共查询到20条相似文献，搜索用时 31 毫秒
1.
Mineral photoelectrons and their implications for the origin and early evolution of life on Earth 总被引：1，自引：0，他引：1
LU AnHuai WANG Xin LI Yan DING HongRui WANG ChangQiu ZENG CuiPing HAO RuiXia YANG XiaoXue 《中国科学:地球科学(英文版)》2014,57(5):897-902
Energy is the key issue of all life activities.The energy source and energy yielding pathway are the key scientific issues of the origin and early evolution of life on Earth.Current researches indicate that the utilization of solar energy in large scale by life was an important breaking point of the early evolution of life on Earth and afterwards life gradually developed and flourished.However,in the widespread biochemical electron transfer of life activities,it is still not clear whether the electron source is sun or how electrons originated from sun.For billions of years,the ubiquitous semiconducting minerals in epigeosphere absorb solar energy,forming photoelectrons and photoholes.In reductive and weak acidic environment of early Earth,when photoholes were easily scavenged by reducing matters,photoelectrons were separated.Photoelectrons could effectively reduce carbon dioxide to organic matters,possibly providing organic matter foundation for the origin of life.Photoelectrons participated in photoelectron transfer chains driven by potential difference and transfer into primitive cells to maintain metabolisms.Semiconducting minerals,by absorbing ultraviolet,also protected primitive cells from being damaged by ultraviolet in the origin of life.Due to the continuous photoelectrons generation in semiconducting minerals and utilization by primitive cells,photoelectrons from semiconducting minerals’photocatalysis played multiple roles in the origin of life on early Earth,such as organic synthesis,cell protection,and energy supply.This mechanism still plays important roles in modern Earth surface systems. 相似文献
2.
Anaerobic ammonium oxidation(anammox) is a relatively new pathway within the N cycle discovered in the late 1990 s. This eminent discovery not only modified the classical theory of biological metabolism and matter cycling, but also profoundly influenced our understanding of the energy sources for life. A new member of chemolithoautotrophic microorganisms capable of carbon fixation was found in the vast deep dark ocean. If the discovery of the chemosynthetic ecosystems in the deep-sea hydrothermal vent environments once challenged the old dogma "all living things depend on the sun for growth," the discovery of anammox bacteria that are widespread in anoxic environments fortifies the victory over this dogma. Anammox bacteria catalyze the oxidization of NH_4~+ by using NO_2~- as the terminal electron acceptor to produce N_2. Similar to the denitrifying microorganisms, anammox bacteria play a biogeochemical role of inorganic N removal from the environment. However, unlike heterotrophic denitrifying bacteria, anammox bacteria are chemolithoautotrophs that can generate transmembrane proton motive force, synthesize ATP molecules and further carry out CO_2 fixation through metabolic energy harvested from the anammox process. Although anammox bacteria and the subsequently found ammonia-oxidizing archaea(AOA), another very important group of N cycling microorganisms are both chemolithoautotrophs, AOA use ammonia rather than ammonium as the electron donor and O_2 as the terminal electron acceptor in their energy metabolism. Therefore, the ecological process of AOA mainly takes place in oxic seawater and sediments, while anammox bacteria are widely distributed in anoxic water and sediments, and even in some typical extreme marine environments such as the deep-sea hydrothermal vents and methane seeps. Studies have shown that the anammox process may be responsible for 30%–70% N_2 production in the ocean. In environmental engineering related to nitrogenous wastewater treatment, anammox provides a new technology with low energy consumption, low cost, and high efficiency that can achieve energy saving and emission reduction. However, the discovery of anammox bacteria is actually a hard-won achievement. Early in the 1960 s, the possibility of the anammox biogeochemical process was predicted to exist according to some marine geochemical data. Then in the 1970 s, the existence of anammox bacteria was further predicted via chemical reaction thermodynamic calculations. However, these microorganisms were not found in subsequent decades. What hindered the discovery of anammox bacteria, an important N cycling microbial group widespread in hypoxic and anoxic environments? What are the factors that finally led to their discovery? What are the inspirations that the analyses of these questions can bring to scientific research? This review article will analyze and elucidate the above questions by presenting the fundamental physiological and ecological characteristics of the marine anammox bacteria and the principles of scientific research. 相似文献
3.
