检索结果-南通市图书馆

Origins of building blocks of life: A review

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2018年第4期9卷 1117-1153页

作者： Norio Kitadai shigenori maruyama Earth-Life Science Institute Tokyo Institute of Technology

How and where did life on Earth originate？ To date, various environments have been proposed as plausible sites for the origin of life. However, discussions have focused on a limited stage of chemical evolution, or emergence of a specific chemical function of proto-biological systems. It remains unclear what geochemical situations could drive all the stages of chemical evolution, ranging from condensation of simple inorganic compounds to the emergence of self-sustaining systems that were evolvable into modern biological ones. In this review, we summarize reported experimental and theoretical findings for prebiotic chemistry relevant to this topic, including availability of biologically essential elements（N and P） on the Hadean Earth, abiotic synthesis of life＇s building blocks（amino acids, peptides, ribose, nucleobases, fatty acids, nucleotides, and oligonucleotides）, their polymerizations to bio-macromolecules（peptides and oligonucleotides）, and emergence of biological functions of replication and compartmentalization. It is indicated from the overviews that completion of the chemical evolution requires at least eight reaction conditions of（1） reductive gas phase,（2） alkaline pH,（3） freezing temperature,（4）fresh water,（5） dry/dry-wet cycle,（6） coupling with high energy reactions,（7） heating-cooling cycle in water, and（8） extraterrestrial input of life＇s building blocks and reactive nutrients. The necessity of these mutually exclusive conditions clearly indicates that life＇s origin did not occur at a single setting; rather, it required highly diverse and dynamic environments that were connected with each other to allow intratransportation of reaction products and reactants through fluid circulation. Future experimental research that mimics the conditions of the proposed model are expected to provide further constraints on the processes and mechanisms for the origin of life.

关键词： Astrobiology Biochemistry Chemical evolution Extraterrestrial life Hadean Earth Hydrothermal systems

Formation of anorthosite on the Moon through magma ocean fractional crystallization

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2017年第2期8卷 299-308页

作者： Tatsuyuki Arai shigenori maruyama Department of Earth and Planetary Sciences Tokyo Institute of Technology2-12-10okayamaMeguro-kuTokyo 152-8551Japan Earth-Life Science Institute Tokyo Institute of Technology2-12-1 OokayamaMeguro-kuTokyo 152-8551Japan

Lunar anorthosite is a major rock of the lunar highlands,which formed as a result of plagioclasefloatation in the lunar magma ocean（LMO）.Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite（mode of plagioclase 〉95 vol.%） is a key to reveal the early magmatic evolution of the terrestrial *** form the pure lunar anorthosite,plagioclase should have separated from the magma ocean with low crystal *** networks of plagioclase and mafic minerals develop when the crystal fraction in the magma（φ） is higher than ca.40-60 vol.%,which inhibit the formation of pure *** contrast,when φ is small,the magma ocean is highly turbulent,and plagioclase is likely to become entrained in the turbulent magma rather than separated from the *** determine the necessary conditions in which anorthosite forms from the LMO,this study adopted the energy criterion formulated by *** composition of melt,temperature,and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the *** plagioclase starts to crystallize,the Mg~# of melt becomes 0.59 at 1291 *** density of the melt is smaller than that of plagioclase for P 〉 2.1 kbar（ca.50 km deep）,and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase（1.8-3 cm）.This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to *** the Mg~# of melt becomes 0.54 at 1263 C,the density of melt becomes larger than that of plagioclase even for 0 *** the Mg~# of melt decreases down to 0.46 at 1218 C,the critical diameter of plagioclase to separate from the melt becomes 1.5-2.5 cm,which is nearly equal to the typical plagioclase of the lunar *** suggests that plagioclase could separate from the *** of the differences between the Earth and the Moon is the presenc

关键词： Moon Anorthosite Magma ocean MELTS Fractional crystallization

United theory of biological evolution:Disaster-forced evolution through Supernova,radioactive ash fall-outs,genome instability,and mass extinctions

