24 Jan 2015

Why does rain smell good?

From This Way Up, 12:20 pm on 24 January 2015


There's nothing quite the like the smell of rain on earth, and now scientists think they've discovered the secret of what makes it smell so good.

Using super slow motion cameras, a team at the Massachusetts Institute of Technology studied how raindrops behave when they hit various porous surfaces. They observed an 'aerosol effect' with the raindrops releasing tiny droplets of liquid that quickly evaporate to disperse an aroma.

An assistant professor of mechanical engineering at MIT, Cullen R. Buie, told This Way Up's Simon Morton that although it's a well known phenomenon, nobody has really studied it before. "The speed of the rainfall, the type of soil, all of these things have an effect on this phenomenon", he said.

Future work aims to look at the process from a slightly different perspective, to see how effectively it transports not just smells but also bacteria and viruses into the sky. "This could be a mechanism that leads to the transfer of chemicals and biological species form the soil to the air."

Rainfall can release aerosols
Aerosol generation after drop impingement on porous media is a three-step process, consisting of bubble formation, bubble growth, and bubble bursting. Image courtesy of Youngsoo Joung.