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Beyond Earthly Skies

Ozone Layers on Alien Earths

11 Oct 2013, 10:00 UTC
Ozone Layers on Alien Earths Scott Richard
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Figure 1: Artist’s impression of an Earth-like planet. Credit: Scott Richard.In the search for Earth-like planets around other stars, the presence of life on these worlds can be determined by looking for various biomarker gases in the planet’s atmosphere. Two promising biomarker gases are oxygen, which is produced almost entirely by photosynthesis on Earth, and ozone, which is produced in the Earth’s stratosphere when ultraviolet (UV) light splits oxygen into individual oxygen atoms where they then combine with other oxygen molecules to form ozone. Ozone is a good indicator of photosynthetic life because even a small amount of atmospheric oxygen can result in a significant concentration of ozone.Segura et al. (2003) developed photochemical and radiative/convective atmospheric models of Earth-like planets around 3 different types of stars: F-type, G-type (Sun) and K-type. This is to see how an Earth-like planet might differ from a planet circling our Sun. The models assume a present-day Earth-analogue planet with an atmospheric oxygen concentration at the present atmospheric level (PAL). Also, the planet’s distance from its host star is scaled according to the star’s luminosity such that the planet’s average surface temperature is 288 K, which is similar to the average surface temperature of present-day ...

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