There may be planets orbiting other stars that have life and also have globally extensive ecosystems. It is generally thought that for a planet to be habitable it must have an average surface temperature between 0 and 30 °C and to maintain its habitability over geologically long periods of time, and it must have a mass between 0.5 and 10 times the mass of Earth. Until recently, extrasolar planets of this size were not detectable. However, Earth-based telescopes have now detected at least one such planet and telescopes soon to be placed in space should be able to detect many more.
The most direct evidence for a global ecology is the presence of an oxygen-rich atmosphere. This could be detected by spectroscopic identification of either oxygen or ozone. Pigments such as chlorophyll may also be detectable and indicate life on the surface.
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