Do You Know What The Smell Of Rain Is Called?

It's raining. The world feels fresh and clean. Rain often brings a sense of peace and calm. Many people find the sound of raindrops very relaxing. Rain comes in different forms. A light, fine rain is sometimes called a drizzle. A heavier rain might be a shower. When lightning and thunder join in, we call it a thunderstorm. Each tiny bit of water that falls is a droplet.

But think about what happens after the rain starts. Have you ever noticed that distinct, earthy smell that fills the air? It’s a very unique scent. Do you know what this smell of rain is actually called? In this article, we'll take a look at the science behind this wonderful aroma and finally reveal the special name for the smell of rain.

What Is The Smell Of Rain Called?

The unique and pleasant scent associated with rain, especially after a long dry spell, is called petrichor (pronounced PET-rih-kor).

Who Named Petrichor and Why?

The term "petrichor" was officially coined in 1964 by two Australian scientists, Isabel Joy Bear and Richard Grenfell Thomas. They published their findings in the journal Nature in a paper titled "Nature of Argillaceous Odour."

The Name's Origin: They created the word from two ancient Greek words:

• ‘petra’, meaning "stone" or "rock".
• ‘ichor’, which, in Greek mythology, was the golden fluid that flowed like blood in the veins of the immortal gods.
• The Meaning: The scientists proposed the name because the smell can be regarded as an "ichor" or "tenuous essence" derived from rock or stone. It literally translates to "the essence of stone".

What Causes the Smell?

Petrichor is not a single scent but a delightful combination of three main components released when raindrops hit the ground:

• Geosmin: This is the primary and most powerful component. It is a metabolic byproduct (an organic compound) produced by certain soil-dwelling bacteria called Actinomycetes. During a dry period, the bacteria release spores that contain geosmin. When water hits the dry ground, it traps tiny air bubbles. These bubbles burst from the droplet, like a miniature aerosol spray, releasing geosmin into the air for us to smell.
• Plant Oils: During dry spells, some plants secrete oils that accumulate on rock and soil surfaces. These oils are released and contribute to the overall petrichor aroma.
• Ozone: Sometimes, especially during thunderstorms, lightning can split oxygen and nitrogen molecules in the atmosphere. They can recombine to form small amounts of ozone (0₃), which can be carried down to the ground by the rain, adding a sharp, clean scent often described as a faint hint of chlorine.

10 Unique Facts About Petrichor

• Humans are incredibly sensitive to the smell of Geosmin. We can detect it at concentrations as low as five parts per trillion—which is better than a shark's ability to smell blood.
• Some scientists believe our powerful attraction to the scent is an evolutionary trait inherited from our ancestors, who relied on rain for survival and could use the smell to locate water.
• The scent is released when raindrops land on porous surfaces (like dry soil). The impact traps air bubbles, which shoot up and out of the drop, creating a fine mist of aromatic compounds (aerosols).
• The strongest petrichor scent is released during light to moderate rain on dry soil. Heavy rain is too fast and suppresses the aerosol-creating process.
• Although humans love the smell of geosmin, they tend to dislike the taste! Geosmin is what gives beets their earthy flavour and can sometimes cause a muddy taste in drinking water or fish.

• Before it was scientifically named, people in India had captured the scent for centuries. They would distil it into sandalwood oil and sell it as an earthy perfume called "Mitti Attar" (Earth's perfume).
• The sharp, clean note in the scent is often the contribution of ozone brought down from the atmosphere during a lightning storm.
• Petrichor is strongest after the first rain following a significant drought, as the oils and geosmin have had a long time to accumulate.
• For the bacteria that produce it, geosmin acts as a signal to attract small soil-dwelling creatures (like springtails) that help disperse their spores.
• Following the creation of "petrichor", a few other related words have been coined, such as "biblichor", which describes the unique smell of old books.