition and Occurrence Process

IPA • Lifestyle

Petrichor is the Smell After Rain: Definition and Occurrence Process

Petrichor is
Written by Pandu

Petrichor is – Rainwater that falls does indeed provide many blessings for those who are grateful for it, such as being able to irrigate rice fields, plantations, prevent drought, and for rain lovers moments like the rainy season are very much anticipated because when it rains it will produce a distinctive earthy smell with a very strong aroma. fragrant.

Are Grameds friends familiar with the smell of the soil right after it rains? If you are familiar with the smell of the soil, there is no mistake that the smell that arises from the soil after rain is called petrichor. In the rainy season, like what happened recently in December, it certainly doesn’t take long to confirm the distinctive smell of the soil because lately it’s been raining heavily every day.

However, do you know why soil when it comes in contact with rainwater can produce a distinctive aroma which is known as petrichor? So, if all of you Grameds don’t know and want to know what petrichor is and how it occurs so that it creates a distinctive aroma, then in this discussion we will provide related information about petrichor.

Further discussion of the petrichor can be seen below!

Petrichor definition

Petrichor, angu or ampo (Indonesian: petrichor) is a natural odor created when it rains on dry land. This word comes from the Greek, petra which means stone, and ichor, the fluid that flows in the veins of the gods in Greek mythology.

The typical smell of rain when it first wets the earth is petrichor or petrichor. The word comes from the combination of the prefix “petr” which refers to stone and “ichor” which refers to a weak aroma.

The Merriam-Webster Dictionary describes petrichor as the pleasant earthy smell associated with rain, especially after hot, dry weather. Odors can also be caused by a combination of volatile vegetable oils and geosmin released from the soil into the air and with ozone.

The term was coined in 1964 by two CSIRO researchers, Isabel Joy Bear (Australia) and Roderick G. Thomas (United Kingdom) for an article published in the journal Nature. They explain in their article that the odor comes from an oil that certain plants secrete in dry weather when the oil is absorbed into the soil and rocks such as clay.

When it rains, the oil is released into the air along with another compound, geosmin, a by-product of actinobacterial metabolism that is released into moist soil and creates its unique aroma. Ozone can also be smelled by lightning. In another paper, Bear and Thomas (1965) showed that the oil inhibited seed germination and early growth of plants. This suggests that the plant secretes an oil to protect the seed from germinating under stress.

In 2015, MIT researchers used high-speed cameras to record the spread of odors in the air. The tests include approximately 600 tests on 28 different surfaces, including engineering materials and soil samples. When rain falls on a porous surface, the air in the pores forms tiny bubbles that float to the surface and become aerosols. Aerosols transport odors as well as bacteria and viruses from the soil. Slower moving raindrops tend to generate more aerosols; This explains why Petrichor is more common during the rainy season.

Some researchers believe that humans like the smell of rain because their ancestors may have depended on monsoon winds to survive.

Petrichor is

How Does Petrichor Smell Occur?

Although rain itself has neither taste nor smell. But when it rains, especially if it hasn’t rained for a long time, it has a distinctive musky scent that is said to be soothing.

Another source of the pleasant rain smell is possibly the flora in the area. Some plants are known to secrete oil during the dry season, and when it rains this oil is released into the air.

These volatile fatty acids, including stearic acid and palmitic acid, can add a pleasant earthy scent to the smell of rain. Another smell associated with rain is ozone. During thunderstorms, lightning can break down oxygen and nitrogen molecules in the atmosphere, which then recombine into nitric oxide.

This substance interacts with other chemicals in the atmosphere to form ozone, which has a strong chlorine-like odor.

If a person smells approaching rain, it is possible that the wind from the approaching storm is carrying ozone from the clouds to the person’s nose.

The phenomenon of petrichor is influenced by many things. There are at least three main factors:
Ozone oil, geosmin, and plant oil.

Here is an explanation of how the petrichor odor occurs:

1. Lightning and Ozone

Rain is usually accompanied by lightning strikes. When lightning strikes, its molecules are diatomic (read: those with two atoms) such as oxygen and nitrogen are broken down to form nitrogen monoxide (NO) and ozone (O3).

The ozone molecule is then carried away with the raindrops. Did you know that ozone has a characteristic odor? This fragrance promotes the petrichor phenomenon.

2. Geosmin

Professor Mark Butter, director of molecular microbiology at the John Innes Center (a center for plant and microbial science research and education in the UK), says that when we smell wet soil, we are actually smelling molecules produced by certain bacteria.

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The distinctive molecular aroma comes from geosmin, a compound produced by actinomycete bacteria in the soil.

Water droplets in contact with the ground cause Geosmin compounds to become airborne, so Geosmin is everywhere.

This geosmin compound is a combination of carbon (79.06%), hydrogen (12.17%) and oxygen (8.77%). Humans are sensitive to geosmin and smell it well. In fact, the human nose can detect geosmin in air at 5 parts per trillion.

3. Natural Plant Oils

Plants produce compounds that can be described as a kind of vegetable oil in the dry season. These compounds accumulate around rocks and in the soil.

When it rains, these compounds are released and dispersed into the air, contributing to Petrichor’s unique odor. This compound contains stearic acid and palmitic acid, a type of fatty acid with a long hydrocarbon chain.

So you can imagine there are many things that contribute to Petrichor’s unique smell. Made from geosmin, vegetable oil and ozone, which are then carried by wind and rainwater, which people smell as a soothing earthy scent.

Interesting Facts About Petrichor

1. Humid air

Humid air also encourages the scent of Petrichor to appear. Actinobacteria decomposition activity during the dry season can be slow because the soil and air are very dry at this time.

However, when it rains, one of the signs is humid air. Same with soil conditions.

These two things then help accelerate the activity of actinobacteria and the formation of geosmin compounds in large quantities.

2. Bau aerosol

When raindrops reach the ground, they usually scatter into tiny particles.

Well, spray particles are called aerosols. This aerosol removes the fresh scent of Geosmin.

Petrichoria are released along with aerosol particles and carried by the wind to the human sense of smell.

3. Petrichor disappears after the rain

As the rain stops and the ground begins to dry, the scent of Petrichor slowly fades. This is because actinobacteria activity slows down, making petrichor odorless.

These microorganisms become active again and produce geosmin compounds, and the plants begin to produce oil and release it when the next rain comes.

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Why Does Petrichor Smell Soothing?

Have you ever felt calm when you smell the rain? According to research, the smell of rain can actually evoke nostalgia. This is supported not only by emotional feelings. Because the brain plays an important role between smell and nostalgic feelings.

This is the part of the brain responsible for storing long-term memories, especially smells. This area is called the piriform cortex. This part of the brain is in charge of storing memories or nostalgia. However, this mechanism only works with the rest of the brain. The process of artificial stimulation stores memories in the brain.

Memories are formed when neurons in the brain communicate with each other through a process called synaptic plasticity. That rain is considered a “memory bearer” is nothing new. There are many components that make rain “make memories”, one of which is the smell of rain-drenched earth. This is Petrichor, the natural scent created when it rains on dry land.

The scent of this rain is responsible for the emotional feelings of many people who smell it. Australian researchers first coined the term petrichor in 1964, according to a report in Science Daily. Experts say that petrichor can form when rainwater falls on certain natural objects, such as plants. Certain types of plants secrete oils during the dry season, which are released into the air when it rains and give off a special aroma.

Additionally, other reactions that produce petrichoria can occur when chemicals produced by soil-dwelling bacteria such as actinomycetes are released. These aromatic compounds create a pleasant petrichor smell when rain hits the ground. Another smell associated with rain is ozone. During thunderstorms, lightning can break apart oxygen and nitrogen molecules in the atmosphere. All of these components can in turn recombine to form nitrogen monoxide.

This substance interacts with other chemicals in the atmosphere to form ozone, which has a strong odor similar to chlorine. Some people who are sensitive to odors can smell this. Those with this ability can predict rain from this odor, which is carried to the surface by ozone winds.

So how can Petrichor generate emotional feelings to trigger memories of certain events? Several studies have shown that smells trigger emotional memories that convey a more intense feeling of being “taken back in time” than pictures. Psychology Today reports that experts say this is due to stimulation of the brain’s anatomy.

Incoming odors are first processed by the olfactory bulb, which starts in the nose and travels along the base of the brain. This organ has direct connections to two areas of the brain that are heavily involved in emotion and memory, namely the amygdala and hippocampus.

Interestingly, visual, auditory (sound), and tactile (touch) do not pass through this brain area. This is why smell, more than any other sense, is so successful at evoking emotions and memories.

The Researchers Behind Petrichor’s Smell

So who is behind the research that later introduced the use of the term “petrichor”?

There were two brilliant scientists from Australia who collaborated and published “Nature of Argillaceous Odor” in the Journal of Nature on March 7, 1964.

As scientists, they are both part of the Commonwealth Scientific and Industrial Research Organization (CSIRO), an Australian government agency responsible for scientific research in Australia.

Richard had been curious for a long time trying to figure out what was causing the smell of rain.

Joy and Richard, who previously worked in Melbourne’s Department of Mineral Chemistry, decided to collaborate and conduct research to more accurately identify and describe the smell of rain. They carried out the experiment on rocks that were exposed to hot, dry conditions outside.

After steam distilling the rock, they found a yellowish oil in the rock and soil that decomposes when exposed to moisture.

This yellowish oil causes petrichor phenomenon.

Petrichor is

A term for people who like the smell of rain

If you love rain, you are called a pluviophile.

By definition, pluviophiles are people who love all things rain including the smell after rain or petrichor. You’re probably used to other people complaining endlessly of being wet and cold. Meanwhile, you dream of a gentle drizzle. If you are a rain lover, not only are you happy with the rain, you are probably a more moody person most of the time. Here are some reasons why people who enjoy rain are happier in life.

1. Enjoy life

People who like rain can usually enjoy their life. They were able to describe rain in great detail with the mesmerizing sound of drops. You feel comfortable and calm when it rains.

2. Enjoy the fragrance after the rain

Soil that has been exposed to rainwater will definitely give off a distinctive aroma and you will enjoy it. This odor is known as petrichor, usually the smell of moist and clean air. As a pluviophile you will absolutely love the smell of rain drenched earth.


So a brief discussion of the definition of petrichor. This discussion does not only discuss the definition of petrichor, but also discusses further how the process occurs, interesting facts about petrichor, research behind the smell of petrichor, and names for people who like petrichor.

Understanding the meaning of petrichor gives us additional knowledge about various interesting phenomena produced by nature, especially when it rains that there is a distinctive aroma that we don’t realize arises naturally shortly after rain falls on dry land called petrichor. Smelling petrichor for some people can also stimulate their brain performance by reviving beautiful memories in their brain memory. Besides that, the smell of petrichor is also claimed to calm the mind when it rains.

Thus a review of the meaning of petrichor. For Grameds who want to learn all about the meaning of petrichor. And science related to other natural phenomena, you can visit to get related books. 

As #FriendsWithoutLimits, Gramedia always provides the best products, so you have the best and latest information for you. To support Grameds in adding insight, Gramedia always provides quality and original books so that Grameds has #MoreWithReading information.

Author: Pandu Akram

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