共查询到20条相似文献，搜索用时 500 毫秒
1.
B. P. Kondratyev 《Astronomy Reports》2018,62(10):705-712
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. 相似文献
2.
Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth
B. P. Kondratyev 《Astronomy Reports》2017,61(8):709-714
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″. 相似文献
3.
我国月球探测的总体科学目标与发展战略 总被引：52，自引：0，他引：52
在简述月球探测的历程与趋势的基础上,强调当代月球探测的总体目标为：①研究月球与地月系的起源和演化,特别是月球大气层与磁场的消失,矿物与岩石的分布和形成环境、月壤和内部层圈结构的形成以及月球演化的历程;②探测月球的资源、能源和特殊环境的开发利用及对人类社会长期可持续发展的支撑。我国不载人月球探测划分为绕、落、回三个阶段。为了全球性、整体性重新认识月球,绕月卫星探测的科学目标是为了获取全月面三维影像,探测14种有用元素的全球分布与丰度,探测月壤厚度并估算氦 3资源量以及太阳活动对空间环境的影响。"落"为月球探测器软着陆就位探测和月球车巡视探测,建立月基光学、低频射电和极紫外天文观测平台。"回"为月球探测器软着陆就位探测和取样返回地面。 相似文献
4.
月球形成和演化的关键科学问题 总被引：4，自引：0，他引：4
我国正开展月球探测和科学研究,其成果将加深认识月球的组成、结构以及形成和演化,同时揭示地球的早期历史。通过对月球研究成果的总结,就月球形成和演化关键科学问题的现状作了较为详细的说明,从而为我国月球探测和科学研究提供有益的启示。主要的关键科学问题包括：地球一月球体系的大撞击成因、月球岩浆洋与月壳形成、39亿年大撞击事件、玄武岩浆喷发与月球内部结构和月球南极艾特肯（Aitken）撞击盆地的形成等。 相似文献
5.
The imprint of orbital cycles, which result from the varying eccentricity of the Earth’s orbit and changes in the orientation of its axis, have been recognised throughout the Phanerozoic rock record. Variations in insolation and their effect on climate are generally considered to be the sole transfer mechanism between the orbital variables and cyclic sedimentary successions. Common oceanographic principles, however, show that the ocean tide also responds to variations in the orbital parameters. The ocean tide has not yet been considered to be a valid, additional transfer mechanism for the orbital variations. In geological studies of Milankovitch cycles in sedimentary successions the insolation paradigm offers satisfying explanations, and the role of long‐term variations of the ocean tide has not yet been appreciated. Variations in the ocean tide, related to changing eccentricity (at present 0·0165, theoretical maximum 0·0728), affect a variety of oceanographic and sedimentary processes. In addition to the widely accepted paradigm of orbitally forced insolation changes, the tidal transfer of orbital signals may explain certain less well‐understood aspects of orbitally induced cycles in the stratigraphic record related to ocean mixing, organic productivity, and tidal processes in shallow seas and deep water. Variations of the ocean tide in relation to the 18·6 year lunar nodal cycle, which has no insolation counterpart by which they may be obscured, indeed show that these relatively small variations can produce significant effects in sedimentary environments that are sensitive to variations in the strength of the ocean tide. In analogy with the 18·6 year lunar nodal cycle, orbital variations of the tide on Milankovitch time scales are likely to have affected sedimentary systems in the past. 相似文献
6.
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. 相似文献
7.
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。 相似文献
8.
Ananth Krishna N. S. Gopinath N. S. Hegde N. K. Malik 《Journal of Earth System Science》2005,114(6):739-748
The Chandrayaan-1 mission proposes to put a 550 kg lunarcraft into Geostationary Transfer Orbit (GTO) using the Polar Satellite
Launch Vehicle (PSLV) which will subsequently be transferred into a 100 km circular lunar polar orbit for imaging purposes.
In this paper, we describe certain aspects of mission strategies which will allow optimum power generation and imaging of
the lunar surface.
The lunar orbit considered is circular and polar and therefore nearly perpendicular to the ecliptic plane. Unlike an Earth
orbiting remote sensing satellite, the orbit plane of lunar orbiter is inertially fixed as a consequence of the very small
oblateness of the Moon. The Earth rotates around the Sun once a year, resulting in an apparent motion of Sun around this orbit
in a year. Two extreme situations can be identified concerning the solar illumination of the lunar orbit, noon/midnight orbit,
where the Sun vector is parallel to the spacecraft orbit plane and dawn/dusk orbit, where the Sun vector is perpendicular
to the spacecraft orbit plane. This scenario directly affects the solar panel configuration. In case the solar panels are
not canted, during the noon/midnight orbit, 100% power is generated, whereas during the dawn/dusk orbit, zero power is generated.
