The Earth-Moon Connection

1989 ◽  
Vol 44 (10) ◽  
pp. 891-923 ◽  
Author(s):  
A. E. Ringwood
Keyword(s):  
Genetic Relationship ◽  
The Moon ◽  
Core Formation ◽  
Earth’S Mantle ◽  
Terrestrial Atmosphere ◽  
The Earth ◽  
Wide Range ◽  
Siderophile Elements ◽  
The Impact ◽  
Close Genetic Relationship

Abstract The early thermal state of the Earth provides important constraints on hypotheses relating to its origin and its connection with the Moon. The currently popular giant impact hypothesis of lunar origin requires the Earth’s mantle to have been completely melted during the impact. Differentiation of a molten mantle would have produced strong chemical and mineralogical stratification, causing the mantle to become gravitationally stable and resistant to convective rehomogenization. The resulting composition and mineralogy of the upper mantle and primitive crust would have been dramatically different from those which have existed during the past 3.8 b. y. It is concluded that the Earth’s mantle was not extensively melted at the conclusion of accretion of the planet and therefore the hypothesis that the Moon was formed by the impact of a martian-sized planetesimal on the proto-Earth is probably incorrect. Nevertheless, a wide range of geochemical evidence demonstrates the existence of a close genetic relationship between the Moon and the Earth’s mantle. The key evidence relates to the processes of core formation in planetary bodies and resultant abundance patterns of siderophile elements which remain in their silicate mantles. Because of the complexity of the core formation process within a given body and the multiplicity of chemical and physical processes involved, the mantle siderophile signature is expected to be a unique characteristic. Thus, the siderophile signatures of Mars and of the eucrite parent body are quite distinct from that of the Earth’s mantle. Lunar siderophile geochemistry is reviewed in detail. It is demonstrated that a large group of siderophile elements display similar abundances in the terrestrial and lunar mantles. The similarity implies that a major proportion of the material now in the Moon was derived from the Earth’s mantle after core formation. This implication, however, does not require that the bulk compositions of the lunar and terrestrial mantles should be essentially identical, as is often assumed. Factors which may contribute to significant compositional differences between the two bodies within the context of a close genetic relationship are reviewed. The most promising mechanism for removing terrestrial material from the Earth’s mantle arises from the impacts of a number of large (0.001 to 0.01 ME) but not giant (≥ 0.1 ME) planetesimals after core formation and at the terminal stage of the Earth’s accretion. These impacts evaporated several times their own masses of mantle material and shock-melted considerably more. However, they did not lead to complete or extensive (e.g. > 50%) melting of the entire mantle. Impact-generated clouds of shock-melted spray and vapours were accelerated to high velocities in the presence of a primitive terrestrial atmosphere that co-rotated with the Earth. This provided an effective means of transferring angular momentum from the Earth to the ejected material which condensed to form a ring of Earth-orbiting planetesimals and moonlets. The Moon was formed by coagulation from material derived from the outer regions of this ring. Accretion of the Earth in the presence of the gases of the solar nebula and the co-rotating primitive terrestrial atmosphere may also have provided a mechanism for generating the rapid prograde spin of the proto-Earth.

Highly Siderophile Element Constraints on Accretion and Differentiation of the Earth-Moon System

Science ◽  
2007 ◽  
Vol 315 (5809) ◽  
pp. 217-219 ◽  
Author(s):  
James M. D. Day ◽  
D. Graham Pearson ◽  
Lawrence A. Taylor
Keyword(s):  
Platinum Group Element ◽  
Group Element ◽  
The Moon ◽  
Core Formation ◽  
Data Set ◽  
Highly Siderophile Elements ◽  
Earth’S Mantle ◽  
The Earth ◽  
Siderophile Elements

A new combined rhenium-osmium– and platinum-group element data set for basalts from the Moon establishes that the basalts have uniformly low abundances of highly siderophile elements. The data set indicates a lunar mantle with long-term, chondritic, highly siderophile element ratios, but with absolute abundances that are over 20 times lower than those in Earth's mantle. The results are consistent with silicate-metal equilibrium during a giant impact and core formation in both bodies, followed by post–core-formation late accretion that replenished their mantles with highly siderophile elements. The lunar mantle experienced late accretion that was similar in composition to that of Earth but volumetrically less than (∼0.02% lunar mass) and terminated earlier than for Earth.

