From Academic Kids
Astrobiology (in Greek astron = star, bios = life and logos = word/science), also known as exobiology (Greek: exo = out) or xenobiology (Greek: xenos = foreign), is an interdisciplinary field, combining aspects of astronomy, biology and geology, which considers the origin of life on Earth and elsewhere. Some major astrobiological research topics include:
- What is life?
- How did life arise on Earth?
- What kind of environments can Earth life tolerate?
- Can we detect life on other planets?
Exobiology and xenobiology are terms also found in science fiction, although typically such terms refer to the speculative biology of an extraterrestrial. A xenobiologist is usually a human doctor or biologist who is expert on the physiology of alien organisms and life forms.
Although astrobiology is an emerging field, the presence of life in the rest of the universe is a verifiable hypothesis (though it has yet to be verified) and hence a valid line of scientific enquiry. A particular focus of current astrobiology research is the search for life on Mars. There is a growing body of evidence to suggest that Mars has previously had a considerable amount of water on its surface; water is considered to be an essential precursor to the development of life, although this has not been conclusively proven.
Missions that have specifically searched for life include the Viking and Beagle 2 probes, both directed to Mars. The Viking results were inconclusive and Beagle 2 failed to reach the surface of Mars. A future mission with a strong astrobiology role would have been the Jupiter Icy Moons Orbiter, designed to study the frozen moons of Jupiter—some of which may have liquid water—had it not been canceled.
Most astronomy-related astrobiological research falls into the category of extrasolar planet (exoplanet) detection, the theory being that if life arose on Earth then it could also arise on other planets with similar characteristics. To that end, a number of instruments designed to detect 'Earth-like' exoplanets are under development, most notably NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin programs. A number of less ambitious ground-based efforts are also underway (see exoplanet).
One estimate for the number of planets with (intelligent) extraterrestrial life can be gleaned 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 is the Fermi paradox, which suggests that if intelligent life is common in the universe then there should be obvious signs of it.
Extremophiles (organisms able to survive in extreme environments) are a core research element for astrobiologists. Such organisms include biota able to survive kilometers below the ocean's surface near hydrothermal vents and microbes that thrive in highly acidic environments. 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.
The fossil record provides the oldest known evidence for life on Earth. By examining this evidence, geologists are able to better understand the types of organisms that arose on the early Earth. Some regions on Earth, such as the Pilbara in Western Australia are also considered to be geological analogs to regions of Mars and as such might be able to provide clues to possible Martian life.
As of 2005, there is no definite evidence of extraterrestrial life. However examination of meteorites from Antarctica which are thought to have originated from the 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 that the source could be (microbial) life.
- Artificial life
- Carbon chauvinism
- Extraterrestrial life
- NASA Astrobiology Institute
- Publications in astrobiology
- Australian Centre for Astrobiology (http://aca.mq.edu.au/)
- The Astrobiology Web (http://www.astrobiology.com/)
- Astrobiology Magazine (http://www.astrobio.net/)
- Possible Connections Between Interstellar Chemistry and the Origin of Life on the Earth (http://pokey.arc.nasa.gov/~astrochm/LifeImplications.html)
- Scientists Find Clues That Life Began in Deep Space - NASA Astrobiology Institute (http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=207)
- Stars and Habitable Planets (http://www.solstation.com/habitable.htm)
- Life Around a Red Dwarf Reading Exercise (http://www.emse.fr/~yukna/researchers/reddwarf.htm)
|General subfields within biology|
|Anatomy | Astrobiology | Biochemistry | Bioinformatics | Botany | Cell biology | Ecology | Developmental biology | Evolutionary biology | Genetics | Genomics | Marine biology | Human biology | Microbiology | Molecular biology | Origin of life | Paleontology | Parasitology | Physiology | Taxonomy | Zoology|