You know that smell in the air after a good rain? Or that smell that permeates the air when you dig into your garden’s soil every spring? Did you know there’s a scientific explanation for that smell?
The science behind that wonderful “fresh earth” aroma is geosmin.
Geosmin is an organic compound produced by a microorganism found in all soil, and it carries a distinct aroma and flavor. It’s what gives beets their earthy flavor. Sometimes if you drink water that’s been sitting out for a while, it develops a musty taste, and that, too, is caused by geosmin. Wine is known to pick up this flavor as well.
The flavor produced by geosmin isn’t always a pleasant one, but the aroma it gives off is quite pleasing to the senses. So where does that smell come from, and why do we get whiffs of it after a nice heavy precipitation? It’s pretty simple: When it rains, water fills the air pockets found in the soil, and the geosmin gets expelled into the air. Sometimes you’ll even get an earthy whiff of geosmin before it rains. How, you ask? Well, a low-pressure system can de-gas the soil and put those geosmin into the air before a drop of water even hits the ground, leading many of us to say things like “It’s gonna rain; I can smell it!”
Read more about geosmin from the Soil Science Society of America.
Steve & Corey Veldheer are organic yard & garden specialists in west Michigan.