WANG XianBin OUYANG ZiYuan ZHUO ShengGuang ZHANG MingFeng ZHENG GuoDong WANG YongLi 《中国科学:地球科学(英文版)》2014,57(5):878-887
The hydrocarbons and other organic compounds generated through abiogenic or inorganic processes are closely related to two science subjects,i.e.,energy resources and life’s origin and evolution."The earth’s primordial abiogenic hydrocarbon theory"and"the serpentinization of abiogenic hydrocarbon theory"are the two mainstream theories in the field of related studies.Serpentinization generally occurs in slow expanding mid-ocean ridges and continental ophiolites tectonic environment,etc.The abiogenic hydrocarbons and other organic compounds formed through the serpentinization of ultramafic rocks provide energy and raw materials to support chemosynthetic microbial communities,which probably was the most important hydration reaction for the origin and early evolution of life.The superposition of biological and abiological processes creates big challenge to the identification of the abiogenic organic materials in serpentinite-hosted ecosystem.Whether abiotic(inorganic)process can form oil and gas resource is a difficult question that has been explored continuously by scientific community for more than a century but has not yet been solved.However,some important progress has been made.The prospecting practice of abiogenic hydrocarbons in commercial gases from the Songliao Basin,China,provides an important example for exploring abiogenic natural gas resources. 相似文献
4.
V. N. Ishkov 《Geomagnetism and Aeronomy》2013,53(8):971-976
A study of solar proton sources indicated that solar flare events responsible for ≥2000 pfu proton fluxes mostly occur in complex active regions (CARs), i.e., in transition structures between active regions and activity complexes. Different classes of similar structures and their relation to solar proton events (SPEs) and evolution, depending on the origination conditions, are considered. Arguments in favor of the fact that sunspot groups with extreme dimensions are CARs are presented. An analysis of the flare activity in a CAR resulted in the detection of “physical” boundaries, which separate magnetic structures of the same polarity and are responsible for the independent development of each structure. 相似文献
5.
Chuanlun Zhang Jian Lin Sanzhong Li Hailiang Dong Fengping Wang Shucheng Xie 《中国科学:地球科学(英文版)》2018,61(4):494-498
Geomicrobiology is a sub-discipline of geobiology and emphasizes the interaction between microorganisms and their environment on Earth. There is a need to explicitly emphasize the biogeochemical processes performed by microorganisms associated with Earth’s tectonic activities, especially under the framework of the modern theory of plate tectonics. Tectonomicrobiology aims to create a better synergy between microbial and active tectonic processes. This explicit synergy should also foster better communications between solid Earth scientists and life scientists in terms of holistic Earth system dynamics at both tectonic and micro-scales. 相似文献
6.
Geobiology is a new discipline on the crossing interface between earth science and life science,and aims to understand the interaction and co-evolution between organisms and environments.On the basis of the latest international achievements,the new data presented in the Beijing geobiology forum sponsored by Chinese Academy of Sciences in 2013,and the papers in this special issue,here we present an overview of the progress and perspectives on three important frontiers,including geobiology of the critical periods in Earth history,geomicrobes and their responses and feedbacks to global environmental changes,and geobiology in extreme environments.Knowledge is greatly improved about the close relationship of some significant biotic events such as origin,radiation,extinction,and recovery of organisms with the deep Earth processes and the resultant environmental processes among oceans,land,and atmosphere in the critical periods,although the specific dynamics of the co-evolution between ancient life and paleoenvironments is still largely unknown.A variety of geomicrobial functional groups were found to respond sensitively to paleoenvironmental changes,which enable the establishment of proxies for paleoenvironmental reconstruction,and to play active roles on the Earth environmental changes via elemental biogeochemical cycles and mineral bio-transformations,but to be deciphered are the mechanisms of these functional groups that change paleoenvironmental conditions.Microbes of potential geobiology significance were found and isolated from some extreme environments with their biological properties partly understood,but little is known about their geobiological functions to change Earth environments.The biotic processes to alter or modify the environments are thus proposed to be the very issue geobiology aims to decipher in the future.Geobiology will greatly extend the temporal and spatial scope of biotic research on Earth and beyond.It has great potential of application in the domains of resource exploration and global change.To achieve these aims needs coordinative multidisciplinary studies concerning geomicrobiology and related themes,database and modeling of biogeochemical cycles,typical geological environments,and coupling of biological,physical,and chemical processes. 相似文献
7.
