We have enjoyed the most beautiful October here in the Westcountry, in fact, I think most of the country has too. The Autumn colours have been fabulous and it has been unseasonably warm and dry ensuring lots of lovely crisp leaves and breathtaking sunsets.
Today, we have had rain for what seems like the first time in months and, as I went outside, I was struck by the ‘smell’ of the rain. Seriously! It’s rather like that wonderful smell you get when you brush against geranium leaves, an earthy richness, a sense of, well… nature!
As is my way, I looked up ‘the smell of rain’ on the internet… and was delighted to find it has a name – petrichor! I am now working at dropping this word into casual conversation at least once a week! Petrichor is ‘the earthy scent produced when rain falls on dry soil’. The word comes from Greek ‘petra’, meaning stone, and ‘ichor’, the fluid that flows in the veins of the gods in Greek mythology, all rather lovely I thought.
Before it hits the ground, rain is just water, it has no smell. But after the drops hit the ground and interact with soil, the fresh and almost sweet fragrance of rain is released. Now, scientists think they’ve identified the exact mechanism that releases this aroma into the environment. When a raindrop hits a porous surface it traps tiny pockets of air. These bubbles then speed upward, like bubbles in a glass of champagne (hic!), before breaking the drop’s surface and releasing microscopic particles, called aerosols, into the air. The researchers think it’s these aerosols that carry the ‘rain like’ aroma.
This set me thinking about a farmer friend who has a very sensitive nose (he does not like all the stinky cheeses I enjoy!) and he always says he can smell rain coming. Pah, I thought, a Devon farmer’s yarn… but no! Following on from my discovery of petrichor, it seems weather patterns really do produce distinctive odours that sensitive noses can sniff out.
Before the rain begins, one of the first odours we may smell, as winds pick up and clouds roll in, is a sweet, pungent zing in the nostrils. That’s the sharp, fresh aroma of ozone — a form of oxygen whose name comes from the Greek word ‘ozein’, to smell.
After a spell of heavy rain has passed, what’s often left is an earthy, musty whiff of wetness. This is the aroma of geosmin, a metabolic by-product of bacteria or blue-green algae. Ok, not quite so romantic, but interesting, nonetheless.
So, what’s the point of all these strange smells? As you may have guessed, Mother Nature doesn’t do anything without a reason and all these chemicals stirred up by the weather carry messages. Some biologists suspect that petrichor running into waterways acts as a cue to freshwater fish, signalling spawning time. Microbiologist think that geosmin’s fragrance may be a beacon, helping camels find their way to desert oases.
Although humans don’t appear to have a built in response to these odours, we do learn to associate them with our experiences. Flooding may forever scar us with moist, ‘mildewy’ memories, but for many of us, the smell of rain is cleansing and refreshing.
So, if I am spotted running around the car park outside the Create & Craft studios, skipping and shouting “Yippee!” in the rain, I haven’t gone mad, I am simply enjoying the scent of petrichor. Well, that’s what I shall tell everyone anyway!