Petrichor is one of my favourite words, a rare experience these days, the fragrance of oncoming rain. For those unfamiliar with the term, petrichor refers to the distinct scent you experience just before rain falls. It is the fragrance of rain. And it is a word coined by Australian scientists; Isabel Joy Bear and Richard Thomas. To be specific, petrichor refers to an oil that is released from rocks and the earth just before or just as rain begins to fall. The word itself literally means blood of the stone, petra (stone) ichor (blood or essence).
Thomas had been fascinated by the natural phenomena. Through steam distillation of rocks and soil, Bear and Thomas discovered a yellow oil trapped in the rocks that was released by moisture. They discovered that when humidity fills the pores of the stones with tiny amounts of water it flushes tiny amounts of oil from the stone releasing it into the air. Further research by a team of scientists at MIT captured the process in slow motion video. With a drop of rain bubbles shoot upwards in a fizz of aerosols, like bubbles in a glass of champagne. How magical is that.
What causes the oil? I believe it is the combination of bacteria and plant oils that have been deposited in the rock. Anyone familiar with summer around the Blue Mountains would be familiar with the blue haze that characterises that region and it is similar oils causing the characteristic blue haze of summer in the Australian bush that are deposited in the rock that forms petrichor. The process is much more complex than I have summarised, there is also believed to be an element of oxidisation at work to create the distinct fragrance. I just love the word and the phenomenon. I also love that someone was so curious about the phenomena they felt compelled to investigate further, just to satisfy their curiosity.
Pity I didn’t notice petrichor on the weekend when the pod got a bit damp in a sudden shower but I noticed nothing over the smell of wet dog at the beach.