JIN ChengSheng LI Chao PENG XingFang CUI Hao SHI Wei ZHANG ZiHu LUO GenMing & XIE ShuCheng 《中国科学:地球科学(英文版)》2014,57(4):579-591
Following the Ediacaran metazoan radiation, the “Cambrian Explosion” set up the major framework of todays’ animal phyla as well as modern marine ecosystem. Here, we present a preliminary investigation on the temporal and spatial (from shallow to deep waters) variations of the early Cambrian ocean chemistry in South China through analyzing a Fe-S-C systematic dataset integrated from literature. Our investigation indicates that the early Cambrian deep ocean in South China was still anoxic and Fe2+-enriched (i.e., ferruginous) although its surface was oxic, and in between a metastable euxinic (anoxic and sulfidic) water zone may have dynamically developed in anoxic shelf waters with an increasing weathering sulfate supply. Furthermore, accompanying marine transgression and regression cycles in the early Cambrian, such a “sandwich” structure in ocean redox chemistry demonstrates five evolutional stages, which can be well correlated to the spatiotemporal patterns of fossil records in South China. The good correlation between metazoan fossil occurrences and water chemistry in South China suggests that early animals possibly possessed ability to inhabit anoxic but generally not euxinic environments as free H2S was fatal to most eukaryotes. This view can well explain why those small shell fauna and sponges disappeared from shelf to slope areas where sulfidic Ni-Mo-rich shales were widely deposited. Thus, we conclude that the spatiotemporal variations of ocean chemistry and its biological effects probably played a key role in the phased animal radiations and “extinctions” in the early Cambrian. 相似文献
8.
The Earth has grown from chaotically mixed small dusts and gases to its present highly differentiated layered structure over the past 4.567 billion years. This differentiation has led to the formation of the atmosphere, hydrosphere,biosphere, crust, mantle, and core. The timing and mechanism for the formation and evolution of these different layers are still subjects of intense debate. This review brings together recent advances in using non-traditional stable isotopes to constrain major events and processes leading to the formation and differentiation of the Earth, including the Moon-forming giant impact, crustmantle interactions, evolution of life, the rise of atmospheric oxygen, extreme paleoclimate changes, and cooling rate of magmas. 相似文献
9.
10.
G. S. Anufriev 《Geomagnetism and Aeronomy》2014,54(6):680-687
A reconstruction of data on ancient (to ～600 Ma ago) solar fluxes of protons and helium has been performed on the basis of isotopic investigations of helium and neon in lunar soil samples from columns delivered by the automatic stations Luna-16 and Luna-24 in 1970 and 1976. Recent investigations have shown the presence of long-term climate variations, which can be explained in the context of solar-terrestrial links. However, the “space” impact, simultaneously with the Sun’s influence on the Earth, takes place in the form of cosmic ray irradiation and as an influence on the Earth that is exerted by the flux of cosmic dust and meteorites (including the very large ones at the early stage of the Earth evolution). Therefore the existence of long-term variability of solar corpuscular fluxes may serve as direct evidence of the manifestation of solar-terrestrial links. The possibility of finding these links appears on the basis of the revealed variations of solar wind fluxes with an age from the contemporary level to the level of ～600 Ma ago. 相似文献
11.
