月球雨海盆地多环结构的厘定及其深部构造研究

雨海盆地是月球正面最大、月球上研究程度最高的多环结构撞击盆地,已有很多学者对其多环结构的边界进行恢复研究,但在多环结构最初始形状、多环位置/数量、盆地大小等方面,至今未能达成共识。本文利用GRAIL自由空气重力异常数据、LOLA激光测高数据进行了多源数据的融合,结果表明,雨海盆地是具有偏心圆的三环结构特点,其直径从外到内分别为1 500 km、1 100 km、665 km。基于欧拉反演结果研究表明,在雨海撞击盆地中部存在两种不同深度、构造运动性质及方向的断裂构造,即：(1)深度大于40 km,向下逐渐向内倾斜、延伸的深部断裂构造;(2)深度在40 km以内,由月表向下逐渐向外倾斜、延伸的浅部断裂构造。结合物质成分及地球物理特征的研究,雨海地区的地质构造演化过程可分为两个阶段：(1)在月球早期阶段(45~38.5亿年),主要以内动力地质作用即岩浆洋冷凝过程为主,形成了雨海盆地深度在40 km以下逐渐向内倾斜、延伸的构造断裂,其为本区在月球早期深部岩浆洋产生、分异及运移提供了通道,该构造断裂代表了雨海盆地撞击前的月球早期深部岩浆洋的构造地质演化阶段;(2)在月球晚期阶段(≤38.5亿年),主要以内、外动力地质作用并重,形成了雨海盆地深度在40 km以内逐渐向外倾斜、延伸的构造断裂,其应为本区不同期次的玄武质岩浆喷出或溢流到月表提供了运移通道,该构造断裂代表了雨海盆地撞击后的月球晚期不同期次玄武质岩浆喷发、充填溢流的月海岩浆活动作用的构造地质演化阶段。     

月球形成演化与月球地质图编研

按照大碰撞假说,月球形成于一次大碰撞事件,抛射出的高能量物质留在绕地轨道上,最后吸积形成月球。月球核幔在早期迅速发生分离,并出现全球性的岩浆熔融,形成了岩浆圈层（岩浆洋）。岩浆洋的结晶分异和固化导致了月壳的形成。随着月壳与月幔发生持续分异,形成了固化的月壳。而在月球后期的演化历史中,撞击作用是最重要的地质作用,形成了多尺度、多期次的撞击盆地和撞击坑,而大型撞击盆地多形成于月球演化的早期。月球地质图是开展月球形成与演化研究的重要手段,从20世纪60年代起,到70年代末止,通过对阿波罗时代探月成果的系统总结,完成了第一轮月球地质图的研制。但尽管从20世纪90年代以来国际月球探测和月球科学的研究进入一个新的高潮,获得了大量有关月球形成和演化的新认识,但还没有正式的新的月球地质图发布,因此开展新一轮月球地质图的编研,系统总结后阿波罗时代的月球探测与研究成果,是非常必要和迫切的。在新一轮月球地质图的编制过程中,需重点关注图件比例尺的选择、月面历史的划分以及月球构造和岩石建造的表达。     

月表构造与深部构造的关系

地球和月球很可能是通过大撞击形成的。在行星地质学中,研究月球的地质-构造现象,对了解月球、地球乃至太阳系的形成与演化历史都有很大帮助。月球的构造分为深部构造与月表构造,寻找它们在分布或成因上的关系,可以为月球甚至地月系的起源和演化历史提供重要参考。利用LROC的宽视角影像数据以及LOLA数据提取解译月表构造,结合深大断裂进行观察分析,并对月球的撞击盆地进行统计,最后以静海地区为例分析构造分布特征,发现月球的质量瘤盆地中具有环状分布的月岭,外侧具有近环状分布的深大断裂,自前酒海纪至酒海纪,具备上述特征的质量瘤盆地占总撞击盆地的比例突然有一个很大的提升,且静海地区西部具有该构造分布特征。推测该特征与撞击、月海沉降等有关,且在酒海纪与雨海纪期间月球有较多的月海玄武岩分布,由此判断静海西部存在质量瘤,发生过撞击与月海沉降。     

介绍一张新全球构造图

在28届国际地质大会上,美国自然历史博物馆斯密森学会和地质调查局奉献了一张展示性的图件,题名这个能动的星球(This Dynamic Planet),副标题是全球火山、地震和板块构造图。该图实际上是一张新全球构造图,即用板块构造的观点来反映地球的构     

