I think only like 2 people have found the second Doctor Who reference in this week’s It’s Okay To Be Smart video. Don’t let me down, Tumblr.
If you said “from the sky,” then congratulations! You are hilarious. But it’s a lot more interesting than that. The pungent perfume that accompanies rainstorms carries special chemical signatures, some born from lightning, some from deep within the soil.
And beyond just being pleasant and nostalgic, those smells are actually useful to some living things, such as telling plants when it’s time to grow, guiding camels across the desert, and even signaling some fish when it’s time to get “romantic”.
Take a big whiff, because there’s a science storm a-comin’!
The chemical structure of geosmin, the compound behind the smell of the Earth after rain, which itself is known as petrichor. Geosmin is a compound released by certain soil bacteria called Actinomycetes, and falling rains cause it to be released into the air. We are sensitive to 10 parts per trillion, or one drop in an Olympic-sized swimming pool.
Next time you’re dancing in the rain with someone you love, tell them how much you like the smell of (4S,4aS,8aR)-4,8a-Dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol.