| • Science | • People | • Locations | • Timeline |
| Contents | ||
Forms of extraterrestrial life, or "life on other planets", range from the humanoid and monstrous beings like those from science fiction works, to life at the level of microbes and bacteria. Since little potential evidence of life on other planets exists, and none which has been confirmed by science, the notion that extraterrestrial life exists is entirely hypothetical.
Extraterrestrial life forms, especially intelligent ones, are often referred to as aliens.
Some theorists believe that life as we know it, namely carbon-based organisms, may not be the only structure upon which what we consider the concept of life (e.g. growth, consumption, reproduction, or even sentience) can be built.
The scientific study of extraterrestrial life is often called xenobiology.
Scientists are searching for extraterrestrial life in two very different ways, directly and indirectly.
They are directly searching for evidence of unicellular life within the solar system: searching Mars and examining meteors which have fallen to Earth, and a proposed mission to EuropaEuropa is a moon of the planet Jupiter, smallest of the four Galilean moons. It is named after Europa, one of Zeus's many love interests in Greek mythology. Although the name "Europa" was suggested by Simon Marius soon after its discovery, this name and t, one of Jupiter's moons with a liquid water layer under its surface, which may contain life.
There is some suggestion of the existence of microbial life on Mars. An experiment on the VikingNASA's Viking program consisted of two unmanned space missions to Mars, Viking 1 and Viking 2. Each mission had a satellite designed to photograph the surface of Mars from orbit, and to act as a communication relay for the Viking lander that each mission 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. Independently, in 19961996 was a leap year starting on Monday (see link for calendar), and was designated the International Year for the Eradication of Poverty''. Events January January 5 Hamas operative Yahya Ayyash is killed by an Israeli-planted booby-trapped cell phone Jan structures resembling bacteria were reportedly discovered in a meteorite known to be formed of rock ejected from Mars. Again, this report is vigorously disputed.
It is theorised that any technological society in space will be transmitting information: man-made electromagnetic radiation is already detectable within an 80 light-year radius of Earth, and is constantly spreading. SETIArecibo Observatory in Puerto Rico. SETI ( pronounced [sEti], to rhyme with "Betty") stands for Search for Extra-Terrestrial Intelligence . Interstellar travel is a common theme in science fiction stories, but so far, in practice, the obstacles to such jo, the Search for Extraterrestrial Intelligence, takes the data gathered by the world's largest radiotelescopes and analyses it for artificial patterns using supercomputers and one of the largest distributed computing projects in the world, SETI@home.
Some scientists believe that some UFOs are the spacecraft of intelligent extraterrestrials; however since these scientists are currently very much 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 extrasolar planetary objects. Future telescopes should be able to image planets around nearby stars, which may reveal the presence of life (either directly or through spectrography revealing, for instance, the presence of free oxygen in a planet's atmosphere). It has been argued that one of the best candidates for the discovery of life-supporting planets may be Alpha Centauri, the closest star system to Earth.