When it rains what is the smell

The word comes from the Greek words 'petra', meaning stone, and 'ichor', which in Greek mythology refers to the golden fluid that flows in the veins of the immortals. In their research, rocks that had been exposed to warm, dry conditions were steam distilled to reveal a yellow coloured oil that had become trapped in the rocks and soil, a substance they discovered was responsible for the smell.

The source of this oil is a combination of oils secreted by plants during dry weather which signals to halt root growth and seed germination and chemicals released by soil-dwelling bacteria. Many people believe they can smell when it is going to rain, and there is some evidence to support this. As part of a team of scientists from Sweden, the UK and Hungary, we discovered the fascinating biology behind this enigmatic compound.

Scientists have known since the s that geosmin is made by microorganisms in the soil, primarily by bacteria with the scientific name Streptomyces. Streptomycetes and their close relatives make thousands of different specialised metabolites — a true treasure trove for the potential discovery of new antibiotics. It turns out that all streptomycetes have the gene for making geosmin, suggesting that it has an important function. But what do these bacteria gain from producing geosmin?

This has been a longstanding mystery. In our recent study , we found that geosmin is part of the chemical language in a mutually beneficial relationship between Streptomyces bacteria and springtails , insect-like organisms that are abundant in the ground.

We discovered this by asking if there could be soil organisms out there that would be attracted to the smell of Streptomyces. The rain reacts with the oil on the rocks and carries it as a gas through the air.

This scent is like bacteria spores in that most people consider it a pleasant, fresh smell. It has even been bottled and sold for its aromatic qualities! These are a few common rain smells, but there are also all sorts of other scents after it rains.

There are lots of aromatic materials that the moisture and impact of rain can stir up, and the moist atmosphere following a downpour is particularly good at carrying these particles through the air. So, when you talk about the after-the-rain smell with a friend, you may mean one thing while your friend is thinking of something else.

You'll both agree, however, that the air has a much stronger aroma to it after a good rain. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close.

Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Bacteria found in soil which are also used to create commercial antibiotics produce a geosmin molecule. When raindrops hit the dry soil, they trap tiny air bubbles, which then shoot up through the raindrop in a kind of fizz, a bit like champagne spraying from a champagne bottle.

This produces aerosols of geosmin and plant oils that remain suspended in the air or carried away by the wind. Heavy rain stops the release of the aerosols of geosmin, so the smell is not as strong. Geosmin is now even used as an ingredient for perfumes.

Download our app. February 22, 5 min read. Before and After the Rain Hands up, who has ever said that they can smell a storm coming?

But what you smell when it rains is different.