Ozone: Nature’s Sunglasses

I think most people know about the ozone layer of our atmosphere. It’s supposedly this thin layer of atmosphere that protects us from getting sunburnt while we lay out on the beach with intentions of becoming oompa loompas (though for many of us, we still end up looking like tomatoes after a few hours). But what is ozone and how does it actually protect us? And why did we make such a fuss when a hole was discovered in the ozone layer?

Ozone is a molecule made up of 3 oxygen atoms (O3). There are actually 3 flavors of Oxygen in our atmosphere–there’s atomic oxygen (O), diatomic oxygen gas that we need to survive (O2) and ozone. There’s not all that much ozone in the atmosphere–it’s just a thin ¬†gaseous layer found in the stratosphere, which is located between roughly 10 and 50 kilometers above the Earth’s surface (right above the troposphere, where weather occurs).

So how does it form? Ozone forms from a chemical reaction that occurs during a 3 molecule collision. One oxygen atom must “collide” simultaneously with an oxygen molecule and a third atom/molecule, which we’ll call Herman. When these three things collide, the oxygen atom and molecule fuse together to form ozone, and Herman flies off unaffected.

And now Herman is no longer happy.

And now Herman is no longer happy.

Ozone is also destroyed naturally. This happens when ozone interacts with energetic particles of light. In chemistry, there are reactions called photodissociation. This is when a molecule collides with a very energetic photon of light, absorbs its energy, and splits apart (dissociates). For ozone in the atmosphere, it will often interact with incoming Ultraviolet (UV) radiation from the Sun, absorb the UV light, and then split back into the oxygen atom and molecule. Because this happens a lot, ozone absorbs a lot of the Sun’s incoming UV radiation, and is therefore an essential piece of protection for plants and animals against UV radiation, which in high doses is highly dangerous!

This is why we like ozone.

This is why we like ozone.

Both creation and annihilation of ozone occurs naturally, and there is a natural balance that keeps the ozone layer healthy. But humans ruined everything, as we always do. There are compounds that used to be used heavily in aerosol sprays and refrigerators called chlorofluorocarbons, or CFCs (sometimes known as Freon). Chlorofluorocarbons, as you may guess, are molecules made up of chlorine, fluorine, and carbon. CFCs are dangerous because they can react with ozone in a way similar to the way Herman did. In chemistry, many reactions are reversible, which means that you can have a reaction go backwards until there’s an equilibrium. Earlier we discussed how oxygen atoms and oxygen molecules can collide with Herman to produce ozone and a slightly annoyed Herman. Well it can go backwards, and Herman can bang into ozone to make an oxygen atom and molecule. And sure enough CFCs can play the role of Herman and act as a catalyst for that reverse reaction, destroying ozone. And unlike the photodissociation reaction, where the UV photon is destroyed as well, the CFC reaction keeps CFC in the atmosphere, allowing it to further destroy more ozone! As a result, we created a large hole in the ozone layer.

Pure molecular evil.

Pure molecular evil.

Our story does get a little better though. In what scientists call “a political miracle”, a UN treaty saw agreeing governments drastically reduce the use of CFCs in aerosols and such in an attempt to solve the problem we created. And after much sweat and worry, the ozone depletion scenario is beginning to improve!

So to recap, ozone (O3) is created naturally and destroyed by UV light, which offers protection to living things, since UV light is dangerous and gets absorbed by ozone photodissociation. We created a hole in the ozone layer with the usage of CFCs, but then we drastically reduced our usage of them and the problem is getting fixed. Moral of the story, when humans are destroying our world by putting dangerous molecules in the air, the problem can be at least partially mitigated by action to reduce the amount of said molecule in the atmosphere. Sound familiar? Now if only we could convince legislators to address other pressing scientific problems pertaining to our atmosphere…

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