基于多源数据的月球大地构造纲要图编制: 以LQ-4地区为例

月球表面的地质构造要素主要包括环形构造、线性构造、地体构造及大型盆地构造等。月球大地构造纲要图从物质组成、构造要素、构造单元上对月表的构造状态进行全面的梳理、统计和分析。利用CE 1 CCD 2C像数据、LROC宽视角影像数据、CE 1 IIM 2C干涉成像光谱仪数据、Clementine紫外可见光影像数据、LOLA激光高度计数据识别月球表面各类矿物组分、线形构造、环形构造、火山构造和穹窿构造以及确定构造要素和构造单元的时代、古老撞击坑和大型盆地边界以及对月球表面撞击坑形态、大小、分布、密度及月球断裂和环形影像解译,充分认识月表基本情况,精细划分月表构造地貌单元,综合利用上述分析结果与国际上研究的进展,确定大地构造区划的基本原则,厘定月表重大构造事件与演化序列。依据岩石、月壤、构造地貌与构造形迹的综合分类,拟定大地构造区划的图例、图识规范,确定不同类型环形构造影像、线性构造影像、高地、盆地和月海等大地构造单元,进而编制大地构造区划图,并对重点区域构造形迹进行研究。虹湾区域(LQ 4)月球数字构造编图研究,充分借鉴国际行星地质编图的已有技术标准和规范,结合国内数字地质编图的技术标准和规范,建立了中国自己的月球与行星地质编图标准、规范和制图流程,也为最终完成月球大地构造区划提供地貌和构造方面的基础信息。     

月球科学的过去、现在和未来——参加第39届月球与行星科学大会有感

综述了2008年3月10～14日在美国休斯敦召开的第39届月球与行星科学大会期间交流的与月球科学相关的会议内容,简要回顾了人类探测月球的历史.当前的月球科学研究归纳为6个主题:①月球和其他类地行星的地质演化;②撞击过程的定量化描述和太阳系历史的关系;③月壤的特征、月壤形成的机械过程和演化过程;④采样返回技术和原型机的开发与运用;⑤月球和其他行星体的内生和外来挥发分;⑥月表的大气和尘埃环境对人类登陆的影响.2007～2008年,日本、中国、印度和美国纷纷推出探月计划,将月球探测推向一个新的高潮.深空探测成为各国展示国力和科学技术水平的试验场,也将有力地促进科学技术的发展;独立探测和国际合作相结合已是大势所趋,数据资料共享将成为必然.公众的积极参与将为月球探测注入新的活力,并成为空间探测的基本动力.     

月球南极艾特肯盆地的地质特征:探索月球深部的窗口

月球南极艾特肯盆地(South Pole-Aitken Basin,简称SPA盆地)是月球上规模最大、最古老的撞击盆地,形成于43~39亿年前的前酒海纪。巨大的撞击可能挖掘出下月壳甚至月幔的物质,因此,它是探索月球深部物质组成的重要窗口。本文通过对SPA盆地形貌和构造特征、物质组成及其分布特征,以及形成机制等方面的分析,综述了艾特肯盆地的地质特征,探讨了SPA盆地对探索早期月球形成演化历史的意义。     

月球探索可能揭示地球上生命起源的信息

天文学家估计，月球表面散落着８００多万吨地球的尘埃．他们认为，收集并研究这些星体碎片能够对生命与行星的起源进行更深入的了解．自太阳系形成以来，小行星及彗星不断地撞击地球、火星和金星，这种猛烈的撞击在大约３９亿年以前，通常被称为“晚期大碰撞”时期达到高峰．西雅图华盛顿大学的JohnArmstrong说：“月球见证并记载下了这一切．”我们的卫星是在约４５亿年以前，在地球与一个火星大小的星体之间巨大的撞击中形成的．Armstrong及其同事通过测量月球上环形山的数量和规模来评估这些撞击．他们推算出这些碰撞会向宇宙抛掷出多…     

月球线性构造分类体系研究

月球线性构造是月球科学研究中的重要组成部分,建立月球线性构造分类体系是月球地质图编研的关键。前人对月球线性构造的分类研究主要基于月表的形貌特征,划分的线性构造类型参差不齐,尚未形成一个公认的、规范的、具有普适性的线性构造分类体系,以至于分类结果的可对比性差、参考性和易操作性较低,不利于月球线性构造纲要图的编制。并且月球线性构造的概念混乱、术语不统一,存在"同物异名、同词异义、异词同义、涵义不明"的现象,不利于全球性的统一制图和成果的展示及使用。鉴于此,本文采用多指标组合的分类方法,以成因机制和形貌特征作为主要指标,兼顾物质组成,再结合线性构造形成的动力学机制,建立了符合月球动力学演化背景的、统一规范的线性构造类型划分的新方案,避免了单以形貌特征为依据来分类出现的混乱状态,具有较好的科学性和可操作性。将月球的线性构造类型划分为:内动力地质作用形成的线性构造,包括皱脊、月溪、地堑、断裂;外动力地质作用形成的线性构造,包括坑缘断裂和坑底断裂,以及多成因机制、多动力来源作用形成的特殊类型如坑链等。在此基础上,并利用多源遥感数据建立了易于判别且具有代表性的线性构造识别标志,可为全月球线性构造的统一制图提供识别依据。     

