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The scent of rain

Petrichor is the earthy scent often associated with rain falling on dry soil or rock. The scent of petrichor is linked to oils that build up in rocks and soil during dry periods and are released by moisture. When raindrops strike porous surfaces they can trap air bubbles that rise and burst as aerosols, which lets scent-carrying material enter the air.

Geosmin contributes to the strong scent known as petrichor that occurs when rain falls after a spell of dry weather or when soil is disturbed. Geosmin is produced by bacteria, especially cyanobacteria, often present in soil and water supplies. Further research suggests that people can detect imminent rain by the ozone that appears just before it, coming from a combination of various soil components and lightning.

Materials of rain accords

Geosmin is a bicyclic alcohol with the formula C₁₂H₂₂O, a derivative of decalin. Geosmin is easily smelled by most people, with an odor detection threshold of 0.006 to 0.01 micrograms per liter in water.

Calone is a white solid that is a derivative of 4-methylcatechol. Calone is similar in structure to brown algae pheromones like ectocarpene and distantly related to the drug diazepam. In the fragrance industry Calone is known as watermelon ketone, and its formula is C₁₀H₁₀O₃.

Helional is chemically an aldehyde with a hydrocinnamaldehyde motif. Dihydromyrcenol is a synthetic organic compound used primarily as a fragrance ingredient. The chemical formula of dihydromyrcenol is C₁₀H₂₀O. Dihydromyrcenol has not been reported to be found in nature. Worldwide use of dihydromyrcenol exceeded 1000 metric tons per year as of 2004.

Related Notes

Explore all seven extraits in the Discovery Set.