Who has not ever smelled the unmistakable and pleasant smell of rain? It is something that mainly comes to our senses in the autumn season with the first rains of the hydrological cycle after the hot summer. It is a very well-known aroma throughout the world and considered one of the most pleasant and the bearer of good sensations that exist. For this reason, it has been named and everything: it is called petrichor.
In this article, we are going to tell you about the characteristics of the petricor and why it smells this way. If you want to know more about this, don't miss this article.
Smell of clouds
From We have always wondered what clouds smell like. We see them in the sky, so fluffy and beautiful that it comes to mind to be able to touch and feel them. Between the different types of clouds there are some that look like pure cotton and we would like to place ourselves on them and navigate through that sea of clouds. However, in reality, we cannot even touch them, since they are still water droplets in the sky.
Given that the water of which the clouds are composed is tasteless, colorless and odorless, we cannot expect much from its pleasant smell. However, when it rains, we get that unmistakable smell that brings us memories, nostalgia and we associate it with the passage of time. Normally, it is a more accentuated smell in autumn, since the land is drier due to little or no rainfall in the summer months.
It is clear that the clouds themselves do not smell of anything. At most, due to the amount of agglomerated water particles that there are, we could notice a slight musty smell, but very slight, as we are not in a closed place where this smell is concentrated. However, the rain does give off an odor. Why is this happening?
The reason for the petricor
The fact that the clouds don't smell like anything and the rain does is a chemical matter. What really smells is not the rain, but the earth wet from the rain. As the first drops of rain fall after a long time of dry land, the petricor smell is stronger than ever. Therefore, it is a more characteristic smell of autumn. If it rains more often, we will not perceive the smell as intense or as often. What's more, if the ground is still wet from the last rains, it won't even smell.
There are many perfumers who, throughout history, have tried to capture it without success to be able to intoxicate different areas with this wonderful smell. However, you have to leave this characteristic to nature and value it for what it is and not for what it can be. If this smell can be removed artificially, it would not evoke that mixture of feelings or satisfaction that it does now.
The petricor is born from the union of several substances that give rise to this smell when they are mixed with each other. There are various odors that make up petricor, but the main component present is geosmin. It is a substance that is manufactured by actinobacteria present in the soil.
It has mainly three components. Two of them are found on earth and one in the atmosphere. When these three components are placed together, it gives rise to the smell of rain.
Smell of heaven and earth
There is also a very characteristic odor that occurs during electric storms. It is produced due to the division of oxygen molecules when rays strike them. These oxygen molecules regroup among themselves leading to the formation of ozone gas. Although individually this smell is not very pleasant, when combined with those of the rain, they make up the smell of rain.
The terrestrial component is a kind of aromatic oil that is released when raindrops come into contact with them. Actinobacteria are the ones that most influence the production of the rain smell. These bacteria inhabit the soil in both rural and urban areas. Even in marine areas or coastal environments, we can also find these bacteria, since they have a large area of distribution.
The function of these bacteria is mainly that of degrading and decomposing organic matter into other simpler substances. These transformed substances serve as food for plants and other microorganisms. The presence of these bacteria in soils then becomes essential for the life and development of biota to take place. When actinobacteria break down organic matter, various by-products are released. Among them is geosmin, mentioned above. It is an alcoholic compound with a characteristic smell that is responsible for the earthy flavor of some vegetables.
Why is it more pronounced in the fall?
When it rains less in the summer time, actinobacteria are less active. Both heat and drought weaken them. Therefore, as the soil begins to moisten with the first drops of rain, the activity of organic matter degrading bacteria begins to proliferate again. The more active they are, the more by-products are discarded in degradation, so more geosmin is released. All this means that when the raindrops come into contact with the ground it gives rise to the petricor.
If the soil is porous, this odor will be intensified by greater aeration and circulation of more geosmin. The petricor is released into the atmosphere and recirculated by the action of the wind until we bring them to our noses and activate all the senses.
Why we like this smell so much is difficult to explain. The answer to this question has not been found, but it follows that it is a matter of our brain. It is a kind of brain evolution that responded positively to this smell because it meant that the crops could prosper and there would be food for everyone.
I hope that with this information you can learn more about the smell of rain.