Wake Up And Smell the Petrichor

[Solstice]

Who hasn't experienced the fresh scent in the air following a rainstorm? It seems like I've always been aware of it but it was only until a couple of days ago that I found out what actually causes it.

It's called petrichor (/ˈpɛtrɪkɔːr/ PET-ri-kor)—the earthy scent produced when rain falls on dry soil. The word was coined by Isabel Joy Bear and Richard Grenfell Thomas, two Australian scientists, in 1964. The word is derived from the Ancient Greek πέτρα (pétra) 'rock' or πέτρος (pétros) 'stone' and ἰχώρ (ikhṓr), the ethereal fluid, the blood of the gods in Greek mythology.

The smell derives from an oil exuded by certain plants during dry periods after it's absorbed by clay-based soils and rocks. During a rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of certain actinobacteria, which is emitted by wet soil, producing the distinctive scent.

The human nose is sensitive to geosmin and can detect it a concentrations as low as 0.4 parts per billion. Some scientists believe that humans appreciate the rain scent because ancestors may have relied on rainy weather for survival. Camels in the desert also rely on petrichor to locate sources of water such as oases.

Enjoy the scent as you get outside today!