Faint young Sun paradox

The paradox of the weak young sun referred to the contradiction between the 3.8 billion years ago significantly lower radiation power of the young sun and clear indications to a warmer climate in the early history of the earth. Taking only about 30 % less radiation power of the sun into consideration water could exist only as ice in the early period of the earth's surface. The geological evidence suggests that the surface temperature was warmer than today during most of the early climate history of the earth. In comparison, a doubling or halving of pre-industrial CO2 concentration of 280 ppm causes the same change in radiative forcing as a change in the solar constant by 2%.

As The Faint Young Sun Paradox, the term was coined in 1972 by the astronomer and author Carl Sagan in the English-speaking world and has established itself since then. [Sm 1] causes and consequences of the paradox throw interdisciplinary questions in geology, astrophysics, biology, climatology and atmospheric physics on. It plays a central role in emergence and persistence of life on earth and is an important aspect when compared with other planets. [ Jk 1]

2.1 Overview
2.2 Interpretation about extreme carbon dioxide greenhouse
2.3 interpretations on mixtures of different greenhouse gases
2.4 Interpretation of the paradox via carbonyl
2.5 Proposed control mechanisms

4.1 Potential climate impact of galactic cosmic rays
4.2 Earth's rotation and orbital parameters
4.3 presumption of a strong, young sun

5.1 Gaia hypothesis and self-regulating role of life
5.2 Life on a young cold ground

6.1 Methodological Challenges 6.1.1 Early life
6.1.2 Formation of ocean crust and
6.1.3 Reconstruction of the temperature profile
6.1.4 Astrophysics and Planetary Sciences

Overview

To explain the paradox of factors into consideration, which play a role in the climate on earth to the present. The paradox is at a time to, in a first atmosphere was just created, and lasts for several billion years away, during which continents and oceans were formed.

High greenhouse gas concentrations are already considered in the early period of development of the earth and atmosphere as essential for the solution of the paradox in most studies. Although the knowledge of the composition of the atmosphere and the climate of early Earth have evolved greatly since the 1970s, the then present concentration of greenhouse gases is still not precisely known. [ Gorm 1]

2009 a possible explanation of the paradox of a photochemically stable contribution of sulfide and highly potent greenhouse gas has been released. The study promises further insights into the formation and composition of the early atmosphere, especially before age of the Earth of 2.4 billion years reducing atmosphere.

Differences in orbital parameters of the earth compared to today are led by Vivien Gornitz as a possible explanation. [ Gorm 1]

A 2003 put forward an alternative explanation of the paradox and the global warm periods and ice ages over a climate effect of cosmic radiation has caused a controversial debate and intensified research on the underlying hypothesis. However, a climate -determining influence of cosmic radiation could not be confirmed in subsequent studies.

Theories that consider an origin of life on Earth and other celestial bodies in cold conditions possible and theories, in which a larger radiation power of the sun than comparable stars is assumed to be equally considered unlikely.

The climate such as the composition and reactions in the different atmospheres of the early geological past is justifiable only with great effort and methodical high measurement uncertainty; Misinterpretations are easily possible in this context.

Soil and a climate history background

Before the hypothesis of a great bombardment of the Earth by asteroids and comets between 4.1 to 3.8 billion, was generally believed that the earth was previously generally a molten state. For geothermal and geological dynamics of the Earth contribute to a significant proportion of residual heat from the time the Earth, radioactive decay processes and kinetic energy from the movement of the earth around its own axis at. The earth's crust and the mantle are insulating; the power delivered to the space energy is now several orders of magnitude smaller than the sunlight.

