Petrichor and the Brain

Can you tell by smell that rain is coming? Some brains can. If there is lightening, ozone may be present and may be carried down from the clouds. There are several scents associated with rainfall that many enjoy—if their brain can decode odors. As it falls, rain—being water—is odorless. But when it hits the earth, something happens. What people find pleasing about rain is due, at least in part, to something called petrichor. Actually, the word petrichor was coined by two Australian scientists in 1964 when they were studying the smells of wet weather. The word is a combination of the Greek word petra, meaning stone, and ichor, that comes from Greek mythology, the fluid that supposedly flowed in the veins of the gods. The odor known as petrichor tends to linger when rain comes after a long dry spell. The scientists found that an oil is released by some plants during dry periods and is absorbed by clay-based soils and rocks. When it rains, the oil is released into the air along with some other compounds. Interestingly, light rain tends to produce more aerosols.