Astrobiology

The exobiology, and astrobiology or xenobiology called ( ancient Greek art words: ἐξωβιολογία, ἀστροβιολογία, ξενοβιολογία, each compound words from exo, except, outside ', astro, star', or xeno, foreign, in away ' and the term biologia, life skills '), is an interdisciplinary science, which explores the possibility of the formation and existence of extraterrestrial life and deals with the general question of life in space (see also: panspermia ).

The term was probably first used astrobiology in the 1930s by Ary J. Sternfeld and 1941 by L. J. Lafleur in a scientific publication. The astronomer Otto Struve used the term in the 1950s, and in 1995 she took over the NASA for their astro biological institute. She is originally characteristic of the access from astronomy. In the English section this term but has since become widely accepted.

The term exobiology was coined by biologist Joshua Lederberg in the 1960s and is often used by a biological point of view. The ESA uses this designation preferred, and the NASA operates a exobiology program. Another name, Cosmobiology, comes from the physicist John Desmond Bernal, is seldom used. In 1982, the International Astronomical Union ( IAU), a Bio- Astronomy Research Council ( Division III Commission 51 Bio - Astronomy ).

In the 1950s, astrophysicist Gavriil Adrianovich Tikhov ( 1875-1960 ) dealt in the former Soviet Union with astrobiological questions. Tikhov headed the Institute for Astro Botany in Almaty, which existed until 1960.

After sub- Steiner ( 2006) exobiology is that interdisciplinary branch of science that studies the origin, distribution and evolution of life in the universe. The NASA Astrobiology Institute ( NAI) defines astrobiology simply as "the study of the living universe." This concludes this science area also issues for further evolution of life on Earth and its possible distribution in the universe with a.

• 3.1 Theoretical considerations

• 5.1 monographs and individual contributions
• 5.2 Periodicals

• 6.1 videos

Workspaces

The exobiology is an interdisciplinary science that encompasses various fields of research:

• Formation of stars and planetary systems
• Geological and geochemical evolution of the planets and their atmospheres
• Geochemistry and the origin of life
• The evolution of life and the development of biodiversity under different, often extreme environmental conditions
• Search for exoplanets and their exploration
• Life in outer space and exploration of the planets of the solar system by space probes.

The aim of this research is to statements and conclusions about the origin ( chemical evolution ) and the evolution of life on Earth and - in parallel - to make in space and to find out if and how life beyond Earth exists or exist could.

Search for extraterrestrial life

Science Philosophical criticism and problems

The exobiology pulled fierce criticism, for example, as "the science which has to yet to show that their research object exists " ( George Gaylord Simpson), or even by Otto Struve, who found that " not yet the time is right " is for astrobiology.

A problem of exobiology is that there is no generally accepted definition of life. While there are actually numerous attempts to define life, none of them has been found to be completely or only satisfactory. One possible conclusion is that a firm dividing line between " animate " and " inanimate " does not exist. As a working definition is in many parts of exobiology, especially when it comes to search directly within the solar system, therefore, " in the form that we know life " spoken of.

Another serious problem is described by the Rare Earth hypothesis. It says that complex life has come down to the earth only by an unusual and highly unlikely combination of factors materialize, so that a search for higher developed life beyond Earth was hopeless. Advocate of exobiology turn against this hypothesis that it only details the circumstances are sought that have led to our form of life to be exactly on the earth. It would all the circumstances that can potentially lead to life. Specifically, the application of the anthropic principle, which is applied to arrive at conclusions about the frequency of intelligent life in the universe, they therefore appear as inappropriate.

Life in our solar system

Theoretically, even outside the earth exist on other planets in the solar system life. Thus, it is assumed in the department of NASA exobiology that the planets Venus and Mars, as well as some of the larger moons, such as those of Jupiter - especially Europe, but also Ganymede and Callisto - life can exist or could. A special position is occupied by Saturn's moon Titan and under a dense atmosphere of nitrogen and methane could prevail conditions similar to those of the primordial Earth. The life- friendly conditions in the solar system beyond Earth seems according to current knowledge, however, of only 500 km wide Saturn 's moon Enceladus has to offer.

To determine the limits of possible life or life -supporting environments, we examine extreme environments on Earth ( volcanoes, deep sea, airless rooms, chemical exposure, Antarctica ) and compares them with the conditions that prevail on planets like Mars.

Next examine exobiologist meteorite fossils. Since 1990 traces were found in some derived from Mars meteorites ( like bacteria) were interpreted as signs of unicellular organisms. This interpretation is controversial and not universally accepted.

Both the innermost planet Mercury as well as in the far-out worlds of ice from Uranus the possibility of life is effectively excluded. On Mercury, the day and night temperatures (and thus also the fluctuations ) to extreme ( -180 ° C to 460 ° C), on the outer planets, the temperature is permanently too low ( below -190 ° C) in order to develop life leave.

Life in other planetary systems

Life as we know it, can develop in a planetary system only in the ecosphere of each star. The Ecosphere is the part of the cosmic environment, on planets or moons liquid water may exist that allows the emergence and survival at least of simple organisms. In order to assess the ecosphere of a star, it is important to know which spectral class he belongs. As a spectral class refers to a system of the Harvard classification, after all the stars are grouped according to their surface temperature and luminosity. The system consists of seven main classes, designated with the letters O, B, A, F, G, K and M. In addition, the now commonly used in astronomy MK classification includes brightness classes that are indicated by the Roman numerals I, II, III, IV and V. I stands for super giant, giant Heller II, III for Normal giant, IV for subgiant and V for a main sequence star. Our Sun is a star according to this classification, the class G2V. The ecosphere extends in class G stars depending on the subclass in a range of 0.6 to 1.6 astronomical units ( AU). For a sufficiently stable ecosphere, that is, with only minor changes over several billion years, come only stars of spectral types FM and the luminosity class V into account.

There are also considerations to very exotic life forms that are not based on carbon ( carbon chauvinism ), planetary proportions assume ( a biosphere as "a " living things ) or even in interplanetary and interstellar space to live. These considerations are however usually associated with the field of science fiction.

Evidence of extraterrestrial life

The exobiology attempts in three ways life beyond Earth to prove.

2010 Cranfield Astro Biological Stratospheric Sampling Experiment ( CASS -E) was launched, which collected with a balloon probe samples from the stratosphere, which are then investigated for possibly existing extraterrestrial microorganisms.

MIT and NASA to develop a device that can process very different samples and prove the fact nucleic acids under the Search for Extraterrestrial Genomes project. 2018 provided a use on Mars.

Theoretical considerations

Cohen and Stewart use the terms universal, universal ' and parochial, limited ' to categorize characteristics, the occurrence of which is very likely in forms of life on others, but in the broadest sense Earth-like planets, or rather less likely ( but possible).

• The principles and physical and chemical functions are called universal, which are found several times and have evolved independently during the evolution on Earth and show the fact that they are at different times and in different places an evolutionary advantage. Locomotion, that is, the very general principle of active or facilitated movement of an individual from place to place, to let, for example, by running, walking, climbing, crawling, swimming, or by appropriate physique drift of wind or water. Especially flying has developed independently of each other in insects, pterosaurs, flying fish, birds and bats.

• Vision in the broadest sense is found in mussels, snails, octopus, insects and vertebrates.
• Echolocation used by bats, whales and cave live birds for orientation and communication.

• Food intake and respiration through the same orifice
• Fünffingrigkeit
• Self- reflective consciousness
• Etc.