In the first atmosphere before about four billion years ago, it is assumed they would similar to today's Vulkanausgasungen largely of water vapor ( H2O) and smaller amounts of carbon dioxide (CO2) and hydrogen sulfide (H2S ) and smaller amounts of nitrogen (N2 ), hydrogen ( H2 ), carbon monoxide (CO), helium, methane and ammonia passed. It is controversial when it came to form a first primeval ocean and the earth's surface had cooled enough to allow precipitation. Possibly previously formed rocks come from the already cooled more strange celestial bodies, these represent a possible source of origin of the terrestrial water dar. already 3.8 billion years ago are clearly detected traces of liquid water. Evidence of life on Earth has existed for at least 3.5 billion years ago.

An important incision is a global glaciation before about 2.4 billion years represents the named after the Huron Huron Ice Age was probably caused by the large oxygen catastrophe. There followed a prolonged warm period, jokingly referred to as boring billion ( boring billion ) respectively. [ Jko 1] Only then, for about a billion years, alternate to the present global cold and warm periods at regular intervals from.

Influence of the atmosphere

The greenhouse effect is caused by a different permeability for the short-wavelength (mainly incoming ) portion of solar radiation compared to the long-wavelength (mainly reflected ) manufactures heat radiation. In the Earth's atmosphere have climate-changing greenhouse gases such as water vapor, carbon dioxide, methane and ozone since the dawn central influence on the climate history and climate. The natural greenhouse effect raises the average temperature at the Earth's surface today at about 33 ° C. to 15 ° C.. Without this natural greenhouse effect, the Earth's atmosphere today would lower the global average only -18 ° C and would be extremely hostile to life. With today's composition of the atmosphere, the surface temperature ( land distribution, albedo) would have been globally colder by approximately 20 ° at the beginning of Earth's history under otherwise identical conditions.

An over several billion years largely stable climate is generally effective mechanisms ahead. [ Jk 1] water in its various states of aggregation alone does not preclude a cooling by a lower radiation power of the sun. [ Jko 2]

The observed climate changes have therefore the effect of other factors such as the formation of clouds, are explained. So low clouds cool the earth's surface by its reflection sun, high clouds warm contrast. The cloud formation is inter alia affected by condensation nuclei, fine particulates and trace gases. Plays an important role here, volcanism, while spent in the atmosphere of gases, dusts and aerosols as well as the consequences of life in the broadest sense.

The activity of vegetation, erosion and weathering has on the formation and composition of loose rock and soil influence on the reflection properties of the Earth's surface and the evaporation and therefore on cloud formation and climate. [ Ipcc 1]

Climate influence besides the parameters of the Earth's orbit and the Earth's axis with respect to the sun. So ice ages and warm periods of the recent past are preferred interpreted on the changed frequently within the Milankovitch cycles Earth's orbital geometry. [ Ipcc 1]

Climate influence the location and formation of oceans and continents

Plate tectonics of the earth and the associated changing distribution of continents and mountain ranges is crucial over the long-term formation of glaciers, the impact and nature of rainfall and ocean currents. It is a peculiarity of the earth compared to Venus and Mars, the corresponding tectonic changes have exhibited or only in the past. The tectonics can trigger climate impacts, such as when temperatures increased at one point to more evaporation and elsewhere to more precipitation and glacier formation contribute or formerly maritime dry or cold regions of the country or mountains are covered and vice versa. Just contributes a shift continental plates in the polar regions, including changes in ocean currents such as the Gulf Stream global and regional climate in significant effects. With no or only a few land masses, an additional warming of about 4 ° C would be based on a simple climate model to adopt.

Course Under geoscientists controversial is still forming a first continent, Ur, which should have been just about as big as today's Australia, already about 3 billion years ago. Rocks of individual islands in a formed by the early hydrosphere primeval ocean may be obtained in Nuvvuagittuq greenstone belt in Greenland. Slightly less questionable is the formation of Kenorland as the first supercontinent, which at the time of archaisischen icing began exactly 2.45 billion years before our time. It was only a billion years ago, with the Neoproterozoic, it came to the merger of the first supercontinent Rodinia, also temporally associated with a significant icing. Since, as far as the still ongoing era, the Phanerozoic, to cold and warm periods change regularly from. Continents and larger islands in the environment of the polar regions appear both as a major factor for stronger cold periods. An important such icing took place in the middle Ordovician, the moderate cold period between Jurassic and Cretaceous about 150 million years ago coincides with the breakup of the supercontinent Gondwana previously formed.

