Geochemical implications of the formation of the Moon by a single giant impact

Nature ◽  
1989 ◽  
Vol 338 (6210) ◽  
pp. 29-34 ◽  
Author(s):  
Horton E. Newsom ◽  
Stuart Ross Taylor
Keyword(s):  
The Moon ◽  
Giant Impact

scholarly journals Isotopic evidence for the formation of the Moon in a canonical giant impact

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sune G. Nielsen ◽  
David V. Bekaert ◽  
Maureen Auro
Keyword(s):  
Solar System ◽  
Isotope Fractionation ◽  
Main Stage ◽  
The Moon ◽  
Giant Impact ◽  
Bulk Silicate Earth ◽  
The Earth ◽  
The Standard Model ◽  
Isotopic Measurements ◽  
Origin Of The Moon

AbstractIsotopic measurements of lunar and terrestrial rocks have revealed that, unlike any other body in the solar system, the Moon is indistinguishable from the Earth for nearly every isotopic system. This observation, however, contradicts predictions by the standard model for the origin of the Moon, the canonical giant impact. Here we show that the vanadium isotopic composition of the Moon is offset from that of the bulk silicate Earth by 0.18 ± 0.04 parts per thousand towards the chondritic value. This offset most likely results from isotope fractionation on proto-Earth during the main stage of terrestrial core formation (pre-giant impact), followed by a canonical giant impact where ~80% of the Moon originates from the impactor of chondritic composition. Our data refute the possibility of post-giant impact equilibration between the Earth and Moon, and implies that the impactor and proto-Earth mainly accreted from a common isotopic reservoir in the inner solar system.

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 Lunar and terrestrial planet formation in the Grand Tack scenario

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130174 ◽  
Author(s):  
S. A. Jacobson ◽  
A. Morbidelli
Keyword(s):  
Total Mass ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
The Moon ◽  
Giant Impact ◽  
Modal Mass ◽  
The Individual ◽  
Impact Phase ◽  
Geochemical Constraints

We present conclusions from a large number of N -body simulations of the giant impact phase of terrestrial planet formation. We focus on new results obtained from the recently proposed Grand Tack model, which couples the gas-driven migration of giant planets to the accretion of the terrestrial planets. The giant impact phase follows the oligarchic growth phase, which builds a bi-modal mass distribution within the disc of embryos and planetesimals. By varying the ratio of the total mass in the embryo population to the total mass in the planetesimal population and the mass of the individual embryos, we explore how different disc conditions control the final planets. The total mass ratio of embryos to planetesimals controls the timing of the last giant (Moon-forming) impact and its violence. The initial embryo mass sets the size of the lunar impactor and the growth rate of Mars. After comparing our simulated outcomes with the actual orbits of the terrestrial planets (angular momentum deficit, mass concentration) and taking into account independent geochemical constraints on the mass accreted by the Earth after the Moon-forming event and on the time scale for the growth of Mars, we conclude that the protoplanetary disc at the beginning of the giant impact phase must have had most of its mass in Mars-sized embryos and only a small fraction of the total disc mass in the planetesimal population. From this, we infer that the Moon-forming event occurred between approximately 60 and approximately 130 Myr after the formation of the first solids and was caused most likely by an object with a mass similar to that of Mars.

scholarly journals Primordial Earth Mantle Heterogeneity Caused by the Moon-forming Giant Impact?

2019 ◽  
Vol 887 (2) ◽  
pp. 211 ◽  
Author(s):  
Hongping Deng ◽  
Maxim D. Ballmer ◽  
Christian Reinhardt ◽  
Matthias M. M. Meier ◽  
Lucio Mayer ◽  
...  
Keyword(s):  
Mantle Heterogeneity ◽  
The Moon ◽  
Giant Impact ◽  
Primordial Earth

PLANETARY SCIENCE: The Giant Impact Formation of the Moon

Science ◽  
2004 ◽  
Vol 304 (5673) ◽  
pp. 977-979 ◽  
Author(s):  
H. Palme
Keyword(s):  
Planetary Science ◽  
The Moon ◽  
Giant Impact

scholarly journals Siderophile element constraints on the origin of the Moon

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130258 ◽  
Author(s):  
Richard J. Walker
Keyword(s):  
The Moon ◽  
Element Abundances ◽  
Giant Impact ◽  
The Earth ◽  
Precision Determination ◽  
Mantle Sources ◽  
Volcanic Glasses ◽  
High Precision Determination ◽  
Origin Of The Moon

Discovery of small enrichments in 182 W/ 184 W in some Archaean rocks, relative to modern mantle, suggests both exogeneous and endogenous modifications to highly siderophile element (HSE) and moderately siderophile element abundances in the terrestrial mantle. Collectively, these isotopic enrichments suggest the formation of chemically fractionated reservoirs in the terrestrial mantle that survived the putative Moon-forming giant impact, and also provide support for the late accretion hypothesis. The lunar mantle sources of volcanic glasses and basalts were depleted in HSEs relative to the terrestrial mantle by at least a factor of 20. The most likely explanations for the disparity between the Earth and Moon are either that the Moon received a disproportionately lower share of late accreted materials than the Earth, such as may have resulted from stochastic late accretion, or the major phase of late accretion occurred prior to the Moon-forming event, and the putative giant impact led to little drawdown of HSEs to the Earth's core. High precision determination of the 182 W isotopic composition of the Moon can help to resolve this issue.

scholarly journals Evaporative fractionation of volatile stable isotopes and their bearing on the origin of the Moon

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130259 ◽  
Author(s):  
James M. D. Day ◽  
Frederic Moynier
Keyword(s):  
Global Scale ◽  
Parent Body ◽  
The Moon ◽  
Magma Ocean ◽  
Volatile Elements ◽  
Giant Impact ◽  
The Earth ◽  
Present Distribution ◽  
Volatile Loss

The Moon is depleted in volatile elements relative to the Earth and Mars. Low abundances of volatile elements, fractionated stable isotope ratios of S, Cl, K and Zn, high μ ( 238 U/ 204 Pb) and long-term Rb/Sr depletion are distinguishing features of the Moon, relative to the Earth. These geochemical characteristics indicate both inheritance of volatile-depleted materials that formed the Moon and planets and subsequent evaporative loss of volatile elements that occurred during lunar formation and differentiation. Models of volatile loss through localized eruptive degassing are not consistent with the available S, Cl, Zn and K isotopes and abundance data for the Moon. The most probable cause of volatile depletion is global-scale evaporation resulting from a giant impact or a magma ocean phase where inefficient volatile loss during magmatic convection led to the present distribution of volatile elements within mantle and crustal reservoirs. Problems exist for models of planetary volatile depletion following giant impact. Most critically, in this model, the volatile loss requires preferential delivery and retention of late-accreted volatiles to the Earth compared with the Moon. Different proportions of late-accreted mass are computed to explain present-day distributions of volatile and moderately volatile elements (e.g. Pb, Zn; 5 to >10%) relative to highly siderophile elements (approx. 0.5%) for the Earth. Models of early magma ocean phases may be more effective in explaining the volatile loss. Basaltic materials (e.g. eucrites and angrites) from highly differentiated airless asteroids are volatile-depleted, like the Moon, whereas the Earth and Mars have proportionally greater volatile contents. Parent-body size and the existence of early atmospheres are therefore likely to represent fundamental controls on planetary volatile retention or loss.

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