petrichor
noun

- a pleasant smell that frequently accompanies the first rain after a long period of warm, dry weather

Lexico

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ORIGIN

“Petrichor” is the earthy scent produced when rain falls on dry soil. The word is constructed from Greek “petra” (rock) or “petros” (stone), and īchōr (the fluid that flows in the veins of the gods in Greek mythology).

In 1891, Thomas Lambe Phipson described the phenomenon as “the odour due to the presence of organic substances … closely related to the essential oils of plants … the fragrance emitted by thousands of flowers … absorbed into the pores of the soil, and only released when displaced by rain”.

T.L. Phipson - “Cause of the Odour Emitted by the Soil of a Garden after a Summer Shower”, The Chemical News (17 April, 1891)

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CAN YOU SMELL THE RAIN?

In 2015, scientists from the Massachusetts Institute of Technology (MIT) used high-speed cameras to record how the scent moves into the air. When a raindrop lands on a porous surface, air from the pores forms small bubbles, which float to the surface and release aerosols.

Such aerosols carry the scent, as well as bacteria and viruses from the soil. Raindrops that move at a slower rate tend to produce more aerosols; this serves as an explanation for why the petrichor is more common after light rains.

The human nose is extremely sensitive to aerosols and is able to detect them at concentrations as low as 400 parts per trillion. Some scientists believe that humans appreciate the rain scent because ancestors may have relied on rainy weather for survival.

Adapted from: Tim Logan - “Why You Can Smell Rain”. The Conversation (August 27, 2018)

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PRACTICE OWAD in an English conversation, say something like:

“PETRICHOR reminds me of summer showers during childhood holidays in Cornwall.”

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THANKS to Anelka for suggesting today’s lovely word.

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Paul Smith