Interpretations of the paradox about greenhouse effects

Overview

Sagan and Mullen [sm 1] first proposed a climate- active role of ammonia ( NH3 = ) in the early atmosphere as a solution of the paradox. However, in the Earth's atmosphere has only a low retention and ammonia is decomposed among other things, through photochemical processes. Sagan and Chyba therefore postulated an organic protective layer, similar to the atmosphere of Saturn's moon Titan, which could have increased the stability of the ammonia. A strong ammonia-containing atmosphere is adopted by several planets outside our solar system.

As an explanation for the paradox of the ammonia hypothesis was soon ousted in favor of a significantly higher ( factor of ten thousand ) proportion of CO2 in the earliest times. This theory prevailed until the early 1990s. [ Jko 2] Due to disagreements with geochemical research was immediately looked for alternative causes. Other authors proposed for increased proportions and blends against other greenhouse gases that occur among others in outgassing from volcanoes to the present and very powerful greenhouse gases. These include nitrous oxide N2O or particular methane, ethane and other hydrocarbons [ jh 1] and various sulfur compounds. [ Jko 2] The question of the photochemical stability arises in the very climate-active hydrocarbons and sulfides as well. The stability of most greenhouse gases was facilitated by the fact that the atmosphere of early Earth was nearly free of oxygen.

Interpretation through extreme carbon dioxide greenhouse

If the CO2 is now stored in limestone would be released entirely in the atmosphere, it would be found in the atmosphere with more than ten thousand times the present value, and would take several bar partial pressure. [ Jk 1] A gradual decrease of such extreme greenhouse exactly parallel the increase in solar power should solve the paradox; 1979 assumed the astrophysicist Michael H. Hart, that the earth would have taken exactly this way. Hart's calculates that this gradual decrease between the first formation of the atmosphere 4.6 billion years ago to the leveling off of the radiation output of the sun at the current level is extremely unlikely and unstable. The earth would have a Mars-like, transformed accordingly at only a few percent decrease or increase in an overheated Runaway Greenhouse as the Venus or in a completely frozen snowball Earth or for life to cold desert planet with little atmosphere. Hart coined the term while the Continuously Habitable Zone ( CHZ ). The origin of life was therefore only possible because the earth was at the precise distance from the Sun, which allowed this. He assumed that the CHZ is at about the distance of the earth to the sun, so a astronomical unit is limited. The extreme instability and improbability of the process as the site used to the hard vielbeachteteten thesis ( cf. Fermi paradox) that life beyond Earth in the entire Milky Way, and possibly in the whole universe is extremely unlikely. [ Jk 1] The hypothesis of an initially extremely high, only a gradual decrease in the concentration of CO2 is what James F. Kasting and others point, which remained in the early climate history unique " Archaic Ice Age " before 2.4 billion years contrary. [ jh 1] geological deposits and air- pointers According to the the relatively warm climate then through to about 1 billion years received before our time. Only after this global glaciations and warm periods alternated periodically.

2011 was reiterated in Nature that the moderate climate of the Archean is not in accordance with the adopted damaligem CO2 content of the atmosphere. The authors see a possible solution in a caused by other substances greenhouse effect.

Interpretations on mixtures of different greenhouse gases

Jacob D. Haqq - Misra and others ( including Kasting ) favored instead of a pure carbon dioxide greenhouse 2007, a mixture of methane (CH4 ), water vapor and carbon dioxide. [ Jh 1] of 2000, Kasting emphasizes the role of CH4 together with Pavlov and, in 2001, the shield doubts of ammonia by organic trace gases in the primitive atmosphere.

