Theories of the origin of the moon new concept ; geochemistry and dynamics

The origin of the Moon remains an unsolved problem of the planetary science. Researchers engaged in celestial dynamics, geophysics, and geochemistry are still discussing various models of creation of our closest cosmic neighbour. The most popular scenario, the impact hypothesis involving a collision early in the Earth's history, has been substantially challenged by the new data. The birth and development of a planet-moon system always plays a role in the formation of an entire planetary system around our Sun or around another star. This way, the story of our Moon acquires broader ramifications for one of the hottest topics of the modern scholarship. All this has motivated the authors of this book to consider a new concept and to compare the currently discussed theories, analyzing their advantages and shortcomings in explaining the experimental data. Introduction 10 I Geochemistry 14 1 The Moon as a celestial body 16 1.1 Size, mass, density 16 1.2 Moment of inertia 16 1.3 Orbital motion 17 1.4 Obliquities and inclinations 18 1.5 Angular momentum 19 1.6 Orbital evolution 20 1.7 Libration points 21 2 The history of the study of the Moon 23 3 The Moon as a geological body 26 3.1 Lunar gravity 26 3.2 Asymmetry of the lunar shape 27 3.3 Magnetic field 28 3.4 Topography 28 3.5 Lunar Rocks 32 3.5.1 Highland rocks 33 3.5.2 Maria rocks 35 3.6 Lunar chronology 36 3.7 Internal structure and temperature 38 4 Similarity and difference in composition of Earth and Moon 42 4.1 Iron content 42 4.2 Redox state 43 4.3 Volatiles 44 4.4 Refractory elements 46 4.5 Thermal evolution 48 4.6 Isotopic composition similarity 49 4.6.1 Oxygen 49 4.6.2 Silicon 52 4.6.3 Titanium 52 4.6.4 Cromium 53 4.6.5 Tangsten 53 4.6.6 Magnesium 54 4.6.7 Litium 54 5 Hypotheses on the origin of the Moon 55 5.1 Early hypotheses 55 5.2 Giant impact concept and its weaknesses 57 6 The model of evaporative accretion 60 6.1 Two possible paths of evolution of the solar nebula 60 6.2 Introduction to the dynamic model 62 6.3 Loss of iron and enrichment in refractories 64 6.4 Asymmetry of accumulation of Earth and Moon 68 7 Geochemical constraints and how the giant impact and evaporative accretion concepts satisfy them 73 7.1 Identity of isotope compositions of the Earth and the Moon 73 7.2 Loss of volatiles without isotope fractionation 74 7.3 Water in the Moon. D/H ratio 78 7.4 Siderophile elements 83 7.5 Constraints following from Hf-W systematic 92 7.6 129I–129Xe and 244Pu–136Xe 94 7.7 U-Pb system. Time of accomplishment of accretion 95 7.8 Rb-Sr system. Time of Moon origin 98 II Dynamics 104 8 Dynamical modeling of fragmentation of the gas-dust cloud 106 8.1 Computational modeling using particle dynamics 106 8.2 Computational technique 111 8.2.1 Classical Barnes-Hut algorithm 111 8.2.2 Data structure 114 8.2.3 Tree traversal 116 8.2.4 Parallelization scheme 117 8.2.5 Comparative analysis of the performance 119 8.2.6 Results of the computations, 2D-model 121 8.3 Evaporation of the particles as an important factor of fragmentation 124 8.4 3D-model of evaporative fragmentation 126 8.4.1 Simulation parameters and numerical experiments 126 8.4.2 Modification of the parameters (interaction potential, angular and random velocities, and dissipation coefficients) 129 8.4.3 Variation of number of particles 134 8.4.4 General trends in the system behavior 136 9 Dynamic modeling of accretion 138 9.1 Computational model 138 9.2 Determination of sizes of Earth and Moon embryos 148 9.3 Consideration of precollapse evolution of the gas-dust cloud 150 9.4 Temperature evolution 152 Conclusions 156 References 158 Index 176 Main description: The origin of the Moon remains an unsolved problem of the planetary science. Researchers engaged in celestial dynamics, geophysics, and geochemistry are still discussing various models of creation of our closest cosmic neighbour. The most popular scenario, the impact hypothesis involving a collision early in the Earth's history, has been substantially challenged by the new data. The birth and development of a planet-moon system always play a role in the formation of an entire planetary system around our Sun or around another star. This way, the story of our Moon acquires broader ramifications for one of the hottest topics of the modern scholarship. All this has motivated the authors of this book to present and compare the currently discussed theories, and to analyze their advantages and shortcomings in explaining the experimental data The Moon As A Celestial Body -- The History Of The Study Of The Moon -- The Moon As A Geological Body -- Similarity And Difference In Composition Of Earth And Moon -- Hypotheses On The Origin Of The Moon -- The Model Of Evaporative Accretion -- Geochemical Constraints And How The Giant Impact And Evaporative Accretion Concepts Satisfy Them -- Dynamical Modeling Of Fragmentation Of The Gas-dust Cloud -- Dynamic Modeling Of Accretion. Erik M. Galimov, Anton M. Krivtsov. Includes Bibliographical References (p. [145]-162) And Index.