Terraforming

Terraforming ( borrowed from the Latin terra and Latin- English forming for the " [ order - ] education to [ Replacement ] Earth" or briefly " Erdumbildung ") is the forming of other planets in habitable Earth-like celestial body by means of future technologies. Planets or moons to be redesigned so that it human life with little or no additional technical effort is possible.

The term goes back to the science fiction novel Collision Orbit by Jack Williamson in 1942 and was later taken up by science, which usually speaks of humification.

• 3.1 Initial conditions
• 3.2 Methods for Mars 3.2.1 Space - mirror
• 3.2.2 Asteroid
• 3.2.3 soot
• 3.2.4 microbes

The limits of habitability

The limits of habitability are appreciated by McKay as follows:

Venus

Initial conditions

On the surface of Venus, temperatures of over 450 ° C and a pressure of about 92,000 hPa Every known form of organic life would burn immediately. In addition, the days are very long on Venus (243 Earth days ). Even if it were possible to reduce the greenhouse effect, would possibly adjust temperature fluctuations between day and night side outside the polar regions.

Another problem is the heat capacity of the rock mantle. Even if the atmosphere after a few centuries artificially tolerable temperatures had been lowered for people, the surface of the rocks around 400 ° C would still be hot - and that cooling could take more centuries.

The atmosphere of Venus consists mainly of CO2. In about 50 km altitude, temperatures between 20 ° C and 100 ° C (depending on height) and air pressure of a few ( Earth ) atmospheres. At this altitude there is sulfuric acid-containing (ie, for many well-known creatures toxic ) clouds.

The problem of the water and the insufficient temperature inversion

Also on Venus there is a temperature inversion ( cf. tropopause on earth).

On Earth at a height 9-17 kilometers a cold layer of air (-60 ° C). This means that there condenses or freezes water vapor. Therefore, the overlying layers of the atmosphere are extremely dry. This means that only very little water is split in the upper layers by UV radiation. As a result, escapes very little water (hydrogen) from the Earth into space.

However, the temperatures on Venus are too high, so that water vapor, although cooled, but is not liquid. The atmosphere is very dense, so it can absorb a lot of water vapor. The hydrogen is gaining impetus. By the solar wind as steady enormous amounts of hydrogen are removed in space. The Venus has thus lost much of their water supplies.

Methods for Venus

Terraforming could be done for example by the introduction of green algae in the CO2 - rich atmosphere. The intended result is an accumulation of oxygen at the same time reducing the greenhouse effect due to the consumption of CO2 by photosynthesis of the algae. The water required for this purpose should be obtained from the decomposition of sulfuric acid or by the capture of comets. Without water, the sulfuric acid is concentrated but too high today. Furthermore, although sulfuric acid is produced as a metabolic end product of earthly bacteria, but there are no organisms that use them as food and split.

In higher layers of the atmosphere pressure and temperature are moderate. There could thus favorable conditions for floating plants, virtually give air plankton. The chemical conditions are characterized by high content of sulfuric acid. The green algae idea does not seem to be directly implemented because the conditions for the survival of the plants would have to be created by these same plants only. However, it is conceivable that the algae produce sulfuric acid from CO2 and water and hydrocarbons and thus transform into their biomass. Such algae are on the earth, however, not known, especially since they would have to exist in a substantially anhydrous environment.

If Venus would come under the critical point of 374 degrees, water would be liquid under the high pressure and rain out. This would remove the greenhouse effect of water vapor that is times as effective as CO2 around 20. In addition, the liquid water would additionally reflect heat back into space. Before the temperatures would continue to rise even through the released water, which is another obstacle to the terraforming of Venus.

Conceivable in connection with a colonization is also the construction of airship -like, floating stations in the upper atmosphere of Venus, and maybe breeding floating, balloon -like plants as food. The floating cities could - according to Zubrin - are connected with shields, which thus cast a shadow and cool the planet. In addition, these shields could be produced from carbon, which is available locally in masses in the atmosphere. The Venus remains what affects the terraforming, still an extremely difficult Planet.