Hence for optimum power generation, canting of the panels is essential. Detailed analysis was carried out to fix optimum canting
and also determine a strategy to maintain optimum power generation throughout the year. The analysis led to the strategy of
180‡ yaw rotation at noon/midnight orbits and flipping the solar panel by 180‡ at dawn/dusk orbits. This also resulted in
the negative pitch face of the lunarcraft to be an anti-sun panel, which is very useful for thermal design, and further to
meet cooling requirements of the spectrometers.
In principle the Moon’s surface can be imaged in 28 days, because the orbit chosen and the payload swath provide adequate
overlap. However, in reality it is not possible to complete the imaging in 28 days due to various mission constraints like
maximum duration of imaging allowed keeping in view the SSR sizing and payloads data input rate, time required for downlinking
the payload data, data compression requirements and visibility of the lunarcraft for the Bangalore DSN. In each cycle, all
the latitudes are swept. Due to the constraints mentioned, only 60‡ latitude arc coverage is possible in each orbit. As Bangalore
DSN is the only station, half of the orbits in a day are not available. The longitudinal gaps because of non-visibility are
covered in the next cycle by Bangalore DSN. Hence, in the firstprime imaging season, only 25% of the prime imaging zones are covered, and an additional threeprime imaging seasons are required for a full coverage of the Moon in two years. Strategy is also planned to cover X-ray payload coverage considering
swath and orbit shift. 相似文献
9.
L. D. Akulenko Yu. G. Markov V. V. Perepelkin L. V. Rykhlova A. S. Filippova 《Astronomy Reports》2013,57(5):391-399
A mathematical model for rotational-oscillatory motions of the Earth is constructed by applying celestial mechanics to the spatial problem of the Earth-Moon system subject to the Sun’s gravitation. Some basic phenomena associated with tidal irregularity in the Earth’s axial rotation and the polar oscillations are studied. It is shown that the perturbing component of the gravitational-tidal forces orthogonal to the plane of the lunar orbit is responsible for some short-term perturbations in the Moon’s motion. The constructed model for the rotational-oscillatory motions of the deformable Earth includes both the main high-amplitude perturbations and more complex small-scale motions attributed to short-term lunar perturbations with combinational frequencies. Numerical modeling (interpolation and forecasting) of the Earth rotation parameters within various time intervals based on astrometric data obtained by the International Earth Rotation Service is presented. 相似文献
10.
11.
Tectonomagmatic evolution of the Earth and Moon 总被引：1，自引：0，他引：1
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. 相似文献
12.
月球形成演化与月球地质图编研 总被引：2，自引：0，他引：2
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。 相似文献
13.
Samples returned from the surface of planetary bodies are both complementary to orbital and in situ observations and provide a unique perspective for understanding the nature and evolution of that body. This unique perspective is based on the scale the sample is viewed (mm-Å), the ability to manipulate the sample, the capability to analyze the sample at high precision and accuracy, and the ability to significantly modify experiments as logic and technology dictates over an extended period of time (decades). Unlike the Apollo missions, robotic sample return missions in the next decade will result in the return of relatively small sample mass. Such robotically returned samples are scientifically more valuable if they can be placed within a planetary context through orbital observations and if information concerning planetary-scale processes and conditions can be extracted from them. Conversely, samples give remotely sensed data ground truth. That is, they act as a “calibration standard” for these data allowing a much enhanced global view to be constructed.The Moon is an example that illustrates how information can be extracted from small samples and then extended to planetary and solar system scales. Three examples from the Moon illustrate this point. First, multi-analytical and experimental studies of minute (10-500 μm) glass beads representing near-primary magmas provide constraints on the composition and condition of the lunar mantle, the style of early planetary differentiation, the history and character of early mantle dynamics and melting, and the isolation of the lunar mantle from late-stages of lunar accretion. Second, trace element analysis of individual mineral grains via ion microprobe and isotopic analysis of small rock fragments representing some of the oldest and youngest periods of lunar magmatism illustrate their usefulness for both fingerprinting distinct episodes of lunar magmatism and reconstructing the evolution of lunar magmatism. Third, mechanisms for primitive planetary mantles degassing and volatile transport on airless bodies can be understood by the analysis of volatile coatings on glass and mineral fragments in the lunar regolith.As many of our insights about the Moon are based on samples that primarily were collected within a limited lunar terrain, our understanding of the Moon is somewhat biased. Future scientifically strategic sampling targets are young mare basalts (Roris basalt in Oceanus Procellarum), far-side mare basalts (Mare Moscoviense), large pyroclastic deposits and potential mantle xenoliths (Aristarchus plateau, Rima Bode) major unsampled crustal lithologies outside the Procellarum KREEP terrane (central peak in Tsiolkovsky crater, South-pole Aitken basin), basin and crater melt sheets (South-pole Aitken basin, Giordano Bruno) and H deposits in permanently shaded areas (South-pole Aitken basin). Sampling these locations would further our understanding of processes at work during the early evolution of the terrestrial planets, provide a comprehensive history of endogenous (e.g., primary volcanic degassing) and exogenous (e.g., solar wind, galactic cosmic rays, volatiles from comets) volatile reservoirs and volatile transport and would provide unique historical information about events and processes that affected the entire inner solar system, a record obscured on the Earth and Mars. 相似文献
14.
