Archive for April, 2009

Things I read today (as it begins to rain – geosmin and petrichor)

Sunday, April 26th, 2009

It’s a wonderful feeling to encounter a scientific explanation for something one has experienced but never quite understood – in this case the distinctive smell that is discernible when rain starts falling…

Geosmin, which literally translates to “earth smell”, is an organic compound with a distinct earthy flavour and aroma, and is responsible for the earthy taste of beets and a contributor to the strong scent that occurs in the air when rain falls after a dry spell of weather (petrichor). The human nose is extremely sensitive to geosmin and is able to detect it at concentrations as low as 5 parts per trillion…

Petrichor is derived from the Greek petros “stone” + ichor “gods’ blood”:

The scent is generally regarded as pleasant and refreshing… In desert regions, the smell is especially strong during the first rain after a long dry spell… The oil yielding the scent can be collected from rocks and concentrated to produce perfume; however, it has yet to be synthesized, perhaps due to its complexity. It is composed of more than fifty distinct chemical substances.


I too love learning these kinds of things and that names sound like characters from a biblical story – magi or young lovers.)