Pavlov and Kasting 2000 and 2003 had led a methane-rich atmosphere after 2.4 billion years ago in the discussion on the paradox .. This presupposes a sulphidic ocean, what Holland is geochemically disputed 2006. Kasting speaks to the contradiction and concludes "We leave this issue to be sorted out elsewhere" ( Kasting and Ono, 2006 [ jko 2], German: " leave this question, we clarify elsewhere " )

Interpretation of the paradox via carbonyl

Yuichiro Ueno, Matthew S. Johnson et al. published in August 2009, investigations of the relationship of sulfur isotopes in rocks of the Pilbara Craton, which dates from the early days of the earth. [ P 1 ] The group studied by spectral analysis a number of greenhouse gases that are found in today's Vulkanausgasungen on their behavior in the range of ultraviolet. Thus would specifically carbonyl sulfide COS can accumulate in an early, reducing the earth's atmosphere and thus can compensate for the paradox. The distribution rates for different sulfur isotopes in rocks could be used as a very good proof of the different composition of the early atmosphere according to the authors.

The photolytic decomposition of sulfur dioxide had been previously accepted as a limiting factor. COS as an effective and stable greenhouse gas is in contrast to the other to prevent Moreover able decomposition of the also climate-active sulfur dioxide. [ P 1 ] The studies of the sulfur-containing sediments were related to different scenarios of the shielding of ultraviolet light with respect. According to the authors the found in the rocks striking enrichment of Schwefelisotops33S can only be explained with the presence of COS in the former atmosphere and its specific shielding effect. [ P 1 ]

The authors can with COS to the paradox be interpreted to the strong cooling in the late Archean before 2.4 billion years. [ P 1 ]. The authors interpret this archaic Ice Age ( Huron icing because of the particular encountered in Canada, probably glacier -related diamictites ) of the early forms of life then increasing the released oxygen. Prior to the global ice age by 2.4 billion years ago, there are only a few references to occasionally available free oxygen. [ Jko 2] In accordance with the COS hypothesis of a general change from a reducing to an oxidizing atmosphere at this time environment is established. [ 2 jko ] The time required for COS reducing atmosphere is then no longer possible.

Kasting already discussed in 2006 differentiated geochemical findings on the role of sulfur compounds in the archaic atmosphere. [ Jko 2]. He referred in particular to the only times ( after 2.4 and before 3.2 billion BC ) occurring Barytvorkommen. Thus ( barite is an extremely sparingly soluble sulfate) would be the deposition of SO2 limited only between 3.2 and 2.4 Ga have been prevented.

Proposed regulatory mechanisms

The carbonate -silicate cycle is considered as a central negative (in the sense of control theory ) and against a rule -controlling mechanism for the climate- active greenhouse gases. With him the weathering of silicates and carbon dioxide concentration in the atmosphere and oceans is linked to the deposit and reprocessing of carbonate rocks on the continents as in the oceans. After Walker 's special in the Erdfrühgeschichte the high initial concentration of the greenhouse gas has been reduced with the formation of continents after about a billion years by the deposition of large amounts of carbonates. Then, an interaction between warming by the greenhouse effect of carbon dioxide in the atmosphere, increased silicate weathering, then increased cooling due to formation of carbonates and warming after re -gassing of carbon dioxide is assumed by volcanic processes.

Changes in cloud formation

Roberto Rondanelli and Richard S. Lindzen 2010 came to the conclusion that even a moderate effect of cirrus clouds (see also Iris hypothesis) could cause a sufficient climate warming in the tropical regions of the early Earth.

According to a published study in 2010, the paradox of the young earth without greatly increased greenhouse gas concentrations can be explained. In the early phase of the Earth 's oceans were higher by about 20% than it is today. Since it ashore, however, were neither plants nor animals at that time, lacked important condensation nuclei for cloud formation. The cloud cover and thus the albedo of the earth was thus considerably lower than previously anticipated.