The Venus soil probably contains large amounts of easily oxidized metals (FeO, MgO, CaO, ...). It is still unclear why the materials in the regolith ( soil Venus ) in larger amounts with carbon dioxide (CaO CO2 → CaCO3) have responded. In the sulfuric acid environment carbonates are unstable.

It was suggested that the soil to plow through strong, so as to bind large amounts of the greenhouse gas with a carbon sink.

Mars

Initial conditions

• The existing atmospheric pressure is 0.75 % of the earth pressure.
• The temperatures at the surface vary (depending on the pole or near the equator ) between -85 ° C and 20 ° C
• The atmosphere consists of 95% CO2.
• As long as the planetary magnetic field is absent, the Mars under the influence of the solar wind can not permanently maintain an atmosphere. Once the inner core is solidified, is formed by the missing dynamo effect no magnetic field.

Thus, the Mars may develop into a so-called " second Earth", the following changes would be necessary:

• The surface temperature would have to be increased by about 60 Kelvin.
• The density of the atmosphere would have to be increased. Lower limit would here, depending on the gas mixture, 300 hPa, which corresponds to 1/3 of the pressure on the ground. A 1000 hPa (1 bar) dense atmosphere would mean due to the lower gravity, that the atmosphere height would be as high as on Earth almost three times. The nitrogen reserves of Mars are considered to be low; Estimates speak here only of an amount of 100-300 hPa nitrogen. Maybe he has also deposited mineral.
• Liquid water should be made available (occurs automatically when a denser atmosphere ).
• The proportion of O2 (oxygen) and inert gases such as N2 ( nitrogen) in the atmosphere would have to be increased, ( a certain percentage of ) nitrogen has the advantage that it allows plant life, but also any other inert gas would be ( or gas mixture as nitrogen with xenon ) is conceivable.
• One would have to interpret the atmosphere so that it has a tropopause in deeper layers, which imprisons below this the water. This effect has protected the soil from drying out. In contrast to Venus, where even the coldest layers are not below 0 ° C, so that the water falls as rain and not more passes in the higher layers. There is then photodissociated and the hydrogen blown by the solar wind into space.

Methods for Mars

When a terraforming Mars may begin on CO2 which is stored in large quantities in Polkappeneis. Estimates include about 50-100 hPa Larger quantities ( 450-900 hPa) of CO2 are bound in the regolith. Thus could theoretically create a dense carbon dioxide-containing atmosphere, but which is toxic to humans. Even plants can only tolerate a lot of about 50 hPa CO2. However, it is known from algae that they feel themselves in pure carbon dioxide atmospheres. Some species of algae thrive even in the best pure CO2. For initiation of the greenhouse effect, various methods are conceivable.

In all methods result from chained reactions following results:

• Denser atmosphere by the liberated CO2. Is this enough proof ( approximately 1/ 3 of the Earth's atmosphere pressure, which corresponds to the air pressure on Mount Everest ), then there is no need for a pressure suit.
• Higher temperatures caused by the greenhouse effect, thereby also further enrichment of the atmosphere by itself reinforcing melting of Marspolkappen.
• Liquid water by pressure and temperature increase.
• Liquid water forms under the influence of the carbon dioxide-rich atmosphere carbon dioxide that can be released from the regolith CO2.
• The carbonic acid extract could possibly nitrogen from the nitrate-rich minerals, thus enriching the atmosphere with nitrogen and thicken.
• The released water vapor is a good greenhouse gas (4-fold effectiveness of CO2).

Space Mirror

A very time-consuming and therefore costly method, the Mars environment to supply the energy needed would be the positioning of multiple gigantic mirror, so-called Solettas, in a Mars orbit. The mirrors have a diameter of only about 100 up to 200 km and possess a mass of a few hundred thousand to several million tons. The light reflected by their mirrored by means of polymer- reinforced aluminum foil surface of sunlight is directed onto the frozen pole regions and these melted. The thus initiated CO2 emissions into the atmosphere would trigger a desired greenhouse effect, which is further heated to Mars.

