Extraterrestrial life

:This article is about the scientific study of extraterrestrial life; for treatment in popular culture, see Extraterrestrial life in popular culture.

Scientific search for extraterrestrial life

The scientific search for extraterrestrial life is being carried out in two different ways, directly and indirectly.

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Direct search

Scientists are directly searching for evidence of unicellular life within the solar system, carrying out studies on the surface of Mars and examining meteors that have fallen to Earth. A mission is also proposed to Europa, one of Jupiter's moons with a liquid water layer under its surface, which might contain life.

Related Topics:
Solar system - Meteors - Europa - Jupiter

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There is some limited evidence that microbial life might possibly exist or have existed 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. However, the lack of corroborating evidence from other experiments on the Viking indicates that a non-biological reaction is a more likely hypothesis. Independently in 1996 structures resembling bacteria were reportedly discovered in a meteorite, ALH84001, known to be formed of rock ejected from Mars. Again, this report is vigorously disputed.

Related Topics:
Viking - 1996 - Bacteria - ALH84001

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In February 2005, NASA scientists reported that they had found strong evidence of present life on Mars (Berger, 2005). The two scientists, Carol Stoker and Larry Lemke of NASA’s Ames Research Center, based their claims on methane signatures found in Mars’ atmosphere that resemble the methane production of some forms of primitive life on Earth, as well as their own study of primitive life near the Rio Tinto river in Spain. NASA officials soon denied the scientists’ claims, and Stoker herself backed off from her initial assertions (spacetoday.net, 2005). However, only a few days after Stoker and Lemke made their claims, scientists from the European Space Agency reported that their own measurements of methane on Mars suggested an organic origin (Michelson, 2005).

Related Topics:
NASA - Mars - Carol Stoker - Larry Lemke - Ames Research Center - Rio Tinto river - Spain - European Space Agency

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Though such findings are still very much in debate, support among scientists for the belief in the existence of life on Mars seems to be growing. In an informal survey of scientists attending the conference at which the European Space Agency presented its findings, 75 percent of the scientists at the conference reported to believe that life once existed on Mars; 25 percent reported a belief that life currently exists there (Michelson, 2005).

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Indirect search

It is theorised that any technological society in space will be transmitting information. Projects such as SETI are conducting an astronomical search for radioactivity that would confirm the presence of intelligent life. A related suggestion is that aliens might broadcast pulsed and continuous laser signals in the optical as well as infrared spectrum http://www.coseti.org/; laser signals have the advantage of not "smearing" in the interstellar medium and may prove more conducive to communication between the stars.

Related Topics:
SETI - Laser

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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 which would reveal key information such as the presence of free oxygen in a planet's atmosphere). The Terrestrial Planet Finder is one NASA programme on the horizon that has generated optimism over the potential discovery of habitable planets. 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, given that two of the three stars in the system are broadly sun-like.

Related Topics:
Extrasolar - Spectrography - Oxygen - Terrestrial Planet Finder - Alpha Centauri

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