Astrophysical interpretations

Potential climate impact of galactic cosmic rays

The Israeli astrophysicist Nir Shaviv suggests the paradox by the inclusion of solar wind and galactic cosmic radiation on the early Earth's climate. [Ns 1] He refers to the Cosmic by Henrik Svensmark and other postulated climate influence radiation. Thus, cosmic rays will modulated by the solar wind and carry through increased cloud formation on to a cooling. The stronger solar wind of the young Sun would the Earth initially shielded from galactic cosmic rays. In combination with a moderate amount of greenhouse gases such as water vapor, methane, CO2 and other that was sufficient to explain a continuous warm period. [Ns 1] The pictured in the diagram above cold phase around 2.4 billion years is consistent with a then increased galactic cosmic radiation match by increased star formation rate in the Milky Way. A contribution of greenhouse gases, especially carbon dioxide is not denied, but settled its effectiveness, the climate sensitivity in the lowest range specified by the Intergovernmental Panel on Climate Change IPCC bandwidth. [Ns 1]

For the time course after Shaviv refers to the stage of maturity have occurred since then the sun with today's corresponding radiation intensity. In his interpretation of the paradox about the cosmic radiation influence he sees the parallel all 143 ± 10 million years held spiral passages of the solar system through the Milky Way as the cause of change of cold and warm periods. This takes place since the global scale at a distance of about 135 ± 9 million years. The influence of Spiralarmdurchgänge would have been previously screened by the increased solar wind. [Ns 1] In addition, periods of elevated star formation rates and correspondingly increased cosmic radiation with various global ice ages were correlated. [ Nsna 1]

Recent work on the relation, as in the Danish SKY experiment, specifically examine the interaction of sulfur-containing aerosols with cosmic radiation in higher layers of the atmosphere. Something similar happens when CLOUD experiment at CERN. 2010 presented a research team led by Frank Arnold from the Max Planck Institute for Nuclear Physics in studies of six prominent Forbush events no correlation between cloud cover and fixed ion concentration. This result is in direct contradiction to a central assumption of Svensmark theory, the resulting According to cosmic radiation ions on the formation of condensation nuclei for cloud formation would influence.

Earth's rotation and orbital parameters

The still slightly varying inclination of the earth's axis to the ecliptic has a significant climate impact. [ Gorm 1] A higher obliquity of the Earth's axis in the early period is indicated by some studies as a possible explanation for higher temperatures in the early days of the earth. [ Gorm 1]

Other possible factors include a formerly more rapid rotation of the earth. With a day length of 14 hours per day 1.5 ° C increase in temperature would be to accept. [Ns 1] For the paradox itself [ns 1] as the entire time course of the first three billion years ago, and for the interpretation of the regular alternation of glacial and interglacial periods subsequently do not meet these influences. [ vk 1] a possible influence on the Earth's rotation as climate and volcanism through to the formation of the Moon had a much-publicized hypothesis is that the impact of Theia (planet ) in the Erdfrühzeit.

Assumption of a strong, young sun

Discussed [gr 1] A moderate ( 10%) heavier sun enough compared to the standard model to compensate for the paradox in the immediate early days - In connection with the paradox was a higher early radiation power of the sun - in contrast to astrophysical standard model.. According to Thomas Graedel For such a hypothesis to speak at the sun and other stars striking depletion of trace elements such as beryllium. [Gr 1] speak against the assumption of long and uniform course of the early warm climate over several billion years. A higher initial weight would have been due to the standard assumptions on the seismic solar short term only, significantly increased radiation performance over just one hundred million years result [ns 1], and indirectly estimated mass losses of the early sun are according to others too small for this. The increased initial weight could not be confirmed by comparative measurements of individual indicators at adjacent, today young suns.

