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[[da:Liv i rummet]] [[de:Exobiologie]] [[eo:Astrobiologio]] [[fr:Exobiologie]] [[ja:&#23431;&#23449;&#29983;&#29289;&#23398;]] [[nl:Astrobiologie]]

'''Xenobiology''' (also known as '''exobiology''' or '''astrobiology''') is the term for a speculative field within [[biology]] which considers the possible variety of [[extraterrestrial life]]. It also necessarily includes the concept of [[artificial life]], since any life form that might naturally evolve elsewhere could conceivably be created in a laboratory using a future technology. It might be difficult to tell whether a truly strange life form had in fact arisen in space, or was designed much nearer to home.

Although this is currently a speculative field, the ''absence'' of [[life]] in the rest of the [[Universe]] is a [[ Falsifiability|falsifiable]] hypothesis (though it is yet to be proven false), making Xenobiology a valid field for [[science|scientific]] enquiry. Likewise, computer simulations of basic life processes have made it possible to do [[exploratory engineering]] of alternate life forms (like left-handed DNA) to determine their characteristics.

For these reasons the search for extraterrestrial life is of great relevance to xenobiologists. Some contend that the number of planets with intelligent extraterrestrial life can be estimated from the [[Drake equation]] if and when we ascertain the values of its variables. However uncertainties in the term of the equation make it impossible to predict whether life is rare or common. Another associated topic in xenobiology is the [[Fermi paradox]], which suggests that if intelligent life is common in the universe then there should be obvious signs of it.

There is no current tangible evidence for intelligent extraterrestrial life ([[as of 2004]]). However examination of [[ALH84001|meteors]] from [[Antarctica]] which are presumed to have originated from the planet [[Mars (planet)|Mars]] have provided what some scientists believe to be microfossils of extraterrestrial life, although that interpretation of the evidence is still controversial. In 2004, the spectral signature of [[methane]] was detected in the Martian atmosphere by both Earth-based telescopes as well as by the [[Mars Express]] probe. Methane has a relatively short half-life in the Martian atmosphere, so there must be a recent source of it. Since one possible source, active volcanism, has thus far not been detected on Mars, this has led scientists to speculate the that the source could be (microbial) life.

Missions to other planets (such as [[MER-A|Spirit]] and [[MER-B|Opportunity]] to Mars, [[Cassini probe|Cassini]] to [[Saturn (planet)|Saturn's]] moon [[Titan (moon)|Titan]], and a future mission to [[Jupiter (planet)|Jupiter's]] moon [[Europa (moon)|Europa]] hope to further explore the possibilities of life on other [[planet]]s in our [[solar system]].

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'''Xenobiology''' also figures in much [[science fiction]] as the fictional science of the biology of [[alien]] organisms. This use of the term demonstrates the speculative generation of possible models of such life, e.g. [[silicon]]-based.

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See also:
* [[Carbon chauvinism]]
* [[artificial life]]
* [[SETI]]
* [[Panspermia]]

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====References====
* Adapted from the [[Wikipedia]] article, "Xenobiology" http://en.wikipedia.org/wiki/Xenobiology, used under the [[GNU Free Documentation License]]