After rain smell caused by ‘champagne effect’

IT’S A smell as familiar to Australians in summer as sunscreen and barbecues. But no one has really been able to say why it smells after it rains. Until now.

IT’S A smell as familiar to Australians in summer as sunscreen and barbecues.

But while the smell of fresh rain after a hot spell is an aroma many of us know well, no one has really been able to explain it - until now.

Scientists at the Massachusetts Institute of Technology think they’ve finally come up with the answer.

The smell, called petrichor, is defined as that which frequently accompanies the first rain after a long period of warm, dry weather.

According to MIT researchers, Australian scientists were actually the first to characterise this phenomenon, however until now it wasn’t known how thedistinctive odour was released into the air.

Scientists believe they have stumbled across the mechanism which releases this very smell, as well as other aerosols into the environment.

The team used high-speed cameras to capture the moment when rain hits a porous surface it traps the tiny air bubbles at the point of contact and carefully analysed it frame by frame.

These bubbles shoot upwards, bursting from the drop in a fizz of aerosols, much like champagne bubbles.

Scientists think these aerosols could carry aromas, along with bacteria and viruses, which are released during rain and spread via wind.

Assistant professor of mechanical engineering at MIT Cullen R. Buie said he was surprised the mystery hadn’t been solved before since it was pretty much always raining somewhere in the world at any given time.

“It’s a very common phenomenon, and it was intriguing to us that no one had observed this mechanism before,” he said.

The team say this research could help explain why rainfall can help spread diseases, such as E.coli through the environment to humans.

Originally published as After rain smell caused by ‘champagne effect’