THE SCENT OF RAIN

 WHY IS IT WE CAN SMELL RAIN?

 

  

There comes with rain somtimes an earthy scent, musky, fresh and pleasant. 

 LET'S GO TO AN ATMOSPHERIC SCIENTIST FOR THE EXPLANATION.  

 

Photo by: Lucy Chian

As the ground moistens a fragrant combination of chemical compounds called petrichor is splattered and tiny particles of aerosols are ejected. The source is an actinobacteria that becomes more active as humidity rises releasing geosmin, a type of alcohol. The human nose can detect just a few parts of geosimin per trillion air molecules. 

 

Source: Dr. Timothy Logan, professor of Atmospheric Sciences at Texas A&M University.

https://atmo.tamu.edu/people/profiles/faculty/logantim.html

 

Actinobacteria are of enormous importance because forests and agriculture depend on their ability to decompose organic matter making smaller molecules that can be taken up again by plants.  Click HERE for more.

 

Once I hypothesized that this was the scent of nitrogen since our air is 80% nitrogen. I imagined falling raindrops picking up nitrogen molecules on the way down but my hypothesis was wrong.  No, raindrops do pick up nitrogen on the way down, but that's not what we detect when we smell rain.

 

Maybe Dr. Logan can tell me why it smells like home when I return to the San Luis Valley of Colorado, my childhood home, or why when I landed in Kenya I said: "Nairobi smells like home." 

 

Well, it's par for the course, whey one question is answered, others pop up in it's place.