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2015年第1期6卷 103-119页

作者： Toshikazu Ebisuzaki shigenori maruyama RIKEN 2-1Hirosawa Earth-Life Science Institute Tokyo Institute of Technology

We present the disaster-forced biological evolution model as a general framework that includes Darwinian ＂phylogenic gradualism＂, Eldredge-Gould＇s ＂punctuated equilibrium＂, mass extinctions, and allopatric, parapatric, and sympatric speciation. It describes how reproductive isolation of organisms is established through global disasters due to supernova encounters and local disasters due to radioactive volcanic ash fall-outs by continental alkaline volcanism. Our new evolution model uniquely highlights three major factors of disaster-forced speciation： enhanced mutation rate by higher natural radiation level, smaller population size, and shrunken habitat size （i.e., isolation among the individual pop- ulations）. We developed a mathematical model describing speciation of a half-isolated group from a parental group, taking into account the population size （Ne）, immigration rate （m）, and mutation rate （μ）. The model gives a quantitative estimate of the speciation, which is consistent with the observations of speciation speed. For example, the speciation takes at least 105 generations, if mutation rate is less than 10 3 per generation per individual. This result is consistent with the previous studies, in which μ is assumed to be 10 3-10-5. On the other hand, the speciation is much faster （less than l0S generations） for the case that μ is as large as 0.1 in parapatric conditions （m 〈 μ）. Even a sympatric （m ~ 1 ） speciatiou can occur within 103 generations, if mutation rate is very high （μ- 1 mutation per individual per generation）, and if Ne 〈 20-30. Such a high mutation rate is possible during global disasters due to supernova encounters and local disasters due to radioactive ash fall-outs. They raise natural radiation level by a factor of 100-1000. Such rapid speciation events can also contribute to macro-evolution during mass extinction events, such as observed during the Cambrian explosion of biodiversity. A similar rapid speciation （though in a much smaller scale）

关键词： Speciation Supernova encounter Continental alkaline volcanism Cichlid Great African ape Cambrian explosion

Nuclear geyser model of the origin of life:Driving force to promote the synthesis of building blocks of life

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2017年第2期8卷 275-298页

作者： Toshikazu Ebisuzaki shigenori maruyama RIKEN Earth-Life Science Institute Tokyo Institute of Technology

We propose the nuclear geyser model to elucidate an optimal site to bear the first *** model overcomes the difficulties that previously proposed models have *** geyser is a geyser driven by a natural nuclear reactor,which was likely common in the Hadean Earth,because of a much higher abundance of 235U as nuclear *** nuclear geyser supplies the following：（1）high-density ionizing radiation to promote chemical chain reactions that even tar can be used for intermediate material to restart chemical reactions,（2）a system to maintain the circulation of material and energy,which includes cyclic environmental conditions（warm/cool,dry/wet,etc.）to enable to produce complex organic compounds,（3）a lower temperature than 100℃ as not to break down macromolecular organic compounds,（4）a locally reductive environment depending on rock types exposed along the geyser wall,and（5）a container to confine and accumulate volatile *** five factors are the necessary conditions that the birth place of life must *** the nuclear geyser can meet all five,in contrast to the previously proposed birth sites,such as tidal flat,submarine hydrothermal vent,and outer *** nuclear reactor and associated geyser,which maintain the circulations of material and energy with its surrounding environment,are regarded as the nuclear geyser system that enables numerous kinds of chemical reactions to synthesize complex organic compounds,and where the most primitive metabolism could be generated.

