(Phys.org) —On Earth, life leaves telltale signals in the atmosphere. Photosynthesis is ultimately responsible for the high oxygen levels and the thick ozone layer. Microbes emit methane and nitrous oxide into the atmosphere, and seaweeds emit chloromethane gas. These chemicals, when present in sufficient quantities, are indicators of life and are known as atmospheric biomarkers. Detecting them in the atmosphere of an exoplanet should, in theory, be a means of discovering whether life exists on any alien worlds.
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