Petrichor (pron.: /ˈpɛtrɨkər/ or /ˈpɛtrɨkɔər/) is the scent of rain on dry earth. The word is constructed from Greek, petra, meaning stone + ichor, the fluid that flows in the veins of the gods in Greek mythology. It is defined as "the distinctive scent which accompanies the first rain after a long warm dry spell".[1]
The term was coined in 1964 by two Australian researchers, Bear and Thomas, for an article in the journal Nature.[2][3] In the article, the authors describe how the smell derives from an oil exuded by certain plants during dry periods, whereupon it is absorbed by clay-based soils and rocks. During rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of bacteria, which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning.[4] In a follow-up paper, Bear and Thomas (1965) showed that the oil retards seed germination and early plant growth.[5] This would indicate that the plants exude the oil in order to safeguard what water there is for themselves.
