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Have you ever noticed the particular smell that comes with rain, especially after a spell of hot dry weather? And how that smell makes us feel?

When it rains, especially after a long dry spell, the earth releases a fragrance. This smell of rain is a real physical thing that is measured by scientists and even has a scientific name: ‘petrichor’.

The word petrichor means literally ‘blood from a stone’. It comes from the Greek ‘petra’ (stone) and ‘ichor’ which, in Greek mythology, is the ethereal blood of the gods. The term was coined in 1964 by two CSIRO researchers in Australia, Isabel Joy Bear and Roderick G. Thomas, for an article published in the journal Nature.[1]

What makes the smell of petrichor?

Certain plants exude an essential oil during dry periods, which is designed to stop seeds from germinating under harsh conditions. This oil is absorbed by clay-based soils and rocks, hence the reference to blood from a stone. When it rains, the oil is released into the air, allowing the seeds to germinate, and producing the familiar smell.

In 2015, scientists at MIT used high speed cameras to record how the process takes place.[2]

When a raindrop hits a porous surface, small bubbles form that float to the surface and release aerosols. Such aerosols carry the scent, as well as bacteria and viruses from the soil. Slower, gentler raindrops tend to release more aerosols, which is why the smell of petrichor is stronger after light summer rains.

Rain has not just one smell, but three

Nature is always communicating with us, in ways both subtle and powerful. The smell of rain has such a natural significance that there are actually three phases to it:

Before rain – Ozone

Ozone is a form of oxygen whose name comes from the Greek work ozein (meaning to smell). Most oxygen has two atoms (O2), but ozone has three (O3).

During a thunderstorm, lightning can split oxygen and nitrogen molecules in the atmosphere. These in turn can recombine into nitric oxide, which interacts with chemicals in the air to form ozone. Ozone also emanates from fertilisers and pollutants, as well as natural sources.

When we smell ozone, we know something is coming . . . a thunderstorm that can bring danger in the form of lightning and fires, but also new life in the oxygen and nitrogen that come with it and fertilise the earth and plants, and the rain to water them and wash the earth clean and fill our waterways.

During rain – Petrichor

Petrichor is first smelt as humidity builds in the atmosphere and tiny droplets of water are absorbed into the rock, releasing the fragrant essential oil from plants that the rocks have absorbed. As light rain falls, the oil is released in full, bringing the smell of summer showers that we love.

After rain – Geosmin

Geosmin is a metabolic by-product of certain bacteria that is given off by wet soil, giving it that distinctive earthy-musty smell after the rain. These bacteria can cause disease in humans, and the smell may serve as a warning to us.

What is the purpose of petrichor?

Being able to smell an impending storm (ozone) makes sense, allowing us to prepare for it and protect ourselves.[3] And being able to smell the damp and mould that can harbour disease (geosmin) can also serve as a warning to us, again with health and survival implications.

But why petrichor? We understand that plants produce an oil to protect their seeds, but why do they go to the trouble of producing a fragrant oil, so that we can enjoy the smell of summer rain? Is the fragrance for them, or for us? Presumably the fragrance is a message, to us and other forms of life, that the rain is coming, seeds will be germinating, and food is on the way. What a lovely way for plants to communicate that they are about to bring us an abundance of food for life.

Nature is always communicating with us, and in ways we are only beginning to understand. Our senses offer us a way to receive these communications, to receive Nature’s messages – her warnings and her blessings – and to live in harmony with her. The smell of rain is a communication from God, his alchemy, his perfume, a gorgeous gift to us that results from the magical interplay of many aspects of nature, all communicating with each other, producing a fragrant potion of love.

Our sense of smell can guide us through life

Perhaps we may be inspired to live in a more true and loving way by our sense of smell. Our sense of smell can be a great guide in life, and our nose, which is a powerful part of our face and gives our face ‘character’, reflects how we use it. Our sense of smell is also a large part of our sense of taste, and tells us whether food is fit to eat; and if our nose is blocked, we don’t enjoy our food nearly as much!

The smells that come off city streets after rain are not quite so lovely as petrichor, and distinctively demonstrate that when we humans get together, we are not always living in harmony – with ourselves, with each other, or with Nature. Perhaps we may be inspired by petrichor to return to living in a more harmonious, sweet-smelling way . . .

Our sense of smell guides us through life, and our true sense of smell is much more than physical, even though there is a physicality to it. We have some lovely sayings in our language that serve to remind us of the truth of this. We say: we can “smell a rat”, we can be “led by the nose”, we can “smell if something is off”, we have a “nose for truth”.

Until now, we have used this knowledge largely to deceive. We give off smells that are not always pleasant, particularly if we are not living in a healthy and loving way, and perfume companies have made a fortune out of creating fragrances and disguising our other smells with them. We are led by the nose much more than we realise when shopping in retail centres, by the clever use of smells. We are seduced by fragrances that mimic the natural hormones we release to communicate desire and pleasure and sexual readiness with each other.

The power of smell is known, but it is not yet being used in a true way. We are using it to override, to deceive, to seduce, to entice, and misusing our senses to take ourselves further away from nature and the truth of life.

What if we were willing to be more aware of what we were smelling, and what nature was communicating with us, the way dogs[4] do, without judgment? For too long we have allowed ourselves to believe that our sense of smell is not as keen as that of animals. Yet studies have now shown that humans have an excellent sense of smell. We can detect and discriminate an extraordinary range of odours, and are in fact more sensitive than rodents and dogs for certain scents.[4]

What if, instead of overriding what we smell and disguising how we smell, we allowed ourselves to embrace all scents, in full awareness of the messages they are bringing us? We would smell that whiff of alcohol or smoke on a person’s breath, the scent of fear, guilt, and sadness, the smell of a lie . . .

. . . and we would open ourselves up to smell the divine fragrance that emanates from an open heart, the heavenly smell of fragrant roses, the sweetness of innocence, and all the other gifts that Nature showers our senses with, including petrichor.

Our nose knows, and if we were more willing to be guided by our sense of smell, we may find ourselves living more openly, honestly, truthfully, and in harmony with our own bodies, each other, our natural world and the Divinity we live in and come from.

References:

  • [1]

    Bear, Isabel Joy; Thomas, Roderick G. (March 1964). "Nature of argillaceous odour". Nature 201 (4923): 993–995. doi:10.1038/201993a0 Retrieved from http://chemport.cas.org

  • [2]

    Chu, Jennifer (14 January 2015). "Rainfall can release aerosols, study finds". MIT News. Retrieved 17 January 2015. Retrieved from http://news.mit.edu/2015/rainfall-can-release-aerosols-0114 and https://www.youtube.com/watch?v=Waqmq_GTyjA

  • [3]

    Yuhas, Daisy (July 18, 2012). "Storm Scents: It's True, You Can Smell Oncoming Summer Rain: Researchers have teased out the aromas associated with a rainstorm and deciphered the olfactory messages they convey". Scientific American. Retrieved July 20, 2012. Retrieved from https://www.scientificamerican.com/article/storm-scents-smell-rain/

  • [4]

    McGann, John P (12 May 2017). “Poor human olfaction is a 19th-century myth”. Science Vol 356, issue 6338, eaam 7263. Retrieved from http://science.sciencemag.org/content/356/6338/eaam7263

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