If the Aktualismusprinzip According to the Natural History equated the history of the sun with the progress in other, neighboring stars at different ages, there is a uniform mass loss, which may explain the paradox no phase. [Ns 1]

A more than three billion years equally strong young sun is also the otherwise protected climate history, so the temporary glaciations at 2.4 (cf. figure) and at times of Snowball Earth about a billion years before present not in compliance. [ JV 1]

Biological interpretations

Gaia hypothesis and self-regulating role of life

The Gaia hypothesis of James Lovelock, according to the life on earth itself is the main control mechanism [ jk 1] without which the earth would possibly know the fate of Mars or Venus. According to the hypothesis of the earth, and in particular the biosphere can be considered as a living organism, which itself creates conditions, receives and further developed. The name is derived from Gaia, the earth goddess of Greek mythology. These include the feedback between vegetation, the water storage capacity and rainfall, as well as of changes induced by vegetation cover and land use albedo. Another services mentioned above in the context of feedback effect is the absorption of carbon dioxide by calcareous marine plankton and corals such as the release of carbon dioxide during the cycle of the rocks.

This is contradicted by various extinction events the soil occasionally appear as malicious Medea or Kali. Important species such as reef-building corals and the many other organisms occurred after the Cambrian explosion about 500 million years in appearance. For the proven stability and the almost continuous life-friendly temperatures during the central paradox for billions of years before they therefore do not come into question.

Jim Kasting agrees to an important role of life in the carbon cycle, such as the impact on weathering and oxygen content to, yet remained the main influencing factors such as physical abiotic nature. [ 1 jk ] [ vk 2]

Life on a young cold ground

In recent decades, it was possible to detect life forms on earth under very cold environmental conditions, in which under the ice of the Antarctic Lake Vostok located. John Priscu According to this should also be applied at Mars. In contrast to the assumption of the hard Continuously Habitable Zone in the solar system has now been extended to near the Mars.

As a possible explanation of the paradox, it plays more of a peripheral role. The early Earth's climate was apparently warmer than today and geological evidence for the presence of liquid water, as opposed to freezing since early times widespread. Put it bluntly, there is evidence of water- based life similar to today on Earth " since there are stones ". [ JV 1] For the continuation of life on earth during interim global glaciations as when considering possible life on other planets and moons is the findings Priscus centrally.

Influence of measurement errors on the paradox

A number of older studies paläoklimatologischen described the climate in the Archean, partly in the entire Precambrian as consistently hot, which was doubted by most geologists because of the intervening glaciations. [ jko 3] The validity of measurement data indicative of an enormously hot average temperature of 70 ° C in the early Archean is controversial. Overall, a moderately warmer average temperature over is now likely. [ Jko 3]

Investigations of different isotopic ratios, according to were the basic elements of the carbon cycle already established 4 billion years ago. [ JV 1] A only up to 100 times higher value of CO2 concentration ( as other greenhouse gases ) compared to today is not in dispute, but, after the majority of older authors did not resolve the paradox. [ns 1] with a significantly increased proportion of carbon dioxide in the atmosphere would have to make with the terrestrial iron Eisenkarbonatmineral siderite in considerable quantity. This has not yet been adequately demonstrated. In contrast, see Haqq - Misra et al. the absence of siderite alone is not a criterion for exclusion to. [ jh 1]. A 2008 study published by Phillip of Paris and other looks for the late Archean and early Proterozoic as a result of modeling with renewed absorption data only an order of magnitude lower Kohlendioxiodkonzentrationen necessary. Accordingly, only 1.5 to 5.5 mbar carbon dioxide would have been necessary (compared to pre-industrial 0.28 mbar) partial pressure for the Late Archean for a moderately warm climate.

Methodological Challenges

From the Cretaceous ( Maastrichtian )

Are already the reconstruction of recent climate history for which there are a variety of indirect climate indicators (see Proxy ( climate research) ), has been accompanied by controversy. However, paleoclimatic determination methods are required for the interpretation of the paradox. These are more difficult and less, the further decline in the geological past and the less fossil traces of life are preserved.

