Origin of the Moon in a giant impact near the end of the Earth's formation

Canup, R. M.; Asphaug, Erik

doi:10.1038/35089010

Cited by 928 publications

(641 citation statements)

References 19 publications

Supporting

Mentioning

616

Contrasting

Unclassified

Order By: Relevance

“…As mentioned above, towards the end of accretion, global melting during the Moon-forming giant impact (Canup & Asphang 2001) may have homogenized the mantle, mixing back the oxygen-enriched lower mantle with the upper mantle. Disproportionated metal would not have been lost as the mantle melted because Fe and Fe 2 O 3 in perovskite would have recombined to produce FeO in the liquid as melting occurred.…”

Section: Disproportionation During Core Formation and Oxidation Of Thmentioning

confidence: 99%

The redox state of the mantle during and just after core formation

Frost

Mann

Asahara

et al. 2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Siderophile elements are depleted in the Earth's mantle, relative to chondritic meteorites, as a result of equilibration with core-forming Fe-rich metal. Measurements of metal-silicate partition coefficients show that mantle depletions of slightly siderophile elements (e.g. Cr, V ) must have occurred at more reducing conditions than those inferred from the current mantle FeO content. This implies that the oxidation state (i.e. FeO content) of the mantle increased with time as accretion proceeded. The oxygen fugacity of the present-day upper mantle is several orders of magnitude higher than the level imposed by equilibrium with core-forming Fe metal. This results from an increase in the Fe 2 O 3 content of the mantle that probably occurred in the first 1 Ga of the Earth's history. Here we explore fractionation mechanisms that could have caused mantle FeO and Fe 2 O 3 contents to increase while the oxidation state of accreting material remained constant (homogeneous accretion). Using measured metal-silicate partition coefficients for O and Si, we have modelled core-mantle equilibration in a magma ocean that became progressively deeper as accretion proceeded. The model indicates that the mantle would have become gradually oxidized as a result of Si entering the core. However, the increase in mantle FeO content and oxygen fugacity is limited by the fact that O also partitions into the core at high temperatures, which lowers the FeO content of the mantle. (Mg,Fe)(Al,Si)O 3 perovskite, the dominant lower mantle mineral, has a strong affinity for Fe 2 O 3 even in the presence of metallic Fe. As the upper mantle would have been poor in Fe 2 O 3 during core formation, FeO would have disproportionated to produce Fe 2 O 3 (in perovskite) and Fe metal. Loss of some disproportionated Fe metal to the core would have enriched the remaining mantle in Fe 2 O 3 and, if the entire mantle was then homogenized, the oxygen fugacity of the upper mantle would have been raised to its present-day level.

show abstract

Section: Disproportionation During Core Formation and Oxidation Of Thmentioning

confidence: 99%

The redox state of the mantle during and just after core formation

Frost

Mann

Asahara

et al. 2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

show abstract

“…We must emphasize that mass fractions of materials differ in literature, which indicates that there are still some uncertainties in the bulk composition of solar system objects. For example, the iron core mass fraction of the Moon is estimated at less than 10% of its total mass -3% is found by Canup & Asphaug (2001). We use both pv and en phase of silicate to calculate the radii, the aim is to test the model approach only.…”

Section: Code Test For the Differentiated Planetsmentioning

confidence: 99%

The silicate and carbon-rich models of CoRoT-7b, Kepler-9d and Kepler-10b

Gong¹,

Zhou²

2012

Res. Astron. Astrophys.

View full text Add to dashboard Cite

Possible bulk compositions of the super-Earth exoplanets, are investigated by applying a commonly used silicate and a non-standard carbon model. Their internal structures are deduced using the suitable equation of state of the materials. The degeneracy problems of their compositions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) The iron core of CoRoT-7b is not more than 27% of its total mass within 1 σ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be compatible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely with a Mercury-like composition, its old age implies that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only superEarth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.

