This simple molecule which is simply three oxygen atoms held together is also known as trioxygen. It is far less stable than the more usual dual oxygen that is more commonly found in the atmosphere at breathing level.

When comfortably floating above the atmosphere as the bright blue envelope that is seen from space photos, it has the ability to do something very important. This stratospheric ozone protects life on Earth from the particularly damaging UVB radiation that would otherwise knock holes in cellular DNA, making life on Earth impossible.

However, when on the ground, ozone is a pollutant that damages crops and causes respiratory ailments. Most people are able to detect it in minute quantities, as low as .01 parts-per-million (ppm) in most cases. It can also cause headaches and burning eyes at fewer than 1 ppm. This tropospheric ozone is chiefly produced by automotive and other fossil fuel emissions interacting with sunlight.