A. V. Smirnov 《Izvestiya Physics of the Solid Earth》2017,53(5):760-768
Reliable data on the paleointensity of the geomagnetic field can become an important source of information both about the mechanisms of generation of the field at present and in the past, and about the internal structure of the Earth, especially the structure and evolution of its core. Unfortunately, the reliability of these data remains a serious problem of paleomagnetic research because of the limitations of experimental methods, and the complexity and diversity of rocks and their magnetic carriers. This is true even for relatively “young” Phanerozoic rocks, but investigation of Precambrian rocks is associated with many additional difficulties. As a consequence, our current knowledge of paleointensity, especially in the Precambrian period, is still very limited. The data limitations do not preclude attempts to use the currently available paleointensity results to analyze the evolution and characteristics of the Earth’s internal structure, such as the age of the Earth’s solid inner core or thermal conductivity in the liquid core. However, such attempts require considerable caution in handling data. In particular, it has now been reliably established that some results on the Precambrian paleointensity overestimate the true paleofield strength. When the paleointensity overestimates are excluded from consideration, the range of the field strength changes in the Precambrian does not exceed the range of its variation in the Phanerozoic. This result calls into question recent assertions that the Earth’s inner core formed in the Mesoproterozoic, about 1.3 billion years ago, triggering a statistically significant increase in the long-term average field strength. Instead, our analysis has shown that the quantity and quality of the currently available data on the Precambrian paleointensity are insufficient to estimate the age of the solid inner core and, therefore, cannot be useful for solving the problem of the thermal conductivity of the Earth’s core. The data are consistent with very young or very “old” inner core ages and, correspondingly, with high or low values of core thermal conductivity. 相似文献
12.
Giorgio Spada 《Surveys in Geophysics》2017,38(1):153-185
Glacial isostatic adjustment (GIA) encompasses a suite of geophysical phenomena accompanying the waxing and waning of continental-scale ice sheets. These involve the solid Earth, the oceans and the cryosphere both on short (decade to century) and on long (millennia) timescales. In the framework of contemporary sea-level change, the role of GIA is particular. In fact, among the processes significantly contributing to contemporary sea-level change, GIA is the only one for which deformational, gravitational and rotational effects are simultaneously operating, and for which the rheology of the solid Earth is essential. Here, I review the basic elements of the GIA theory, emphasizing the connections with current sea-level changes observed by tide gauges and altimetry. This purpose is met discussing the nature of the “sea-level equation” (SLE), which represents the basis for modeling the sea-level variations of glacial isostatic origin, also giving access to a full set of geodetic variations associated with GIA. Here, the SLE is employed to characterize the remarkable geographical variability of the GIA-induced sea-level variations, which are often expressed in terms of “fingerprints”. Using harmonic analysis, the spatial variability of the GIA fingerprints is compared to that of other components of contemporary sea-level change. In closing, some attention is devoted to the importance of the “GIA corrections” in the context of modern sea-level observations, based on tide gauges or satellite altimeters. 相似文献
13.
Andrew H. Knoll Michael Carr David J. Des Marais Woodward W. Fischer Scott M. McLennan Christian Schröder Nicholas J. Tosca 《Earth and Planetary Science Letters》2005,240(1):179-189
Sedimentary rocks exposed in the Meridiani Planum region of Mars record aqueous and eolian deposition in ancient dune and interdune playa-like environments that were arid, acidic, and oxidizing. On Earth, microbial populations have repeatedly adapted to low pH and both episodic and chronic water limitation, suggesting that, to a first approximation, the Meridiani plain may have been habitable during at least part of the interval when deposition and early diagenesis took place. On the other hand, the environmental conditions inferred for Meridiani deposition would have posed a challenge for prebiotic chemical reactions thought to have played a role in the origin of life on Earth. Orbital observations suggest that the combination of sulfate minerals and hematite found in Meridiani rocks may be unusual on the martian surface; however, there is reason to believe that acidity, aridity, and oxidizing conditions were broadly distributed on ancient Mars. When these conditions were established and how much environmental heterogeneity existed on early Mars remain to be determined. Because sulfates and iron oxides can preserve detailed geochemical records of environmental history as well as chemical, textural and microfossil signatures of biological activity, Meridiani Planum is an attractive candidate for Mars sample return. 相似文献
14.
