The smell of rain

That musky scent so many people adore about the rain when it first begins to fall is apparently not the raindrops at all. Instead, there is a complex array of soil organisms and their by-products that give rain its distinctive smell.

Tim Logan wrote in a piece for The Conversation that a naturally occurring soil chemical called petrichor is principally responsible for the smell of rain, noting that rain itself has no smell.

“Petrichor is a combination of fragrant chemical compounds,” Logan wrote. “Some are from oils made by plants. The main contributor to petrichor are actinobacteria. These tiny microorganisms can be found in rural and urban areas as well as in marine environments. They decompose dead or decaying organic matter into simple chemical compounds which can then become nutrients for developing plants and other organisms.

“A byproduct of their activity is an organic compound called geosmin which contributes to the petrichor scent. Geosmin is a type of alcohol, like rubbing alcohol. Alcohol molecules tend to have a strong scent, but the complex chemical structure of geosmin makes it especially noticeable to people even at extremely low levels. Our noses can detect just a few parts of geosmin per trillion of air molecules.

“During a prolonged period of dryness when it has not rained for several days, the decomposition activity rate of the actinobacteria slows down. Just before a rain event, the air becomes more humid and the ground begins to moisten. This process helps to speed up the activity of the actinobacteria and more geosmin is formed.”

Source: https://getpocket.com/explore/item/why-you-can-smell-rain

jamiehart

Content creator and Chewbacca cosplayer.

See author's posts