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.
Was this article helpful?