关键词： Origin of life Chemical evolution Natural nuclear reactor Aqueous electron Radiation chemistry

Reactions between olivine and CO2-rich seawater at 300℃:Implications for H2 generation and CO2 sequestration on the early Earth

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2017年第2期8卷 387-396页

作者： Hisahiro Ueda Yusuke Sawaki shigenori maruyama Department of Earth and Planetary Sciences Tokyo Institute of Technology2-12-1 OokayamaMeguro-kuTokyo 152-8551Japan Earth-Life Science Institute Tokyo Institute of Technology2-12-1 OokayamaMeguro-kuTokyo 152-8551Japan

To understand the influence of fluid CO2 on ultramafic rock-hosted seafloor hydrothermal systems on the early Earth,we monitored the reaction between San Carlos olivine and a CO2-rich NaCl fluid at 300 C and 500 *** the experiments,the total carbonic acid concentration（∑XO2） in the fluid decreased from approximately 65 to 9 mmol/*** minerals,magnesite,and subordinate amount of dolomite were formed via the water-rock *** H2 concentration in the fluid reached approximately 39 mmol/kg within 2736 h,which is relatively lower than the concentration generated by the reaction between olivine and a CO2-free NaCl solution at the same *** seen in previous hydrothermal experiments using komatiite,ferrous iron incorporation into Mg-bearing carbonate minerals likely limited iron oxidation in the fluids and the resulting H2 generation during the olivine *** carbonate mineralogy over the temperature range of natural hydrothermal fields,H2 generation is likely suppressed at temperatures below approximately 300℃ due to the formation of the Mg-bearing ***,H_2 concentration in fluid at 300℃ could be still high due to the temperature dependency of magnetite stability in ultramafic ***,the Mg-bearing carbonates may play a key role in the ocean-atmosphere system on the early *** studies suggest that the subduction of carbonated ultramafic rocks may transport surface CO2 species into the deep *** process may have reduced the huge initial amount of CO2 on the surface of the early *** approximate calculations demonstrate that the subduction of the Mg-bearing carbonates formed in komatiite likely played a crucial role as one of the CO2 carriers from the surface to the deep mantle,even in hot subduction zones.

关键词： Olivine CO2-rich condition Early Earth Hydrothermal alteration Serpentinization Experiment

在线全文

学校读者我要写书评

暂无评论

Habitable Trinity

Geoscience Frontiers 2015年第1期6卷 95-101页

作者： James M.Dohm shigenori maruyama Earth-Life Science Institute Tokyo Institute of Technology

Habitable Trinity is a newly proposed concept of a habitable environment. This concept indicates that the coexistence of an atmosphere （consisting largely of C and N）, an ocean （H and 0）, and a landmass （supplier of nutrients） accompanying continuous material circulation between these three components driven by the Sun is one of the minimum requirements for life to emerge and evolve. The life body consists of C, O, H, N and other various nutrients, and therefore, the presence of water, only, is not a sufficient condition. Habitable Trinity environment must he maintained to supply necessary components for life body. Our Habitable Trinity concept can also be applied to other planets and moons such as Mars, Europa, Titan, and even exoplanets as a useful index in the quest for life-containing planetary bodies.

关键词： Habitable Trinity Ocean Atmosphere Landmass Sun

Triggers and sources of volatile-bearing plumes in the mantle transition zone

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2015年第5期6卷 679-685页

作者： Inna Safonova Konstantin Litasov shigenori maruyama V.S.Sobolev Institute of Geology and Mineralogy SB RAS Novosibirsk State University Earth-Life Science Institute Tokyo Institute of Technology

The paper discusses generation of volatile-bearing plumes in the mantle transition zone(MTZ) in terms of mineral-fluid petrology and their related formation of numerous localities of intra-plate bimodal volcanic series in Central and East *** plume generation in the MTZ can be triggered by the tectonic erosion of continental crust at Pacific-type convergent margins and by the presence of water and carbon dioxide in the *** probable sources of volatiles are the hyclrated/carbonated sediments and basalts and serpentinite of oceanic slabs,which can be subducted down to the deep *** erosion of continental crust supplies crustal material enriched in uranium and thorium into the mantle,which can serve source of heat in the *** heating in the MTZ induces melting of subducted slabs and continental crust and mantle upwelling,to produce OIB-type mafic and felsic melts,respectively.

