Research Article
Putative fossil life in a hydrothermal system of the Dellen impact structure, Sweden
- Paula Lindgren, Magnus Ivarsson, Anna Neubeck, Curt Broman, Herbert Henkel, Nils G. Holm
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- Published online by Cambridge University Press:
- 23 April 2010, pp. 137-146
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Impact-generated hydrothermal systems are commonly proposed as good candidates for hosting primitive life on early Earth and Mars. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is rarely reported in the literature. Here we present the occurrence of putative fossil microorganisms in a hydrothermal system of the 89 Ma Dellen impact structure, Sweden. We found the putative fossilized microorganisms hosted in a fine-grained matrix of hydrothermal alteration minerals set in interlinked fractures of an impact breccia. The putative fossils appear as semi-straight to twirled filaments, with a thickness of 1–2 μm, and a length between 10 and 100 μm. They have an internal structure with segmentation, and branching of filaments occurs frequently. Their composition varies between an outer and an inner layer of a filament, where the inner layer is more iron rich. Our results indicate that hydrothermal systems in impact craters could potentially be capable of supporting microbial life. This could have played an important role for the evolution of life on early Earth and Mars.
Lithology, mineral assemblages and microbial fingerprints of the evaporite-carbonate sediments of the coastal sabkha of Abu Dhabi and their extraterrestrial implications
- Fadhil N. Sadooni, Fares Howari, Howell G.M. Edwards, Ayman El-Saiy
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- Published online by Cambridge University Press:
- 29 March 2010, pp. 147-156
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Deep-core and surface samples collected from the coastal sabkha of Abu Dhabi were subjected to a multi-proxy study, including petrographic, geochemical and spectroscopic analyses. The sediments studied are composed of biochemical carbonate-evaporite mineral suites, such as calcite, dolomite, aragonite and gypsum, as well as clastic minerals, such as quartz, feldspar and serpentine. These sediments were also strongly influenced by microbial activities as reflected by the presence of cyanobacterial mats, boring, gas bubble structures, pustular and other macro and micro textures. A combination of marine, fluvial, aeolian, and groundwater processes shaped the geomorphology of the area and led to the formation of such mineral suites, as well as their microbial contents. Data collected from Mars indicate that its surface regolith contains sandstone composed of siliciclastic basaltic debris, as well as carbonate (e.g. magnesite) and evaporite (e.g. jarosite and relics of gypsum) mineral assemblages. Additional data suggest the presence of geomorphic features, characteristic of an arid climate, such as sand dunes and desert varnish. The hydrological model for the Late Noachian-Hesperian period of the plant proposed the existence of a surficial layer containing endolithic and stromatolitic cyanobacterial lamina. The combination of the coastal sabkha of Abu Dhabi with its carbonate-evaporite mineral suites, the neighbouring sand dune fields of the Empty Quarter Desert and the basaltic sediments resulted from weathering the ophiolitic Northern Oman Mountains to form a candidate terrestrial geologic province that may explain the mineral association of Mars and its potential biosignatures. The lithological features and the mineral association of the sabkha can be recognized by the present day detection equipment used on Mars, and even if their biosignatures are degraded, their existence may be inferred from these features.
Plasma and collision processes of hypervelocity meteorite impact in the prehistory of life
- G. Managadze
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- Published online by Cambridge University Press:
- 29 March 2010, pp. 157-174
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A new concept is proposed, according to which the plasma and collision processes accompanying hypervelocity impacts of meteorites can contribute to the arising of the conditions on early Earth, which are necessary for the appearance of primary forms of living matter. It was shown that the processes necessary for the emergence of living matter could have started in a plasma torch of meteorite impact and have continued in an impact crater in the case of the arising of the simplest life form.
It is generally accepted that planets are the optimal place for the origin and evolution of life. In the process of forming the planetary systems the meteorites, space bodies feeding planet growth, appear around stars. In the process of Earth's formation, meteorite sizes ranged from hundreds and thousands of kilometres. These space bodies consisted mostly of the planetesimals and comet nucleus. During acceleration in Earth's gravitational field they reached hypervelocity and, hitting the surface of planet, generated powerful blowouts of hot plasma in the form of a torch. They also created giant-size craters and dense dust clouds. These bodies were composed of all elements needed for the synthesis of organic compounds, with the content of carbon being up to 5%–15%.
A new idea of possible synthesis of the complex organic compounds in the hypervelocity impact-generated plasma torch was proposed and experimentally confirmed. A previously unknown and experimentally corroborated feature of the impact-generated plasma torch allowed a new concept of the prehistory of life to be developed. According to this concept the intensive synthesis of complex organic compounds arose during meteoritic bombardment in the first 0.5 billion years at the stage of the planet's formation. This most powerful and destructive action in Earth's history could have played a key role and prepared conditions for the origin of life.
In the interstellar gas–dust clouds, the synthesis of simple organic matter could have been explained by an identical process occurring in the plasma torch of hypervelocity collisions between submicron size dust particles. It is assumed that the processes occurred in the highly unbalanced hot plasma simultaneously with the synthesis of simple and complicated organic compounds, thereby ensuring their ordering and assembly.
