Petrichor

A brief note on the phenomenon by Thomas Lambe Phipson [fr] (1833–1908) appeared in The Chemical News on 17 April 1891[3] and was re-published in its entirety, a month later, in The Scientific American,[4] in which he wrote, "This subject, with which I was occupied more than twenty-five years ago, appears from a paragraph in the last number of the Chemical News[3] to have recently attracted the attention of Professor Berthelot and [Monsieur G.] Andre."

Phipson was referring to a short paper read by Berthelot and André at the meeting of the French Académie des Sciences on 23 April 1891, and printed in Volume 112 (1891) of Comptes Rendus, entitled "Sur l'odeur propre de la terre" ("On the earth's own smell").

The phenomenon was first scientifically described in a March 1964 paper by Australian researchers Isabel Bear and Dick Thomas, published in the journal Nature.

[11] 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 certain actinobacteria, such as Streptomyces,[12] which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning.