origin: (20th century) Greek; γεω-= "earth" + ὀσμή= "smell".
noun [plural, geosmins]
A derivative of decahydronaphthalene (C₁₂H₂₂O), an organic compound, that creates the musty earth-like smell after rain or yard work - known as "petricor" (the scent before rain is "ozone").
Human noses, one of the least sensitive in the animal kingdom, are especially attuned to geosmin (we can detect 0.7 parts per billion), but Earth worms are attracted to it too. Camels may use it to sniff out an oasis in the desert. Insects use it to find plants for eating and reproduction cycles.
This compound also adds to the flavor of beets, potato skin, spinach, mushrooms, catfish, etc. which is why some do not like them (although I personally love those foods). You may also detect geosmin in mold, like rotten food such as a green potato chip or moldy roll, perhaps a cork that spoiled the wine, which may explain why some people are hyper-sensitive to geosmin scents/flavors and reject them.
You're not alone if you do -- fruit flies hate the smell as well!
French biochemists Berthelot & André, isolated "‘l’odeur propre de la terre’", Gerber & Lechevalier of America tracked down the main odour component to a single compound in 1965, which they called geosmin (geo = Earth, osme = odour). It has since been discovered in connection with at least 70,000 compounds. Geosmin is a main component of spores and Earth's way of recycling organic matter and is ancient, this has opened it up as a pathway to "travel through time" via analyzing the evolution of organic matter. One would be able to smell geosmin over 400 million years ago! In fact it existed billions of years ago, when there was only bacteria.
Clearly, geosmin is deeply connected to life on this planet!
We hope to continue to develop deeper understandings of this compound, not only to understand Earth's evolution better via microbiology, but in order to develop "green technology" such as bio-fuels that are more in harmony with the environment.