Portal:Astrobiology/Selected article

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Selected articles

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Earth is the only planet currently known to support life
Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and sustain life. Life may develop directly on a planet or satellite or be transferred to it from another body, a theoretical process known as panspermia. As the existence of life beyond Earth is currently uncertain, planetary habitability is largely an extrapolation of conditions on Earth and the characteristics of the Sun and Solar System which appear favourable to life's flourishing—in particular those factors that have sustained complex, multicellular organisms and not just simpler, unicellular creatures. Research and theory in this regard is a component of planetary science and the emerging discipline of astrobiology.
...Archive/Nominations

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The aerial of the Arecibo Observatory
The search for extraterrestrial intelligence (SETI) is the collective name for a number of activities people undertake to search for intelligent extraterrestrial life. Some of the most well known projects are run by Harvard University, the University of California, Berkeley and the SETI Institute. SETI projects use scientific methods to search for intelligent life on other planets. For example, electromagnetic radiation is monitored for signs of transmissions from civilizations on other worlds. The United States government contributed to early SETI projects, but recent work has been primarily funded by private sources.
...Archive/Nominations

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Blacksmoker in Atlantic Ocean.jpg
Extremophiles (organisms able to survive in extreme environments) are a core research element for astrobiologists. Such organisms include biota which are able to survive several kilometers below the ocean's surface near hydrothermal vents (example pictured) and microbes that thrive in highly acidic environments. It is now known that extremophiles thrive in ice, boiling water, acid, the water core of nuclear reactors, salt crystals, toxic waste and in a range of other extreme habitats that were previously thought to be inhospitable for life. It opened up a new avenue in astrobiology by massively expanding the number of possible extraterrestrial habitats. Characterization of these organisms—their environments and their evolutionary pathways—is considered a crucial component to understanding how life might evolve elsewhere in the universe. According to astrophysicist Dr. Steinn Sigurdsson, "There are viable bacterial spores that have been found that are 40 million years old on Earth - and we know they're very hardened to radiation."
...Archive/Nominations

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The structure of Silane
Hypothetical types of biochemistry are forms of biochemistry speculated to be scientifically viable but not proven to exist at this time. While the kinds of living beings we know on Earth commonly use carbon for basic structural and metabolic functions, water as a solvent and DNA or RNA to define and control their form, it is possible that undiscovered life-forms could exist that differ radically in their basic structures and biochemistry from that known to science.

The possibility of extraterrestrial life being based on these "alternative" biochemistries is a common subject in science fiction, but is also discussed in a non-fiction scientific context.

...Archive/Nominations

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The Earth seen from Apollo 17.jpg
In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life (metazoa) on Earth required an improbable combination of astrophysical and geological events and circumstances. The term "Rare Earth" comes from Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist.

The rare earth hypothesis is the contrary of the widely accepted principle of mediocrity (also called the Copernican principle), advocated by Carl Sagan and Frank Drake, among others. The principle of mediocrity concludes that the Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Hence it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the solar system, and our region of the Milky Way are very rare.

By concluding that complex life is uncommon, the Rare Earth hypothesis is a possible solution to the Fermi paradox: "If extraterrestrial aliens are common, why aren't they obvious?"

...Archive/Nominations

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The Wow! signal
The Wow! signal was a strong narrowband radio signal detected by Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University then located at Ohio Wesleyan University's Perkins Observatory, Delaware, Ohio. The signal bore expected hallmarks of potential non-terrestrial and non-Solar System origin. It lasted for the full 72-second duration that Big Ear observed it, but has not been detected again. The signal has been the subject of significant media attention.

Amazed at how closely the signal matched the expected signature of an interstellar signal in the antenna used, Ehman circled the signal on the computer printout and wrote the comment "Wow!" on its side. This comment became the name of the signal.

...Archive/Nominations

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