Excerpt from usatoday.com

It turns out bubbles may be to thank for that earthy we get after it rains, according to a study from researchers at the Massachusetts Institute of Technology.

Youngsoo Joung and Cullen R. Buie used high-speed cameras to raindrops falling on 28 different of surfaces and studied what happened to the rain on impact.

Joung and Buie found that when rain hits a porous surface, like soil, tiny champagne-like bubbles of air are trapped and shoot , according to a from MIT. The researchers contend those bubbles, or aerosols, may release aromatics (i.e. that earthy smell) and possibly other things stored in soil, such as viruses and types of bacteria.

“It’ a very common phenomenon, and it was intriguing to us that no one had observed this mechanism before,” Buie, an assistant professor of mechanical engineering at MIT, said in the statement.
The study may serve as a jumping off for other research about chemicals in soil and how they “can be delivered in the environment, and possibly to humans,” Joung in the release.
Joung and Buie conducted approximately 600 experiments for the study that was published recently in Nature Communications.