The Clementine mission —A 10-year perspective

Clementine was a technology demonstration mission jointly sponsored by the Department of Defense (DOD) and NASA that was launched on January 25th, 1994. Its principal objective was to use the Moon, a near-Earth asteroid, and the spacecraft’s Interstage Adapter as targets to demonstrate lightweight sensor performance and several innovative spacecraft systems and technologies. The design, development, and operation of the Clementine spacecraft and ground system was performed by the Naval Research Laboratory. For over two months Clementine mapped the Moon, producing the first multispectral global digital map of the Moon, the first global topographic map, and contributing several other important scientific discoveries, including the possibility of ice at the lunar South Pole. New experiments or schedule modifications were made with minimal constraints, maximizing science return, thus creating a new paradigm for mission operations. Clementine was the first mission known to conduct an in-flight autonomous operations experiment. After leaving the Moon, Clementine suffered an onboard failure that caused cancellation of the asteroid rendezvous. Despite this setback, NASA and the DOD applied the lessons learned from the Clementine mission to later missions. Clementine set the standard against which new small spacecraft missions are commonly measured. More than any other mission, Clementine has the most influence (scientifically, technically, and operationally) on the lunar missions being planned for the next decade.     

Genetic relations between meteorites and terrestrial and lunar rocks

According to their genesis, meteorites are classified into heliocentric (which originate from the asteroid belt) and planetocentric (which are fragments of the satellites of giant planets, including the Proto-Earth). Heliocentric meteorites (chondrites and primitive meteorites genetically related to them) used in this study as a characteristic of initial phases of the origin of the terrestrial planets. Synthesis of information on planetocentric meteorites (achondrites and iron meteorites) provides the basis for a model for the genesis of the satellites of giant planets and the Moon. The origin and primary layering of the Earth was initially analogously to that of planets of the HH chondritic type, as follows from similarities between the Earth’s primary crust and mantle and the chondrules of Fe-richest chondrites. The development of the Earth’s mantle and crust precluded its explosive breakup during the transition from its protoplanetary to planetary evolutionary stage, whereas chondritic planets underwent explosive breakup into asteroids. Lunar silicate rocks are poorer in Fe than achondrites, and this is explained in the model for the genesis of the Moon by the separation of a small metallic core, which sometime (at 3–4 Ga) induced the planet’s magnetic field. Iron from this core was involved into the generation of lunar depressions (lunar maria) filled with Fe- and Ti-rich rocks. In contrast to the parent planets of achondrites, the Moon has a olivine mantle, and this fact predetermined the isotopically heavier oxygen isotopic composition of lunar rocks. This effect also predetermined the specifics of the Earth’s rocks, whose oxygen became systematically isotopically heavier from the Precambrian to Paleozoic and Mesozoic in the course of olivinization of the peridotite mantle, a processes that formed the so-called roots of continents.     

The Moon 35 years after Apollo: What's left to learn?

With the cancellation of the Apollo program after Apollo 17 returned from the Moon in 1972, the focus of NASA switched to other areas of the Solar System. Study of the Moon did continue through analysis of the returned samples and remotely sensed data sets (both orbital and surface), as well as through Earth-based telescopic studies. In the 1990s, new orbital data were obtained from several missions (fly-by and orbital), the first being Galileo that allowed the lunar farside to be mapped, followed by global mapping by the Clementine and Lunar Prospector missions.Interest in the Moon started to increase at the beginning of the 21st century as other nations focused their space exploration programs on the Moon. The speech by President Bush in January 2004 put the Moon back into the critical exploration path for NASA, paving the way for humans to return to the lunar surface by 2020. This return will be critical for developing technologies and protocols for the eventual human exploration of other parts of the solar system. At the time of writing (June 2008), the SELENE/Kaguya mission (Japan and Chang’e-1 (China) are orbiting the Moon, with Chandrayaan-1 (India) and Lunar Reconnaissance Orbiter (USA) being scheduled to launch later in 2008.The past (and present) exploration of the Moon begs the question “what's left to be done?” With the renewed focus on the Moon, now that it is on the pathway for the exploration of Mars (and beyond) a similar question has been raised - what should the astronauts do on the Moon? The publication of the New Views of the Moon book [Jolliff et al., 2006. New Views of the Moon, Reviews in Mineralogy, vol. 60. American Mineralogical Society, 721pp] highlighted a number of important scientific questions that remain unanswered as well as posing many more on the basis of the currently available data. These questions resonated in three Lunar Exploration Analysis Group (LEAG) reports pertinent to this discussion, which were also published (on line) during 2006 (http://www.lpi.usra.edu/leag), and in the National Research Council of the National Academies [2007. The Scientific Context for Exploration of the Moon. National Academies Press, Washington, DC, 112pp] report entitled “The Scientific Context for Exploration of the Moon”. This paper synthesizes these recent studies, along with those from the 1980s and 1990s, to emphasize the lunar science questions that remain unanswered. In addition, it summarizes the missions already flown to the Moon along with those that are planned in order to give the reader an idea of exactly what lunar science has been and will be conducted in the hope that it will inspire proposals for missions to address the outstanding science questions.     