《Chemie der Erde / Geochemistry》2022,82(3):125858
The Moon is generally depleted in volatile elements and this depletion extends to the surface where the most abundant mineral, anorthite, features <6 ppm H2O. Presumably the other nominally anhydrous minerals that dominate the mineral composition of the global surface—olivine and pyroxene—are similarly depleted in water and other volatiles. Thus the Moon is tabula rasa for the study of volatiles introduced in the wake of its origin. Since the formation of the last major basin (Orientale), volatiles from the solar wind, from impactors of all sizes, and from volatiles expelled from the interior during volcanic eruptions have all interacted with the lunar surface, leaving a volatile record that can be used to understand the processes that enable processing, transport, sequestration, and loss of volatiles from the lunar system. Recent discoveries have shown the lunar system to be complex, featuring emerging recognition of chemistry unanticipated from the Apollo era, confounding issues regarding transport of volatiles to the lunar poles, the role of the lunar regolith as a sink for volatiles, and the potential for active volatile dynamics in the polar cold traps. While much has been learned since the overturn of the “Moon is dry” paradigm by innovative sample and spacecraft measurements, the data point to a more complex lunar volatile environment than is currently perceived. 相似文献
15.
Manned lunar exploration has recently attracted renewed interest. This includes the NASA Constellation program to return humans to the Moon by 2020, the ESA Aurora program which may use the Moon as a way station to prepare for major interplanetary exploration by 2025, and the PRC program to send a human to the Moon by 2030 and build a temporary manned lunar base by 2040. One of the problems demanding a solution is the stresses on the mechanical characteristics of the lunar regolith under the microgravity environment. The gravity on the Moon is about 1/6 that on Earth. The regolith is subject to very low confining stresses under a microgravity environment and the mechanical properties can change correspondingly. Because of the limited amount of lunar regolith brought back to Earth by the Apollo missions, a lunar regolith simulant was developed using silicon carbide to investigate the properties of the lunar regolith. Based on triaxial tests, this study analyzed the mechanical properties of the lunar regolith simulant at low stresses including the shear strength, peak strength and dilatation angle. The research results provide useful information on lunar regolith characteristics for astronauts returning to the Moon and for building a temporary manned lunar base. 相似文献
16.
Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the
higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics,
which extend orbit life through passive orbit maintenance. The spherical harmonic terms that make major contributions to the
orbital behaviour are identified through many case studies. It is found that for low circular orbits, the 7th and the 9th
zonal harmonics have predominant effect in the case of orbits for which the evolution is stable and the life is longer, and
also in the case of orbits for which the evolution is unstable and a crash takes place in a short duration. By analysing the
contribution of the harmonic terms to the orbit behaviour, the appropriate near-circular orbit characteristics are identified. 相似文献
17.
Years-long data series of Earth’s natural pulse electromagnetic fields (EPEMF) from the Talaya station near Lake Baikal indicates their mainly terrestrial origin and includes a component of poorly understood stable diurnal and annual crustal rhythms. The short-period crustal motion may drive mechanic-to-electric conversion in rocks and be responsible for diurnal and annual VLF electromagnetic pulses.The lithospheric rather than atmospheric origin of many recorded EPEMF signals is supported by their links with nucleation of earthquakes and respective perfect match of the EPEMF and seismicity diurnal patterns. Joint spectral analysis of the Talaya EPEMF and seismicity time series and comparison with the known spectra of lunar and solar tides shows no direct correlation between the short-period rhythms and the gravitation effects.We suggest that the diurnal and annual EPEMF periodicity may be associated with differential motion of the core and lithosphere and use this hypothesis to model an annual core path. As the model predicts, the inner solid core is never at the Earth’s geometric center but moves relative to the latter along a closed orbit; the plane of the core orbit is normal to the equatorial plane and tilted 45° to the direction to the Sun and to the Earth’s orbit; the core rotates 1.1 deg/yr faster than the Earth. The suggested model of core motion is consistent with the known instability of Earth rotation. 相似文献
18.
