It was a serious proposition: Without ozone, the world as we know it would not exist. Ozone is a key element of the atmosphere, the blanket of gases surrounding our planet that is made up of discernable layers, which differ in temperature, density, and gas composition. The lowest level, the troposphere, extends about 11 km (7 miles) up from Earth’s surface. This level is familiar to us: It is the air we breathe and where our weather occurs. The next level in the atmospheric blanket, the stratosphere, rises to 50 km (31 miles) above Earth’s surface. The stratosphere is much less dense than the troposphere but contains a “layer” of ozone (abbreviated as O₃ because it contains three oxygen atoms), a region where most of the atmosphere’s ozone is found.

Without ozone, the world as we know it would not exist.

Solar radiation enters the atmosphere every day, including three forms of ultraviolet (UV) radiation: UV-A, UV-B, and UV-C. Each form of radiation travels at a different wavelength, and each differs in its ability to penetrate materials, like skin. In humans, exposure to UV-B radiation increases the risk of cataracts, skin damage, and cancer. Fortunately, ozone prevents most of the UV-B radiation from reaching Earth’s surface, minimizing the damage it can cause to living things. About 50% of incoming UV-A radiation still reaches Earth’s surface, where it can damage skin, cause sunburn, prematurely age the skin, and cause skin cancer. A suntan is actually a response by the skin to the damaging effects of UV radiation and will not necessarily protect an individual from further Sun damage. Stratospheric (good) ozone should not be confused with ground-level (bad) ozone found in the troposphere. Ground-level ozone is a component of smog and is harmful to living things (see Chapter 20). INFOGRAPHIC 2.1

Arriving at McMurdo Station, Solomon knew she had to apply the scientific process to understand why the ozone layer was thinning in the Antarctic. And she already had a culprit in mind.

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