Heat. Your feet in dusty sandals ache for rest.
As you sit down, wiping your forehead, you look up.
Dark clouds and the promise of rain hover above you.
The first drops fall on the dusty path.
And release the scent of summer.
The earthy scent produced when rain falls on dry soil has inspired poets and writers long before it was scientifically described in 1964. Two Australian researchers, Isabel Bear and Dick Thomas named the unique aroma “petrichor”. The word was coined from Greek petros, meaning “stone” and ichor, meaning "the fluid that flows in the veins of the gods”.
Bear and Thomas concluded that the scent was a combination of plant oils and geosmin, a molecule produced by certain soil bacteria. The plant oils are absorbed by soil. When it rains the oil is released together with the geosmin formed by Actinomyces.
The exact mechanism of how aerosols are released during summer rains and carrie the scent of petrichor was demonstrated by scientists from MIT in 2015. They used high-speed cameras to capture the process.