The contribution made by V.V. Beloussov (1907–1990), an outstanding Earth scientist in the former Soviet Union and Russia, to the development of planetary geophysics is considered. Beloussov was a brilliant coordinator of international cooperation and direct inspirer of international scientific programs of paramount importance. He took up one of the key positions in organizing and holding the International Geophysical Year (IGY) in 1957–1958. In 1960, Beloussov was elected President of the International Union of Geodesy and Geophysics and proposed the project “The upper mantle and its influence on the Earth’s crust,” which subsequently became known worldwide as the Upper Mantle Project. The project underlined that the experience of the IGY should be extended to studies of the deep structure of the Earth and the processes taking place in the Earth’s interior. The fulfillment of this and the subsequent Geodynamic project resulted in a breakthrough in the knowledge about the deep structure of the Earth, particularly the structure of the oceans. Beloussov actively advocated integrating science of the Earth, geonomy, and in his scientific research sought a geonomic approach incorporating the entire complex of geological, geophysical, and geochemical data. Beloussov’s scientific heritage contains propositions that are of current importance and can be involved in modern developments of the Earth sciences. 相似文献
15.
This paper gives a report about experiments with the geomagnetic field-balance with ribbon suspension of the FANSELAU-type under extreme climatic conditions. These experiments were carried out by several institutions. The results show that the field balances “H” and “Z” give right records even under extreme conditions. 相似文献
16.
During the early stages of the study of the origin of life, not enough attention was paid to the question of the correlation
of chemical evolution on Earth and the all-important evolution of the still-to-be understood early Sun. Today, due to the
advent of a significant fleet of space missions and the possibility of performing experiments in the International Space Station
(ISS), a meaningful study begins to be possible concerning factors that led to an early onset of life on Earth. We wish to
review and update recent work concerning the frontier between Space Weather (SpW) and Astrobiology. We argue that the present
robust programs of various space agencies reinforce our hope for a better understanding of the bases of Astrobiology. Eventually,
with a more realistic model of the Sun, more reliable discussions of all the factors influencing the origin of life on Earth,
and hence Astrobiology, will be possible. 相似文献
17.
18.
The data that describe the long-term reversing behavior of the geodynamo show strong and sudden changes in magnetic reversal frequency. This concerns both the onset and the end of superchrons and most probably the occurrence of episodes characterized by extreme geomagnetic reversal frequency (>10–15 rev./Myr). To account for the complexity observed in geomagnetic reversal frequency evolution, we propose a simple scenario in which the geodynamo operates in three distinct reversing modes: i—a “normal” reversing mode generating geomagnetic polarity reversals according to a stationary random process, with on average a reversal rate of ～3 rev./Myr; ii—a non-reversing “superchron” mode characterizing long time intervals without reversal; iii—a hyper-active reversing mode characterized by an extreme geomagnetic reversal frequency. The transitions between the different reversing modes would be sudden, i.e., on the Myr time scale. Following previous studies, we suggest that in the past, the occurrence of these transitions has been modulated by thermal conditions at the core-mantle boundary governed by mantle dynamics. It might also be possible that they were more frequent during the Precambrian, before the nucleation of the inner core, because of a stronger influence on geodynamo activity of the thermal conditions at the core-mantle boundary. 相似文献
19.