Bona fide experimental evidence presented below indicates that the physical fields generated in the plasma environment in the process of the formation and expansion of the torch meet the main requirements toward “true” local chiral fields. These fields were very likely to be capable to trigger the initial, weak breaking of enantiomer symmetry and determine the “sign” of the asymmetry of the bioorganic world.
These fields could have worked as “trapping” fields influencing spontaneous processes occurring in highly overheated and nonequilibrium plasma in the state that is far from the thermodynamical branch of equilibrium and may have contributed to the formation of an environment needed for the synthesis of homochiral molecular structures, which, in turn, were needed for the emergence of the primary forms of living matter.
It has been shown experimentally that the plasma-chemical processes in the torch have high catalytic properties and assure the rise of the chemical reaction rates by 10–100 million times. In the process of the plasma flyaway this in turn can assure the fast formation of simple and complicated organic compounds, including hyper-branched polymers. It is possible to assume that predominantly inorganic substances from meteorites were used for the synthesis of complicated organic compounds on early Earth.
A laboratory experiment with hypervelocity impact plasma torch modelling by a laser with a Q-switch mode has shown the possibility of high-molecular organic compound synthesis, with mass of approximately 5000 a.m.u. by meteorite impact with an effective diameter of 100 mkm. The target contained only H, C, N and O elements in inorganic forms. The approximation of the curve received in these experiments has shown that molecular structures comparable in mass with the protoviroid (a hypothetical primogenitor of the biosphere) and could have been synthesized as a result of the impact of a meteorite of a millimetre-size range.
Observable characteristics of the synthesis processes suggest high catalytic activity of the plasma medium and high speed of plasma-chemical reactions, combined with ordering and assemblage processes. This suggests that the plasma torch with a huge local density of energy and matter may be the optimal medium for the synthesis of complex organic compounds needed for prebiotic evolution and the development of the primary form of living matter.
A new view of the impact crater provides the most interesting and unexpected consequence of the concept proposed. When considering the problem, it became evident that at a prebiotic stage of evolution there should be an environment in which a photogenic creature could have survived. The crater of the meteoric impact, which is capable of producing ‘a primogenitor of the biosphere’ environment sated with organic matter, moderate temperature and water for considerable time and becoming ‘a life cradle’, appears to be such an environment.
Having enormous energy, the meteorite impact is capable of injecting the newly created complicated organic compounds deep into the space body surfaces, including subsurface water reservoirs, such as Europe, Enchilada and Titan. In this case the meteorite impact has no natural alternative in the creation of initial conditions for the origin of extraterrestrial life. This possibility was confirmed by a laboratory impact model experiment, in which the plasma torch was created under the water surface.
The concept proposed is based on physical processes occurring in nature and on experimental results of impact experiments and subsequent modelling of their analogues in laboratory conditions. Thus, the realizability and survivability of this concept should be taken as well grounded due to the simplicity and clarity of the physical processes.
The entropy principle, and the influence of sociological pressures on SETI
- V. Bozhilov, Duncan H. Forgan
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- Published online by Cambridge University Press:
- 27 May 2010, pp. 175-181
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We begin with the premise that the law of entropy could prove to be fundamental for the evolution of intelligent life and the advent of technological civilization. Building on recent theoretical results, we combine a modern approach to evolutionary theory with Monte Carlo realization techniques. A numerical test for a proposed significance of the law of entropy within the evolution of intelligent species is performed and results are compared with a neutral test hypothesis. Some clarifying aspects on the emergence of intelligent species arise and are discussed in the framework of contemporary astrobiology.
Study of putative microfossils in space dust from the stratosphere
- Kani Rauf, Anthony Hann, Max Wallis, Chandra Wickramasinghe
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- Published online by Cambridge University Press:
- 19 May 2010, pp. 183-189
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Interplanetary dust particles (IDPs) were recovered from the stratosphere by a cryosampler flown below a balloon flying at altitudes of 20–41 km. The present study uses high-resolution scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) spectrophotometry to examine fresh samples collected at 38–41 km. The SEM observations confirm the presence of 7–32 μm sized clusters of coccoidal (0.4–1.3 μm in diameter) and rod-shaped (0.6–2.5 μm in length) objects as components of the IDP complex. Many single globules (1.6–9.0 μm in diameter) are also observed, some of which exhibit a rough surface with filamentous features of variable lengths. The spectrophotometry of the particles in aggregate reveals a prominent peak centred at 216 nm, which is remarkably similar to that of diatoms and close to the UV astronomical feature of 217.5 nm that has been identified as the spectral characteristic of aromatic hydrocarbons. The evidence presented here suggests that the stratospheric particles are IDPs comprising an assortment of materials among which are included microfossil-like features in variable sizes and forms, such as coccoids, rods and filaments.
Front Cover (OFC, IFC) and matter
IJA volume 9 issue 3 Cover and Front matter
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- Published online by Cambridge University Press:
- 27 May 2010, pp. f1-f2
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Back Cover (IBC, OBC) and matter
IJA volume 9 issue 2 Cover and Back matter
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- Published online by Cambridge University Press:
- 27 May 2010, pp. b1-b5
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