A unified model for hydrogen in the Earth and Moon: No one expects the Theia contribution

The Moon is thought to have formed after a planetary embryo, known as Theia, collided with the proto-Earth 4.5 billion years ago. This so-called Giant Impact was the last major event during Earth’s accretion, and its effects on the composition of the Earth and the newly forming Moon would be measureable today. Recent work on lunar samples has revealed that the Moon’s water was not lost as a result of this giant impact. Instead, the Moon appears to contain multiple hydrogen reservoirs with diverse deuterium-to-hydrogen (D/H) ratios. For the first time, we incorporate hydrogen isotopic measurements of lunar samples to help constrain the composition of Theia. We show that the Moon incorporated very low-D/H (δD ≈ -750‰) materials that only could have derived from solar nebula H₂ ingassed into the magma ocean of a large (∼0.4 M_E) planetary embryo that was largely devoid of chondritic water. We infer Theia was a very large body comparable in size to the proto-Earth, and was composed almost entirely of enstatite chondrite-like material. These conclusions limit the type of impact to a “merger” model of similarly-sized bodies, or possibly a “hit-and-run” model, and they rule out models that mix isotopes too effectively.     

月球佩塔维厄斯幅(LQ-21)数字地质填图与区域地质演化特征

佩塔维厄斯幅月球地质图(LQ-21)位于近月面与远月面交接位置,又处于月海和月陆的过渡区,周边邻近酒海、丰富海、史密斯海等大型撞击盆地,是月球数字地质填图工作中的一个典型区域。研究该地区的地质发育概况有助于了解月球的发展演化历史。本文利用中国探月工程所获得的“嫦娥一号”(CE-1)CCD影像数据、干涉成像光谱仪(IIM)数据、激光高度计(LAM)数据和“嫦娥二号”(CE-2)CCD影像数据以及其他已有的月球地质资料,应用ArcGIS平台,开展月表物质成分、构造要素、地质时代信息的研究和数字填图工作,编制了1: 2 500 000佩塔维厄斯幅(LQ-21)数字月球地质图,总结了该地区区域地质演化历史并建立地质图空间数据库。     

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。     

月球电离层探测与研究

从20世纪60年代到本世纪初,人类发射了一系列绕月飞船,对月球大气和月球电离层进行研究。科学家发现,月球电离层主要出现在向日面。在表面几百米高度范围内,由太阳辐射导致的光致电离使得月球向日面出现密度不超过10^10／m2的电离层等离子体。进一步研究表明,由于月球没有内禀磁场,月球电离层与太阳风中的行星际电场耦合在一起,时刻处在“飘动”中。电离层密度的变化与月相、当地的月表剩磁、太阳风条件、当地的月壤特性等相联系。     

Photoelectric Observations of the Lunar Occultation of the Star SAO 79361 during a Total Lunar Eclipse

The results of photoelectric observation of the occultation of the visual binary star SAO 79361 = ADS 6038 by the Moon during the total lunar eclipse of January 9, 1982 are presented. The upper limit of the angular diameter of the brighter component A is estimated to be d_ul ? 0.0011″ based on direct measurements, which is in agreement with indirect estimates. Accurate estimates for the magnitude difference between components A and B, their angular separation, p ? 3.2″, and the inclination of the Moon’s edge’s at the point of occultation to the mean lunar horizon, θ ? +25°, are obtained. The time of the geometrical occultation of the center of the stellar disk of component A is determined with an accuracy of 1 ms. The results obtained for this star are unique among observations worldwide.     

High energy X-γ ray spectrometer on the Chandrayaan-1 mission to the Moon

The Chandrayaan-1 mission to the Moon scheduled for launch in late 2007 will include a high energy X-ray spectrometer (HEX) for detection of naturally occurring emissions from the lunar surface due to radioactive decay of the²³⁸U and²³²Th series nuclides in the energy region 20–250 keV. The primary science objective is to study the transport of volatiles on the lunar surface by detection of the 46.5 keV line from radioactive²¹⁰Pb, a decay product of the gaseous²²²Rn, both of which are members of the²³⁸U decay series. Mapping of U and Th concentration over the lunar surface, particularly in the polar and U-Th rich regions will also be attempted through detection of prominent lines from the U and Th decay series in the above energy range. The low signal strengths of these emissions require a detector with high sensitivity and good energy resolution. Pixelated Cadmium-Zinc-Telluride (CZT) array detectors having these characteristics will be used in this experiment. Here we describe the science considerations that led to this experiment, anticipated flux and background (lunar continuum), the choice of detectors, the proposed payload configuration and plans for its realization     

我国月球探测的总体科学目标与发展战略

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。     

Differentiation of crusts and cores of the terrestrial planets: Lessons for the early Earth?

It now appears probable that all of the terrestrial planets underwent some form of global chemical differentiation to produce crusts, mantles, and cores of variable relative mass fractions. There is direct seismic evidence for a crust on the Moon, and indirect evidence for distinct crusts on Mars and Venus. Substantial portions of these crusts have been in place since the time that heavy bombardment of the inner solar system ceased 4 Ga ago. There is direct evidence for a sizeable core on Mars, indirect evidence for one on Mercury, and bounds on a possible small core for the Moon. Core formation is an important heat source confined to times prior to 4 Ga ago for Mercury and the Earth, but was not closely linked to crustal formation on the Moon nor, apparently, on Mars. The tectonic and volcanic histories of the surfaces of the terrestrial planets Moon, Mars, and Mercury can be used, with simple thermal history models, to restrict the earliest chemical differentiation to be shallow (outer 200–400 km) for the first two bodies and much more extensive for Mercury. Extension of these models to an Earth-size planet leads to the prediction of a hot and vigorously convecting mantle with an easily deformable crust immediately following core formation, and of the gradual development of a lithosphere and of plates with some lateral rigidity in Late Archean—Proterozoic times.     

Launch strategy for Indian lunar mission and precision injection to the Moon using genetic algorithm

The Indian lunar mission Chandrayaan-1 will have a mass of 523 kg in a 100 km circular polar orbit around the Moon. The main factors that dictate the design of the Indian Moon mission are to use the present capability of launch vehicles and to achieve the scientific objectives in the minimum development time and cost. The detailed mission planning involves trade-off studies in payload optimization and the transfer trajectory determination that accomplishes these requirements. Recent studies indicate that for an optimal use of the existing launch vehicle and space-craft systems, highly elliptical inclined orbits are preferable. This indeed is true for the Indian Moon mission Chandrayaan-1. The proposed launch scenario of the Indian Moon mission program and capabilities of this mission are described in this paper, highlighting the design challenges and innovations. Further, to reach the target accurately, appropriate initial transfer trajectory characteristics must be chosen. A numerical search for the initial conditions combined with numerical integration produces the near accurate solution for this problem. The design of such transfer trajectories is discussed in this paper.     

月球构造新认识：基于60m高精度全月月形图的月球构造形态学研究

一直以来月球上都没有发现像地球上一样的全球板块构造现象,被认为是属于单板块构造的行星体并且是不活动的。随着月球地形探测精度的提高,人们逐渐发现了一些地质现象表明月球并不像之前想象的一样是不活动的。高精度的月形数据显示出了月球上除了存在众所周知的(撞击作用产生的)复杂的撞击构造外,仍然存在许多可能由内生作用产生的构造特征:如裂谷、山脊、火山群等。本文利用最新高精度月球激光高度数据(LOLA数据)建立了全月60m(相当于7秒网格)高精度月形图。由于数据量超大(TB级别),作者编写了基于并行架构的集群计算处理代码,其计算效率提高了近300倍。基于这些图件,作者在全球范围内找出许多重要的构造现象,并根据其构造及地质特征进行分类研究。研究结果表明并不像之前认识一样,月球上的确存在许多地质构造体是由月球的内生地质作用所产生,并建立对于月球结构和构造的新认识。此外,通过对比发现,像地球上全球尺度的线性山脉只是板块构造运动的结果;另一方面,在无板块构造的行星上,就像月球一样,会产生大面积的高地(月陆)和低地(月海地区),这种地质现象很有可能是行星地壳岩浆演化的直接结果。在文章最后,作者还将制作出的60m分辨率的全月月形系列图件附后并公开,以方便其他科研人员进一步开展相关研究;并以此敬献中国地质科学院60周年庆典。     

Mechanical characteristics of a lunar regolith simulant at low confining pressure

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.     

The early history of the earth—moon system

The study of the Earth—Moon system provides the connecting link between purely astronomical studies of the origin of the solar system and its planets, and geophysical and biological studies of the evolution of the Earth's geology, its surface features, atmosphere and hydrosphere, and of terrestrial life.A coherent account is presented here, based on the hypothesis that the Moon formed separately and was later captured by the Earth. The adoption of this hypothesis, together with the observed depletion of iron in the Moon, sets some important constraints on the development of condensation and agglomeration phenomena in the primeval solar nebula, which led to the formation of planetesimals, and ultimately to planets.Capture of the Moon also defines a severe heating event within the Earth, whereby its kinetic energy of rotation is largely dissipated internally by the mechanism of tidal friction. From this melting event dates the geologic, atmospheric, and oceanic history of the Earth. An attempt is made to account for the unique development of the Earth, especially in relation to Mars and Venus, its neighboring planets.     

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.     

A review of geophysical methods used in archaeology

Geophysical methods have been used with increasing frequency in archaeology since 1946; aerial photography has been used since 1919. The geophysical methods that are most commonly used at present are electrical resistivity, magnetics, and ground-probing radar. Magnetic detectors, particularly when used in a gradient mode or with a continuously recording base station, are used at almost all sites where any geophysical methods are used. Portable, noncontacting electromagnetic soil-conductivity systems are also being increasingly used because of their very high rate of data acquisition. Less commonly used methods include self-potential (sometimes called spontaneous potential), microgravity, radiometric, thermal infrared imagery, and sonic or seismic techniques. Recent developments in image processing and graphic representation have contributed substantially to the archaeologist's ability to do “rescue archaeology,” that is, to carry out high-speed, nondestructive reconnaissance surveys for ancient human cultural evidence in advance of modern industrial development.     

月球岩浆洋演化的实验岩石学研究进展SCIEI北大核心CSCD

由于缺少直接来自月球深部的岩石样品,实验和计算模拟是认识早期月球演化过程的有效方法和手段。20世纪70年代以来,陆续开展了大量的实验岩石学和实验地球化学工作对月球岩浆洋(lunar magma ocean,LMO)演化模型进行验证和修正。但是,学界对LMO模型中的两个关键性参数,即初始物质组成和熔融深度,仍然存在不同的认识。根据月震和重力探测数据推测的平均月壳厚度的差异、月球样品含水量的研究以及新的遥感数据解译发现月表广泛分布富镁铝尖晶石(Cr#<5)等等,直接影响我们对月球初始物质组成和LMO深度以及月球深部高压矿物相的评估。本文通过整理高温高压实验岩石学和实验地球化学在研究LMO演化方面的一系列研究成果,主要聚焦以下几个科学问题:(1)月球初始物质组成中的难熔元素和挥发分含量,以及LMO深度对月壳厚度、结晶矿物的种类及含量有着决定性的影响;(2)高压矿物相石榴子石在月球深部稳定存在的可能性及其对残余岩浆中微量元素的分配行为的制约;(3)特殊类型的月球样品(包括火山玻璃、镁质岩套等)的成因机制对月球深部物质组成具有指示意义;(4)月核的不同物质组成对LMO模型的初始成分含量,特别是微量元素的限定作用。我们以最新的观测数据和月球样品的分析结果为依据,对已有的LMO演化模型进行重新评估,提出月球深部含有石榴子石的LMO演化模型的可能性,并对该方向亟需开展的工作进行探讨。     

月球哥白尼纪地层特征与地质演化研究

月球哥白尼纪地层是月球演化历史中最年轻的地层单元,哥白尼纪撞击坑数量较少,但其形成的哥白尼纪地层却是全球性的、非常显著的,大多学者普遍认为哥白尼纪基本没有岩浆活动与构造活动。通过对月球哥白尼纪地层进行地质填图,认为月球高地地区撞击坑辐射纹相对月海地区辐射纹发育更好,推测其原因可能为高地与月海岩石性质不同,或撞击的小天体体积、能量、物质特征以及撞击的角度、速度不同等原因导致的;哥白尼纪地层可划分为早哥白尼世地层(C_1)、中哥白尼世地层(C_2)和晚哥白尼世地层(C_3),通过对各世典型撞击坑的分析与研究,阐述了哥白尼纪各世地层的特征,为开展月球晚期撞击作用特征与效应的研究提供了资料。对哥白尼纪-爱拉托逊纪地层界限进行了初步探讨,提出月球年代学多源数据综合判别法方案,以重新厘定哥白尼纪年代下限。