Stochastic Late Accretion to Earth, the Moon, and Mars

Science ◽  
2010 ◽  
Vol 330 (6010) ◽  
pp. 1527-1530 ◽  
Author(s):  
William F. Bottke ◽  
Richard J. Walker ◽  
James M. D. Day ◽  
David Nesvorny ◽  
Linda Elkins-Tanton
Keyword(s):  
Size Distribution ◽  
Asteroid Belt ◽  
The Moon ◽  
Core Formation ◽  
Highly Siderophile Elements ◽  
Earth’S Mantle ◽  
Distribution Matching ◽  
Siderophile Elements ◽  
Impact Basins

Core formation should have stripped the terrestrial, lunar, and martian mantles of highly siderophile elements (HSEs). Instead, each world has disparate, yet elevated HSE abundances. Late accretion may offer a solution, provided that ≥0.5% Earth masses of broadly chondritic planetesimals reach Earth’s mantle and that ~10 and ~1200 times less mass goes to Mars and the Moon, respectively. We show that leftover planetesimal populations dominated by massive projectiles can explain these additions, with our inferred size distribution matching those derived from the inner asteroid belt, ancient martian impact basins, and planetary accretion models. The largest late terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially modified Earth’s obliquity by ~10°, whereas those for the Moon, at ~250 to 300 kilometers, may have delivered water to its mantle.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

VI. The nature of the Moon’s surface - The lunar surface and the U. S. Ranger programme

1967 ◽  
Vol 296 (1446) ◽  
pp. 399-417 ◽  
Keyword(s):  
The Moon ◽  
Martian Surface ◽  
Mountain Ranges ◽  
The Earth ◽  
Time Dependencies ◽  
The Alps ◽  
Mare Serenitatis ◽  
The Impact ◽  
Characteristic Colour ◽  
Lunar Maria

The unaided eye can see roundish dark spots on the Moon set in a brighter back­ground. Telescopic observation of these dark spots, called maria (plural of mare , sea) reveals that they are nearly level terrain sparsely covered with craters. The brighter surroundings or terrae are from shadow measurements found to be higher, some 1 to 3 km above the maria. The terra elevations scatter widely, reaching several kilometres in the mountain ranges. The most prominent of these ranges occur as peripheral mountain chains around the near-circular maria. Examples are the Apennines, the Alps, the Carpathians, and the Altai Scarp. These arcuate chains surround the maria as the crater walls surround crater floors, an analogy that can be carried further and implies, apart from scale, a similar origin. This origin is almost certainly impact by massive objects. In the case of the impact maria and pre-mare craters, the source of the objects appear to have been a satellite ring around the Earth through which the Moon swept very early in its history, in its outward journey from its position of origin very near the Earth (Kuiper 1954, 1965). The post-mare craters are presumably mostly asteroidal (and partly comet­ary) in origin and related to the craters observed by Mariner IV on Mars. The estimated time dependencies of these two crater-forming processes are shown schematically in figure 1. A fuller discussion of this problem has been given else­where (Kuiper, Strom & Poole 1966; Kuiper 1966). The higher asteroidal impact rate on Mars, by a factor of about 15, as derived from the Mariner IV records, is interpreted as being due to the greater proximity to the asteroid ring. The num­erical factor approximately agrees with theory. Mars apparently lacks the equiva­lent of the initial excessively intense bombardment of the Moon (attributed to impacts by circumterrestrial bodies); unless, of course, the entire Martian surface has been molten and is directly comparable to the lunar maria. This does not seem probable but can at present not be ruled out; if true, the earliest surface history would have been erased. The nature of the mare surface has, during the past decade, been an object of much, perhaps too much, speculation. With the several recent successful lunar reconnaissance missions completed, the older interpretation of the maria as lava beds, based on telescopic observation, has been abundantly confirmed. Four options discussed in recent literature are analysed in Kuiper (1965, §§A, B, pp. 12–39). Among the most potent arguments for the lava cover of the maria are the prominent lava flows observed on Mare Imbrium and Mare Serenitatis, each having a characteristic colour. A map of some Mare Imbrium flows is found in figure 2.

