DALLAS — “Do you smell it? That smell. A kind of smelly smell. The smelly smell that smells... smelly.” - Eugene Krabs, 1999
Mr. Krabs was talking about those annoying anchovies. I would like to talk about a different smell: the rain! If you didn’t see it today, you might have smelled it. So, what’s up with that? Water doesn’t have a stench, so why does rain? The quick answer is, it doesn’t.
“Petrichor” is what you’re smelling. Petrichor is a combination of chemical compounds that gives a familiar ‘stank’ that we call rain. Most of those compounds come from plants and dirt. The main contributor to the “rainy smell” is actinobacteria. These helpful bacteria help decompose dead, organic matter and produce the byproduct geosmin -- another big contributor to petrichor. After a long spell of dry weather, which we’ve most definitely had, decomposition from actinobacteria slows down, geosmin production reduces, and things take a bit of a pause.
Here comes the rain again….
When rain and moisture return, it accelerates the processes of the actinobacteria and more geosmin is generated. But how does it all travel from the ground to your nose? The smack of the rain drops on the ground causes a splatter that traps the petrichor into little tiny aerosols. These aerosols travel in the air and are driven even farther by the wind produced by the rain. That wind-carried “smell of rain” will make it to your nose before the drops hit your head. It’s a nice little alert system that nature has so perfectly designed.
