Ooh, this is a lovely word. It describes the scent you smell when rain hits dry soil. It’s one of the few words we have for a specific smell – most, like fresh-cut grass or frying bacon, are just descriptions of what they are.
Photo by Zachary Gilseth on Unsplash.
In the words of Jennifer Aniston, here comes the science… So, certain plants exude an oil during dry weather, which is then absorbed by clay-based soil and rocks. When it rains this is released into the air, alongside another compound called geosmin (a metabolic byproduct of bacteria) which is emitted by wet soil. And together they make the smell petrichor. Hmmm, I’m glad someone came up with a nice word for it, cos it sounds gross.
Origin-wise, even though ‘petrichor’ sounds all Latiney or Ancient Greeky, it’s actually quite a modern word. It was coined in 1964 by two researchers called Isabel Joy Bear and Richard G Thomas in the scientific journal Nature. The reason it looks like ye olde word is because our researchers took its parts from Greek. ‘petra’ means ‘stone’ (you can also find this in words like ‘petrified’ and ‘petrol) and ‘ichor’ is basically a fancy word for fluid (it’s also the stuff that flows in the veins of the gods of Greek mythology apparently).
If you’re a fan of Doctor Who then you’ve probably come across ‘petrichor’ already – it was used by the TARDIS as part of a password to open a back-up control room in ‘The Doctor’s Wife’, and was also the name of a perfume that Amy Pond modelled in ‘Closing Time’.
Interesting fact alert: our noses are super sensitive to geosmin – we can detect it at concentrations as low as five parts per trillion (which is good…?). Some scientists think this is because it might have been handy for survival for our ancestors to know when rainy weather was on the way.