Glossary term: Ozone

Description: Ozone is a colorless or pale blue-colored gas in which each molecule consists of three oxygen atoms. It has the chemical formula O₃ and it is poisonous to humans. Its proportion in the atmosphere is small, and in some areas it may not exceed one part in a million. Depending on where the ozone is, it can protect or harm life on Earth.

Most of the ozone is located in the stratosphere, where it acts as a shield that protects Earth's surface from ultraviolet radiation from the Sun. This armor has weakened due to human introduction of chlorofluorocarbons into the atmosphere, thus increasing the risk of skin cancer, cataracts, and weakened immune systems. In 1987, the Montreal Protocol banned use of these gases as refrigerants and aerosol spray propellants with the result that the stratospheric ozone layer has begun to recover.

Near Earth's surface and within the troposphere, ozone is a very harmful pollutant and can cause damage to lung tissue and plants.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".