月球的撞击历史及其对月表物质的改造

外来天体物质的高速撞击作用贯穿了月球形成和演化的全部历史。撞击作用是塑造月球全球地貌、改造月表物质的物理化学特征、影响月球多圈层演化的重要地质营力。月球上的撞击过程、撞击历史及其对月表物质的改造，一直是月球科学研究的重要内容，也是月球探测的重点研究对象。本文综述了近十年来国、内外在月球的撞击过程、撞击历史和撞击改造浅表层物质研究中的重要进展，重点介绍了基于我国嫦娥探月工程获取的科学数据的相关研究成果，展望了该研究的发展方向，并对未来探测的重要观测目标提出了建议。     

1:250万月球地质图符号库的设计与实现

为解决1:250万月球数字地质图在多单位协同编图过程中缺乏统一、规范的地质图符号、制图模板造成不同图件之间信息不统一的问题,通过ArcGIS平台,和其他矢量图形软件,参照我国第一幅1:250万月球地质图（虹湾幅）的符号,设计编制了一套月球地质图符号,其包含月球撞击坑物质、盆地建造、构造和岩石特性等地质信息.并建立了分类存储、可移植的符号库和统一的编图模板.该套标准化符号、符号库、编图模板有利于多单位共同规范的开展1:250万数字化月球地质图编图项目,提高编图效率,同时也为我国开展其他类地行星地质编图的国际合作,编制统一、规范化的地质图奠定基础.      

The split fate of the early Earth,Mars, Venus,and Moon

Plate tectonics shaped the Earth, whereas the Moon is a dry and inactive desert, Mars probably came to rest within the first billion years of its history, and Venus, although internally very active, has a dry inferno for its surface. Here we review the parameters that determined the fates of each of these planets and their geochemical expressions. The strong gravity field of a large planet allows for an enormous amount of gravitational energy to be released, causing the outer part of the planetary body to melt (magma ocean), helps retain water on the planet, and increases the pressure gradient. The weak gravity field and anhydrous conditions prevailing on the Moon stabilized, on top of its magma ocean, a thick buoyant plagioclase lithosphere, which insulated the molten interior. On Earth, the buoyant hydrous phases (serpentines) produced by reactions between the terrestrial magma ocean and the wet impactors received from the outer solar system isolated the magma and kept it molten for some few tens of million years. The planets from the inner solar system accreted dry: foundering of wet surface material softened the terrestrial mantle and set the scene for the onset of plate tectonics. This very same process also may have removed all the water from the surface of Venus and added enough water to its mantle to make its internal dynamics very strong and keep the surface very young. Because of a radius smaller than that of the Earth, not enough water could be drawn into the Martian mantle before it was lost to space and Martian plate tectonics never began. The radius of a planet is therefore the key parameter controlling most of its evolutional features.     

The Deviation of the Lunar Center of Mass to the East of the Direction toward the Earth. A Mechanism Based on Rounding of the Figure of the Moon

It is known that the center of mass (CM) of the Moon does not coincide with its geometrical center of figure (CF), and that the CF–CMline deviates to the Southeast of the direction toward the center of the Earth. An investigation of this phenomenon, which has remained incompletely understood, has been carried out in two stages. One mechanism can explain part of the eastward shift of the lunar CM as being due to tidal evolution of the lunar orbit. A second mechanism is considered here, which relates this shift of the lunar CM with evolution of the shape of the Moon. A differential equation describing the shift of the lunar CMto the East in the course of the physically inevitable rounding of its shape as it moves away from the Earth is derived and solved. This mechanism not only explains the eastward shift of the lunar CM, but also predicts that the oblateness of the Moon could have been appreciable at earlier epochs, reaching values ε ≈ 0.31. The theory of figures of equilibrium in a tidal gravitational field is used to determine how close to the Earth the Moon could have formed.     

Accretion of Moon and Earth and the emergence of life.