Re-Os同位素体系是理解月球强亲铁元素的分布规律和示踪月球的后期增生历史的重要手段。目前人们对月球物质Re-Os同位素成分的了解还是十分有限的,已有的Re-Os同位素数据显示一些能代表月幔成分特征的月海玄武岩具有很低的Re和Os的浓度,以及类似于球粒陨石的187Os／188Os成分特征,而月球火山玻璃和月壤等表现出相对高的Re-Os丰度和相对富放射成因Re-Os同位素成分。一般认为月球月幔的Re、0s和其他强亲铁元素相对球粒陨石是非常亏损的,而地球地幔则具有相对较高的强亲铁元素丰度（0．008倍CI球粒陨石的丰度）。新的Re-Os同位素结果证明月幔确实是亏损的,但是月球和地球在太阳系演化的较晚时期都有外来的球粒陨石物质的大量加入,即后期增生（late accretion）过程,导致了月球和地球上部物质（如月球火山玻璃、月壤等）相对地富集Os同位素和强亲铁元素,这些外来物质的后期增生可能是长期和持续的,增生过程主要发生在3．9～4．4Ga。但目前仍不清楚后期增生的陨石物质是被逐渐加入的,还是在一个相对较短的时期大量加入的,因此尚需对更多的月球物质做进一步的Re-Os同位素和强亲铁元素成分的研究。 相似文献
19.
SMART-1 after lunar capture: First results and perspectives 总被引：1，自引：0，他引：1
B. H. Foing G. D. Racca A. Marini E. Evrard L. Stagnaro M. Almeida D. Koschny D. Frew J. Zender D. Heather M. Grande J. Huovelin H. U. Keller A. Nathues J. L. Josset A. Malkki W. Schmidt G. Noci R. Birkl L. Iess Z. Sodnik P. McManamon 《Journal of Earth System Science》2005,114(6):689-697
SMART-1 is a technology demonstration mission for deep space solar electrical propulsion and technologies for the future.
SMART-1 is Europe’s first lunar mission and will contribute to developing an international program of lunar exploration. The
spacecraft was launched on 27th September 2003, as an auxiliary passenger to GTO on Ariane 5, to reach the Moon after a 15-month
cruise, with lunar capture on 15th November 2004, just a week before the International Lunar Conference in Udaipur. SMART-1
carries seven experiments, including three remote sensing instruments used during the mission’s nominal six months and one
year extension in lunar science orbit. These instruments will contribute to key planetary scientific questions, related to
theories of lunar origin and evolution, the global and local crustal composition, the search for cold traps at the lunar poles
and the mapping of potential lunar resources 相似文献
20.
Alan D. Brandon Thomas J. Lapen Brian L. Beard Clive Neal 《Geochimica et cosmochimica acta》2009,73(20):6421-17609
The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Mars-sized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision 142Nd/144Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled 142Nd-143Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth.To further examine this issue, the same six lunar mare basalt samples measured in Rankenburg et al. [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372] were re-measured for high-precision Nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than ±3 ppm (2σ) for 142Nd/144Nd ratios. The measurements were repeated in a distinct second analytical campaign to further test their reproducibility. Evaluation of accuracy and neutron fluence corrections indicates that the multidynamic Nd isotope measurements in this study and the 3 in Boyet and Carlson [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516] are reproducible, while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk Moon with either chondritic or superchondritic Sm/Nd ratios. The multidynamic data are best explained by a bulk Moon with a superchondritic Sm/Nd ratio that is similar to the present-day average for depleted MORB. Hafnium isotope data were collected on the same aliquots measured for their 142Nd/144Nd isotope ratios in order to assess if the correlation line for 142Nd-143Nd systematics reflect mixing processes or times at which lunar mantle sources formed. Based on the combined 142Nd-143Nd-176Hf obtained we conclude that the 142Nd-143Nd correlation line measured in this study is best interpreted as an isochron with an age of 229+24−20Ma after the onset of nebular condensation. The uncertainties in the data permit the sources of these samples to have formed over a 44 Ma time interval. These new results for lunar mare basalts are thus consistent with a later Sm-Nd isotope closure time of their source regions than some recent studies have postulated, and a superchondritic bulk Sm/Nd ratio of the Moon and Earth. The superchondritic Sm/Nd signature was inherited from the materials that accreted to make up the Earth-Moon system. Although collisional erosion of crust from planetesimals is favored here to remove subchondritic Sm/Nd portions and drive the bulk of these bodies to superchondritic in composition, removal of explosive basalt material via gravitational escape from such bodies, or chondrule sorting in the inner solar system, may also explain the compositional features that deviate from average chondrites that make up the Earth-Moon system. This inferred superchondritic nature for the Earth similar to the modern convecting mantle means that there is no reason to invoke a missing, subchondritic reservoir to mass balance the Earth back to chondritic for Sm/Nd ratios. However, to account for the subchondritic Sm/Nd ratios of continental crust, a second superchondritic Sm/Nd mantle reservoir is required. 相似文献