Astrobiology
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Astrobiology combines sciences like astrology, biology and geology. Astrobiology investigates how life arose, its distribution and evolution. Research has started searching our solar system to find life outside of Earth. Mars has been a focus as there is building evidence that water once covered its surface.
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Mars
It has not been proven that life exists anywhere else but Earth, however two points give hope. The study of meteorites, believed to be from Mars, that may contain microfossils and the detection of the spectral signature of methane, (a possible by-product of microbial activity) a gas with a short half-life, in the atmosphere of Mars.
New missions have been planned to Mars, Saturn’s moon and Jupiter’s moon. Research has determined planets are common but uncertainty exists about solar systems as bias exists to non-Solar layouts.
Star systems
Star systems were revealed with belts of dust and asteroids that may illustrate the formation of planets. The images may also contain planets. Chemicals around stars which may contribute to the origin of life have been identified.
Three major assumptions are made to simplify astrobiology. The first, that all life-forms are carbon based life-forms. The second, that water is necessary for life. The third assumption focuses on Sun-like stars which exist within 100 light-years of our Sun.
Exoplanet detection
Astronomy-related research is mainly exoplanet detection. The hypothesis is life arose on Earth, it could arise on other similar planets. Instruments to detect 'Earth-like' exoplanets, image them and determine the composition of their atmosphere and surface are under development. Computer modelling is used to create 'virtual' planets.
Estimates of the number of planets with alien life are calculated from the Drake equation but the equation is unlikely to fall within acceptable error limits. Associated is the Fermi paradox, that if life is common in the universe there should be obvious signs. Another area is solar system formation as it is possible the uniqueness of our solar system increased the probability of life. Extremophiles (organisms surviving in extreme environments) are important to astrobiologists. Understanding extremophiles is crucial to understanding how life might evolve.
Origin of life debate
The origin of life versus the evolution of life is also debatable. Two theories exist, first, the formation of the organic components of life from inorganic compounds occurred on Earth and second, the first elements formed on a different planet and then transferred to Earth.
Recognition problems
Astrobiology struggles for respectability. Questions arise as to whether it is distinct from its parent disciplines and if extrapolation of Earth’s conditions into non-Earth environments is unscientific as the assumption is that Earth-like life presents the most likely template of life. This reluctant acceptance is reflected by specialisations being available but the thought that a degree in astrobiology is unlikely. A degree program has however recently been introduced.
Xenobiology
Xenobiology is now considered separate from astrobiology by many. They define astrobiology as the search for earth-like life external to our solar system. Xenobiologists however are concerned with the possibility that life need not be carbon-based or oxygen-breathing, once it displays the prerequisites for life.