A recent study conducted by a team of scientists explains what causes the scent of rain: raindrops hit the ground they release into the air a compound called aerosol.
Thanks to advanced technology, the scientists were able to film the raindrops falling to the ground using high-speed cameras.
They discovered that when a drop of rain falls on a porous ground, it captures small bubbles of air just before hitting the surface. These tiny air bubbles then shoot up and get out of the raindrop, releasing a spray of aerosols into the air.
Cullen R. Buie, assistant professor of mechanical engineering at the Massachusetts Institute of Technology, said in a news release that although rain is such a common natural phenomenon, no one really studied why it smells the way it does.
The scientists conducted almost 600 experiments using 28 types of surfaces, including 16 samples of natural soil and 12 materials that were man-made.
They measured the permeability of each sample by putting the samples into long tubes, then pouring water to the bottom of each tube. The researchers then measured how fast the water rose up through the surface of the soil.
The scientists placed single drops of water on each of the soil surfaces and simulated different rainfall intensities by adjusting the height of the water drops.
Raindrops were caught on camera and the scientists saw how the bubbles rose through the drop of water. The study revealed that when there is a light and moderate rainfall, there are more aerosols produced compared to the number of aerosols released during a heavier rain.
The scientists believe that the scent of rain comes from the bubbling process when the drops of rain hit the ground and release the aerosols into the air.
Scientists from the Massachusetts Institute of Technology believe the study is also very important in understanding the way microbe organisms and other chemicals that exist into the soil can travel and reach people.
The recent study on the scent of rain was published in the journal Nature Communications.
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