The discrepancy between the impact records on the Earth and Moon in the time period, 4.0-3.5 Ga calls for a re-evaluation of the cause and localization of the late lunar bombardment. As one possible explanation, we propose that the time coverage in the ancient rock record is sufficiently fragmentary, so that the effects of giant, sterilizing impacts throughout the inner solar system, caused by marauding asteroids, could have escaped detection in terrestrial and Martian records. Alternatively, the lunar impact record may reflect collisions of the receding Moon with a series of small, original satellites of the Earth and their debris in the time period about 4.0-3.5 Ga. The effects on Earth of such encounters could have been comparatively small. The location of these tellurian moonlets has been estimated to have been in the region around 40 Earth radii. Calculations presented here, indicate that this is the region that the Moon would traverse at 4.0-3.5 Ga, when the heavy and declining lunar bombardment took place. The ultimate time limit for the emergence of life on Earth is determined by the effects of planetary accretion--existing models offer a variety of scenarios, ranging from low average surface temperature at slow accretion of the mantle, to complete melting of the planet followed by protracted cooling. The choice of accretion model affects the habitability of the planet by dictating the early evolution of the atmosphere and hydrosphere. Further exploration of the sedimentary record on Earth and Mars, and of the chemical composition of impact-generated ejecta on the Moon, may determine the choice between the different interpretations of the late lunar bombardment and cast additional light on the time and conditions for the emergence of life.     

The Deviation of the Lunar Center of Mass to the East of the Direction Toward the Earth. A Mechanism Based on Orbital Evolution

It is known from observations of the gravitational field and figure of the Moon that its center of mass (COM) does not coincide with its geometric center, with the line connecting these two points deviating to the Southeast of the direction toward the center of the Earth. The deviation of the lunar COM to the South was explained earlier. Here, the deviation of the lunar COMto the East of the direction toward the Earth is considered. The theory of the optical libration of a satellite orbiting synchronously about a planet for an observer at the secondary (free) focus of the orbit is first refined. It is shown that the main axis of inertia of the satellite undergoes asymmetric, non-linear oscillations whose amplitude is proportional to the square of the orbital eccentricity. A mechanism for the evolution of the orbit has been developed, taking into account the preferred direction of the axis of inertia of the Moon toward the empty focus. Of two alternative scenarios—evolution of the lunar orbit with decreasing or increasing eccentricity—only the latter scenario is consistent with the observed eastward shift of the lunar COM. This mechanism predicts that the lunar orbit had a lower eccentricity in the past than it does today. This conclusion is consistent with the results of observations and also with the fact that the eccentricity of the Moon’s orbit is indeed currently increasing, indicating that it was lower in the past than its current value, e = 0.0549. It is shown by averaging themotion over a rapid variable that thismechanismfor the orbital evolution can explain about 18% of the currently known eastward shift of the lunar COM. The results obtained refine the theory of the tidal evolution of the Moon.     

Tectonic aspects of Precambrian metallogeny of gold and uranium

A cause-and-effect relation is established between historical metallogeny of gold and uranium and extraterrestrial factors (impact events, evolution of the distance between Earth and Moon, rotation geodynamics), which significantly affected the Early Precambrian tectonic evolution of our planet. It is shown by the example of the complex Witwatersrand deposit that the Precambrian polygenetic Au and U deposits of the quartz–pebble type were formed within a near-equatorial epi-Archean supercontinent and were related to extraterrestrial factors under a rotation regime of the plume vertical tectonics. The beginning of breakup of the epi-Archean supercontinent in the Paleo- and Mesoproterozoic (2.0 ± 0.3 Ga) was related to the abrupt decrease in the velocity of the Earth’s axial rotation followed by the dominant regime of subhorizontal plate tectonics and formation of rich U deposits of the nonconformity type (which are structurally related to the horizontal inertial detachments at the contacts of the consolidated crust) and Meso- and Neoproterozoic sedimentary complexes.     

A possible anorthositic continent of early Mars and the role of planetary size for the inception of Earth-like life

