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Revision as of 23:41, 22 September 2002 by 62.252.64.7 (talk)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Extraterrestrial life refers to such life forms that exist outside planet Earth.
There are many questions about what extraterrestrial life is, including:
- Could there be non-carbon based life forms, e.g. life forms based on other elements like silicon (See Carbon chauvinism)?
- How does life differ depending on the type of structure (unicelluar life, multicelluar, intelligent, advanced technological)?
- What range of conditions are required for the evolution of life?
The scientific study of extraterrestrial life is called exobiology or astrobiology.
Scientists are searching for extraterrestrial life in two very different ways. Firstly, they are searching for evidence of unicellular life within the solar system: searching Mars and meteors which have fallen to Earth, and a proposed mission to Europa, one of Jupiter's moons with a liquid water core, which may contain life.
There is some evidence for the existence of microbial life on Mars. An experiment on the Viking Mars lander reported gas emissions from heated Martian soil that some argue are consistent with the presence of microbes, though the lack of corroborating evidence from other experiments on the Viking indicates that a non-biological reaction is a more likely hypothesis. Indepedently, in 1996 structures resembling bacteria were discovered in a meteorite known to be formed of rock ejected from Mars.
Secondly, it is theorised that any technological society will be transmitting information: man-made electromagnetic radiation is alread detectable within an eighty light-year radius of Earth, and is constantly spreading. SETI, the Search for Extraterrestrial Intelligence, analyse the data gathered by the world's largest radiotelescopes and analyse them for artificial patterns using supercomputers and one of the largest distributed computing projects in the world, SETI@home.
Some scientists now accept that some UFOs are the spacecraft of intelligent extraterrestrials, however since these scientists are currently in the minority, work such as SETI continues in the hopes that a signal will be detected.
Astronomers also search for extrasolar planets that would be conducive to life. Current radiodetection methods have been inadequate for such a search, as the resolution afforded by recent technology is inadequate for detailed study of extarsolar planetary objects.
Panspermia holds that (extraterrestrial) life is prevalent through space in a form analogous to spores.
Extraterrestrial life forms, especially intelligent ones, are often referred to as aliens.
See also UFO