Why Rain Smells So Good: Raindrops Release Bubbling Aerosols on Impact (VIDEO)

There's nothing like the smell after a rainstorm. Now, scientists have uncovered exactly why the outdoors smell so good after rain falls. It turns out that raindrops release aerosols upon impact.

So how did the researchers find this out? It's all thanks to technology. The scientists used high-speed cameras to capture raindrops upon impact. They found that when a raindrop hits a porous surface, it traps tiny air bubbles at the point of contact. These bubbles then shoot upwards and burst from the drop in a fizz of aerosols.

"Rain happens every day-it's raining now, somewhere in the world," said Cullen R. Buie, an assistant professor of mechanical engineering at MIT, in a news release. "It's a very common phenomenon, and it was intriguing to us that no one had observed this mechanism before."

The new findings didn't come easily. The researchers conducted roughly 600 experiments on 28 types of surfaces that included 12 engineered materials and 16 soil samples. In the lab, the scientists measured each soil sample's permeability by first pouring the material into long tubes, then adding water to the bottom of each tube and measuring how fast the water rose through the soil.

The researchers then deposited single drops of water on each surface, simulating different intensities of rainfall by adjusting the height of each drop. The scientists caught each raindrop on camera, and revealed the bubbles that rise through the droplet. It seems as if more aerosols are produced in light and moderate rain, while fewer aerosols are created with heavy rain.

The findings reveal where that smell after rain falls comes from exactly. It's very possible that the smell comes from the bubbling mechanism that the researchers discovered.

The findings are published in the journal Nature Communications.

Want to learn more? Check out the video below, courtesy of YouTube.

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