Rain is water and water is odorless. But then where does the special smell come from that you can only smell after a summer rain and why does it smell so good?
In 1964, Australian mineralogists Isabel Bear and Richard Thomas found the cause of the special smell after a summer rain and gave it the name Petrichor. Petros means stone, and Ichor, according to Greek mythology, was the liquid that flowed through the veins of the gods. Petrichor is therefore the "blood of the gods of stones".
The fragrance consists of two ingredients: Geosmin, an earthy-smelling alcohol produced by soil bacteria, and an oil secreted by plants during drought. The impact of raindrops causes both substances to mix and disperse in the air. The intensity of the odor is determined by three factors: the porosity of the soil, its moisture, and the amount of precipitation. The drier the soil, the more odor can develop, because more particles are released from the dry soil. The more porous the soil, the more cavities for petrichor air bubbles can form. The petrichor smell is particularly intense in light rain after a long dry spell, because then the odorous substances spread particularly well.
But why do we humans like the smell of rain so much? Here, too, science has a theory. In all regions of the world, rain, especially the first rain of the season after a drought, is associated with plant and animal growth - in other words, with food. This is what science calls "cultural synesthesia" - the evolutionary blending of different sensory experiences throughout society.
If you now absolutely want to smell rain or the "blood of the gods of the stones", you should take an extensive walk in the summer rain with an umbrella from us. If you can not wait for the next rain, there are several options. You can buy perfumes with petrichor as an ingredient, or you can stand in the garden with a lawn sprinkler. But if you have neglected gardening for a long time and are looking for an incentive, here's the best tip: dig up the garden, because this will also produce Petrichor.