无论在行星大小、质量还是轨道速度等方面,金星都是太阳系中与地球最相似的行星.自1960年代初期开始,金星一直是人类深空探测的重要目标.本文简要地回顾了人类探索金星的历史,总结了对金星已有的认识,梳理了金星的主要科学问题,最后介绍了未来的国际探测计划,并建议了我国的金星探测目标.早期对金星的探测以苏联的金星计划(Венера)和美国的水手系列(Mariner)为代表,后期的探测器以欧盟、日本等国家的“金星快车(Venus Express)”、“拂晓号(Akatsuki)”为代表.这些探测结果为我们认识金星大气成分、地表地形和内部结构提供了重要的数据.金星的大气组成以CO2为主,含少量N2,与现在地球的大气组成显著不同,类似早期地球的大气组成.虽然金星地表目前没有液态水,但部分理论模拟工作表明金星地表可能曾经有液态水.一系列探测器对金星地表成分的分析表明,金星地表主要由玄武岩组成.在地形地貌方面,由于金星特殊的地表环境,金星表面风化作用对地表地貌影响很小.金星的地表主要受控于比较年轻的火山作用,发育了许多不同于地球的地貌特征,主要包括区域平原、盾状火山平原、冕状地形以及瓦片状地形等,其动力学机制可能是地幔柱—岩石圈相互作用或地幔对流,至今未发现与板块构造相关的地貌.现阶段金星没有太多大型的、活跃的火山热点,虽然无法估测准确的火山活动速率,但相比地球来说火山活动速率小很多.在内部结构方面,金星具有与地球类似的核幔壳结构.金星的内部组成也与地球类似,例如金星地幔很可能是与地球相似的橄榄岩成分.不存在内部磁场和缺乏板块构造是金星区别于地球的两个重要特征.关于金星为什么没有自身磁场,主流观点是金星地核缺乏对流,无法演化出磁场.而针对金星为什么没有演化出板块构造,目前认为主要有三个可能的原因:地表温度过高,没有软流圈,金星缺乏液态水,其中液态水的缺乏接受度最广.从大气组成、地表岩石组合、构造作用等角度来看,金星都与早期地球非常相似,是我们理解类地行星演化的天然实验室.研究金星和地球为什么会朝不同方向演化,是深入理解包括系外行星在内的行星的宜居性形成与演变的重要途径。因此,金星一直是优先级别最高的深空探测目标之一.近几年,美国、俄罗斯以及欧洲等国家和地区分别针对金星目前主要的科学问题,例如金星是否存在早期海洋、金星的宜居性以及结构和重力场等,先后提出各自的金星探测计划.我国在新的国际竞争中应该、也必然有所作为. 相似文献
20.
R. T. Pierrehumbert 《地球物理与天体物理流体动力学》2013,107(1-4):285-319
Abstract We consider the mixing of passive tracers and vorticity by temporally fluctuating large scale flows in two dimensions. In analyzing this problem, we employ modern developments stemming from properties of Hamiltonian chaos in the particle trajectories; these developments generally come under the heading “chaotic advection” or “Lagrangian turbulence.” A review of the salient properties of this kind of mixing, and the mathematics used to analyze it, is presented in the context of passive tracer mixing by a vacillating barotropic Rossby wave. We then take up the characterization of subtler aspects of the mixing. It is shown the chaotic advection produces very nonlocal mixing which cannot be represented by eddy diffusivity. Also, the power spectrum of the tracer field is found to be k ? l at shortwaves—precisely as for mixing by homogeneous, isotropic two dimensional turbulence,—even though the physics of the present case is very different. We have produced two independent arguments accounting for this behavior. We then examine integrations of the unforced barotropic vorticity equation with initial conditions chosen to give a large scale streamline geometry similar to that analyzed in the passive case. It is found that vorticity mixing proceeds along lines similar to passive tracer mixing. Broad regions of homogenized vorticity ultimately surround the separatrices of the large scale streamline pattern, with vorticity gradients limited to nonchaotic regions (regions of tori) in the corresponding passive problem. Vorticity in the chaotic zone takes the form of an arrangement of strands which become progressively finer in scale and progressively more densely packed; this process transfers enstrophy to small scales. Although the enstrophy cascade is entirely controlled by the large scale wave, the shortwave enstrophy spectrum ultimately takes on the classical k ? l form. If one accepts that the enstrophy cascade is indeed mediated by chaotic advection, this is the expected behavior. The extreme form of nonlocality (in wavenumber space) manifest in this example casts some doubt on the traditional picture of enstrophy cascade in the Atmosphere, which is based on homogeneous two dimensional turbulence theory. We advance the conjecture that these transfers are in large measure attributable to large scale, low frequency, planetary waves. Upscale energy transfers amplifying the large scale wave do indeed occur in the course of the above-described process. However, the energy transfer is complete long before vorticity mixing has gotten very far, and therefore has little to do with chaotic advection. In this sense, the vorticity involved in the enstrophy cascade is “fossil vorticity,” which has already given up its energy to the large scale. We conclude with some speculations concerning statistical mechanics of two dimensional flow, prompted by our finding that flows with identical initial energy and enstrophy can culminate in very different final states. We also outline prospects for further applications of chaotic mixing in atmospheric problems. 相似文献