Asteroid

Although the manipulation of the trajectory of an asteroid expected to fantastic, but it is at least theoretically possible. An asteroid or comet with a large content of volatiles ( volatiles ) is to be performed by manipulating its flight path to Mars and would be free upon entry into the Martian atmosphere or upon impact with the surface of these materials. Thus he activated similarly to other methods a self-amplifying the greenhouse effect. Probably the high water content of a comet would bring additional large amounts of water vapor in the atmosphere. The thereby caused huge impact could also release additional underground water reservoirs. Although this method has so far not technically feasible, but could be the lying in the distant future time, should be performed on the terraforming of Mars, be available.

Soot

The easiest way to warm Mars, consists of the distribution of carbon black or other light-absorbing materials on the ice or dry ice of the polar caps. The stronger absorption of light causes a temperature increase, which melts the ice or dry ice sublimate.

Microbes

Furthermore, increases quite "early" during the Terra forming microbes, bacteria are located on the ground on Mars that may exist under low pressure, with little or no sunlight and no oxygen ( how on earth in volcanoes on the sea floor or in sulfur sources). Also there is the idea that microbes with pigments, so dark cell membrane - spread over the poles - could bring the ice to melt, since dark colors in the light of better heat than light.

Partial terraforming

Due to the melting of the polar ice caps (which both consist of dry as water ice ) so could be to create a much denser atmosphere, however, this would consist almost entirely of carbon dioxide. From the Viking probes is known that the Marsregolith releases under the influence of carbon dioxide and water large amounts of oxygen. The regolith thus appears to be a potential source of oxygen here. The question, however, whether there is enough water on Mars and how this release in the Martian atmosphere could. Although carbon dioxide is a greenhouse gas, but even a complete release of the total carbon dioxide in the form of dry ice and regolith from 1,000 to 2,000 hPa would not likely be sufficient to raise the temperature to the required 60 Kelvin. Other, more effective greenhouse gases such as CFCs (where CFCs break down a possible ozone layer) or octafluoropropane ( it has 8000 times the global warming potential of carbon dioxide, is over 2600 years -resistant and can coexist without damage with a ozone layer) should here also be supplied in large quantities to achieve these branded and durable to allow liquid water. Higher humidity would also increase the greenhouse effect. Also, the " import" of asteroids with high methane and ammonia content could perform more effective greenhouse gases.

At the end of this process would be a warmer, more humid and surrounded by a dense Kohlendioxidatmospähre Mars as he possibly existed before 3.5 to 4 billion years. Since this process can be chemically pure set in motion and no biological processes requires, could this be already realized in a relatively short time of 100 to 1,000 years. At the end of the requirements for terrestrial plant growth would be given and a stay of people outdoors would be possible (with an oxygen mask ).

Full terraforming

For a complete terraforming the high carbon dioxide content would have to be reduced, which is likely to take significantly longer periods of time. This could be reduced by plants so far that it is respirable to humans. However, since carbon dioxide contributes to the greenhouse effect, a reduction would again lead to a cooling. To prevent this, would here again greenhouse gases are introduced which compensate for this effect. Next to the oxygen, the atmosphere would also be a buffer gas obtained in significant amounts. On Earth, this buffer gas of nitrogen, which accounts for nearly 80 percent of the Earth's atmosphere. The proportion on Mars would not be so high, but it should at least correspond to the amount of oxygen. Whether sufficient nitrogen is present on Mars, however, is questionable. In addition to nitrogen, argon or other inert gases serve as a substitute or in combination could ( with a minimum amount of nitrogen should be present to ensure a plant growth ).