The Moon has an anorthositic primordial continental crust. Recently anorthosite has also been discovered on the Martian surface. Although the occurrence of anorthosite is observed to be very limited in Earth's extant geological record,both lunar and Martian surface geology suggest that anorthosite may have comprised a primordial continent on the early Earth during the first 600 million years after its formation. We hypothesized that differences in the presence of an anorthositic continent on an Earthlike planet are due to planetary size. Earth likely lost its primordial anorthositic continent by tectonic erosion through subduction associated with a kind of proto-plate tectonics(PPT). In contrast, Mars and the Moon, as much smaller planetary bodies, did not lose much of their anorthositic continental crust because mantle convection had weakened and/or largely stopped, and with time, they had appropriately cooled down. Applying this same reasoning to a super-Earth exoplanet suggests that, while a primordial anorthositic continent may briefly form on its surface, such a continent will be likely transported into the deep mantle due to intense mantle convection immediately following its formation. The presence of a primordial continent on an Earth-like planet seems to be essential to whether the planet will be habitable to Earth-like life. The key role of the primordial continent is to provide the necessary and sufficient nutrients for the emergence and evolution of life. With the appearance of a "trinity" consisting of(1) an atmosphere,(2) an ocean, and(3) the primordial continental landmass, material circulation can be maintained to enable a "Habitable Trinity" environment that will permit the emergence of Earth-like life. Thus, with little likelihood of a persistent primordial continent, a super-Earth affords very little chance for Earth-like life to emerge.     

月球起源研究进展

月球是地球唯一的天然卫星,早期学者认为地月系统是普遍存在的行星一卫星系统的一员,但是月球又有许多特征,如质量异常大,挥发分和Fe元素亏损等,传统理论难以解释这些特征.因此,针对月球的起源提出了四种学说:捕获理论,共增生理论,分裂理论和大碰撞假说.目前对大碰撞假说研究较多,但研究者们始终无法较好解释地月系统氧同位素的高度一致等特征.本文试探性提出新的月球起源分裂模型,能较好的解释某些月球特征,引起研究者们对月球起源新的思考.     

月球探测与人类社会的可持续发展

1959年至1976年的18年是人类第一次月球探测高潮，美国和前苏联共成功发射了45个月球探测器，获取了382kg的月球岩石和月壤样品，这些探测资料和月球样品的系统分析与研究，大大促进了人类对月球、地球和太阳系的认识，并带动了一系列基础科学的创新，促进了一系列应用科学的发展。通过从1976年至1994年近18年浩如烟海的月球探测数据和资料的消化、分析与综合研究后，1994年Clementine环月探测器的发射，标志新的一轮探月高潮的开始。当前，国际探月活动刚进入重返月球、逐步建设月球基地的阶段，而逐步开发利用月球矿产资源、能源和特殊环境，建设月球基地，为人类社会的可持续发展服务，已成为新世纪月球探测的总体目标。本在系统分析已有的探测与研究资料基础上，论述了开发利用月球上具有的巨大能源库、丰富的矿产资源和独特的环境资源将对人类社会可持续发展所具有的深远意义。     

Tectonomagmatic evolution of the Earth and Moon

The Earth and Moon evolved following a similar scenario. The formation of their protocrusts started with upward crystallization of global magmatic oceans. As a result of this process, easily fusible components accumulated in the course of fractional crystallization of melt migrating toward the surface. The protocrusts (granitic in the Earth and anorthositic in the Moon) are retained in ancient continents. The tectonomagmatic activity at the early stage of planet evolution was related to the ascent of mantle plume of the first generation composed of mantle material depleted due to the formation of protocrusts. The regions of extension, rise, and denudation were formed in the Earth above the diffluent heads of such superplumes (Archean granite-greenstone domains and Paleoproterozoic cratons), whereas granulite belts as regions of compression, subsidence, and sedimentation arose above descending mantle flows. The situation may be described in terms of plume tectonics. Gentle uplifts and basins (thalassoids) in lunar continents are probable analogues of these structural elements in the Moon. The period of 2.3–2.0 Ga ago was a turning point in the tectonomagmatic evolution of the Earth, when geochemically enriched Fe-Ti picrites and basalts typical of Phanerozoic within-plate magmatism became widespread. The environmental setting on the Earth’s surface changed at that time, as well. Plate tectonics, currently operating on a global scale, started to develop about ∼2 Ga ago. This turn was related to the origination of thermochemical mantle plumes of the second generation at the interface of the liquid Fe-Ni core and silicate mantle. A similar turning point in the lunar evolution probably occurred 4.2–3.9 Ga ago and completed with the formation of large depressions (seas) with thinned crust and vigorous basaltic magmatism. Such a sequence of events suggests that qualitatively new material previously retained in the planets’ cores was involved in tectonomagmatic processes at the middle stage of planetary evolution. This implies that the considered bodies initially were heterogeneous and were then heated from above to the bottom by propagation of a thermal wave accompanied by cooling of outer shells. Going through the depleted mantle, this wave generated thermal superplumes of the first generation. Cores close to the Fe + FeS eutectics in composition were affected by this wave in the last turn. The melting of the cores resulted in the appearance of thermochemical superplumes and corresponding irreversible rearrangement of geotectonic processes.