Researchers using high-speed cameras have figured out how rain produces a distinct earthy smell and shown how soil-based pathogens can travel over large areas. Ben Gruber reports.
STORY: Ever wonder what that earthy scent is right before or after a rain shower? Well, now researchers from the Massachusetts Institute of Technology in Boston have an answer. Using high speed cameras in more than 600 experiments, the scientists figured out that when raindrops hit a porous surface like soil they flatten and trap tiny air bubbles derived from the soil, which then rapidly shoot up and release into the air, much like the fizz in a flute of champagne. Those air bubbles contain oils and aromatics from the soil which produce the earthy scent. But, the researchers found, soil-based bacteria like e.coli and viruses can be also be released as these tiny bubbles burst - which could explain the spread of disease over large areas. The research finds that once released, these particles can travel long distances by winds, carrying that smell of rain with it. So next time, instead of looking for storm clouds, smelling for rain may be a better option.