Criticism

Critics call the theories of terraforming unrealistic for several reasons:

• None of the theoretically drawn for terraforming the planet into consideration is ever explored enough to make even a semi- well-founded statements.
• None of the processes that are required to address the terraforming is so far understood the extent that the effects of the methods can be predicted with sufficient accuracy.
• Temporal, material and energetic dimensions of a terraforming beyond any acceptable for a west - industrial in character, culture framework.
• It whether Mars could hold so mobilized atmosphere at all, or if not, for example, through the forced defrost also would evaporate into space that there remaining remnants of the water and the planet is moreover entirely unclear, yet ultimately by the so-called terraforming would be made ​​less " livable " than he already is. In addition, Mars has no appreciable magnetic field, which causes the particle to the solar winds, the gas molecules uninhibited " wash away " would.
• The transfer of entire machinery or huge facilities such as mirrors, methane or CFC- producing factories located outside any range; of a five-member team to the moon of a transport buggies, a small water tank and is the current limit of the possible. The consumption of the whole today exploitable energy resources of humanity would bring a fraction of the required materials in orbit, nothing more. However, the limits of the possible change every day.
• It is pointless to worry about the Bewohnbarmachung foreign planet, as long as it does not even succeed on the earth, economically sensible to colonize the comparatively habitable, but almost uninhabited areas in perpetuity in deserts and steppes. In fact, not even the opposite process is stopped, the desertification and desertification continues.
• Similarly, there are ethical and environmental arguments against a terraforming, since any existing ecosystem would be destroyed by terraforming. This dilemma is, inter alia, in the science- fiction novel Red Mars well set out, would show the law of a foreign environment on preservation. Before so should still be investigated whether there have developed ecosystems - and whether they would grow better at higher temperatures or even die.
• The purely economic dimension of terraforming has barely developed, which should be considered as a necessary condition to make resources available for terraforming. In simpler terms: How much does it cost to transport a ton of stuff to Mars?
• Ownership and use issues terraformierten space are not yet clear, both formal- legal and international law.

Paraterraforming

Precisely because of the wastefulness of a complete terraforming has also the concept of a para or Pseudoterraforming, also known as World House concept emerged.

When Paraterraforming a livable habitat is constructed which allows free breathing. This construction is considerably larger than a dome and is made of a one to several kilometers high roof is mounted on towers and cable, hermetically enclosed and provided with a breathable atmosphere. Also, there is in principle the possibility of a protective sheath only with the help of the inner ruling overpressure and without support, a blimp equal to inflate. The pressure would be required anyway, since the pressure of the Martian atmosphere for human life is too short. The cables and towers served more to preserve the design before it is accepted instead of the collapsing.

Paraterraforming could be achieved faster and extended as modular, from a small region to the encirclement of an entire planet. Supporters of this concept claim that this could be achieved already with today's technology. Finally, not the amount of gas is required as the actual terraforming, but only a small portion. Because of its modularity it can be implemented even on asteroids that can hold no atmosphere whatsoever.

However, a major disadvantage is the effort required for construction and maintenance. A world house would be endangered by leaks. This could be reduced by sectioning and assurance mechanisms. The hazards caused by meteorite comes into play.

The para- terraforming, however, can be found as a supplement and an intermediate step to a complete or partial terraforming use are in the single habitable for humans regions surrounded by a world house while the rest of the planet has thus far been converted with the traditional terraforming that sufficient pressure and temperature for respiration of plants is available.

Attempts to develop an autonomous ecosystem on Earth, there was in the projects and Biosphere 2 Biosphere 3

Other possibilities

For more options, hostile places ( planets, asteroids, etc.) to use, is not the place to terraform, but adapt to humans - by changing his physique through genetic engineering, biotechnology ( Cyborg and others). Examples would be adjusting the organs of low gravity, the larger the like of lung volume for atmospheres with low oxygen concentration, an exoskeleton for large pressure ratios, and. However, should - apart from currently existing biotechnological implementation difficulties - especially by the enormous psychological impact resistance to an implementation are mobilized. In addition, the application would still be limited, since no of eligible celestial body has problems, for which the said solutions would be sufficient according to current ideas.