Science and Exploration of the Moon: Overview

2021 ◽  
Author(s):  
Bradley L. Jolliff
Keyword(s):  
Solar System ◽  
Nearest Neighbor ◽  
Space Environment ◽  
Cold Trap ◽  
The Moon ◽  
Early Solar System ◽  
Geologic History ◽  
The Earth ◽  
History Of ◽  
The Impact

Earth’s moon, hereafter referred to as “the Moon,” has been an object of intense study since before the time of the Apollo and Luna missions to the lunar surface and associated sample returns. As a differentiated rocky body and as Earth’s companion in the solar system, much study has been given to aspects such as the Moon’s surface characteristics, composition, interior, geologic history, origin, and what it records about the early history of the Earth-Moon system and the evolution of differentiated rocky bodies in the solar system. Much of the Apollo and post-Apollo knowledge came from surface geologic exploration, remote sensing, and extensive studies of the lunar samples. After a hiatus of nearly two decades following the end of Apollo and Luna missions, a new era of lunar exploration began with a series of orbital missions, including missions designed to prepare the way for longer duration human use and further exploration of the Moon. Participation in these missions has become international. The more recent missions have provided global context and have investigated composition, mineralogy, topography, gravity, tectonics, thermal evolution of the interior, thermal and radiation environments at the surface, exosphere composition and phenomena, and characteristics of the poles with their permanently shaded cold-trap environments. New samples were recognized as a class of achondrite meteorites, shown through geochemical and mineralogical similarities to have originated on the Moon. New sample-based studies with ever-improving analytical techniques and approaches have also led to significant discoveries such as the determination of volatile contents, including intrinsic H contents of lunar minerals and glasses. The Moon preserves a record of the impact history of the solar system, and new developments in timing of events, sample based and model based, are leading to a new reckoning of planetary chronology and the events that occurred in the early solar system. The new data provide the grist to test models of formation of the Moon and its early differentiation, and its thermal and volcanic evolution. Thought to have been born of a giant impact into early Earth, new data are providing key constraints on timing and process. The new data are also being used to test hypotheses and work out details such as for the magma ocean concept, the possible existence of an early magnetic field generated by a core dynamo, the effects of intense asteroidal and cometary bombardment during the first 500 million–600 million years, sequestration of volatile compounds at the poles, volcanism through time, including new information about the youngest volcanism on the Moon, and the formation and degradation processes of impact craters, so well preserved on the Moon. The Moon is a natural laboratory and cornerstone for understanding many processes operating in the space environment of the Earth and Moon, now and in the past, and of the geologic processes that have affected the planets through time. The Moon is a destination for further human exploration and activity, including use of valuable resources in space. It behooves humanity to learn as much about Earth’s nearest neighbor in space as possible.

scholarly journals Accretion of the Moon from non-canonical discs

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130256 ◽  
Author(s):  
J. Salmon ◽  
R. M Canup
Keyword(s):  
Angular Momentum ◽  
Rotation Period ◽  
Major Axis ◽  
The Moon ◽  
Large Excess ◽  
Semi Major Axis ◽  
Earth’S Mantle ◽  
The Earth ◽  
Post Impact ◽  
Impact Simulations

Impacts that leave the Earth–Moon system with a large excess in angular momentum have recently been advocated as a means of generating a protolunar disc with a composition that is nearly identical to that of the Earth's mantle. We here investigate the accretion of the Moon from discs generated by such ‘non-canonical’ impacts, which are typically more compact than discs produced by canonical impacts and have a higher fraction of their mass initially located inside the Roche limit. Our model predicts a similar overall accretional history for both canonical and non-canonical discs, with the Moon forming in three consecutive steps over hundreds of years. However, we find that, to yield a lunar-mass Moon, the more compact non-canonical discs must initially be more massive than implied by prior estimates, and only a few of the discs produced by impact simulations to date appear to meet this condition. Non-canonical impacts require that capture of the Moon into the evection resonance with the Sun reduced the Earth–Moon angular momentum by a factor of 2 or more. We find that the Moon's semi-major axis at the end of its accretion is approximately 7 R ⊕ , which is comparable to the location of the evection resonance for a post-impact Earth with a 2.5 h rotation period in the absence of a disc. Thus, the dynamics of the Moon's assembly may directly affect its ability to be captured into the resonance.