show abstract

“…A few tens of millions of years after the Moon-forming event, the EM system reaches an optimal capacity for excitation via gravitational encounters: a dynamically excitable system co-existing with a significant remnant body population. The angular momentum of the EM system at the time of its origin is a central feature diagnostic of various giant impact scenarios proposed to date 1,3,4,18 . Given that the lunar orbit provides a sensitive dynamical measure of encounters with the EM system following its origin, we can ask whether such gravitational interactions were effective at injecting or extracting angular momentum.…”

mentioning

confidence: 99%

“…In Figure 2, we show results of simulations of the excitation of the lunar inclination due to interaction of the system with a small amount of mass (equivalent to 0.0075-0.015 M E eventually accreted to the Earth), for different values of the strength of tidal dissipation and the number of bodies delivering the mass (constrained to be <20 colliding with Earth via models of late accretion 10,11 ). Several The angular momentum of the EM system at the time of its origin is a central feature diagnostic of various giant impact scenarios proposed to date 1,3,4,18 . Given that the lunar orbit provides a sensitive dynamical measure of encounters with the EM system following its origin, we can ask whether such gravitational interactions were effective at injecting or extracting angular momentum.…”

mentioning

confidence: 99%

“…The change in angular momentum corresponding to modern inclination excitation of ~5 degrees is likely a few tens of percent or less. Hence, the standard giant impact scenario 4 followed by little subsequent dynamical modification is compatible with the dynamical state of the modern system, while a high angular momentum impact scenario 3,5 would require another dynamical mechanism such as the evection resonance 3,12,16 to be reconciled with the modern EM system. Each suite of simulations is composed of two subsets: one with late accretion delivered via 1 body (greater excitation), the other 4 (lesser excitation).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Collisionless encounters and the origin of the lunar inclination

Pahlevan

Morbidelli

2015

Nature

View full text Add to dashboard Cite

The Moon-forming impact is thought to have generated a compact circumplanetary disk (within < 10 Earth radii) from which the Moon rapidly accreted. Like Saturn's rings, the proto-lunar disk is expected to become equatorial on a timescale rapid relative to its evolutionary timescale. Hence, so long as the proto-lunar material disaggregated into a disk following the giant impact, the Moon is expected to have accreted within ~1° of the Earth's equator plane 6 . Tidal evolution calculations suggest that for every degree of inclination of the lunar orbit plane relative to the Earth's equator plane at an Earth-Moon (EM) separation of 10 Earth radii (R E ), the current lunar orbit would exhibit ~1/2° of inclination relative to Earth's orbital plane [7][8][9] . The modern ~5° lunar inclination wouldwithout external influences -translate to a ~10° inclination to Earth's equator plane at 10 R E shortly after lunar accretion. This ~10x difference between theoretical expectations of lunar accretion and the EM system has become known as the lunar inclination problem.Previous work on this problem has sought to identify mechanisms such as a gravitational resonance between the newly formed Moon and the Sun 12 or the remnant proto-lunar disk 13 that can excite the lunar inclination to a level consistent with its current value.Neither of these scenarios is satisfactory, however, as the former requires particular values of the tidal dissipation parameters while the latter has only been shown to be viable in an idealized system where a single, fully-formed Moon interacts with a single pair of resonances in the proto-lunar disk. Moreover, prior works have all assumed that the excitation of the lunar orbit was determined during interactions essentially coinciding with lunar origin. Here, we propose that the lunar inclination arose much later as a consequence of the sweep-up of remnant planetesimals in the inner Solar System. After the giant impact and at most ~10 3 years 14,15 , the Moon has accreted, interacted with 13 and caused the collapse of the remnant proto-lunar disk onto the Earth 6 , passed the evection resonance with the Sun 3,12,16 , and begun a steady outward tidal evolution. On a timescale (~10 6 -10 7 years) rapid relative to that characterizing depletion of planetesimals in the final post-Moon formation stage of planetary accretion 17 (called "late accretion"), the lunar orbit expands through the action of tides to an EM separation of ~20-40 R E . In this time, the lunar orbit transitions from precession around the spin-axis of Earth to precession around the heliocentric orbit normal vector 8 , and its inclination becomes insensitive to the shifting of the Earth's equatorial plane via subsequent accretion 18 .However, as we show below, lunar inclination becomes more sensitive to gravitational interactions with passing planetesimals as the tidal evolution of the system proceeds. The sensitivity is such as to render the lunar orbital excitation a natural outcome of the sweepup of the leftovers of accretion and to yield ...

show abstract

Origin of the Moon in a giant impact near the end of the Earth's formation

Cited by 928 publications

References 19 publications

The redox state of the mantle during and just after core formation

The redox state of the mantle during and just after core formation

The silicate and carbon-rich models of CoRoT-7b, Kepler-9d and Kepler-10b

Collisionless encounters and the origin of the lunar inclination

Contact Info

Product

Resources

About