关键词： Asis Pacific-type convergent margin Continental cr

Expanding-contracting Earth

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2013年第3期4卷 341-347页

作者： Taku Tsuchiya Kenji Kawai shigenori maruyama Geodynamic Research Center Ehime UniversityMatsuyamaEhime 790-8577Japan Department of Earth and Planetary Sciences Tokyo Institute of TechnologyMeguroTokyo 152-8551Japan Department of Earth Science University of CaliforniaSanta Barbara 93106CAUSA

The Earth was born from a giant impact at 4.56 Ga. It is generally thought that the Earth subsequently cooled, and hence shrunk, over geologic time. However, if the Earth＇s convection was double-layered, there must have been a peak of expansion during uni-directional cooling. We computed the expansion- contraction effect using first principles mineral physics data. The result shows a radius about 120 km larger than that of the present Earth immediately after the consolidation of the magma-ocean on the surface, and subsequent shrinkage of about 110 km in radius within about 10 m.y., followed by gradual expansion of 11 km in radius due to radiogenic heating in the lower mantle in spite of cooling in the upper mantle in the Archean. This was due to double-layered convection in the Archean with final collapse of overturn with contraction of about g km in radius, presumably by the end of the Archean. Since then, the Earth has gradually cooled down to reduce its radius by around 12 km. Geologic evidence supports the late Archean mantle overturn ca. 2.6 Ga, such as the global distribution of super-liqnidus flood basalts on nearly all cratonic fragments （〉35 examples）. If our inference is correct, the surface environment of the Earth must have undergone extensive volcanism and emergence of local landmasses, because of the thin ocean cover （3-5 km thickness）. Global unconformity appeared in cratonic fragments with stromatolite back to 2.9 Ga with a peak at 2.6 Ga. The global magmatism brought extensive crustal melting to yield explosive felsic volcanism to transport volcanic ash into the stratosphere during the catastrophic mantle overturn. This event seems to be recorded by sulfur mass-independent fractionation （SMIF） at 2.6 Ga. During the mantle overturn, a number of mantle plumes penetrated into the upper mantle and caused local upward doming of by ca. 2-3 km which raised local landmasses above sea-level. The consequent increase of atmospheric oxygen enabled life evolutio

关键词： Mantle overturn Expanding Earth Global unconformity Nutrients Eukaryotes

Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2018年第4期9卷 1033-1048页

作者： shigenori maruyama M.Santosh Shintaro Azuma Earth-Life Science Institute Tokyo Institute of Technology Institute for Study of the Earth’s Interior Okayama University Centre for Tectonics Resources and ExplorationDepartment of Earth SciencesUniversity of Adelaide School of Earth Sciences and Resources China University of Geosciences Beijing Faculty of Science Kochi University

When plate tectonics began on the Earth has been long debated and here we argue this topic based on the records of Earth-Moon geology and asteroid belt to conclude that the onset of plate tectonics was during the middle Hadean（4.37-4.20 Ga）. The trigger of the initiation of plate tectonics is the ABEL Bombardment, which delivered oceanic and atmospheric components on a completely dry reductive Earth, originally comprised of enstatite chondrite-like materials. Through the accretion of volatiles, shock metamorphism processed with vaporization of both CI chondrite and supracrustal rocks at the bombarded location, and significant recrystallization went through under wet conditions, caused considerable eclogitization in the primordial continents composed of felsic upper crust of 21 km thick anorthosite, and 50 km or even thicker KREEP lower crust. Eclogitization must have yielded a powerful slab-pull force to initiate plate tectonics in the middle Hadean. Another important factor is the size of the bombardment. By creating Pacific Ocean class crater by 1000 km across impactor, rigid plate operating stagnant lid tectonics since the early Hadean was severely destroyed, and oceanic lithosphere was generated to have bi-modal lithosphere on the Earth to enable the operation of plate *** the importance of the ABEL Bombardment event which initiated plate tectonics including the appearance of ocean and atmosphere, we propose that the Hadean Eon can be subdivided into three periods：（1） early Hadean（4.57-4.37 Ga）,（2） middle Hadean（4.37-4.20 Ga）, and（3） late Hadean（4.20-4.00 Ga）.

关键词： Initiation of plate tectonics ABEL Bombardment Eclogitization Stagnant lid tectonics Primordial continents