Early life

Indirect evidence of life form, inter alia, in chemo fossils and fossils are where organically formed structures such as stromatolites found or suspected .. The detection of early life and the estimation of fluxes in the atmosphere in different geological periods was the finest on the high-resolution study graphite and gas inclusions and microfossils facilitated in minerals.

Formation of ocean crust and

Introduction, widespread evidence of an early crust and water on the surface of the earth were given 3.8 billion. Even earlier, before 4.4 billion years ago, this was at Zirkonkristallen from the Pilbara Craton in Western Australia the case. With uranium-lead date they were identified as previously oldest minerals on the earth. In addition, evidence was found to already existing at the time separation of the crust and ocean. Zircons can repeatedly go through the cycle of rocks. They are extremely resistant to geological factors such as weathering and even high-grade metamorphism and allow addition of a radiometric age determination isotopengeochemisch to find clues to their formation conditions. Such studies require extensive sampling and preparation as well as a high-resolution complex analysis such as electron probe microanalysis and mass spectrometry.

Reconstruction of the temperature profile

Similarly consuming to make data series to the temperature gradient in the early geological history. For measurements, the earliest average temperatures systematic shifts in the underlying Sauerstoffisotopiemessungen are possible, also influencing today's measured values by intervening influences is criticized. Overall applies during the Archean a moderately warmer average temperature than today than likely. [ Jko 3]

Astrophysics and Planetary Sciences

Some insights into the paradox as principle for exobiology and Planetology were recovered from meteorites that are found especially in Antarctica. This after Addi Bischoff space probes of the little man allow the study of extraterrestrial materials and influences, without the need to leave Earth. The evidence of possible organic molecules in Martian meteorites have also further boosted the research as speculation ( primitive ) life on Mars.

Role of the paradox at Mars and Saturn's moon Titan

The paradox also relates to our neighboring planet Mars, liquid water on its surface, therefore, ought not to occur. [Sm 1] On the other hand was the atmosphere of Mars in the past ( billions of years ) is significantly closer to the results of the previous soundings. On the surface of the Red Planet abundant liquid water was present. Regular, sometimes may throw on water-based erosion returning large structures like the so-called Martian canals, in extensive grave fault systems such as the Valles Marineris through to small-scale cryoturbation and give therefore still give rise to a wide variety of speculations.

In Saturn's moon Titan, an orange fog was observed, which consists of organic compounds of unknown composition. The astrophysicist Carl Sagan coined the term " Tholins ". Sagan suspected in just such a layer in the early Earth a significant contribution to the emergence of life. With these assumptions the titanium one of the most interesting locales in the solar system. Sagan had also adopted a warming effect through this fog. Other authors disagree with Sagan's theory and formulate an "anti- greenhouse effect".

Recent research suggests that an aerosol can of branched hydrocarbons (instead of spherical droplets - as previously thought ) may well have had a great influence on the absorption behavior of the atmosphere. Such an aerosol absorbs ultraviolet light, but is sufficiently transparent to visible light.

Side aspects

The paradox is used among other things in the environment of young-earth creationists and supporters of the so-called Intelligent Design as a ( bogus) argument against the many scientific dating of the age of the Earth at about 4.6 billion years.

Conclusion

Taken together, the sometimes dramatic changes in the composition of the early atmosphere [ vk 3], in particular by biotically formed oxygen, given the uniformly moderate warm climate history over several billion years and the periodic ups and downs after the boring billion from 2.4 to 1 billion before our time more questions unanswered. [ jko 2]

" This time is not boring for a climatologist, she screams for an explanation, especially because the sun was significantly less bright than today. (...) The question why the middle Proterozoic was warm and why it is cooled so dramatically by 750 million years before our time, is fascinating, but goes beyond the analysis under this research. "

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