Petrichor: why does rain smell so good?
It turns out it's not just gratitude that makes rain smell so appealing after a long period of dry weather. There's actually some chemistry involved too. Bacteria, plants and even lightning can all play a role in the pleasant smell we experience after a thunderstorm; that of clean air and wet earth. Known as petrichor, the scent has long been chased by scientists and even perfumers for its enduring appeal. Wet earth First named by two Australian researchers in the 1960s, the warm, earthy fragrance we experience when rain hits dry ground is produced by bacteria. "These critters are abundant in soil," explained Prof Mark Buttner, head of molecular microbiology at the John Innes Centre. "So when you're saying you smell damp soil, actually what you're smelling is a molecule being made by a certain type of bacteria," he told the BBC. That molecule, geosmin, is produced by Streptomyces. Present in most healthy soils, these bacteria are also used to create commercial antibiotics. Drops of water hitting the ground cause geosmin to be released into the air, making it much more abundant after a rain shower."Lots of animals are sensitive but human beings are extremely sensitive to it," added Prof Buttner. sabel Bear and RG Thomas, the researchers who first named the scent petrichor, found that as early as the 1960s it was being captured to sell as a scent called "matti ka attar" in Uttar Pradesh, India. Now, geosmin is becoming more common as a perfume ingredient. "It's a really potent material and it smells just like the concrete when the rain hits it," said perfumer Marina Barcenilla. "There's something very primitive and very primal about the smell." "Even when you dilute it down to the parts per billion range, [humans] can still detect it," she added. Source