scholarly journals Boundary conditions for the formation of the Moon

2015 ◽  
Vol 95 (2) ◽  
pp. 131-139 ◽  
Author(s):  
M. Reuver ◽  
R.J. de Meijer ◽  
I.L. ten Kate ◽  
W. van Westrenen
Keyword(s):  
Angular Momentum ◽  
Boundary Conditions ◽  
Total Angular Momentum ◽  
Nuclear Explosion ◽  
Moment Of Inertia ◽  
The Moon ◽  
Moon System ◽  
Giant Impact ◽  
The Earth ◽  
The Impact

AbstractRecent measurements of the chemical and isotopic composition of lunar samples indicate that the Moon's bulk composition shows great similarities with the composition of the silicate Earth. Moon formation models that attempt to explain these similarities make a wide variety of assumptions about the properties of the Earth prior to the formation of the Moon (the proto-Earth), and about the necessity and properties of an impactor colliding with the proto-Earth. This paper investigates the effects of the proto-Earth's mass, oblateness and internal core-mantle differentiation on its moment of inertia. The ratio of angular momentum and moment of inertia determines the stability of the proto-Earth and the binding energy, i.e. the energy needed to make the transition from an initial state in which the system is a rotating single body with a certain angular momentum to a final state with two bodies (Earth and Moon) with the same total angular momentum, redistributed between Earth and Moon. For the initial state two scenarios are being investigated: a homogeneous (undifferentiated) proto-Earth and a proto-Earth differentiated in a central metallic and an outer silicate shell; for both scenarios a range of oblateness values is investigated. Calculations indicate that a differentiated proto-Earth would become unstable at an angular momentum L that exceeds the total angular momentum of the present-day Earth–Moon system (L0) by factors of 2.5–2.9, with the precise maximum dependent on the proto-Earth's oblateness. Further limitations are imposed by the Roche limit and the logical condition that the separated Earth–Moon system should be formed outside the proto-Earth. This further limits the L values of the Earth–Moon system to a maximum of about L/L0 = 1.5, at a minimum oblateness (a/c ratio) of 1.2. These calculations provide boundary conditions for the main classes of Moon-forming models. Our results show that at the high values of L used in recent giant impact models (1.8 < L/L0 < 3.1), the proposed proto-Earths are unstable before (Cuk & Stewart, 2012) or immediately after (Canup, 2012) the impact, even at a high oblateness (the most favourable condition for stability). We conclude that the recent attempts to improve the classic giant impact hypothesis by studying systems with very high values of L are not supported by the boundary condition calculations in this work. In contrast, this work indicates that the nuclear explosion model for Moon formation (De Meijer et al., 2013) fulfills the boundary conditions and requires approximately one order of magnitude less energy than originally estimated. Hence in our view the nuclear explosion model is presently the model that best explains the formation of the Moon from predominantly terrestrial silicate material.

scholarly journals Late Accretion on the Earliest Planetesimals Revealed by the Highly Siderophile Elements

Science ◽  
2012 ◽  
Vol 336 (6077) ◽  
pp. 72-75 ◽  
Author(s):  
Christopher W. Dale ◽  
Kevin W. Burton ◽  
Richard C. Greenwood ◽  
Abdelmouhcine Gannoun ◽  
Jonathan Wade ◽  
...  
Keyword(s):  
Body Size ◽  
Solar System ◽  
Oxidation State ◽  
Parent Body ◽  
The Body ◽  
The Moon ◽  
Core Formation ◽  
Highly Siderophile Elements ◽  
The Core ◽  
Siderophile Elements

Late accretion of primitive chondritic material to Earth, the Moon, and Mars, after core formation had ceased, can account for the absolute and relative abundances of highly siderophile elements (HSEs) in their silicate mantles. Here we show that smaller planetesimals also possess elevated HSE abundances in chondritic proportions. This demonstrates that late addition of chondritic material was a common feature of all differentiated planets and planetesimals, irrespective of when they accreted; occurring ≤5 to ≥150 million years after the formation of the solar system. Parent-body size played a role in producing variations in absolute HSE abundances among these bodies; however, the oxidation state of the body exerted the major control by influencing the extent to which late-accreted material was mixed into the silicate mantle rather than removed to the core.

