Hit-and-run planetary collisions

Asphaug, Erik; Agnor, C. B.; Williams, Quentin

doi:10.1038/nature04311

Cited by 310 publications

(271 citation statements)

References 41 publications

Supporting

Mentioning

264

Contrasting

Unclassified

Order By: Relevance

“…The assumption to date has been that the larger of the two colliding bodies generally grows, but under some conditions a significant amount of material may be ejected (Asphaug et al 2006). This has two potential consequences.…”

Section: Formation Of the Earthmentioning

confidence: 99%

“…The lower limit is certainly too low to account for the Earth's inventory of water, and the upper value may be only marginally generous enough provided the Earth sits near the dry end of its possible range of water values, and loss by impacts is minimal. In view of the fact that the upper value pertains to accretion prior to core formation, when the Earth was perhaps significantly less massive than today, loss of material (including water) during collisions with other embryos may have been too extensive (Asphaug et al 2006) to admit the carbonaceous chondritic source.…”

Section: Early Earth J I Lunine 1723mentioning

confidence: 99%

See 1 more Smart Citation

Physical conditions on the early Earth

Lunine

2006

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

The formation of the Earth as a planet was a large stochastic process in which the rapid assembly of asteroidal-to-Mars-sized bodies was followed by a more extended period of growth through collisions of these objects, facilitated by the gravitational perturbations associated with Jupiter. The Earth's inventory of water and organic molecules may have come from diverse sources, not more than 10% roughly from comets, the rest from asteroidal precursors to chondritic bodies and possibly objects near Earth's orbit for which no representative class of meteorites exists today in laboratory collections. The final assembly of the Earth included a catastrophic impact with a Mars-sized body, ejecting mantle and crustal material to form the Moon, and also devolatilizing part of the Earth. A magma ocean and steam atmosphere (possibly with silica vapour) existed briefly in this period, but terrestrial surface waters were below the critical point within 100 million years after Earth's formation, and liquid water existed continuously on the surface within a few hundred million years. Organic material delivered by comets and asteroids would have survived, in part, this violent early period, but frequent impacts of remaining debris probably prevented the continuous habitability of the Earth for one to several hundred million years. Planetary analogues to or records of this early time when life began include Io (heat flow), Titan (organic chemistry) and Venus (remnant early granites).

show abstract

Section: Formation Of the Earthmentioning

confidence: 99%

Section: Early Earth J I Lunine 1723mentioning

confidence: 99%

Physical conditions on the early Earth

Lunine

2006

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

show abstract

“…The anomalous eucrites could have avoided being shocked and brecciated during the Late Heavy Bombardment because at that time they were residing in small asteroids (~10 km in diameter) that had been derived earlier from Vesta-sized bodies. If the iron and stony-iron meteorites come from bodies that formed inside 2 AU and were eviscerated by protoplanetary impacts before reaching the asteroid belt (Bottke et al, 2006;Asphaug et al, 2006), this would help to explain why some differentiated asteroids were catastrophically destroyed but others were not. Vesta and the parent bodies of the anomalous eucrites might have escaped catastrophic disruption because they formed in the asteroid belt or because they were scattered there without being eviscerated.…”

Section: Origin Of Unbrecciated Eucritesmentioning

confidence: 99%

Oxygen isotopic constraints on the origin and parent bodies of eucrites, diogenites, and howardites

Scott

Greenwood

Franchi

et al. 2009

Geochimica et Cosmochimica Acta

148

177

View full text Add to dashboard Cite

A few eucrites have anomalous oxygen isotopic compositions. To help understand their origin and identify additional samples, we have analyzed the oxygen isotopic compositions of 18 eucrites and four diogenites. Except for five eucrites, these meteorites have ∆ 17 O values that lie within 2σ of their mean value viz., -0.242±0.016‰, consistent with igneous isotopic homogenization of Vesta. The five exceptional eucrites-NWA 1240, Pasamonte (both clast and matrix samples), PCA 91007, A-881394, and Ibitira-have ∆ 17 O values that lie respectively 4σ, 5σ, 5σ, 15σ, and 21σ away from this mean value. NWA 1240 has a δ 18 O value that is 5σ below the mean eucrite value. Four of the five outliers are unbrecciated and unshocked basaltic eucrites, like NWA 011, the first eucrite found to have an anomalous oxygen isotopic composition. The fifth outlier, Pasamonte, is composed almost entirely of unequilibrated basaltic clasts. Published chemical data for the six eucrites with anomalous oxygen isotopic compositions (including NWA 011) exclude contamination by chondritic projectiles as a source of the oxygen anomalies. Only NWA 011 has an anomalous Fe/Mn ratio, but several anomalous eucrites have exceptional Na, Ti, or Cr concentrations. We infer that the six anomalous eucrites are probably derived from five distinct Vesta-like parent bodies (Pasamonte and PCA 91007 could come from one body). These anomalous eucrites, like many unbrecciated eucrites from Vesta, are probably deficient in brecciation and shock effects because they were sequestered in small asteroids (~10 km diameter) during the Late Heavy Bombardment following ejection from Vesta-like bodies. The preservation of Vesta's crust and the lack of deeply buried samples from the hypothesized Vestalike bodies are consistent with the removal of these bodies from the asteroid belt by gravitational perturbations from planets and protoplanets, rather than by collisonal grinding.

show abstract

“…Numerous models (e.g. Benz & Asphaug 1999;Agnor & Asphaug 2004;Asphaug et al 2006) have reported that collisions are commonly nonaccretionary and lead to erosion of the outer layers of a growing planet. The inference that one might make here is that this process should have taken place at a very early stage (within the first few million years after the beginning of the Solar System) and have led to the removal of an early formed crust on the planetesimals that ultimately formed the Earth, Mars and the Moon.…”

Section: (B ) the Nd-isotope Composition Of The Terrestrial Planetsmentioning

confidence: 99%

Early differentiation of the Earth and the Moon

Bourdon

Touboul

Caro

et al. 2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

We examine the implications of new 182 W and 142 Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182 W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60 Ma after the formation of calcium-aluminium-rich inclusions (4.568 Gyr). This is not inconsistent with the apparent U-Pb age of the Earth. The new 142 Nd data for Martian meteorites show that Mars probably has a superchondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142 Nd-143 Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142 Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200 Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50-100 Myr could have yielded the 200 Myr model age.

show abstract

Hit-and-run planetary collisions

Cited by 310 publications

References 41 publications

Physical conditions on the early Earth

Physical conditions on the early Earth

Oxygen isotopic constraints on the origin and parent bodies of eucrites, diogenites, and howardites

Early differentiation of the Earth and the Moon

Contact Info

Product

Resources

About