Petrichor (from Greek petros, stone + ichor) is the scent of rain on dry earth; more specifically, it is the name of the organic oil that yields this scent. The term was coined by two Australian researchers in 1964 for an article in the journal Nature. In the article, the smell is shown to derive 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.
The scent is generally regarded as pleasant and refreshing, and is one of the most frequently cited "favorite smells". Petrichor has yet to be synthesized, perhaps due to its complexity: it is composed of more than fifty different substances.