Mare basalt petrogenesis and the composition of the lunar interior

1977 ◽  
Vol 285 (1327) ◽  
pp. 577-586 ◽  
Keyword(s):  
Experimental Investigation ◽  
Recent Literature ◽  
Bulk Composition ◽  
The Moon ◽  
Compositional Model ◽  
Earth’S Mantle ◽  
Source Regions ◽  
Lunar Interior ◽  
Wide Range ◽  
Mare Basalts

Mare basalts, which are believed to form by partial melting at considerable depths in the lunar interior, are capable of providing a wealth of information concerning the compositions of their source regions. Conversely, any acceptable estimate of the lunar bulk composition must in principle be able to provide source regions capable of yielding mare basalts. A wide range of lunar bulk compositions has been proposed in the recent literature. These differ principally in the proportions of involatile elements, e.g. Ca, A1, to elements of moderate volatility, e.g. Mg, Si, Fe. A detailed experimental investigation has been made of the capacity of the Taylor—Jakes compositional model (8.2 % A12O3) to provide source regions for mare basalts. It is demonstrated that this composition is much too rich in alumina to be acceptable. Other lunar bulk compositions even richer inA12O3 such as those advocated by Ganapathy & Anders, Wanke and co-workers and Anderson can likewise be rejected. In order to produce mare basalts, particularly the least fractionated varieties represented by some Apollo 12 and 15 basalts, lunar bulk compositions containing only about 4 % of A12O3 appear to be required. This is similar to the alumina content of the Earth’s mantle. The relative abundances of many other involatile elements, e.g. Ga, U, Ti, r.e.e., Zr, Ba, Sr, may likewise be similar in the Moon and in the Earth’s mantle. These relationships point towards a common origin for the Moon and for the Earth’s mantle.

Constitution of terrestrial planets

1981 ◽  
Vol 303 (1477) ◽  
pp. 287-302 ◽  
Keyword(s):  
Bulk Composition ◽  
Parent Body ◽  
The Moon ◽  
Volatile Elements ◽  
Earth’S Mantle ◽  
The Earth ◽  
History Of ◽  
Relationship Of ◽  
Reduced State

Reliable estimates of the bulk composition are so far restricted to the three planetary objects from which we have samples for laboratory investigation, i.e. the Earth, the Moon and the eucrite parent asteroid. The last, the parent body of the eucrite— diogenite family of meteorites, an object that like Earth and Moon underwent magmatic differentiations, seems to have an almost chondritic composition except for a considerable depletion of all moderately volatile (Na, K, Rb, F, etc.) and highly volatile (Cl, Br, Cd, Pb, etc.) elements. The Moon is also depleted in moderately volatile and volatile elements compared to carbonaceous chondrites of type 1 (Cl) and also compared to the Earth. Again normalized to Cl and Si the Earth’s mantle and the Moon are slightly enriched in refractory lithophile elements and in magnesium. It might be that this enrichment is fictitious and only due to the normalization to Si and that both Earth’s mantle and Moon are depleted in Si, which partly entered the Earth’s core in metallic form. The striking depletion of the Earth’s mantle for the elements V, Cr and Mn can also be explained by their partial removal into the core. The similar abundances of V, Cr and Mn in the Moon and in the Earth’s mantle indicate the strong genetic relationship of Earth and Moon. Apart from their contents of metallic iron, all siderophile elements, moderately volatile and volatile elements, Earth and Moon are chemically very similar. It might well be that, with these exceptions and that of a varying degree of oxidation, all the inner planets have a similar chemistry. The chemical composition of the Earth’s mantle, for which reliable and accurate data have recently been obtained from the study of ultramafic nodules, yields important information about the accretion history of the Earth and that of the inner planets. It seems that accretion started with highly reduced material, with all Fe as metal and even Si and Cr, V and Mn partly in reduced state, followed by the accretion of more and more oxidized matter.

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