New slow motion video shows particles being released into the air as a raindrop hits the ground.

You've probably noticed that distinctive, earthy smell after rainfall.

It's called petrichor. The word was coined by scientists in the 1960s and the smell itself is a mixture of compounds. One of those compounds is called geosmin and is given off by bacteria in soil, adding an earthy smell (it’s also found in beetroot). Other smells come from plant or animal matter that has accumulated in the ground.

BBC / Via itsokaytobesmart.com

Scientists knew that these compounds were being released from the soil somehow. But it's only now scientists from MIT have recorded high-speed video of it happening that they think they know how it works.

This video shows the process in more detail.

youtube.com

When a raindrop hits a porous surface it traps tiny air bubbles that are then released as aerosols.

Aerosols are particles suspended in a gas, like those that come out of a spray can. If you look closely you can see it happening here.

MIT / youtube.com

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